Workshop: Sorption Science Innovations in Cellulosic Material Characterization

Hello everyone and thank you for joining us for today's Surface Measurement Systems Online workshop. Today we're very happy to be partnered with the University of British Columbia on today's online event and are extremely happy and elated to have guest speaker Dr. And Professor Orlando Rojas from the University of British Columbia here to speak with us about some of his work today. Just before we kick into the presentations, I wanted to let everyone know about just some of the House rules for today's workshop. We ask that everyone for the duration of the presentation, keeps their microphone muted just to avoid any background noise or feedback having a negative effect on the audio quality of today's session. For those of you who have any questions for any of the speakers, whether these come from your knowledge of your questions on the topic in general or questions that arise from the presentations themselves, there will be a live Q and A session at the end of each presentation. And how do you submit your questions through this I hear you ask. There are two ways you can raise your hand at the end of the session, at which point I will let you know when you can unmute your microphone and you can ask the question yourself over your microphone. Or alternatively, there is a Questions panel in the webinar Control tab Control panel. So all you need to do is go to the Questions tab and submit your question there and I will put your question to the speaker when it comes around to the Q and A at the end of the presentation. So that once again you can either raise your hand for us to let you know when you can unmute your microphone and ask the question yourself, or you can submit your question in writing through the Questions tab and we will ask the speaker to address it. To kick us off here today is Surface measurement system, North America's very own Vice President, Dr. Daniel J. Burnet. Working out of our North American headquarters in Allentown, his team works on research studies and science applications for many prominent companies. He received his Bachelor's Degree in Professional Chemistry from the Eastern Michigan University in 1997 and a PhD in chemical engineering from the University of Michigan in 2001. Dr. Burnett has authored and co authored over 25 papers in peer reviewed journals and presented at numerous national and international conferences. So without further ado, I will now hand over to Dr. Burnett to begin his presentation.

