# DIY Potato Aerogel: Free Cooling from Your Kitchen?

## Метаданные

- **Канал:** NightHawkInLight
- **YouTube:** https://www.youtube.com/watch?v=J87Qyxzm_fQ
- **Источник:** https://ekstraktznaniy.ru/video/42435

## Транскрипт

### Segment 1 (00:00 - 05:00) []

we might be able to turn potatoes into passive electricityfree air conditioning. Today, we're going to learn how you can make dozens of incredible bioplastic materials with ingredients that you may already have in your kitchen. Some of these plastics are clear as glass, waterproof, biodegradable, and very possibly they might be the future of radiative sky cooling coatings. My name is Ben and on this channel we take cutting edge scientific research and find ways to achieve the same results with items often available at the local grocery store. Bioplastics are particularly well suited for this goal because many of them start with ingredients that are edible. For example, this plastic bag of noodles is made from gelatin. The recipe starts with 2 tablespoons added to one4 cup of water where it will sit for several minutes to become hydrated. In the meantime, 1 tsp of honey is added to 2 cups of water and brought to a simmer. Honey acts as a plasticizer, which means that it will make the resulting plastic softer and more flexible. The hydrated gelatin is stirred in until it is fully dissolved and then the mixture is ready to be poured into a silicone mold. These are available at Amazon or various cooking websites. You might even find them at some grocery stores. It will take a few days for the gelatin sheets to dry at room temperature or just a few hours in a food dehydrator, yielding a pristine plastic sheet. The amazing thing about this particular film is that it is a true thermoplastic, meaning that it remelts under heat so that you can seal it with a hot iron to make things like this instant noodles where the packaging is completely edible and dissolves in hot water. This film can resist cold water for about 2 hours of constant exposure before failure, which is not the best that bioplastics can offer, but it makes for reasonably effective packaging in a case like this. This is not me. As much work as I have done with bioplastics, it doesn't come close to this guy. This is Giestas and his YouTube channel is a gold mine not only for making these plastics but also learning how to turn them into practical items. — I have I don't know you see like many samples. So back then I was doing these uh slippers. This is the plastic bag that you see on the video. — I know that's at least a year old. That's more than a year old now. This is and it's still you can still put stuff inside. It still works. — I'm working on a video about bioplastics. The reason why I like your videos so much is because there are scientists that show some bioplastic videos of them working in a lab and making some polymer. You've done a really good job of documenting like how to make these plastics with kitchen wear. So I'm a high school teacher at a public school in Lisbon in Portugal. We I was discussing with my colleagues, another teacher, colleague of mine who is also a designer. You mentioned that maybe we could try and do some bioplastic experiments with the kids. But then we quickly realized that none of us knew how to do that. — Okay. I tried the first experiment of all was with the protein of milk from which you can make a really tough material that looks like stone. — Yes, that uh qu casein plastic I think — and from then on I just kept experimenting and then I realized my first instinct was to resort to YouTube. There was no single resource. So I thought well I guess I'll have to make it myself. Let's reference an early video from Gestus to learn how to make one of the simplest bioplastics with surprising scientific relevance from starch. This mixture can be measured by volume with ingredients consisting of four parts water and one part of any starch. Corn, potato or cassava will be fine. And then 1/3 part of both vinegar and glycerin. The glycerin is again a plasticizer to soften the plastic like the honey used previously. Either one works and we'll explore other options later. The mixture is heated ideally in a double boiler until the starch begins to gel. The gel is then poured into a silicone mold and to make very strong films. It can then be reinforced with cotton gauze before drying. This mixture becomes very thick and is prone to trapping bubbles which can remain in the finished plastic. To adjust for this is fairly simple. Just add more water to the recipe to thin it

