Using nature to grow batteries - Angela Belcher

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I thought I would talk a little bit about how nature makes materials. I brought along with me an abalone shell. This abalone shell is a biocomposite material that's 98% by mass calcium carbonate and 2% by mass protein. Yet, it's 3,000 times tougher than its geological counterpart. A lot of people might use structures like abalone shells like chalk.

I've been fascinated by how nature makes materials, and there's a lot of secrets to how they do such an exquisite job. Part of it is that these materials are macroscopic in structure, but they're formed at the nanoscale. They use proteins that are coded at the genetic level that allow them to build these really exquisite structures.

So, something I think is very fascinating is: what if you could give life to non-living structures, like batteries and like solar cells? What if they had some of the same capabilities that an abalone shell did, in terms of being able to build really exquisite structures at room temperature and room pressure using non-toxic chemicals and adding no toxic materials back into the environment?

So that's kind of the vision that I've been thinking about. What if you could grow a battery in a Petri dish? Or what if you could give genetic information to a battery so that it could actually become better as a function of time and do so in an environmentally friendly way?

Going back to this abalone shell, one thing that’s fascinating is when a male and female abalone get together, they pass on the genetic information that says, "This is how to build an exquisite material. Here’s how to do it at room temperature and pressure using non-toxic materials." Same with diatoms, which are shown right here, which are glassy structures.

Every time the diatoms replicate, they give the genetic information that says, "Here’s how to build glass in the ocean that’s perfectly nanostructured." You can do it the same over and over again. So, what if you could do the same thing with a solar cell or a battery?

I like to say my favorite biomaterial is my four-year-old. But anyone who's ever had or known small children knows they are incredibly complex organisms. If you wanted to convince them to do something that they don’t want to do, it's very difficult.

When we think about future technologies, we actually think of using bacteria and viruses. Simple organisms. Can you convince them to work with a new toolbox so that they can build a structure that would be important to me?

Also, when we think about future technologies, we start with the beginning of Earth. It took a billion years to have life on Earth, and very rapidly they became multicellular. They could replicate and could use photosynthesis as a way of getting their energy source.

But it wasn't until about 500 million years ago during the Cambrian geological time period that organisms in the ocean started making hard materials. Before that, there were all soft fluffy structures. It was during this time that there was increased calcium, iron, and silicon in the environment, and organisms learned how to make hard materials.

That’s what I would like to be able to do: convince biology to work with the rest of the periodic table. Now, if you look at biology, there are many structures like DNA, antibodies, and proteins, and ribosomes that you've heard about that are already nanostructured.

So, nature already gives us really exquisite structures on the nanoscale. What if we could harness them and convince them to not just be an antibody that does something like HIV, but what if we could convince them to build a solar cell for us?

Here are some examples of some natural shells and natural biological materials: the abalone shell here. If you fracture it, you can look at it; the fact that it's nanostructured. There are diatoms made out of SiO2, and there are magnetotactic bacteria that make small single-domain magnets used for navigation.

What all these have in common is these materials are structured at the nanoscale, and they have a DNA sequence that codes for a protein sequence that gives them the blueprint to build these really wonderful structures.

Going back to the abalone shell, the abalone makes this shell by having these proteins. These proteins are very negatively charged, and it can pull calcium out of the environment, put down a layer of calcium, and then carbonate calcium.

It has the chemical sequences of amino acids which say, "This is how to build the structure. Here's the DNA sequence, here's the protein sequence in order to do it." An interesting idea is: what if you could take any material that you wanted, or any element on the periodic table, and find its corresponding DNA sequence that coded for a corresponding protein sequence to build a structure?

But not build an abalone shell. Build something that, through nature, has never had the opportunity to work with yet. Here’s the periodic table. I absolutely love the periodic table! Every year for the incoming freshman class at MIT, I have a periodic table made that says, "Welcome to MIT, now you're in your element."

You flip it over, and it’s the amino acids with the pH at which they have different charges. I give this out to thousands of people, and I know it says MIT but this is Caltech. I have a couple extra if people want it.