Thank you John for the introduction and I'm going to share my screen so hopefully everybody can follow along. And to kick things off in the workshop today, I will just very briefly introduce vapor absorption techniques which SMS has pioneered and worked with pretty much exclusively for 30 years. And then we'll go into some absorption mechanisms. But the bulk of the presentation will be a heavily application focused talk on dynamic vapor absorption and how, whether it be the isotherm and or kinetics, can be applied to a wide range of materials with a focus on cellulose based or natural materials. So to set the stage and to kind of give an overview of where SMS technology and molecular probe techniques fit into your characterization toolbox, I very often categorize materials characterization experiments into a couple different fields. One is using energy as a probe. So this could be lights or x rays or lasers. And you look at how that light or that energy is absorbed, adsorbed, refracted, reflected, whatever it may be. But in general, you're going to look at analytical and structural information. You can use heat as a probe, looking at heat gain, heat loss, heat transfer, heat capacity changes, whatever it may be. But in general, you're going to look at some thermodynamic information with these calorimetric techniques. Where the technologies we'll be focusing on today, at least for Annette and myself, will be using molecular probe techniques. This is where we're going to look at as a molecule and how that molecule interacts with the material. And depending on what molecule you use, what conditions, what variable you select, you can look at thermodynamic, chemical and structural information. So in general, the first two categories is basically limited by energy transfer, which is relatively fast, Whereas molecular probe techniques, you're looking at mass transfer, which is relatively slow. So generally speaking, these molecular probe techniques, other molecular probe techniques outside of SMS technology could be classic nitrogen volumetric bet, surface area analysis, density by pychometry, chemisorption, other type of absorption techniques. All of these are based on mass transfer. We have to get the probe to the surface or through the bulk of the sample. And relatively speaking, they're not extremely fast techniques. Whereas these can be done in seconds or minutes or hours. Most of these techniques to do them fully take hours to min, to days, and for some experiments, several days to run. So when I start using words like adsorption and absorption, I thought I'd just show a little cartoon with a sample in blue. We have our vapor molecule, in particular these little water molecules. And those molecules can be adsorbed, which means they only interact with the surface of the sample or they can be absorbed. If the sample is amorphous or highly soluble in the particular vapor, we can get a significant amount of bulk absorption and then those molecules could come out. They don't always come out. So sometimes you get some irreversible adsorption. But essentially, with all of the techniques that we'll be talking about, Annette and myself will be talking about, we look as a vapor interacts with material, either the surface through adsorption, the bulk through absorption, and then how those molecules are released. So what I will be focusing on in the first half of the presentation, the workshop today is dynamic vapor absorption. This was a technique that was invented by the owner of our company, Dr. And Professor Darrell Williams, over about 30 years ago now. And it was a method where some companies came to Darrell to see if they could replace the desiccator or jar method of measuring water absorption isotherms. So in this technique, you would have several desiccant jars at different relative humidities. Through some saturated salt solutions, you may have a series of 5, 6, 8, 10 of these different desiccator jars at different humidity conditions, and you would manually take the sample out and weigh it over a period of time. Obviously this is a rather slow and labor intensive and high margin of error method. If you want to get gross information, you could use it. But if you want to get very high fidelity data in vapor absorption, we needed a better way. So Darrell came across and invented and pioneered the technique of dynamic vapor absorption, which is a dynamic technique where you have a flow of carrier gas, typically dry air or dry nitrogen. The sample is continuously weighed and monitored on a microbalance. So there's no need to take a sample on and off to weigh it periodically. The mass is constantly weighed and monitored by a very sensitive balance that can go down to 0.1 micrograms or 100 nanograms. And then what happens is that the airflow going across this sample can be humidified or partially humidified by mixing a fully saturated flow with a fully dry flow. And these can mix in different proportions to deliver the requested relative humidity to the sample. And then we can measure the mass change as a function of time, as a function of relative humidity, and as a function of temperature, as this entire instrument is held at an isothermal condition. So a very typical output of a standard, excuse me, experiment, and probably roughly 75 to 80% of the experiments done with the dynamic vapor absorption are to ultimately measure the water content or the moisture content as a function of relative humidity, or the isotherm, which I'll show you next. But here we can see, in red is the mass response as a function of time. In blue is the relative humidity as a function of time. And very often what is done is the sample is dried at 0% relative humidity, make a step change to another RH, measure the mass gain until it reaches equilibrium, then go to another RH, and so on and so on. And then from these equilibrium points we can construct the isotherm. Now this is on a rice starch sample and I'm just highlighting the fact that we can do multiple cycles, adsorption going up, desorption coming down, adsorption, desorption, and just not that all experiments take 12,000 minutes, but you can see you get a very good baseline and stability in the balance. And if necessary you can do experiments over very large time scales. But from the adsorption desorption equilibrium points, which is where the mass has reached equilibrium. At each of these steps, we can construct the sorption and desorption isotherm. So, so the sorption isotherm is in red, the desorption is in blue, and the difference in uptake between the sorption isotherm and the desorption isotherm is called the hysteresis. So the shape, size and location of this hysteresis and the shape size of the isotherm can give us a lot of information about the mechanism, about how moisture or whatever vapor you're studying interacts with your material. So for instance, this is on a amorphous carbon sample. And you can see that this has a sorption isotherm and a desorption isotherm with a well defined hysteresis between 40 and 70% partial pressure. And this is indicative of a typical mesoporous isotherm. Mesoporous being the pores are between 20 and 500 angstroms. This is due to capillary condensation. Here we can see this is on a silica material. Again you can see some hysteresis at this higher end. And this can often again be to capillary condensation or some other effects here. But you can see relatively low uptake until you get to about 70%, 80% and then the uptake increases significantly. It is possible to hyphenate the DVs with some orthogonal techniques to get additional information. In addition to the mass change. One of those things we can do is we can input a camera in situ so we can in real time look at any physical changes to the sample. For instance, this is a maltodextrin at 0% relative humidity. We step change to 95% RH at time equals zero. So initial exposure to 95% RH after 30 minutes and after 50 minutes you can see the sample has swelled and the physical form has changed significantly. Here's looking at a wood pellet. This is a study we did a few years ago and presented the Society of Wood Science Technology with some collaborators at ubc. And we can see that this is at time equals zero and at zero percent of relative humidity. And here we can have a scale bar to actually get quantitative information. And we can see as we go up in relative humidity until we get all the way here to 95% relative humidity. We can see that this is this wood pellet, which was kind of cut in half. And we're looking at the radial portion, not the longitudinal portion of this wood pellet. We can see that this material has swelled significantly and measurably as a function of rh. So we can use this grid lines to get quantitative information or pseudo quantitative information. We can look at, at least in an axial direction, what the swelling rate was as a function of relative humidity. Here I plotted the cross sectional area that we see here as a function of rh. And you can see relatively unchanged until we get to about 50% relative humidity. And then we can see that the material swells significantly. An additional information we can get is we can have, we have some access ports to put in some fiber optic probes so we can get things like Raman spectroscopy, near eye spectroscopy. We could put in a UV light source, but we have some additional ports if we want to measure additional responses from the sample as a function of rh. So not only would you get the mass change, we can get some spectroscopic information. So here is on a microcrystalline cellulose material, we can have the DVS data where we have the mass change as a function of rh. And we can get corresponding spectroscopic information through the Raman at the same conditions in real time. So here we can see this is in blue at 0% relative humidity, then 20, then 40, then 60, then 80% rhythm. And we can see how there may be some more subtle structural changes that we could not pick up from the simple gravimetric data. But the spectroscopic data clearly shows some differences as we change as material swells and picks up moisture. So moving on away from, as I mentioned, we can do other things which I'll not talk about today, but we can put in an in situ near ir. We've had other customers that looked at UV light to see activating or curing or aging materials as a function of UV light. We've also used some IR temperature probes and other things like that. So the footprint and the functionality of the instrument allows for a fair bit of modularity to add in other techniques during your water absorption experiment. So just to move into some relatively varied applications, and I won't go into details, we do have either posters or papers or application notes on most of the applications or case studies that I'm showing in this talk. You can message us if you'd like to get some more information. But here we did a study with Historical Society in the UK looking at historic building materials. Obviously when they need to be repaired, you want to replace them with materials that will have similar thermal and moisture absorption behavior. So we were looking at some wood and mortar and brick samples from a historical building and our collaborators were measuring some of the thermal properties. Here we're looking at some of the water absorption properties and the idea was that you could pair both the thermal and mechanical response to some replacement or restorative materials that'll have similar behaviors. Here we're looking at just some examples of wood and not only would the species of the wood give different moisture absorption properties, but but also the physical form. So for instance, on the left hand side in part A here this is on sawdust. And in part B, on the right hand side is a solid wood sample. So you can see both the hysteresis, the difference in uptake between the sorption and desorption, and the total uptake. So you can see this caps out around 10%, whereas the sawdust picks up a sinibly amount more moisture, most likely because it has a higher surface area than the wood sample. But the DBS can use wood samples from, you know, fine powders to films, to fibers or slabs. As long as you can put it on the microbalance, we can measure it here looking at not only as I mentioned, the physical form, but the nature or the history of the sample can make a difference. So here we're looking at adsorption isotherms of basically three different types of cellulose. This was taken from the literature, this is not our work, so it is referenced here. And you can see that the source of the material will affect the moisture absorption behavior. You can clearly see both the kinetics and the isotherms are different for the different types of cellulose. Here again we're looking on some other natural materials, this is some hemp material. And again the source or type of material can have a significant impact on the kinetics, which is how quickly or slowly does it pick up and lose water. But also the uptakes, you can see this sample caps out around 15% and this one around in between 25 and 30% by weight uptake. And here are the isotherms from the corresponding kinetic data in the previous slide. And again, you can clearly see that there's a difference in both the uptake and the hysteresis of the two samples that we've shown here. And this is looking at, as I mentioned, the form and the source, but also the temperature. So we can control the temperature of the isotherm. And we can see here, this is in red at 5 degrees Celsius and this is at 15 degrees Celsius. In blue, we can see as we go up in temperature, we can see that the uptake increases, particularly at lower relative humidities, and we can see that it is much faster. As well, we can look at the effects of storage temperature or processing temperature, or to more widely characterize the stability of these materials over a wide range range of conditions. Again, this is not our work. This is pulled from the literature just to show you some examples on another historical application. This was published several years ago now, but it's an interesting application of looking at the moisture absorption of some archaeological wood samples. And this was from a Swedish warship. But just highlighting the information you can get on a wide range of materials using, using the dbs, it is possible, I didn't go into too much detail, but the reservoir of where you put in the vapor, we can vary that so we can do organic solvents, but we can also use deuterium. And this is a, a study that was done by Professor Hill's group and they were using instead of water in the dvs, they were using deuterium or heavy water. And they were looking at the exchange of the water that was native to the wood species to the water that was introduced. So we can see is the water being exchanged or to see if we can identify and quantify the OH groups to see if that water is bound, meaning the water doesn't likely come out of the sample in its native state or is it exchanged with the deuterium in the vapor phase. Just highlighting another case study was looking at a straw based material as an alternative building material. And as you can imagine, with any building material, whether it be wood or natural materials, the moisture absorption behavior will affect dimensional changes and also structural stability as the water may plasticize or swell or change the structural integrity of that particular material. So here we're looking at the moisture absorption of a raw wheat straw and one that was treated at 50 degrees C with a 4% sodium hydroxide solution. And we can clearly see that this is a little bit busy slide. But we can see that the surface area is relatively unchanged. So we're not really changing the size or available area of the material or clearly changing both the surface and bulk chemistry of the straw sample. Because we can see that for the raw sample the uptake is maybe below 20%. But for the treated sample, particularly at high relative humidities, we can see a significant uptake. So moisture is penetrating these samples to a much higher degree, particularly at high relative humidities. This is just highlighting that this is looking at the the weed straw again as received and then afterwards and looking at the recovery of the after treatment, you can see that not only does the moisture absorption change, but other properties change as well. Pardon me, it looks like I have a slide in there twice. So I will just maybe I've gone on the wrong. Here we go. Okay, so here again we are looking at different forms of cellulose and we are looking at the relative humidity for these different forms of cellulose. And again, this is not done by sms, but taken from the literature as it's is appropriately referenced here. And we're looking at different forms of microcrystalline cellulose, different forms of cotton cellulose and different forms of spruce pulp samples. And we can see that the uptakes of these different materials will change significantly based on the source of the material. For some reason, some of these slides got mixed up maybe at the last minute. So I apologize for this. These somehow got mixed up and not in the right order. So this is the same deuterium exchange. So I don't know what happened, so I apologize for that. But here is just looking at the cycles of the deuterium exchange. And again it is referenced by Dr. Hill's group here in the bottom reference there. So moving away from the equilibrium values, but the kinetics or the diffusion information can be extracted by using different models. So if we assume a geometry, whether it be a fiber geometry, a film geometry, or a spherical geometry, or a slab geometry, whichever one we choose, we can apply the right model. And if we assume a Fician or first order diffusion coefficient from the uptake, the initial uptakes, it's typically a linear portion, we can extract a diffusion coefficient. So at this point we don't really care as much about the equilibrium value. Here we're looking at the rate of uptake into the material. Again that could be into a film, into a fiber, into a powder. And depending on what the geometry is, you apply the appropriate model and you can back calculate the diffusion coefficient. So here we're looking at the diffusion coefficient going from 0 to 20% RH, 20% RH back down to 0, up to 40, back down to 0 and so on up to 60. And we can see how the diffusion coefficient changes as we change the boundary conditions for this particular sample. If you want to measure permeation, so this is diffusion into a material. If you want to measure permeation or flux across a membrane or a film or a barrier, we've developed this diffusion cell which we also call the pain cell. And it's a small sample cup where you place a zeolite or a desiccant typically on the inside. And then we change, we seal a film or a piece of material or a membrane and that gets sealed. So we have an effective 0% relative humidity on the inside of the cup. We change the relative humidity on the outside of the cup and then we can measure the mass gain as it comes across and travels through here. And we can get the steady state flux of water or moisture going across the membrane and being picked up by the zeolite or desiccant on the inside. Alternatively, you can measure in what's called the wet cup method is where you put water on the inside. You can even put this film upside down. So the water is in constant contact with whatever material you have here at this film cell. And then if you measure mass loss as that is being removed from the sample, as we change the flow and relative to humidity and temperature exposed on the outside. So just to highlight, we can do this these experiments over a range of humidities. We can also look at a range of thicknesses. So we can do this over a wide range of different types of membranes or barriers or films. Water is a typically a very strong plasticizer. So sometimes when I expose a sample to moisture, not only does it pick up in weight, but I can change the mechanical and physical properties of that particular material. I can force it to go through a moisture induced glass transition. For some low molecular weight materials, it may even go through an amorphous crystalline transformation. I can also look at hydration versus dehydration. So all of these things we can look at and monitor by using different types of experiments with the dbs. So for instance, here we're looking at some dehydration kinetics. So what we did is we fully hydrated the sample and then we dropped it down to zero to look at the drying conditions. And this plot is showing fraction dehydrated. So at Time equals zero is where it's fully hydrated. Then we turn off the moisture and just dry it out at 0% relative humidity until it's completely dry. And so here we are at fully dehydrated and here we're at fully hydrated. And we can see we can do this at different temperatures. This is at 15 degrees C and this is at 30 degrees C. So we can clearly see the dehydration kinetics is a strong factor on temperature. And then you can apply various solid state models and then I could predict the drying behavior over a range of temperatures and or conditions. As I mentioned, water does act as a strong plasticizer and we can. When a sample is well below the glass transition point, molecules typically only interact with the surface. As it approaches the glass transition point, molecular mobility of the material increases significantly and we get a strong absorption or water penetrating or dissolving into the bulk. And if it does recrystallize, it'll return to surface sorption domination only. And this is just showing on a lactose sample, an amorphous lactose, we get it to a critical relative humidity, it'll actually collapse and we see a decrease in mass because the crystalline phase has a much lower absorption capacity than the amorphous phase. Here we can use that phenomena to pinpoint where these moisture induced transitions will occur. Unlike an isotherm experiment, we can do a linear ramp in relative humidity. This would be similar to a DSC experiment where you ramp the temperature and you're looking at a temperature which will induce these phase changes. Here we do the experiments isothermally. We pick a particular temperature, we dry the sample, make a linear increase in relative humidity in blue, and we can see the mass response is nonlinear because the absorption process goes through several different regimes. We can see here a relatively low and monotonic increase in relative humidity. And then we see a significant increase in uptake as the sample goes through its moisture induced glass transition. Because as we mentioned previously, when it goes through the glass transition, molecular mobility of the sample increases dramatically and we see a large uptake in mass. This particular sample is relatively low molecular weight. So if you get to a critical relative humidity, it'll actually recrystallize. So we could potentially do these experiments over different temperatures. And then we can get kind of a phase diagram of a. This is the glass transition point, a function of temperature. This is the re spontaneous recrystallization point as a function of temperature. And we know if we keep the sample below this glass transition point, it'll be relatively stable. If it's in between here, it's only a matter of time before the sample eventually relaxes and will recrystallize. How long that take could be several orders of magnitude in time. But the closer you are to the spontaneous point, the quicker it'll happen. Just showing on some cellulose based materials, this is looking at some nanocellulose and here you can clearly see this is the transition point between surface domination dominated absorption and bulk dominate absorption. And from that inflection point is the glass transition, relative humidity which was 58% RH for nanocellulose. This is some filter paper, around 76% and so on and so on. It's part of a larger study we did with the Imperial College of London looking at these kind of conditions. So you can do this over a wide range of materials, a wide range of temperatures and you can see how the glass transition might change with different cellulose or natural based materials. So I'd like to wrap up with my portion of the presentation of the, of the workshop and hopefully I showed you some applications and touched very briefly on the possibilities. There certainly are many more types of experiments that you could run, multiple applications, but hopefully I've whet your appetite in what's possible by DBS on cellulose based or natural materials. So thanks for your time and attention. Thank you to my current and former colleagues who helped work on this work and I'd be happy to entertain any questions. John, if you need to point me in the right direction to answer those questions, I'd be happy to do so.

