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Harnessing Biology to Make New Materials for Applications Such as Gas Storage, Energy Storage, and Chemical Remediation

Angela Belcher, Massachusetts Institute of Technology

Angela Belcher, the James Mason Crafts Professor of Biological Engineering and Materials Science at the Massachusetts Institute of Technology (MIT), began by noting that her work has been funded by the Department of Defense, the National Science Foundation, and the National Institutes of Health along with some commercial companies. For additional context, she noted that she felt fortunate to have spent time in the Defense Science Study Group¹ as a young faculty member. She noted that what struck her when she traveled with the Defense Science Study Group was that many of the servicemen and women she interacted with who assisted her with things such paratrooper training were the same age as the freshmen and sophomores in her classes. She said that realization inspired her to focus her work on technologies that were important to the welfare of the warfighter.

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¹ See the Defense Science Study Group website at https://dssg.ida.org/.

Belcher presented a slide that showed a timeline for Earth, beginning in prehistory, because she drew her inspiration from what organisms from that time were able to accomplish. She said that the main focus of her work is trying to understand how nature makes materials; she described her work as borrowing ideas from nature and applying them to problems nature has not had the opportunity to work on yet.

Belcher said that when she thinks of future technologies, she begins by thinking about the beginning of Earth. She said that it only took a billion years for life to develop, but that the really exciting events started happening roughly 500 million years ago. This is when organisms began to make hard materials, such as the materials that would become mammalian bones, as well as the organisms in the ocean, such as shells, diatoms, and so on. She said that prior to that, life was soft and easily damaged, but then a change occurred in the ocean that increased the availability of calcium, iron, and silicon, which led to organisms being able to incorporate those elements into their structures.

This idea drove Belcher to ask herself the question of whether it was possible to use simple biological organisms like bacteria, viruses, and yeast to build things like solar cells and batteries, given that nature had been able to extract elements from the ocean and build very exquisite, silica-based and calcium carbonate–based materials. She said that her laboratory focuses on the intersection of nanotechnology and biomaterials. Further, because it is very application-focused, it works on applications related to energy, health care, and the environment. She noted that her laboratory is working on applications for solar cells and batteries, fuel, enhanced oil recovery, carbon dioxide (CO₂) sequestration and storage, cleaner mining, air/chemical neutralization, water purification, therapeutics, and imaging. She admitted that it seems like a broad spectrum of topics, but all of their activities are focused on making new materials, whether those new materials are made biologically or have some kind of biological enhancement that allows them to perform better under desired conditions.

When Belcher considered the periodic table elements that were available during the evolution process she described earlier, she

realized they were calcium, silicon, and iron materials. However, she said, she wanted to use the transition metals because those could become semiconductors. Throughout this presentation, Belcher often referred to an abalone shell as an example of this creation of material. The shell is a biocomposite material; it is 98 percent by mass calcium carbonate and 2 percent by mass protein, but it is 3,000 times tougher than its geologic counterpart.

In order to leapfrog 50 million years of evolution, she said, her team borrowed an idea from the drug discovery industry, which was to apply combinatorial biology to chemistry and material science to find a DNA sequence that would code for materials to make a better battery or a better solar cell or that could filter out and neutralize a chemical warfare agent. Belcher said that her team used a type of virus, a bacteriophage, that only infects bacterial hosts and has just a few genes; the genes it does have code for the proteins it comprises. She noted that once injected with a random DNA sequence, the bacteriophage codes for a random peptide sequence, a process that can be repeated a billion times and will yield a billion bacteriophage viruses that are all genetically identical to each other except for a few amino acids. The location of those amino acids can appear in different parts of the virus.

Having explained her combinatorial approach in general, Belcher explained how she and her team approached altering the result of 50 million years of evolution to have the virus work with the elements in which they were interested. She began by explaining the structure of viruses and displaying one composed of alpha helices that are crystographically related to each other, highlighting the small peptide sequences she had added to the virus to give it a new functionality. She said that she considers the viruses to be beautiful reaction vessels where different amino acid sequences are coming off of them, and that viruses adorned with these amino acid sequences can be harnessed to do what you want them to do, such as to build

a cathode material, or an anode material, or wire itself to a current collector.

Belcher thinks of viruses as toolkits, and that by making changes in DNA sequences, those changes will make changes in peptide sequences or protein sequences, causing them to perform the desired function. She said that the process is based on construction of random DNA libraries. In her example, she had made minor changes in the minor protein at the tip of the virus, but said it was possible to make changes in the 2,800 protein molecules that make up the entire virus. She explained that she was attempting to provide genetic ability to many different parts of chemical engineering that normally would not have genetic control, such as solar cells, batteries, catalysts, or drop-in fuel replacements. She continued that her laboratory has also been able to get viruses to grow biological structures.