### Segment 2 (05:00 - 10:00) [5:00]

out. About twice as much water to make a 7:1 ratio with the starch. At this ratio, the bubbles become smaller and it's easier to avoid whipping them into the gel. The price for this is a longer drying time to get rid of the excess water. This starch-based film is surprisingly waterresistant. After 72 hours of water exposure, the plastic softens, but it retains its shape and does not easily dissolve at room temperature. This is probably the most common bioplastic that is made as a simple school science experiment since the ingredients are so inexpensive and readily available. But there is an issue to solve in order to make this a practical material. — So this is like starch with orange peel. So it's tough enough uh and you can work with it fine. But it has a disadvantage which is the materials that make it flexible and that can be glycerin or even honey. They are aggroscopic. So they suck the moisture from the air and uh in the summer it's nice. It's a perfect material. And in the winter it gets some condensation on it. Not so useful. — I was thinking about trying oils, uh things that weren't hyroscopic. Have you tried anything like that? — I think it works. I already made some uh starch with coffee and oil. — Okay. and it worked out fine, but the surface was a little bit oily to the touch. If it's for some application where you don't mind, then I think it's will be a good option. Also, — in spite of these problems that still need solving, I focused a lot of my own effort into these starchbased bioplastics. In part because they're just so easy to make directly from plants that I happen to already grow in my garden. All you need is to grind up a starchy vegetable in water, strain out the pieces, and the starch settles to the bottom of the liquid. I could have done a better job cleaning up this potato starch, but it still worked perfectly fine to make a bioplastic sheet. Pretty cool. But my real interest in these starchbased bioplastics can be found in this paper which is called ultra white structural starch film for sustainable cooling. Starch, it turns out, is a very good infrared emitter in exactly the right bandwidth to send its heat straight through the atmosphere. Basically, this type of material can bypass the greenhouse effect, which requires a little bit more explanation to really understand, but the end result is a material that becomes colder than the air around it as long as it faces a clear sky. The paper that I'm referencing turned starch into a type of aerogel. They did this by adding 8 g of potato starch to 100 gram of pure water, heating it into a gel and then freezing the gel in an ice cube mold. Incredibly simple method so far. But then they use a freeze dryer to remove the water from the gel without collapsing its internal structure. And that's the step that I don't like. Freeze dryers have become significantly less expensive than they used to be. In fact, I found several used ones for sale within close driving distance. However, they're still not cheap, and they can only process a few trays of material at a time, which means that anything that requires freeze drying is inherently very difficult to make in large quantities that would be required for many practical uses. The paper goes on to take their freeze-dried starch aerogel and compress it into a flat film, which is the final cooling material with an average cooling of 6. 8° C below air temperature in full sunlight. That is 87 watts of cooling power per square meter of film. And it also has twice the tensil strength of wood. Not a bad result for a film made from pure starch. No plasticizer to absorb water in this method. So, you can see why starch bioplastics have caught my interest. For the past month, I have been freeze drying a sample of starch gel in my home freezer by just leaving it frozen with an open top. This encourages freezer burn, which is exactly the same process as freeze drying. It just happens way slower in a home freezer compared to a machine that's made specifically for the task. You can see in my sample after a month in the freezer, it has dried about 5 mm deep, leaving behind a layer of bright

### Segment 3 (10:00 - 15:00) [10:00]

white starch aerogel. Another few months and I might be ready to press this into a cooling film. All right. So, this method may still be a bit impractical, but you can absolutely try this at home, and there's a good chance that you could compete with the results of cuttingedge research in your own kitchen. A goal for most of my videos is to get other people working on things. This is like a really good thing for people to experiment with at home. And that is exactly the sort of thing that I like to invite people to start experimenting with. You actually could be the one that comes up with a practical way to make radiative cooling films from starch or some of the other bioplastics that we'll dig into next. To remove your personal information from the internet, check out my sponsor, Delete Me. There are thousands of data brokers, companies that make money by collecting your private information and selling it to scammers, telemarketers, and anyone that wants to know more about you. Legally, data brokers have to stop selling your information if you ask them to. But they don't have to make that process easy, even if you can find all of them to begin with. Delete Me scans the internet for you, digging up data brokers that have your information and submitting takedowns on your behalf. Delete Me was able to identify and remove my personal information from hundreds of data broker websites and continues to submit takedowns when new sites are discovered. If you'd like to make it a lot harder on telemarketers, scammers, and identity thieves to get your information and that of those you care about, check out Delete Me. You can get a 20% discount on a US consumer plan by using my link, joined deleteme. com/nighthawk, and by using the code nighthawk on checkout. As we look into material options that might be compatible with radiative cooling technology, there are other bioplastics that may be strong candidates. Now, I don't want to get totally sidetracked on my cooling project because you'll find that these plastics are useful for all sorts of things with each type having very different properties. Gelatin has the benefit of being a heatsealable thermoplastic and starch is very inexpensive and readily available. But both of these need protection from water for long-term effectiveness. Not so for our next examples. — If it comes from animals like gelatin, it has the disadvantage of being um kind of fragile when it comes to water resistance. Agar or algenate which come from algae seaweed. These are more resistant to water and algenate is also resistant to high temperatures. So let's talk about sodium elgenate. This is one of the most interesting natural materials that I have ever experimented with. This is a natural edible compound that is extracted from seaweed and it easily dissolves in water. However, if this dissolved solution of elgenate comes into contact with a solution of calcium, an incredible reaction takes place. These drops of elgenate solution have instantly turned solid and are now completely insoluble in water. Actually, as of this moment, they are not entirely solid because the reaction with calcium occurs so quickly that a solid skin forms on the outside of these drops, protecting the inside from reacting further. Each one of these is basically a tiny water balloon with a fully encapsulated liquid center. As you might imagine, this reaction has been used to make all sorts of very unusual food items since you can turn almost any liquid into a tiny edible water balloon. But the applications don't stop there. natural chemicals that are water soluble but can be made into waterproof rubberlike solids on command. That is a rare attribute. This works through a mechanism called cross-linking. In solution, elgenate is something like these little bits of chain free to move around and slide past each other. Calcium cross-linking is like if I threw some magnets into this mix. Suddenly these bits of chain get stuck together and we have a flexible solid. Adding more calcium is like adding more magnets. And so the firmness and flexibility of the resulting solid can be adjusted by the amount of calcium we use. This process is also reversible. If we add a chemical that is even more strongly attracted to calcium like sodium citrate, it will remove the calcium and restore the algenate to its original form. The strength of the calcium network actually makes it a little bit tricky to

