Angela Belcher: Using nature to grow batteries

60,563 views ・ 2011-04-27

TED


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I thought I'd talk a little bit about how nature makes materials.
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I brought along with me an abalone shell.
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This abalone shell is a biocomposite material
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that's 98 percent by mass calcium carbonate
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and two percent by mass protein.
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Yet, it's 3,000 times tougher than its geological counterpart.
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And a lot of people might use structures like abalone shells,
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like chalk.
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I've been fascinated by how nature makes materials,
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and there's a lot of secrets to how they do such an exquisite job.
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Part of it is that these materials are macroscopic in structure,
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but they're formed at the nano scale.
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They're formed at the nano scale,
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and they use proteins that are coded by the genetic level
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that allow them to build these really exquisite structures.
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So something I think is very fascinating is:
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What if you could give life to non-living structures,
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like batteries and like solar cells?
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What if they had some of the same capabilities
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that an abalone shell did,
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in terms of being able to build really exquisite structures
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at room temperature and room pressure,
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using nontoxic chemicals
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and adding no toxic materials back into the environment?
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So that's kind of the vision that I've been thinking about.
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And so what if you could grow a battery in a Petri dish?
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Or what if you could give genetic information to a battery
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so that it could actually become better as a function of time, and do so
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in an environmentally friendly way?
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And so, going back to this abalone shell,
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besides being nanostructured, one thing that's fascinating is,
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when a male and female abalone get together,
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they pass on the genetic information that says,
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"This is how to build an exquisite material.
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Here's how to do it at room temperature and pressure,
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using nontoxic materials."
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Same with diatoms, which are shown right here,
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which are glasseous structures.
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Every time the diatoms replicate,
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they give the genetic information that says,
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"Here's how to build glass in the ocean that's perfectly nanostructured."
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And you can do it the same, over and over again."
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So what if you could do the same thing with a solar cell or a battery?
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I like to say my favorite biomaterial is my four year old.
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But anyone who's ever had or knows small children knows,
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they're incredibly complex organisms.
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If you wanted to convince them to do something they don't want to do,
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it's very difficult.
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So when we think about future technologies,
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we actually think of using bacteria and viruses --
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simple organisms.
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Can you convince them to work with a new toolbox,
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so they can build a structure that will be important to me?
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Also, when we think about future technologies,
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we start with the beginning of Earth.
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Basically, it took a billion years to have life on Earth.
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And very rapidly, they became multi-cellular,
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they could replicate, they could use photosynthesis
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as a way of getting their energy source.
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But it wasn't until about 500 million years ago --
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during the Cambrian geologic time period --
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that organisms in the ocean started making hard materials.
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Before that, they were all soft, fluffy structures.
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It was during this time that there was increased calcium,
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iron and silicon in the environment,
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and organisms learned how to make hard materials.
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So that's what I would like to be able to do,
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convince biology to work with the rest of the periodic table.
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Now, if you look at biology,
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there's many structures like DNA, antibodies, proteins and ribosomes
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you've heard about,
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that are nanostructured --
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nature already gives us really exquisite structures on the nano scale.
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What if we could harness them
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and convince them to not be an antibody that does something like HIV?
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What if we could convince them to build a solar cell for us?
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Here are some examples.
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Natural shells, natural biological materials.
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The abalone shell here.
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If you fracture it, you can look at the fact that it's nanostructured.
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There's diatoms made out of SiO2,
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and there are magnetotactic bacteria
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that make small, single-domain magnets used for navigation.
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What all these have in common
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is these materials are structured at the nano scale,
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and they have a DNA sequence that codes for a protein sequence
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that gives them the blueprint
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to be able to build these really wonderful structures.
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Now, going back to the abalone shell,
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the abalone makes this shell by having these proteins.
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These proteins are very negatively charged.
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They can pull calcium out of the environment,
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and put down a layer of calcium and then carbonate, calcium and carbonate.
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It has the chemical sequences of amino acids which says,
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"This is how to build the structure.
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Here's the DNA sequence, here's the protein sequence
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in order to do it."
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So an interesting idea is,
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what if you could take any material you wanted,
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or any element on the periodic table,
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and find its corresponding DNA sequence,
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then code it for a corresponding protein sequence to build a structure,
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but not build an abalone shell --
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build something that nature has never had the opportunity to work with yet.
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And so here's the periodic table.
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I absolutely love the periodic table.
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Every year for the incoming freshman class at MIT,
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I have a periodic table made that says,
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"Welcome to MIT. Now you're in your element."
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(Laughter)
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And you flip it over, and it's the amino acids
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with the pH at which they have different charges.
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And so I give this out to thousands of people.
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And I know it says MIT and this is Caltech,
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but I have a couple extra if people want it.
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I was really fortunate to have President Obama visit my lab this year
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on his visit to MIT,