Absolutely. Thank you so much, Daniel. And we've got a few questions in already. So just to remind our audience, if you would like to ask a question, you can raise your hand and we will let you know when you can unmute your microphone or you can submit a question in the questions tab. So our first question from Monique Nguyen and they ask what type of molecules are used in the molecule probe?

Well, it depends on what you're trying to learn about the material. So in our instruments we use vapors, so we can use a wide range of vapors. From water is the most commonly used probe in the dbs. But you can use a wide range of organic solvents ranging from decane to hexane to toluene to ethanol to methanol to basically in our instrument, as long as you can, we bubble through a bottle to generate the vapor, as long as it has a reasonable vapor pressure. So from a practical standpoint, if the boiling point is below 200 degrees C. We typically do not have any problems. We can generate the vapor appropriately. So it really depends on what you're trying to learn about your sample. What chemistry of the probe molecule you're interested in will probe a certain chemistry of the material. The next presentation on IGC will cover. Typically we use a broader range of probe molecules in that instrument. But basically any vapor you can do. Other probe molecule techniques use gases or inert gases like nitrogen. We typically use vapors that have different chemistry, so we can probe different chemistry of the surface.

Monique has followed up with the question asking if the probe can be solid.

No, we don't vaporize or heat the material. So it does have to be a liquid at the measurement temperature. So. Or it has to have a significant vapor pressure. I mean, I have run menthol, but it's a little bit tricky to do. So it typically does have to be a liquid at the temperature that we're measuring it. So if it's a liquid at 70 degrees C, you could run it. But the probe cannot be a solid. We often get questions about monomers of a polymer. It has to be a solid. So it just depends on. I apologize. It has to be a liquid at the temperature that you're measuring it. Because everything is. If I go back up to here, maybe I go through this a little bit more. And I didn't probably make it clear in my slide when I showed the diagram of the instrument. The reservoir for the liquid is held at the same temperature as the sample. So in here is a reservoir of whatever liquid I'm going to saturate with the carrier gas and deliver to the sample.

Great, thank you. Our next question from Alice Medak, and they ask, is hysteresis always based on finite kinetics or could it be thermodynamic in special cases?

That's a great question. Absolutely. It can 100% be both thermodynamically controlled and kinetically controlled. Because in particular, this example is looking at more of a bulk hysteresis, which is probably predominantly kinetically controlled. But you can have the case where the material forms a hydrate or forms a different state, and on the desorption side, it is due to kinetics. This case here is due to thermodynamics because it's due to capillary condensation. Even if I leave it there for a long period of time, this hysteresis gap will not narrow. It's because it has to overcome the surface tension of the liquid in a small pore before it desorbs and you can also have some, like I said, some thermodynamic reasons for this hysteresis is because this material at low humidity is thermodynamically different than the material at high humidity. And so there are both thermodynamic and kinetic reasons for hysteresis.

Brilliant. Thank you. We do have a few hands raised. So for now we will go to Alan Wang. Alan, if you could unmute your microphone, I'll unmute you from this end and you can ask Daniel your question. Oh, unfortunately he's lowered his hand. So unfortunately we'll move on to our next person. Abu Sahra Jiddun. If you would like to unmute your microphone, you can ask the question directly.

Yeah, my name is Abu Sirajuddin. I'm from St. John's University in New York. My question is also about the hysteresis group. I have done some work with celluloses. I found that if I increase the time at a certain humidity, for example, if I am at a 40% humidity, and while raising the humidity to 40% to 50%, if I keep the threshold of my change in humidity to 0.1%, I get a very big hysteresis loop. And while I am reducing low, low, low to 0.001%. So if there is a change of 0.001% humidity or less, then the humidity will go up. In that case, I can lower or practically make the hysteresis very low, you know, very narrow. So in my experience, this is more a time dependent phenomenon. But you also mentioned about the, you know, capillary condensation. So can you please maybe reflect on it?

Yes, absolutely. So you're 100% correct. And there's a very nice paper by the U.S. forestry Department where they give recommended values for, for the equilibrium criteria for cellulose based materials. And it is a trade off in the DVS experiment in terms of how long the experiment takes and to exactly what equilibrium criteria I want to use. So if this is just due to a material like cellulose, where you have a bulk absorption mechanism, it can be relatively slow and your equilibrium criteria can affect the ultimate hysteresis loop. So you are correct for cellulose based materials. And I know wood based materials. And like I said, the US Forestry Department published a very nice paper on choosing the right conditions for that. But there. So that's on a kinetic basis and that's typically manifested when I have a broad hysteresis across the entire humidity range. There's no Clear transition of where that occurs. And that's typically just due to bulk absorption, which is relatively slow. And I can decrease that hysteresis by giving it more time. However, when I have a hysteresis that is well defined, in a well defined humidity range, this is very often indicative of when I might have, in this case, capillary condensation. And that's a true thermodynamic effect. If I. Even if I leave it there for much longer periods of time on the desorption side, it won't come out. And that's due to. Because I don't know if I can draw on this or not. But it's basically because I have a small pore and the water is creating a meniscus in the capillary condensation. And it needs to get to a lower humidity on the outside to overcome the surface tension of that liquid before those molecules can be released. In pharmaceutics, you can have a hydrate like a stoichiometric hydrate, and you can often get a hysteresis that may look similar to this, where at a critical relative humidity, it'll go up and form the hydrated stage. And the desorption side, it will dehydrate at a much lower relative humidity. And it doesn't matter how long you leave it there. I've done experiments. I left it there for days and days and days. It still doesn't dehydrate. That's because the thermodynamic state of the hydrate of a stoichiometric hydrate or maybe even a channel hydrated or a hemihydrate is different than the anhydrous phase. So there can be true thermodynamic reasons. And what I typically see as the telltale sign is that you'll see a very, you know, there'll be a range or a region where the hysteresis occurs and a region where it doesn't occur. And that's when it's not just kinetically limited, it's actually thermodynamically controlled. Whereas here it's more just kinetically limited, where I see a hysteresis across the entire humidity range because it's just a matter of time. I hope that helps.

No, yeah, it's very helpful. Yeah. Thank you very much.

Yeah. Thank you, Abby. So on to our next question from Juliet Truquette. And they ask, you have talked about the effect of sample nature, that is sawdust versus wood, but what is the effect of mass? So, for example, 2 milligrams versus 10 milligrams or even 10 milligrams versus 50 milligrams.

That's a very good question. And it does come down to time. As I mentioned, this is a mass transfer process. It's relatively slow. So from a. And as the previous question alluded to, it can be time consuming. And it comes down to a balance between how long do I want the experiment to take versus how well defined or what, how, what, what quality isotherm data do I want? So if I use a 10 milligram sample or a 50 milligram sample versus a 2 milligram sample, the larger sample will take a longer period of time to reach equilibrium. So we typically recommend to use the smallest sample that's representative for your material. So if I have a homogeneous powder, 1 or 2 milligrams could be quite sufficient. If I have, you know, maybe a wood sample or a heterogeneous material, I may have to use more material and it just takes longer if you get good quality data. The good news is there have been some studies, and this was by Professor Jerome. I apologize, I'm probably saying that wrong. Up at Sherbrooke Inner University now they did some studies where they did isotherms on microscopic materials like you would run in the DBS, which may be maximum 100 milligrams. And those properties did correlate to bulk large macroscopic pieces of wood. So you can use microscopic data to predict macroscopic behavior. But the quality, the ultimate quality of the isotherm will depend on a time balance between how much time do I want to take and what fidelity or what, what quality of data I want. So there, there can be some trade off and say, okay, is this the true, true isotherm? Maybe I'm 1% off, but maybe it's good enough to compare different materials of what I'm looking at. So very good question.

Brilliant. Thank you, Daniel. We do have more questions, but I'm afraid we are pushing to the end of our first slot, so we are going to have to move on. But please rest assured, anyone who has submitted a question, we will get back to you either during this session or after the session is concluded by email. So apologies, we can get back to your question now. So thank you again, Dan, for a fantastic presentation and for engaging with the questions from our audience.

Thanks for your attention, everybody. I'll pass it on to the next speaker.