Belcher’s team has defined DNA sequences for roughly 150 kinds of materials, which can be categorized by usage, such as catalysis and energy storage, solar, magnetic, and a “miscellaneous” use category that includes materials such as transparent aluminum.

Belcher said that as part of a Defense Advanced Research Projects Agency (DARPA) program called Living Foundries,² she was tasked with making as many different kinds of materials biologically as possible; she and her students developed 100 materials and then selected them for applications. Many of the applications were then transitioned to DoD laboratories for continued development. Belcher showed a slide of transitioned applications for the new bionanomaterials that included masks, filters, and cloths for neutralizing chemical warfare agents. Other transitioned applications included new materials for storage of gases such as oxygen, carbon dioxide (CO₂), and methane. Focusing on the oxygen storage, she said her team was developing a backpack-like cylinder to replace rigid, metal cylinders, which would have many applications in medicine as well as for the warfighter. Her team has also worked on new biologic-based materials with unusual electronic properties, obscurants, and nanomaterials that are for storage of very reactive materials. She briefly described ongoing work in her laboratory that has not yet been transitioned. These include structural batteries

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² See Defense Advanced Research Projects Agency, “Living Foundries,” by Renee Wegrzyn, https://www.darpa.mil/program/living-foundries.

(making the wing of an unmanned aerial vehicle into a battery), replacements for lithium batteries to sodium batteries, extremely high–capacity CO₂ batteries, urea fuel cells, and transparent aluminum, all made under biological processes.

Belcher’s team has done work on genetically coding devices to create improvements in energy storage. She said that although most of this work has been on lithium ion batteries, they have also worked in lithium oxygen batteries, lithium air batteries, sodium batteries, and metal CO₂ batteries. She added that the batteries have run the spectrum in size and capacity, from very small batteries to batteries that could be used one day for electric vehicle applications, and now the team working on microgrid and grid-based storage.

Belcher described her team’s early work to create cobalt oxide battery anodes and the process it used. The team began with a set of proteins in the virus that was good at nucleating cobalt oxide as a nanomaterial and then gave it a second gene to code for a second material. Because the team wanted a material that would be both a good electrical conductor and a good ionic conductor, it chose to bind gold; in essence, using biology to code for improving device function.

As another application of this technique, the team took a virus and got it to bind single-walled carbon nanotubes (which will be used for electron transport) and then gave it another gene so that it could grow a good iron phosphate material. Eventually, through additional genetic engineering, Belcher’s team went from a one-gene battery to a two-gene battery to their best two-gene battery, which at the time was state of the art for capacity and for other performance factors.

Building on this success, Belcher said her team applied the same technology to lithium air batteries; it wanted to reduce over-potential, increase current density, increase cycle life, and improve cost efficiency. It began by using biology to make new catalyst electrodes for lithium ion batteries, again using multiple genes to grow multiple kinds of materials. She said that by incorporating palladium, the team was able to show a seven-fold improvement in current density with a decreased presence of total noble metals.

Belcher said that her students are interested in finding replacements for cobalt- and lithium-based batteries. Her goal is to

focus on materials that are environmentally friendly, can be made or mined in the United States, and are Earth abundant. She said they started by looking at sodium ion batteries. In the “pros” section, she noted that similar to electrochemistry, the fact that sodium is very cheap and abundant, and switching to sodium would allow for the use of less expensive aluminum current collectors instead of expensive copper ones. In the “cons” section are the following: the redox of sodium is higher than that of lithium, sodium is larger, and the difference in phase behavior leads to poor electrokinetics and cycling stability.

Using biology, Belcher’s team achieved very good energy densities, on the order of 300-watt hours per kilogram, cycle life above 1,000, and a fairly good rate capability that surpassed current lithium ion batteries. She said they realized a 37-percent improvement in capacity (which is the voltage versus capacity in milliamp-hours per gram) when they used biology to grow these materials.

Belcher then described another direction that emerged from her work with the DARPA program; her team started to make biological carbon nanofiber materials. She said that the team was looking at virus-based carbon materials for enhanced oil recovery applications when it discovered that those materials are very good at soaking up small molecules. Based on that find, Belcher and her team began working on a project with Jared Decoste and Greg Peterson at the Army’s Combat Capabilities Development Command (CCDC). She described how her laboratory began to investigate applications for carbon nanofibers, ranging from electrocatalysis to energy storage to applications that take advantage of their ability to absorb.