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and I really wanted to give him a periodic table.
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So I stayed up at night and talked to my husband,
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"How do I give President Obama a periodic table?
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What if he says, 'Oh, I already have one,'
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or, 'I've already memorized it?'"
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(Laughter)
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So he came to visit my lab and looked around -- it was a great visit.
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And then afterward, I said,
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"Sir, I want to give you the periodic table,
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in case you're ever in a bind and need to calculate molecular weight."
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(Laughter)
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I thought "molecular weight" sounded much less nerdy than "molar mass."
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(Laughter)
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And he looked at it and said,
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"Thank you. I'll look at it periodically."
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(Laughter)
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(Applause)
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Later in a lecture that he gave on clean energy,
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he pulled it out and said,
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"And people at MIT, they give out periodic tables." So ...
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So basically what I didn't tell you
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is that about 500 million years ago, the organisms started making materials,
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but it took them about 50 million years to get good at it --
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50 million years to learn how to perfect how to make that abalone shell.
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And that's a hard sell to a graduate student:
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"I have this great project ... 50 million years ..."
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So we had to develop a way of trying to do this more rapidly.
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And so we use a nontoxic virus called M13 bacteriophage,
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whose job is to infect bacteria.
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Well, it has a simple DNA structure
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that you can go in and cut and paste additional DNA sequences into it,
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and by doing that, it allows the virus to express random protein sequences.
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This is pretty easy biotechnology,
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and you could basically do this a billion times.
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So you can have a billion different viruses
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that are all genetically identical,
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but they differ from each other based on their tips,
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on one sequence,
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that codes for one protein.
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Now if you take all billion viruses, and put them in one drop of liquid,
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you can force them to interact with anything you want
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on the periodic table.
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And through a process of selection evolution,
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you can pull one of a billion that does something you'd like it to do,
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like grow a battery or a solar cell.
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Basically, viruses can't replicate themselves; they need a host.
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Once you find that one out of a billion,
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you infect it into a bacteria, and make millions and billions of copies
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of that particular sequence.
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The other thing that's beautiful about biology
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is that biology gives you really exquisite structures
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with nice link scales.
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These viruses are long and skinny,
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and we can get them to express the ability
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to grow something like semiconductors
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or materials for batteries.
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Now, this is a high-powered battery that we grew in my lab.
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We engineered a virus to pick up carbon nanotubes.
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One part of the virus grabs a carbon nanotube,
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the other part of the virus has a sequence
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that can grow an electrode material for a battery,
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and then it wires itself to the current collector.
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And so through a process of selection evolution,
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we went from being able to have a virus that made a crummy battery
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to a virus that made a good battery
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to a virus that made a record-breaking, high-powered battery
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that's all made at room temperature, basically at the benchtop.
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That battery went to the White House for a press conference,
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and I brought it here.
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You can see it in this case that's lighting this LED.
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Now if we could scale this,
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you could actually use it to run your Prius,
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which is kind of my dream -- to be able to drive a virus-powered car.
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(Laughter)
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But basically you can pull one out of a billion,
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and make lots of amplifications to it.
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Basically, you make an amplification in the lab,
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and then you get it to self-assemble into a structure like a battery.
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We're able to do this also with catalysis.
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This is the example of a photocatalytic splitting of water.
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And what we've been able to do is engineer a virus
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to basically take dye-absorbing molecules
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and line them up on the surface of the virus
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so it acts as an antenna,
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and you get an energy transfer across the virus.
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And then we give it a second gene to grow an inorganic material
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that can be used to split water into oxygen and hydrogen,
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that can be used for clean fuels.
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I brought an example of that with me today.
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My students promised me it would work.
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These are virus-assembled nanowires.
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When you shine light on them, you can see them bubbling.
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In this case, you're seeing oxygen bubbles come out.
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(Applause)
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Basically, by controlling the genes,
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you can control multiple materials to improve your device performance.
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The last example are solar cells.
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You can also do this with solar cells.
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We've been able to engineer viruses to pick up carbon nanotubes
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and then grow titanium dioxide around them,
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and use it as a way of getting electrons through the device.
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And what we've found is through genetic engineering,
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we can actually increase the efficiencies of these solar cells
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to record numbers
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for these types of dye-sensitized systems.
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And I brought one of those as well,
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that you can play around with outside afterward.
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So this is a virus-based solar cell.
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Through evolution and selection,
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we took it from an eight percent efficiency solar cell
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to an 11 percent efficiency solar cell.
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So I hope that I've convinced you
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that there's a lot of great, interesting things to be learned
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about how nature makes materials,
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and about taking it the next step,
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to see if you can force or take advantage of how nature makes materials,
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to make things that nature hasn't yet dreamed of making.
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Thank you.
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(Applause)
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