As Daniel mentioned, we'll now be proceeding to our next speaker and that would be of course Professor Orlando Rojas from the University of British Columbia. Professor Rojas is a Canada Excellence Research Chair and Director of the Bioproducts Institute at the University of British Columbia. He's a recipient of the Anselm Parvin Award, the highest recognition in the area of cellulose and renewables materials. Professor Rojas is elected as a Fellow of the American Chemical Society, the Finnish Academy of Science and Letters and the recipient of the TAPI nanotechnology Award in 2015. With a H index of 73 and over 26,000 citations, he has authored about 430 peer reviewed papers related to the core research of his group, mainly dealing with nanostructures from renewable materials and their utilization in multi phase systems. As I mentioned, we are really really fortunate to have Professor Rojas to be able to be with us here today. So once again a big thank you to him and Orlando. I will now pass over Great.

So I hope that you can hear me clearly and also that my screen is being shown. If not, please yell at me.

We can hear and see you.

Okay, perfect. Excellent. So very good. Very happy to join you. I have not direct instrumental experience with DBS or inverse gas chromatography, but my students actually are active in the area so this is very nice. We use these tools plus many others to look into surfaces and interactions with water, looking into particles and thin films. My background is in colloid chemistry and that means that these aspects are very important in our area. Recently, the last maybe 15 years or so, main focus in my research relates to lignocellulose materials. What you see on the left is pretty much a condensation of what I will introduce today. So I was putting the presentation yesterday and trying to put something together in such a way that is easy to follow for all audiences. And this is an image of one of my PhD students. She draws realistic images, but in this particular case she had ventured in a different type with this aquarella and that was to illustrate a review paper that we worked together in the area of cellulose based hydrogels. And every detail in that image tells a story and I cannot tell all the stories because there is only limited time. But I will use three of the aspects that are shown here to discuss what I want to share with you. That is pretty much to make us more aware about the importance of this subject. That would be my main goal. I start saying that we really don't yet understand fully the interactions between water and plant based materials. This is very important as we think about the future bioeconomy Think about the fact that if we use plant based materials to replace for instance plastics, or at least to come up with new solutions to all our material needs. These are already things that are happening as we think about single use plastics, packaging materials to just name a new. If we want to consider this and that will happen eventually and it's already taking place, you need to identify that interactions with water is very important because natural materials are usually in close connection with water. We need to suspend the materials in water, hydrate or dehydrate the materials in their processing. Quite different than all base materials. And so far what we have been doing actually is to start to scratch the surfaces in a figurative but also direct way. I mentioned the work here. Surfaces and the tools that are used in this type of endeavors include those that you see in the bottom. At least these are the ones that in my group we have been using quartz crystal microbalance, small angle X ray scattering, dbs, IGC that we're discussing today, dsc, NMR and others. There are plenty of different approaches and they can be quite complementary. Before I go into the more detailed aspects, I want to tell you a little bit about what we do here in Canada. In ubc. In the Bioproducts Institute that I direct here, we have a number of different research streams. You can identify those in the bubbles. Many of those again relate to particles, lignocellulose particles, plant based materials that goes from the very small scale to larger scales. If we think about the biorefinery applications, this is a very important effort within the university with a high impact in Canada and is again to look into plant based materials, residual streams and also wood into fulfilling our material needs. The same happens to the other affiliation before coming to UBC was in Aalto University. We had a flagship consortium, very large flagship, called finceres, where we had also similar ideas about looking into lignocellulose to applications like future refineries, future plastics, even electronic material. This has become very popular. But notice on the far left that fundamentally one of the research streams that is very important here that we recognize very early on is water interactions and characterization of water interactions. This is very, very hot topic, I would say nowadays, and will continue to grow in its importance in this regard. One of the very early outcomes of these efforts in this flagship relates for instance to the capture of microplast. And for doing this, our colleagues in Finland have been using cellulosic based materials. These are called nanocellulosis microcelluloses. This is the network in the background that given capillary forces and very high surface area and surface energy allows the system to be very effective to function as a membrane to trap microplastics in liquid environments or liquid media, just as an example. So this is a practical issue that really will just grow in its importance. But again, the limitations I would say are as far as how to measure those interactions. And I show one of those. And that will be in the case of wood materials, wood itself, looking into scattering, a small angle x ray scattering. In this case, that coupled with molecular models can help to describe the interactions of the microfibrils in the wood fibers with water. And again, just to highlight that this is far to be well understood. So an additional example of the current interest in the research arena in this area, one tool that we have introduced in the case of, together with other colleagues in the case of cellulosic and lignin materials are show here. I think these are quite complementary, but I bring this up because they help us a lot to look into the interactions with water, especially the one on the right. Quartz crystal microbalance. QCM is a tool that we have used since 2004 to look into interactions between films, thin films of cellulose, with surfactants, polymers, small molecules, but also with water for that. The same principle that applies to the dynamic vapor absorption is used here. We have a piezoelectric resonator. It vibrates and when it interacts with substances in the medium, and the medium can be air or it can be water, the frequency of vibration will change and that will tell us information about absorption of molecules and water coupling. So in the right, this is very important. And in fact this is the same principle that we use in the dbs. Now, what is that that we're missing here? You realize that to use this unit you need to create very thin films of cellulose, lignin, et cetera. And that really draws away an important factor and that will be the structure. This is what really DVS complements in the sense that in the DVS type of approximation, we can use the material as it is, keeping the porous three dimensional aspects still in place so that we can understand better. The structure plays a very important role, cannot be disregarded. These are the tools. DVS has been explained very nicely by Daniel. And I'm not going to add to that. Then after me, Annette will be talking about igc. As I start, I want to acknowledge Annette. She has been very helpful in our work. She has run a lot of different collaborations using this instrumentation. We have been looking into milk powder as a colloidal behavior using these instruments. We have been using lignin particles that we analyze also by these techniques, as well as surface modification of cellulose by different techniques that we follow to understand the changes in the surface energy. In fact, we have two of the instruments on the left. DBS and IGC have been pretty much with collaboration with Annette. So thank you, Annette. So let me go back to the drawing here. And the first thing that I want to focus is on the table. This is a wooden table, as it happens, and I want to tell that surface matter. And I will illustrate this with a few examples why this is the case, why surface matters, and for interactions with water, DBS and igc, this needs to be well understood. So let me go back to the drawing board into more fundamental aspects. And this is the interaction forces between colloidal materials. On the left you can see the most typical non specific surface interactions going from van der Waal forces, double layered forces, hydrophobic hydration, hydrogen bonding, steric and region effects. All of them are very important, especially when materials are immersed in an aqueous media. That factor is of course very relevant. Besides that medium, of course, then also the forces itself that will happen when two objects are in close proximity. And this is defined by the forces that can be described. So van der Waal forces will be very important, very ubiquitous. It's always present van der Waal forces and of course they are very well described. But let me tell you why or how I explain how van der Waal forces matter so much, especially under the influence of the very top nano layer of a solid body material. Let me take an example. Object alpha and beta. We call this an asymmetric system because it's not the same material, but two different materials. It can be anything that you can imagine. Alpha and beta. They have given refractive indices, dielectric properties, and when they are a given distance D, they will start to interact. And that interaction energy we can define by the letter W that you can see there. The van der Waal forces will be dictated by the dielectric properties of the materials involved medium and alpha and beta. And for describing those interactions, we use a constant called the Hamaker constant. So let me just go deeper into that constant, not to go into the calculation or the details, but just to bring the issue of the very top layer that is on each of these objects. Let's imagine that we have made some surface modification and that can be in the form of an absorbed layer or a coating material. It can be an ultra thin film or a, any organic molecule. That is absorbed. Let's look at the force of interactions Vanderbilt forces normalized by the radius of the particles. In this case, if they are spherical, this is the way we actually measure the interaction forces. They scale with the interaction energy. And that has to do with the geometry. And the geometry is expressed in the case of the spherical particles by R. If we calculate the Hameker constant, then what you will notice is that this Hamaker constant, a effective in the vertical axis, will depend on the separation distance that is in the horizontal axis. Notice that if we have the bodies far from each other, the Hameker constant is negative. But as soon as we start to pass a given threshold of distance, and that the particles become closer and closer, the Hamecker constant actually becomes positive. This is very interesting, because what it means is that we go on the far distance from a van der Waal force that is actually in this case repulsive. Because van der Waal forces can be either attractive or repulsive. So in this particular case will be repulsive van der Waal forces. And as we get the materials closer together, they will become attractive. And the reason is that in the case of long distances between the objects, what really matters are the objects itself. But when they are closer together, what matters is the top nanometer surface coating that we have on the surface. What this means is that if we plot the force versus distance, you can exactly see how the van der Waal forces look at long distances. Very little interaction, at most repulsive, but then at shortest distances they become dominant, attractive. And that change is just to highlight the importance of the top layer on a material. And that means that phenomena such as flocculation, aggregation and interaction association will be dictated by the top nano scale layer. So this is all I wanted to say actually about the surface. Surface matters. And I have given only one single simple example using Vanderbilt forces, to illustrate my point, where Hamaker constant takes a very important role. Anyway, that top nano layer of absorbed molecules is important in interactions. And I only again put the example of Vandervals. Now let me move on to waters. Water matters. So surface matter. Water, of course, as well. Here you can see in the image pointing to the water. The case of cellulose is very characteristic in cellulose materials. We talk about fibers, fibrillas, crystals. There is no time to go into each of those. But I just want to bring something that was stated in 1985. This is very interesting. There was this idea, even if it was not proven at the time, that the surface of fibers of cellulose in General, to generalize, can be seen as cellulose chains looking like eel grass on the bottom of a pond. That's what it is. That was in 1993 that was proven that those so called dangling tastes of cellulose are on the surface of fibers. What that means is that in the very top surface of cellulosic structures, we have a gel like system that can be interacting very strongly with water that swells and interacts as a poly electrolyte gel. This is very important because that will define many of the interactions between the system. In this case celloxic materials when immersed in aqueous media. Going back to what I said earlier, all the interactions that we discuss briefly will be at play. And those interactions will be defined very critically by the state of the water. That is for instance, the Ph. D, ionic strength, the counter ions, the type of counter ions and other aspects related to the chemistry. It's a beautiful example about how we should depict how we need to think about cellulose not as a solid material, but actually at the surface layer as a hydrogel. That is very important to consider. Let me now go ahead and give some examples. And for that I will start with wood. I will go with paper and then nanocellulose. Where all these ideas will be somewhat integrated with the short time and limits that we have in this seminar. When we think about wood and in general plants, of course, water interactions is super important. I put here one review paper that we published recently with our colleagues in Brazil. Of course, water interactions when we think about plants probably are directed impacting agriculture, efficient plant protection and production. In this example, we were looking into target delivery systems on the foliage on the leaves of plants. So here already the surface matter, because interaction between the given agents on the leaves, the plant leaves and the surfaces are going to be very important. This is how we see things from the outside as far as the surface. But when it comes to looking to the wood or plant based components with water mixed with water, then we immediately think about hydrogels. In hydrogels, of course, there is plenty of literature and the applications of hydrogels since 10 years or so ago span a number of issues that you can see in this bar plot where we take a lot of inspiration from nature, but talking more directly about the wood based hydrogels. And mainly we speak here about cellulose based hydrogels. There is a lot of activity in this area, which is summarized in another review paper. That is in the bottom that you can take as a reference. The idea here is that from Wood, as you see on the top, we can structure, deconstruct the different elements going from the fibers to the nanofibrils to the cellulose. And that will be one of the players that we have talked about, as well as the lignins. And those components are very important in producing hydrogels. As you go in smaller sizes, as you go from fibers to nanofibers from left, actually, given the higher surface area that the surfaces are exposed more to water, then the interactions with water become more and more prevalent. And that means that these materials produce or form very easily, very nice gel materials, hydrogels. Now, if we go back to wood, let me show how water interactions, starting with wood, are important. And the first thought that came to my mind is the following. If you take a cross section of wood, you will observe that there are the growing rings, and in countries with the different stations, then you will see a very nice differentiation between summer wood and late wood, that is spring wood and the summer wood. And the main difference is, as you can appreciate in this cross section image of a wood block, is that the fibers that make part of wood will have a different layer thickness as the cell goes in the actual direction. So different layer thickness, different density. And this is interesting because in a way, plants adjust their morphology according to the water interactions, because