May 04 2021

Living Materials

Sometimes technology is developed to serve a specific purpose or need. At other times technology is developed simply because it can be, and then people search for an application. Probably most of the time there is a combination – the technology is developed with a vague idea of how it can be used, but then has to find specific applications. This is partly what makes the future of technology difficult to predict. It is easier to predict if a technology is plausible and can be developed, and more difficult to predict if or how it will be used.

That is what I feel about living materials. A recent paper presents advances in, “Bioprinting of Regenerative Photosynthetic Living Materials.” The technology for 3D printing with biological materials is advancing nicely, with the most obvious application being medical, such as the printing of skin for grafting, and hopefully one day the printing of functional organs. This process looks at 3D printing of photosynthetic material into a fabric.

The process uses cellulose as a non-living structure. Cellulose is the material in plants that gives them their strength. It is a durable, flexible, and strong material that has the ability to retain its strength. Now before you get too excited, cotton is mostly cellulose. We are already making our clothing out of cellulose, and have been harvesting plant fibers for this purpose for thousands of years. The ability to 3D print cellulose directly into a fabric material is nice, and may have some specific uses. In this case the cellulose is designed to contain living microalgae. These algae can survive for several days without additional water or nutrients, and they can undergo photosynthesis. This period can be extended by providing water and nutrients. The material can also be “regenerated” in that they can be reused by adding new microalgae, or combined with new material.

OK, so now what?

The reporting suggests three types of applications – artificial leaves, photosynthetic skins, or photosynthetic bio-garments. The first one seems the most plausible. An “artificial leaf” is simply a device that can replicate photosynthesis by turning water and carbon dioxide into oxygen and energy storage (usually in the form of sugars, that can be turned into fuel). There is a great deal of research developing artificial leaves, which could be an efficient way to simultaneously capture and store solar energy. So the application here is to print artificial leaves as a way to mass produce them. Except in this case the leaf part is a living microalgae. The real advantage is that the result is mostly leaf, without having to produce roots or stems that do not produce energy but take up resources. But of course they are replaced by the cellulose structure. In the end, which is more efficient. It would not surprise me if just growing algae was more efficient.

But this could have applications in very specific settings, such as aboard space stations (including lunar and Martian). This could form a living wall, kept alive with nutrient mist, that produces food, oxygen, and fuel.

The next application, photosynthetic skins, is imagined as a temporary skin graft. It would function as a covering, and perhaps the oxygen produced might help healing at the surface. It could be kept alive long enough for healing to take place and then removed. This seems semi-plausible to me. Obviously a lot of testing would need to be done to see if this application would be safe and effective.

Finally the authors imagine this technology might have uses in the fashion industry. This, I think, is the biggest stretch. Are people going to want to wear clothing made from algae? What would be the point? More importantly, what would be the smell? They tout the fact that such clothing would be biodegradable. But again, anything made of cellulose is just as biodegradable. I just don’t see this happening, unless I am missing something. At best this would be a novelty with tiny market penetration.

I think it is good to develop technology just for the sake of doing so. You can never predict the clever ways in which people will use it, and it may be a stepping stone to an actually useful technology. There is something to be said for just filling the space with many different kinds of technology and letting it sort itself out. I’d be very surprised if people are walking around in 10 years wearing 3D printed microalgae clothing. But 3D printing itself is becoming increasingly useful, and printing with biomaterials is also a potentially useful technology. I don’t think this is the “killer app” but it is perhaps one side branch on the way to more useful applications.

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