The team’s approach was to use very old chemistry, cinolic resins, which is usually done on the micron scale, converted to the nano scale by using biology. The result was microporous carbon materials with extremely high porosity, on the order of 2,000 m²/g. Belcher explained that this is the equivalent of 2.5 hockey rinks of surface area in a gram of material. This porosity makes them extremely absorbent, and Belcher said that her team considered them for applications such as soaking up small molecules (e.g., from drug overdoses or spills). She noted that they are 30 times faster

than standard materials. She asked the audience for an example of a molecule that one would want to soak up very quickly. Kosal suggested “sarin,” which turned out to have been the molecule that Belcher had chosen, too. In fact, Belcher’s team found that their carbon-based materials were very good at taking up nerve agents such as Sarin, Soman, and VX, as well as other toxic industrial chemicals. The performance of their materials was 2 to 105 higher removal capacity than current benchmarks.

Because CCDC has a need for multifunctional materials that can be used for suit protection or filtration or decontamination, Belcher modified her team’s biological materials for those types of applications. The team started by looking at different generations of the material in which it was trying to remove Sarin, Soman, and VX, and found that it could take different chemical modifications or different metals or metal oxides and add them to these materials for increased performance. Her team also worked on filtering mustard gasses, hydrogen sulfide, and sulfur dioxide. Belcher said that with modifications it made the materials broad spectrum to remove most of the bad agents or make them very specific.

Although the team’s original work was focused on filtration masks for the warfighter, Belcher said that is has also been able to weave the material into protective clothing. She showed a photograph of an infinity scarf made from a polymer that was woven with filter material; it could be worn as a scarf or pulled up over the face for protection by first responders or people who do not know whether they are facing a situation involving chemical weapon agents. She said that it was also possible to make wipes that can test for the presence of agents or for decontamination.

Belcher explained that these materials not only absorb the chemical weapon agents, but also break them down into nontoxic products. She pointed out that having a protective mask absorb

chemical weapon agents while snug against one’s face results in a concentrated form of the chemical being pressed against your skin. However, masks using her team’s material actually break down the chemistry into nontoxic byproducts.

Belcher added that the material could be used in filters for smog and pollution. Her team also interested in using it to exclude small viruses and have performed tests where the filter stopped the MS2 virus, which is much smaller than a flu virus or a corona virus.

Belcher said it was actually her collaborators who suggested trying to use the material for storing gases. This suggestion led to the idea of a soft backpack that could hold oxygen to use when jumping from an aircraft. Additionally, the team started looked at storing CO₂, scrubbing CO₂, and storing methane.

Belcher’s team is also investigating obscurant applications. Because of its success with storing CO₂, the team wanted to explore its use for other CO₂ products and built a very high energy–density CO₂ battery, which could be thought of as grid storage.

Belcher described her team’s work on cleaning up nuclear spills, such as radioactive strontium in seawater. Its approach was to genetically engineer yeast to change its transports to handle the desired substance and separate out materials of interest. Citing her recently published paper on cleaning up oil sands in Canada,³ she showed that within a few hours, drinkable water was achieved, in terms of Environmental Protection Agency standards, from sands that were high in copper, cadmium, mercury, lead, and zinc. She said her team has achieved similar success for radioactivity.

Belcher wanted to leave the audience with the message that “you can convince biology to do a lot of things that it wasn’t naturally evolved to do, it just needs the opportunity.”

Mallory Stewart, a planning committee member, asked about what international restrictions Belcher has, if any, with respect to collaboration, student participation, and communication, citing not only Belcher’s unique status at MIT and the academic environment, but also her input into the national security dialogue and her national security clients.

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³ G.L. Sun, E.E. Reynolds, and A.M. Belcher, Using yeast to sustainably remediate and extract heavy metals from waste waters, Nature Sustainability 3:303-311, 2020, doi:10.1038/s41893-020-0478-9.

Belcher replied that she cannot put restrictions on funds she receives, or whether international students can work on projects, so all the work performed in her laboratory at MIT has to be unclassified, basic science research. However, she also has access to MIT Lincoln Laboratory, where more sensitive work can be done. She added that many of the materials she makes are sent to U.S. Army laboratories, to her collaborators, for continuing work. She noted that is where all the Clean Water Act (CWA) work is done. Belcher has students who work with the DoD laboratories on CWA-related material, but they are U.S. citizens, except for one who is Canadian. However, she again emphasized that all the work done at her laboratory is really basic science.