depending on the season, there will be more or less water. So it's amazing how nature really adjusts itself to maximize interaction with water. And again, these are very little understood. But to put the point, if you look at the early wood that is also called spring wood, in the growing season, you can see that the wall thickness of the fibers are thinner. The fibril angle, that is the way the nanocellulose is located, with respect to the axis will be higher, the cellulose content is lower. And there are other features, structural features that are quite different, that really speaks to the fact that water interactions are important. In this example, if we go deeper into the fibers, we recognize already on the left, but also showing bigger magnification, that those cell elements contain open spaces, they're lumens. And this is what also can be thought of as pour, pour in wood, they are usually filled with water, but also maybe just filled with air. This is where free water flows. And this is important as far as the interaction with water. Then on the cell wall of the elements of the fibers here seen in cross section, we see the cell wall. And this is where inside water can also be bound strongly. And this is a so called bound water. And what that means is that the interactions between these elements and water will have very different aspects depending if we're talking about free water or bound water. And a very nice way to measure those types of water is by thermoporometry and cryoporometry, where we use for instance, dynamic scanning calorimetry to see the different states of water. Because given the different restriction of space, then the melting temperature and freezing temperature of water will change. This is given the theory of Gibson, Thompson and also the Laplace equation. So the melting and freezing temperature of water will be dependent on whether the water is in the bulk state or if it is constrained in a very small scale. That's what really defines the free water and bound water. Now in the QCM that I introduced earlier, this cannot be measured at least to the degree we want. The only way to go here or one of the ways of course, as I said before, can be cryoporometry, but also DBS for instance. What is the importance of this? Well, a very simple idea. We want to measure water content. If you want to be comfortable in a house. We hope to have relative humidity between 30 and 60%. And wood does a very good job at regulating the temperature and the humidity in given environments. That's the reason why wood for construction is just increasing in popularity. We're going back to construction with wood and what I show as an example on the right is a building that we have in campus. At the time when it was built, I believe 2017 was the tallest timber construction. And now in downtown Vancouver there is also plan for even taller building in the same fashion. So very important here, these elements that are based on wood will be dry as exposed to air with lower relative humidity. And what I show on the left is what is the equilibrium moisture in wood as we reduce the relative humidity. Pretty much what we saw before with the dbs. The main conclusion here is very interesting is that up to say about 30%, that's roughly the so called the fiber saturation point. The water is easily removed because it's being moved from the pore, from the bigger spaces, the so called free water. So up to that point we have really exchanged the free water. But then as we dry wood that as it becomes drier, then we're now dealing with the water that is in the cell wall. And this is actually what we call before the bound water. And then the isotherm that you see will change. So completely different isotherm at higher than 30% relative humidity compared to the more difficult to remove water at lower than 30%. Anyhow, this very fact is the one that explains why we feel comfortable in wooden houses. This is the reason. Now, this still requires a lot of more insightful information. And I can tell you that experimental data on cellulose water interactions, especially in wood in the native cell wall, is still very limited. What I want to say here is that there is plenty of room for us to engage in research in this area. Let me move from wood to go to paper, and especially paper water interactions. And here I use this book on the left and look into this. So this is a statement that I like to use very much. Cellulose and fibers in paper will have a very complicated relationship with water. And the question is, can we control it? There are many things here. The first one to be mindful is a cellulose as a molecule, not as a structure is an amphiphilic molecule. And this is why cellulose is obviously shown to be insoluble in water. That's an important part. Not only amphiphilicity, also is the hydrogen bonding that is established between the different cellulose molecules. Anyway, here of course, the importance of water is really critical because depending on the structure, then that water structuring can be quite different. But water structuring in itself is actually pretty difficult to characterize. But to make the point even more obvious, in thinking with the industry, hat if we think about how we produce paper, pretty much we take wood fibers that may be dry, we put them in water and a very large volume of water, so wet fibers, and then we dry again. So it's very strange sort of paradox that to make paper we add water and then we take water away. That tells you a little bit about the significance of water interactions. Or even worse, we sell water by a process, sorry, swell fibers by a process called refining. We make the fibers to absorb as much water as possible to make them to swell. And then when drying, then we de swell the material to get the properties that we want. Something that is very obvious maybe, but as far as the industry, but looking into the fundamentals, very complicated. So let me talk about paper making. In fact, very simple paper making. Here we go from forming to wet pressing and then drying. So in forming we use filtration of water. In wet pressing we use mechanical energy to remove water. And in drying we use thermal energy. And you can see how the evolution of the dryness or the water content changes as you go from left to right. Now, if you look at the changes on the fiber, now I'm not talking about wood, but the fiber itself. First, the Lumen, the pores that we talked earlier will become closer as you move from left to right and the area and the wrinkling will start to happen as you go from left to right. That is, as the fibers become drier. In the paper making process. What about the water removal? Initially we removed free water, but then we have the bound water. And here we classify this in two, the freeze bound and non freezing bound water. Super interesting phenomena. That means that what we saw earlier with the isotherms is much more complicated. If we try to understand what happens with a very simple process such as that of paper making, and to make my case even more clear, when we have very little water, when we're drying the material, if we imagine that the flat surfaces, there is maybe two parallel fibers. Or if you want, imagine that these are two paper films. When we have water and we remove water, the more water is removed means that then eventually we will reach this type of situation where we have created a meniscus. So that's the meniscus that will be the water in between the two surfaces and that meniscus with a given radius R1. If you calculate using this young Laplace equation in the bottom, what you will determine is that the capillary pressure is really several atmospheres, super strong forces that draw the surfaces together. So the reason for this type of. We were talking earlier about kinetic and thermodynamic effects. Those kinetic effects relate to these type of issues. The surfaces that are being dry become together and the distances get smaller. And then you lock the system with a very strong hydrogen bonding. This is the mechanism for us to make paper, such a structure that is stronger than steel by unit weight. To make a case further for water interactions and the importance, let's look at the hysteresis that was presented earlier. So here I can go rather quick. If we look at the relative humidity of a piece of the environment and how that makes a change in the moisture content of a paper, then you can see what was explained before. As we go from left to right, from a dry material to a wet material, because it's exposed to higher relative humidity, then the water will be absorbed by the fibers. And then that will be the absorption isotherm going up. As we dry the material, then we go in a different direction. That's of course called hysteresis. Notice that if the fibers are of one type, I just illustrated the case of chemical fibers is quite different than those of mechanical fibers. So the chemical composition of the fiber matters, but also matters many other things. The structure the degree of refining, also the history of how you dry and how you wet the material, even the rate of drying will be very important. So this speaks to the tricks of water interaction and how DBS techniques can help us to understand this phenomena. And this phenomena is important. An example that I put here is paper curling. If you take a paper and you let it dry after being humid, then you can see this effect curling. This, in fact, is more important than the strength of paper as far as many of the operations in conversion and many others. But let me just go a little bit deeper before going to nanocellulose, to the case of paper. In the absorption of paper, we can think about two things that are happening at the same time. When fibers, cellulosic fibers, are exposed to water as a liquid, it can absorb it, and at the same time, the fibers will swell. Now, there are two ways that we can do this. It can be that in the green pathway, the pores in the fibers get in water. So that would be pore sorption of water. And in that case, the degree of swelling is very little. Essentially, water is entering the pore spaces in the lumen in the fibers that I introduced earlier. Then the water will start to penetrate the cell wall. And that's what we call fiber absorption. The green pathway is one that is possible, but it could also be that we do the opposite, that water starts to penetrate the cell wall of the fibers. And then with the pores, of course, you can imagine what is the preferred pathway. In fact, in regular paper, it's a combination of the two. But initially the pore sorption is going to happen in combination with fiber absorption. But the fiber sorption will be more dominant when you have more water and as time elapses for longer time. Right? And then that will come also with a higher degree of swelling. These type of things we can understand better by techniques like the ones that I have introduced before. Okay, let me shift now to nanocellulose and water interactions. So I go from very typical objects, from wood and paper, now looking into more exotic nanomaterials that are the ones that actually my group does research in a more deeper sense. And here, of course, one thing that I always like to bring is, you know, this differentiation between wood on top and nanocellulose that are structures that belong to wood, but we remove from wood, taking the power of nanotechnology, but in the bottom, of course, as an object, a house, and how we can then 3D print materials using nanocellulose and the Main unique features of nanocellulose. And here I will refer to only one of the types of nanocellulose is cellulose nanocrystals. There are two things that I want to bring up at this point. First, chirality, those nanocrystals are twisted. And that twisting is important in the self assembly, but also in interactions with water. I will illustrate my point in a couple of slides. The second one is the surface energy. Those crystals have different surface energy, different crystal phases that have different surface energy and therefore different interactions with water. Then the last one, chemical isotropy, I will skip. But the crystals are different in one end compared to the other. If they are the so called cellulose, one polymorph. But for the time being, we can escape that chirality if we take a nanocrystal in water and we let it dry. Given the twisting and the chirality that we mentioned before, it will form these chiral pneumatic structures, these helicoidal structures that you see on the right. These are all shown as well on the left in this cross section of the dry material where you can get a feeling for this helicoidal structuring of the crystals in space. Where we have removed water. Now I just said that word, we remove water. And removal of water here is super critical. How fast you remove water, in what way you remove water. To make my point, very important here, let's run the following experiment. We take the cellulose nanocrystals, we put the crystals in suspension in water and deposit them on a cantilever that is fixed to one end, to the left and we let it dry. We let the water to evaporate. That's what is called evaporation induced self assembly. What I mean is that the crystals will start to get closer to each other. Eventually they form this chiral pneumatic order that you see on the far right. That by the way gives rise to the so called structural color. It's another subject, but it's a beautiful phenomena that happens in this nanomaterial. My point here with water is that when we evaporate water, there will be a point where the system starts to gel and there will be a colloidal arrest. That means that the crystal will be locked on the surface of the glass. If we use a glass. Let me just show this more clearly now. If we take that glass that I just explained and we take a cross look at the glass, we can see how with drying, what happened with that glass that is fixed to the left but is free on the right. What you're seeing is the water is receding, the system is becoming drying. And then the forces are so strong that we see this deflection. And this deflection actually correlates with what we see on the right. That didn't play, but now I play. It is that with time, the deflection increases and then you get the maximum deflection. So first those forces are so strong that you can deflect the material. In this case, a glass slide that is fixed to the left. And this is what is called the drying stresses. Those are very important in industry. Imagining coatings in films and layers, very important. And those drying stresses happen because interactions with water. You can illustrate this on the, on the top here, where water is in between the different crystals. Cellulose, nanocrystals, CNCs, this is a cross section. And then the meniscus that I illustrated earlier for paper also are active here in the nanomaterial. And those forces, as you dry and dry more and more, produce a very high capillary forces that pull the materials together. And that effect is the one that makes the CNC to contract and to vertically become uneven and shrink. And that's what we call the drying stresses. And you know, in industry, this is one of the most important things. In paintings and coatings, drying stresses are important, especially if we are dealing with particles like cellulosic particles. This type of interactions can be only understood if we use the tools that I have mentioned, including DBS and eventually also igc. Another example is super adhesives. But given the time, I think I'm already at the limit of the time. I just want to point to the fact here that same phenomena will happen when you use cellulose as a glue between two surfaces. Anyway, I think this is the end of my conversation. I have much more to share. I didn't talk about surface modification and how IGC can be used for that purpose. But I hope that you get a better feeling of the importance of water interaction from the point of view of hydration, wetting and swelling and capillary diffusion. These all are very important phenomena that happen in social systems. Just to just wrap up about the future prospects so that you give also a feeling how ourselves and many of my colleagues in campus and everywhere in the world are very active in this area where water interactions are critical. An example is in the top here. Sensing in mono assays are important. Here we have a microfluidic material that is based on nanocellulose. And there, if we want to put an analyte, of course, in water in saliva. In this example, we flow through the capillary structure. What not a better example of the effect of water in diffusion and capillary action so that we can get a sensing unit to work, or in the case also of modifying cellulose. An example here that is very recent is surface modification to hydrophobic cellulose. Actually in the presence of water, that makes this effect much nicer. Other examples, for instance, stretchable hydrogels that are resistant to dehydration or also resistant to ultra low temperatures or multifunctional wearables, as well as cholesterolic films, some of which I explained earlier. These are examples in the nanotechnology arena that are very relevant to what we do with EVS and igc. Well, with this I finished my talk. I went through surface and to state that surface matters, water matters, and especially for wood paper and nanocellulose. Thank you.