I was really fortunate to have President Obama visit my lab this year during his visit to MIT, and I really wanted to give him a periodic table. I stayed up at night and I talked to my husband: how do I give President Obama a periodic table? What if he says, "Oh, I already have one," or "I've already memorized it?"

So, he came to visit the lab, looked around, and it was a great visit. Afterwards, I said, "Sir, I want to give you the periodic table in case you're ever in a bind and need to calculate molecular weight." I thought "molecular weight" sounded much less nerdy than "molar mass."

He looked at it and said, "Thank you, I'll look at it periodically." Later in a lecture that he gave on clean energy, he pulled it out and said, "Look, people know, like they give out periodic tables."

Basically, what I didn’t tell you is that it was about 500 million years ago that organisms started making materials, but it took them about 50 million years to get good at it. It took them about 50 million years to learn how to perfect how to make that abalone shell. That’s a hard sell to a graduate student: "I have this great project, 50 million years.”

So we had to develop a way of trying to do this more rapidly. We use a virus that’s a non-toxic virus called M113 bacteria phage. Its job is to infect bacteria. It has a simple DNA structure that you can go in and cut and paste additional DNA sequences into it.

By doing that, it allows the virus to express random protein sequences, and this is pretty easy biotechnology. You can basically do this a billion times, so you can go in and have a billion different viruses that are all genetically identical, but they differ from each other based on their tips on one sequence that codes for one protein.

If you take all billion viruses and put them in one drop of liquid, you can force them to interact with anything you want on the periodic table. Through a process of selection and evolution, you can pull one out of a billion that does something you'd like it to do, like grow a battery or grow a solar cell.

Basically, viruses can’t replicate themselves; they need a host. Once you find that one out of a billion, you infect it into a bacteria, and you make millions upon millions of copies of that particular sequence.

The other thing that’s beautiful about biology is that biology gives you really exquisite structures at nice length scales. These viruses are long and skinny, and we can get them to express the ability to grow things like semiconductors or materials for batteries.

This is a high-powered battery that we grew in my lab. We engineered viruses to pick up carbon nanotubes. One part of the virus grabs a carbon nanotube, and the other part of the virus has a sequence that can grow an electrode material for a battery, and then it wires itself to the current collector.

Through a process of selection and evolution, we went from being able to have a virus that made kind of a crummy battery to a virus that made a good battery to a virus that made a record-breaking high-powered battery that’s all made at room temperature, basically at the bench top.

That battery went to the White House for a press conference, and I brought it here. You can see it in this case, that’s lighting this LED. Now, if we could scale this, you could actually use it to drive your Prius, which is kind of my dream: to be able to drive a virus-powered car.

Basically, you can pull one out of a billion, you can make lots of amplifications to it. You can make an amplification in the lab, and then you get it to self-assemble into a structure like a battery.

We’re able to do this also with catalysis. This is the example of a photocatalytic splitting of water. What we've been able to do is engineer a virus to basically take D-absorbing molecules and line them up on the surface of the virus, so it acts as an antenna.

You get a energy transfer across the virus, and then we give it a second gene to grow an inorganic material that can be used to split water into oxygen and hydrogen, which can be used for clean fuels. I brought an example with me of that today. My students promised me it would work.

These are virus-assembled nanowires. When you shine light on them, you can start seeing them bubbling. In this case, you’re seeing oxygen bubbles come out. By controlling the genes, you can control multiple materials to improve your device performance.

The last example is solar cells. You can also do this with solar cells. We’ve been able to engineer viruses to pick up carbon nanotubes and then grow titanium dioxide around them, which we use as a way of getting electrons through the device.

What we found is through genetic engineering, we can actually increase the efficiencies of these solar cells to record numbers for these types of sensitized systems. I brought one of those as well, which you can play around with outside afterwards.

This is a virus-based solar cell. Through evolution and selection, we took it from basically an 8% efficiency solar cell to an 11% efficiency solar cell.

So, I hope that I’ve convinced you that there’s a lot of great and interesting things to be learned about how nature makes materials, and taking it the next step to see if you can force or whether you can take advantage of how nature makes materials to make things that nature hasn't yet dreamed of making.

Thank you.