### Segment 4 (15:00 - 20:00) [15:00]

use cross- linked algenate as a bioplastic. As we saw with the drops that fell into this solution of calcium, the skin forms so quickly that the center of the drops is protected and remains liquid. One very simple bioplastic can be made just by dissolving sodium algenate in water and allowing it to dry into a film as is. But then it's not cross-lin and therefore it remains water soluble. We can give it a water-resistant coating by spraying the surface with a calcium solution so that at least the top layer cross links. But just like with the liquid drops, that waterproof layer will only be skin deep. In order to make the algenate react with calcium evenly all the way through its thickness, we have to be a bit more clever. Calcium comes in many forms. I've been using calcium chloride in the reaction so far, which easily dissolves in water where it can quickly react with algenate. Calcium carbonate, which is available as limestone powder or even as the main ingredient in many ant acid tablets, is almost completely insoluble in water and unable to react with algenate until it contacts an acid. I actually gave myself a stomach obstruction by drinking this once, which I was thankfully able to clear by following it with some citrate to reverse the cross-linking of the gel. And I don't recommend that you try any part of that process. In any case, when this mixture of elgenate and calcium carbonate reacts with acid, like this container of vinegar, the calcium dissolves and becomes available for the reaction. So you end up with a partially cross-lin gel. Still, there is a liquid center because the acid reacts with the outside first and forms that protective skin. But we're halfway there. We just need a way to acidify this mixture more slowly and evenly instead of pouring it directly into a jar of vinegar. This can be accomplished with a chemical called GDL, glucono delta lacone. And this is cool. I think the use of GDL with Elgenate has been pretty rare knowledge outside of industry and laboratory uses until now. GDL is a slow acidifier. When mixed with water, it breaks down into a mild acid over the course of 10 or 20 minutes at room temperature, giving you plenty of time to mix it into an algenate and calcium carbonate solution without any reaction occurring in the first few minutes. Then over time, the mixture will acidify, releasing the calcium ions very evenly throughout the entire mixture at once, so it cures solid, like a two-part seaweed derived epoxy rubber. How cool is that? You can purchase elgenate based mold making kits where you mix two parts together to form this sort of slow cure silicon-like gel. And I'm not certain that this is the same chemistry that those kits use, but it sure seems like the same result. This is a water insoluble deep pore curable gel. The softness depends on its water content, and it will become somewhat brittle if dried, unless a plasticizer is added, like we've used in previous recipes. Glycerin or honey is an easy choice with more experimentation needed with oils. Dried and cross- linked algenate remains insoluble in water and is remarkably resistant to fire. While starch is an almost perfect material in terms of its infrared emissive properties for radiative sky cooling, elgenate is not far behind. Its ability to be cured into a solid prior to drying allows us to do some very interesting things. For example, by adding a little bit of dish soap to an elgenate solution with some added calcium carbonate, we can use an immersion blender to generate billions of highly reflective bubbles. Then, a little extra water with dissolved GDL is added into the mixture and then poured into a mold. Over the next few minutes, the Elgenate cures into a solid foam which reflects a high percentage of sunlight and after drying has excellent infrared emissive properties for radiative sky cooling. I have not yet achieved sub ambient temperatures with this particular material. But that's why I'm sharing this. I want to equip you to run with these ideas so that as a community we can make big things happen.