Thank you so much, Orlando. That was a fantastic presentation. So just to remind our audience, we'll now be taking questions for Professor Rojas to respond to. So just to remind you, you can submit these through the questions panel or you can raise your hand and we'll give you the chance to unmute and ask your question directly. So our first question, Orlando, from Farida Baraka, they ask, did you see the same phenomenon in cellulose nanofibers?

Definitely, and I didn't show it. But this is very important because if we use cellulose nanofibers that are much longer, we have a very capability to produce a network. This is not the case of cnc. With nanofibers, we have very nice networks in water, and when you remove water, it makes very strong hydrogels. Those hydrogels will depend on the charge of the fibrils. Of course, the higher the electrostatic charge, the more the water binding ability and therefore the stronger the hydrogels. My point is that with nanofibrils, exactly the same happens. It doesn't form these cholesteric assemblies that I show for CNC for the cellulose nanocrystals, but the same phenomena occurs as far as water interactions. In fact, nanofibrils are known are being shown. We published a paper on this and many of my colleagues are also very active in this area. We have shown that if you take nanofibrillar cellulose in contact with different materials that can be mineral materials, organic materials, yeast, pollen, metals, when you dry the material, then it will really bind the different components in making a composite. And this is all Driven by the capillary forces that are activated as you dry water, as I explained with the paper, but in this case with nanocellulose. So that makes cellulose anofibrillus, a universal binder is an area that is not fully exploited but is super important.

Thank you. We do have a hand raised by Benjamin Sao. So Benjamin, I will unmute you from this side if you would like to unmute yourself and ask Orlando your question.

Hello.

Hi, can you hear me? Yes, we can hear you clearly.

Very wonderful talk. What's your explanation between the free spawned water and the non freeze bond water?

Yeah, I didn't, because of time, I didn't go into, into that. But when you have water in a very narrow space, imagine as a, in a pore, very small pore, then the radius of curvature or the confinement of water makes that confinement makes that radius of curvature, makes the water to have a different behavior as far as the, for instance, freezing and the freezing and melting, essentially, as you know from colligative properties, if you have a change, for instance in those properties when you add salts, is an example of what you can do. But in the case of pure water, that confinement, that curvature mixed with a surface tension of water, that is the liquid with the highest surface tension, except for mercury, that makes that curvature, that is forming the meniscus in the very small scale that makes that force very, very high. What that means is that the vapor pressure of water is quite different than in the bulk because vapor pressure is the one that dictates evaporation, for instance, and change of phase. What that means is that in a very small narrow space, the temperature of melting and the temperature of freezing will be different for the same water compared to the bulk. And that measurement of the phase transition temperature tells you about the size of the pores. That's why DSC dynamics scanning calorimetry can be used to determine the size of the pores just by looking at the melting and the freezing temperature according to an equation, by the way, that is called Laplace equation.

Thank you. I think we have time for just one more question and then I'm afraid we do have to move on to our final presentation. So this question from Abdelhak Benkador, and they are, and they say I'm interested in detecting microplastic in water bodies. I saw some microplastics are captured in cellulosic materials in the first slides of your presentation. Would you mind explaining the interaction between cellulose and microplastics?

This is a very difficult question. In fact, Starting with the definition, the definition of microplastics is very loose. And the characterization of microplastics is nowadays a challenge how to characterize microplastics. So that's a very important issue and challenge and people are working on this. So this is from that perspective. Microplastics, by the way, are generated essentially by fossil carbon plastics that are very persistent in the environment. So if you take your clothes, polyester and cotton, and you put in the washing machine, eventually this goes to the water. And the difference between the polyester and the cotton, the cellulose, is that the polyester will form microparticles. And those microparticles will be very persistent in the ecos medium. Those are generated by cotton, actually will be more numerous. You will generate more microparticles, in fact. But these are very easily biodegraded in the marine environment. So that means that the cellulose as a microparticle also have the same issue than the typical microplastics, except that they can be biodegraded. Now, as far as the capture here, what we use is this nanocellulose network. That is of course, you saw, it is a network that can allow us to play with size exclusion because the interstices, the spaces between the fibers can be nicely controlled in the case of cellulose nanofibers. And then we have the capillary effects and surface forces effects between the particles and the material. So altogether that makes the nanocellulose to be an interesting option, as has been show, to trap microplastics of given sizes. Of course, that depends on the size. And there is a paper that is out related to the subject. So the mechanism is actually very interesting to follow using these techniques that we have talked. But the reality is that those forces that I mentioned at the beginning are at play in these nanostructures. And these are the ones that allow for the micro particles to be trapped in the network of nanocellulose.

Thank you, Orlando. We do have a few more questions, but I'm afraid we really must get onto our final presenter of the day. So we will get. We will give Orlando the opportunity to get back to you after the presentation for your questions. So thank you again to Professor Rojas for taking the time to be here today and share his findings with us.

Thank you.

Thank you, Orlando. So moving on to our final speaker for the day, and this is of course, Dr. Annette Condor. Annette is the IGCSEA product manager and product specialist for Surface measurement systems. Since 2005, Annette has been working on gas chromatographic and inverse gas chromatographic techniques. She studied chemical engineering at the University of Pannonia, Hungary where she received her Master's in Chemical Engineering and also her PhD in chemistry environmental Science. She is a multiple peer reviewed and published author collaborating with research groups from around the world. Her research interests lie in the area of surface characterization and of different solid materials and improvements in the IGC technique. So without further ado I will hand over to Annette to give her presentation.

Thank you John for the introduction. Thanks for everyone taking the time to attend on this workshop. My presentation will be about comprehensive surface characterization and water sorption isotherm of cellulose based materials using sorption techniques of course and just a little repeat and summary again what then also explained and perfectly introduce so spectroscopic techniques will normally yield analytical information such as what is present, where does it present and how much. There's not too many techniques which can provide physical chemical information about the solid material. AFM has limitation in regards of morphology of the sample and the condition of the experiment. Therefore, the most applicable techniques for determining surface, thermodynamic and bulk properties of solid materials are sorption techniques which use vapor phase molecules as molecular probes for studying gas solid interactions. An IGC is a very old, quite old technique was developed in the 60s. The first commercial IGC system was released in 2000 and then SMS improved and later released the first purpose built commercial IGESI system. It's called IGE SCA Surface Energy Analyzer because it's specially designed to determine the surface and surface energy heterogeneity. Nevertheless suitable to measure different surface and bulk properties of solid materials such as adsorption, isotherms, heat absorption, glass transition temperature and so on. IGC is a bit different from the classic analytical gas chromatography. The analytical gas chromatography is used for separation. It can be used to determine quality and quantity information about the injected compound and in this case the solid phase is always known. In case of inverse gas chromatography, the solid phase is our sample of interest. So we pack a column with our solid material and place it into the oven and then we inject through this column single pure organic vapors, different type of organic molecules, alkanes and different polar probes. From the retention time of the different organic vapors we can determine different physicochemical properties of the solid material. Our IGC SCA system looks like this presented on the picture presented on the slide. It has a special injection manifold system Based on gas phase injection, like a headspace injection in case of analytical GC. It has two column positions. The standard oven has a 20250 degrees C operating range. It's equipped with the flame ionization detector, which is the most sensitive detector for organic vapors and it's not sensitive for water. So we can provide our instrument with the background humidity controller which allows you to run experiment under humid condition. And you can measure the impact of the relative humidity on the different surface properties, which is quite important. And it's one of the benefits of our instrument because there's humidity everywhere during production of solid materials, during the application of solids, during storage, and how this humidity affects the surface properties, the surface area or surface energy. It's important and very informative to know. Our IGC is also equipped with different safety features. And on this slide you can see a schematic graph of the instrument. The carrier gas comes into the system and split it to different lines. The carrier gas can be helium or nitrogen. And then the mixed line is going to the column and at the end of the column there's the detector. And we collect the data and analyze with our own sea analyzer software. It's quite simple and the experiments are straightforward. The other instrument we used in in the studies, but I will show later is the DBS dynamic vapor sorption system. Then in the first presentation perfectly introduced this technique. So I'm not going into the details. It can measure water and organic vapor sorption curves and also gases. Specifically we used the DBS endeavor in the studies, but I will show you which can analyze five samples simultaneously, parallel. So each sample zone can be accessed individually. And there's five ultrabalances you can see on the picture. This instrument. So we use this instrument for the study is what I will show you later and just quickly summarize the principle of dbs. So it's based on the graviometric method. So the heart of the instrument is ultra balanced. The sample is placed on the sample pan and control the flow of water vapor flowing through the sample chamber and the amount of absorbed water. So the weight changes is constantly measured and recorded at each relative humidity. And from these kinetic curves we can directly and automatically get sorption and desorption curves. The first study, what I'd like to show you today is on bathroom tissues, recycled and non recycled bathroom tissues. So cellulose can be found in nature. And there's an increasing interest for cellulose produced by bacteria. It's free from wax, lignin, pectin, and hemicelluloses which are commonly found in cellulose prepared from plants. But the cost of cellulose prepared from bacteria is relatively high. Therefore, planned cellulose is preferred for mass production due to lower cost. And also recycled paper also preferred for mass production like for balsam tissues. Recycling steps are the production of the recycled pulpit from recovered papers and the manufacturing paper by using this pulp alone or mixed with other pulps which can be virgin or recycled. The second step is similar with the production of paper from virgin pulp. But the first step is completely different because it contains different treatments to produce the pulp from the recovered from the recycled paper. For example, like there's bleaching and dinking process in this step which affects the surface properties of the final recycled paper. The samples what we characterized during this study were toilet papers. Four different toilet papers, different sources. So one was industrial UK toilet tissue and the other was 100% recycled toilet tissue from Sainsbury in UK. And the third one was a classic clean toilet tissue with pure cotton fiber. And the last sample was an Asian industrial toilet paper which was one ply toilet paper. And it's in some side on Internet I found that sometimes they mentioned that one ply toilet paper is more water soluble than the other papers. So that was the whole starting point of this study. Is it really better in this water absorption behavior? At first we measured the BT specific surface area of this toilet papers using octane isotherm at 30 degrees C. And in the table you can see the bet specific surface area of all four toilet papers. And you can see that the recycled toilet paper has a higher specific surface area compared with the others. And this higher surface area indicates higher surface roughness and more irregularities on the surface which could caused by the different production process in case of this paper compared with the non recycled ones. After the BT specific surface area we determine the surface energy. To measure the surface energy we injected the first alkanes series of alkanes and measured the retention time of these alkanes and we could determine the Gibbs free energy. And from the slope of this alkane line we could get the dispersive surface energy injecting. The resulting is a different concentration the surface energy profile. The heterogeneity of the surface energy can be easily determine. And from the profile we determine we could determine the surface energy distribution curve which a little bit more illustrative manner of the surface and edge changes on the surface of the solid. So based on the the results we concluded that this recycled tissue toilet paper has a higher Dispersive and specific surface energy which could be caused by the additional treatments during production of the recycled pulp. Like the bleaching for example, which could definitely affect the specific surface energy of this recycled toilet paper. Also all the other toilet papers had the same specific surface energy, just this recycled toilet paper had a bit higher, quite significantly higher specific surface energy. Also we found difference in dispersive surface energy. So it was also interesting. After the surface energy we determined the specific Gibbs free energy values of the different polar probes. What we injected through also the column in case of IGC measurements. The way to determine this specific Gibbs free energy value is that first we have the alkanes. So from that we have the alkane line which represents the dispersived wonderwals interactions. And then we inject the polar probe. And the polar probe free energy value will be above this alkane line. Because alkane can interact only with dispersive interactions on the surface. But polars can interact with other interactions as well. So to determine the specific part of this free energy value, the polar data point is projected to the alkane line. And the vertical difference between the polar data point and the projected point will give us the specific Gibbs free energy value of the polar probe. And this value can be attributed to higher concentration of polar surface group or different surface groups with higher specific surface energy. In case of the tissue paper, we measured four different polar probes. And in this table you can see the Gibbs free energy values of all the four polar probes. In case of all the samples, you can see that ethanol has a quite high specific Gibbs free energy values on all the samples. And this means that all the samples has a high affinity for hydrogen bond interactions which was also expected based on the structure of the cellulose and what we also could found that the recycled toilet paper has the highest Gibbs free energy values for all the polar probes. It's due to the higher specific surface energy of this sample. And this result also supported the specific surface energy results. So after the IGC measurements we determine the watersorption curves of all the samples. But what information can be extract from this watersorption curves as also then explained. For example, the the hysteresis can tell us a lot of things about the sample. If there's no hysteresis on the surface, there's only surface absorption. But it can happen in case of crystalline samples. For example, probably if there's long narrow hysteresis, that means there's bulk absorptions as well. If desorption curve Going back to the same starting point as adsorption curve. It means it's a reversible process or reversible desorption process. The highest point gives the water uptake level. So all this information what we can get from the watersorption curves. And here's the watersorption curves for all the four samples. All the four samples has relatively similar and high uptake, around 22 or 20%. And all of them shows a long narrow hysteresis gap which could indicate swelling. In case of these samples folk absorption. Our plan to do more experiments with the camera to see the effect of this watersorption. So the conclusions of this study was that all of the samples have have high and similar water uptake. This similarity in shape and height of the isoterm plot can be associated with the identical general structure of the samples which are composed of cellulose. The difference in surface chemistry between the four samples which were highlighted by the IDC data does not affect overall and the equilibrium watersorption performance. Surface chemistry can affect the adhesion of the tissues with for example, the packing material or adhesion of the sheets to one another. To investigate this a little bit more, we need more experiments. Moreover, the data collected using DBS mainly indicates the presence of bulk absorption, which is reinforced by the presence of consistent hysteresis gap across the entire relative humidity range. And what we could also conclude that IGC is more sensitive compared with the dbs. So it can be used to quantify very small differences in surface chemistry. So we saw in this study that recycled products, recycled paper for example, can have a different surface properties compared with the non recycled products. And as sustainability is in the focus and the aim at every industry, it's important and helpful to measure the recycled products and non recycled products surface properties. Because in some cases it can affect the application of the recycled product if there's even more significant difference between them. Surface properties of the product can be also affected if there's a supply chain issue. Sometimes this issue can force producers to use a different source or new raw materials in their production line. And then showed some examples how the different source of raw material affects the properties of solid samples. So in this case, surface characterization can help to adopt to changes in production easily and to investigate the effect of these changes on the on the product. Product development can also generate changes in production and can affect the property of the product. So in this case also to measure the raw material or the reference materials and the new product properties can be also very helpful and very informative. The next Study and the last study, what I'd like to show you today is the BET specific surface area analysis of cellulosic materials. We did this study in collaboration with University Vienna and Imperial College. So during this study we determined the specific surface area using volumetric nitrogen absorption technique, inverse gas chromatography and DBS dynamic vapor absorption technique. In case of volumetric nitrogen absorption, we measured the nitrogen absorption at liquid nitrogen condition. The degassing was an external procedure. In case of igc, the degassing was an in situ degassing and the sample amount was much smaller than in case of volumetric. In case of dvs, also degassing was an in situ and the measurement was at room temperature like in case of igc. So in the table you can see the conditions of the the measurement compared with the different instruments. So in case of volumetric technique, the adsorptive gas was nitrogen for deviance and igc, the adsorptive vapor was octane, carrier cast was nitrogen and the temperature was 25 for IDC and DBS. And in case of volumetric measurements it was a liquid nitrogen condition. So minus 196°. The duration of the experiment was the longest for DVSS due to the kinetic and the equilibrium and works quickest in case of igc. So the result we investigated three different samples. We measured crystalline powder evicel sample. We also measured cellulose, nano paper aerogel, freeze dried bacterial cellulose which was roughly 89% crystalline. So the first sample is the freeze dried bacterial cellulose. I'd like to show you and the first challenge, what we faced at the beginning when we had to pack the sample tube for the volumetric measurements, it was quite challenging. We had to push through the sample to that long tube and I had to place the sample to the bottom of this sample tube. Because of IGC and dbs it was much easier. For dbs we just had to place the sample on the sample pan. In case of igc you don't have to push the sample to the middle or to the bottom. You can just place it to the top section. That's enough. So it was easier the sample preparation, the preconditioning process. So in case of volumetric we use this device and for IGC and DVS it was an in situ conditioning. We used exactly the same conditions, 120 degrees C for 24 hours. And the carrier gas during conditioning was nitrogen. So method setup was for all. The instrument was similar. So there wasn't any difficulties on any systems. Here's some isotherms this isotherm is with IGC octane, all the three isotherms with igc, the subsorption curves, the nitrogen sorption curves with volumetric and finally the kinetic graph with DBS and the curves using DBS and all the three DVS sorption curve. So after the first measurements we repeated three times. Each experiment was repeated three times on the same sample, on the same column or tube. IGC and DVS results were consistent. We got the same values. However, with the volumetric we saw a decreasing trend between experiments, between repeats. So we decided to do another experiment and we prepared another batch because we couldn't interrupt the results. So the second batch of the freeze dry bacterial cellulose was measured only with IGC and volumetric technique. We skipped AVS because that was the longest and actually DBS and RGC provided the same results. So we just decided to use one of this option technique. And in this case there was an increasing trend between runs. So the specific surface area using volumetric nitrogen sorption is still not reproducible. So the next step was to check the reliability of the IGC result. So we varied the flow during the measurements. This is how you can check the IGC results are reliable and there was equilibrium. And we measured almost the same surface area with the different flow rate. So the IGC results were reliable and still consistent. So what we concluded from all this results that the measured BET specific surface area values by IGC are more reliable and accurate. Easy sample preparation instituted guessing, good reproducibility and the experiment was the quickest. But we also were thinking why volumetric doesn't work in case of freeze dried bacterial cellulose is because there's no equilibrium maybe during volumetric measurements and there's no kinetic information. And also maybe there's the condition has an effect on the on the sample. So there's a thermal shock, maybe sample shrinking. Because if we think about the sample tube is packed in a lab environment so room temperature and then it's attached to the instrument and the liquid nitrogen container is moved up and basically it's dipped into the liquid nitrogen. So more than 200 degrees C temperature changes in a very short time. So could cause some changes in the sample. The next sample, what we investigated was nano paper from Imperial College Aeronautic department. So packing was a little bit challenging in case of volumetric measurements. It wasn't challenging for IGC or dbs. What was surprising that the shape of the isotherm what we got in case of volumetric technique we repeated still the Same and then we repeated of course, because an experiment or two experiments are not experiment. So all the tree isoturn shape was undefinable for us. So we couldn't really classify based on the UPAC classifications for isotherms. And it's not surprising because as we discussed with other researchers who's working with nano paper and try to measure the specific surface area, they also measured similar isotherms. So wasn't surprising, but sometimes it was surprising for us that if there's a negative soption curve, how the bet in some cases, which was in case of the first run, how the bet could be a positive curve. So we checked the equations and the calculations. So it's mathematically possible. Of course, scientifically it's a bit weird that there's a negative slope isotherm and then at the end there's a positive curve. Luckily, IGC measurement was much more straightforward and easy to interpret. The octane isotherm was nice and normal, easy to classify and the bet plot was also nice. And the results and the R square of the curve was also good. I skipped the crystalline cellulose results because that would be quite a long presentation. But if you are interested we can send you over those results as well. So, based on all the, all the measurements and all the different cellulosic materials, we made this little table which summarized basically the challenges on specific surface area analysis of cellulosic materials using these three techniques. And what we found that volumetric is quite challenging in the DBS and IGC have low challenge level. And the overall conclusion for us was that the most applicable method for pet specific surface area analyze it depends of the sample. So it's sample specific. We would not define a standard method, but for cellulosic materials we think that IGC and DVS is much more applicable and we recommend to use these two techniques compared with volumetric. And thank you for your attention and I'm happy to answer your questions. If you have or if you have any comments, feel free to do so.