### Segment 5 (20:00 - 25:00) [20:00]

Look at that flexible, bright white reflective foam. Awesome. By the way, if you're unfamiliar with my radiative cooling series, I'm interested in foams because tiny air gaps in a material is an excellent way to scatter light. The more sunlight that is scattered and reflected off of a material's surface, the less will be absorbed as heat, and cooling effects then become much more effective. Foams of course are useful for many other things like thermal insulation and absorbing impacts. My own pet projects are just the tip of the iceberg here. On the subject of foams, Gestus had a lot of information to contribute. — So, this was my first experiment with a gelatin foam. — Okay. — And it's a very squishy. This one has a lot of uh grains of gelatin that didn't solve because I didn't know what I was doing back then. I was thinking if it was possible to make it a foam without resorting to dish soap. So if I add another way of making it bubble. So I tried baking soda which react with an acid and it also makes it a foam like this. Here I'm not whipping air myself. It's just bubbling up. All right. — And when I tried with the AAR, it turns out it's a bit more difficult. But if you're trying to make a kind of a foam which is much more solid. So you can see I have to this one I have to press much more. — Yeah. — Agar. — So the last category of bioplastics that we'll cover is agar. Another seaweed derived product. Agar is commonly used to create gels that are used for growing bacteria and fungi on petri dishes. So, it is very biodegradable. But this attribute depends on a high water content. Once dried, agar can last for a very long time, forming crystalclear films that are surprisingly waterresistant. After several days of water exposure, the strength of an agar film is barely affected until the point that it begins to actually decompose as the water content allows microbes to break it down. I was successful at making agar based foams with the following recipe. 20 gram of agar heated in 100 ml of water until it thickens and then 2 ml of dish detergent to help with foaming. This forms a stiff peaked foam very quickly with an immersion blender. And unlike elgenate, which needs to be cross- linked before drying, agar foams are stable enough to hold their shape without any extra chemistry. I didn't add plasticizers to my foams, but Gestus very kindly shared many of his own recipes for much stronger rubbery foams that are made with the addition of glycerin or honey. Every one of the recipes that we have discussed here have infinite variations, adding more or less plasticizer, more or less water content, mixtures of multiple ingredients to combine their properties. It really is endless. And to that point, Giestas had a really great piece of advice. — I can try so many different materials with so many different properties that I might lose myself in the middle of all this experimentation. But if I have a goal in mind, like for example, I set out to make a vegan slipper. — Yeah. — Then that helps me to focus my attention. Okay, I'm looking for a material which is flexible, but it also has to be tough to walk on the floor. And then having that specific goal helps me a lot in fine-tuning my experiments. — I feel a sense of overwhelming possibility very often in this longunning radiative cooling project. We've made paints, coatings, fabric, and now I'm experimenting with these foams. An alternate path I could follow is using the starch-based bioplastic as a binder for paint or lime wash, which may be a very effective and inexpensive cooling coating. This sample used calcium carbonate microspheres mixed into gelled starch, and it made for an extremely durable paint, although not quite reflective enough to reach sub ambient temperatures in sunlight. So far, all of these options I could literally spend my life investigating, but I hope I don't have to. What I like about exploring these water-based bioplastics in particular is that if you have a kitchen in your home, that is an appropriate workspace to experiment with these ingredients. You can take the recipes that I've presented in this video and start contributing to radiative cooling research. Watch my

### Segment 6 (25:00 - 28:00) [25:00]

previous videos in this series if you need to learn more on the topic and then dive in. Let's make some citizen science happen together. If you were to recommend like someone for someone to start making a bioplastic, is there a particular one you would recommend? And then are there like common mistakes that you would want to uh like make people aware of? The first thing that comes to mind is the same thing that you just said which is keep in mind that even though this uh the results might look awesome. So for example, if I show you something which is finished like this bag with grains in it. I know it looks awesome but it's still an imperfect material. And if you make it with the expectations that will be as good as what I find in a supermarket, it won't be as good because obviously I can't reproduce with my own experience in my kitchen the same results that uh oil company with chemical engineers and millions of investment can make. So the first thing is you should keep in mind that there are inherent limitations to these materials. So that's the first thing. And then if you want to make them, you need to let them dry. And that usually takes quite some time. It might take 5 days, it might take even 10 days if it's the winter and it's humid around. And then if you keep these two things in mind that they are inherently imperfect and they take some time to make, then you can try any of them. So all of these if you find the ingredients, go for it. just uh try it, make it. If you can make uh the chocolate cake, you can also make uh biodegradable material for sure. Last of all, if you are not in a position to start doing experiments yourself, the best way that you can help is by supporting those who are able to spend their time on projects that you care about. Watching a video like this one and leaving comments is an amazing motivator to keep going. I also would not be in a good position to keep going with this stuff if it were not for the consistent amazing contributions of those of you who support me on Patreon. Thank you so much for that. — I wanted to say a special thanks because at this moment in time you're my only Patreon supporter and when — yeah when I saw it it's like oh nighting light no way it's him. Oh man, other people. Hey, anybody watching this, pick it up on his Patreon, man. — Because when I saw you were supporting, I thought it was a really special. It was like um kind of an encouragement that I was going in the right direction. So, special thanks. — Oh, cool. So, check out Gestus' YouTube channel, especially if you would like more details on any of the bioplastics mentioned here and many more variations. His channel will be linked in the video description below. Thank you everyone so much for watching. I'll see you next time.