Thank you, Annette. That was a fantastic presentation. We do have a question in from Jerry King who has raised his hand. So Jerry, if you are able to unmute your microphone, I'll unmute you from our side and you can ask Annette your question. Just give him a moment to unmute his microphone.

Sure.

Okay. He's still muted, but. But he has submitted the question in writing, so I can, I can ask on his behalf. So.

Okay.

Jerry asks, can turpine and sesquiterpine solutes be used successfully as probe molecules? For example, with polymer packaging materials, cannabis and hemp substrates.

Just. I have to check that question because I couldn't understand the substrates. If I can see the questions. But in the meantime we do measurements on packaging materials. We have a collaboration with a German company, they are developing packaging materials for food from biopolymers and we help them to measure diffusion coefficients and different soption analysis. Also what we are doing to them. Yeah.

Have you been able to find Jerry's question?

Yeah, terpene. Yeah. Yes, terpene. It depends of the vapor pressure of this. During my PhD I measured fragments adsorption on different cotton surfaces and we used quite heavy substrates to inject and yeah, it's possible. Probably it requires a little modification of the instrument so we have to change the reservoir temperature a little bit higher. But I think it's. It's doable.

Great, thank you. See if we have any more questions. I think we don't have any more questions, but we've also come to the end of our time. We've overrun a bit, so I think we might have to wrap it up there for the day, unfortunately. Thank you so much in that it was a fantastic presentation.

You're welcome. Thank you, John. Thank you, Orlando.

Yes, just to further a massive thank you again to Professor Orlando Rojas for being with us today from the University of British Columbia. Would you like to add anything before we finish up for the day, Orlando?

No, my pleasure. It was wonderful to share with you our thoughts. It's a very interesting area that will be growing just in impact. Super important. And the takeaway is consider surface energies, but also consider the structure. And these two elements coalesce very nicely with this set of instruments. So thank you for listening and if there are any questions, please send me emails and I will be happy to answer by offline. Thank you.

Thank you, Orlando. Yes, and just to further that, if anyone does have any more queries for any of our speakers, you can send them through to scienceurfacemeasurementsystems.com and we will make sure Orlando receives your questions and can get back to you himself. And we will of course get back to any questions that have been submitted today that we were unable to address in today's presentations.

Thank you.

So thank you everyone for joining us today. Before we finish, we would like to invite you all to join our next session, another workshop we're putting on next week, organizing partnership with Imperial College London. So please do visit our website to find out more about that. And once again, a huge thank you to our North American Vice President Dr. Daniel Burnett for taking taking the time to deliver this presentation today. A big thank you to Surface Measurement Systems Annette Condor reporting all the way from Budapest. And another huge thank you to Dr. Orlando Rojas for being with us today from the University of British Columbia. And another big thank you to all of our attendees for being with us today and for taking the time to learn about surface energy. If anyone does have any questions again, please send them through to Science at surfacemeasurementsystems. Com. Otherwise, have a lovely remainder of your day. Thank you everyone.