Women of MIT: Celebrating Science and Engineering Breakthroughs (Session II)

PRESENTER: Good afternoon. Welcome to the second session this afternoon of celebrating science and engineering breakthroughs. We have yet another all-star cast with two speakers from the School of Engineering and two from the School of Science.

Our first speaker this afternoon is Angela Belcher. She is the W.M. Keck Professor of Energy. She's a full professor in two departments in the School of Engineering, Material Science and Engineering and Biological Engineering. Professor Belcher earned her BA in creative studies at the University of California Santa Barbara in 1991, and her PhD in Chemistry from the University of California Santa Barbara. She was a member of the faculty of the University of Texas Austin from 1999 to 2002. And then she came here to MIT.

Her awards are numerous and extraordinary. I've picked just a couple to tell you about. She won a MacArthur Fellowship award in 2004 and has also received the Presidential early career award in science and engineering and the DuPont Young Investigators award. In 2006 she was named Scientific Americans Research Leader of the Year and was named a member of the Scientific American 50 for her outstanding technological leadership in the use of custom evolved viruses to advance nanotechnology. Her work has been published in many prestigious scientific journals, including Science and Nature, and she has been reported in the popular press including Fortune, Forbes, Discover, The New York Times, the Wall Street Journal. It's with great pleasure I introduce Professor Belcher.

BELCHER: Well, thank you for that introduction, thank you for the invitation to be part of this really extraordinary symposium. Being at MIT I always say it's like being at Disneyland for scientists and engineers where everything is so exciting that's going on around us and that's definitely been true since I've been here. Today I'm going to talk about giving life to materials for energy and the environment. And I put that I'm with my dream team because the group of students, graduate students, and postdocs, and undergraduates I've been working with over the last couple years are just extraordinary. And it really has been a dream come true to work with these students and then also with my collaborators here at MIT.

So I'm going to tell you a little bit about giving a genetic information to nonliving structures. I've been interested in abalone shells for a long time. These are biocomposite materials made out about 90% by mass calcium carbonate 2% by mass protein yet they have a lot of really extraordinary properties. One of the things that's exciting to me is not only about their beautiful structural properties, but when a male and female abalone get together they pass on the genetic information that says, this is how to build an extraordinary structure.

Here's the DNA sequence. The codes for an extraordinary structure that allows an organism to grow in ocean temperatures, in ocean pressures using nontoxic materials and not adding toxic materials back into the environment. So that's been fascinating to me for quite awhile. How can you give genetic information to organisms that haven't had the opportunity to have evolution. And that's the focus of our work. So we basically say how do you go from a beautiful structure like this that's had millions of years of ability to go through evolution to something like this, which is a battery that I'll talk a little bit about today.

So again, looking at the abalone shell, when a male and female abalone get together they pass on the genetic information and make baby abalone. These abalone go along and basically replicate these beautiful structures, these organic, inorganic hybrid materials. Say with diatoms made of silica, made out of glass, there's at least 10,000 different species of diatoms. These are glasseous structures here. And they differ from each other based on their structure. So this structure, this star versus this round structure versus the spaceship kind of structure, are all coded at the genetic level. And these are made under very environmentally friendly conditions.

And so we focus on how do you give genetic information to a solar cell or how do you give a genetic information to a battery. And when we think about future technologies we first start at the beginning of time, this is the beginning of Earth actually. It only took about a billion years to have life on Earth. And they were doing pretty incredible things but it wasn't until about 500 million years ago during this Cambrian geologic time period that there was an explosion of new kinds of organisms making materials. And during this time there's increased calcium and iron and silicon in the ocean and now the organisms had the opportunity to start making hard structures. Before that they were soft bodied kinds of creatures. And so what we thought about is how do you start to get control over organisms to get them to work with anything we'd like them to be able to work with on the periodic table.

Here's a picture of one of my favorite biomaterials. This is my oldest sitting next to one of his favorite biomaterials, the triceratops. And anyone who has young children know their incredibly complex organisms. And so this one won't really do whatever I ask him to do and so you think about how do you start to get control over having an organism grow and construct what you want it to be able to do. And so we focus on simple organisms like bacteria and viruses and yeast. Can we work with these organisms to convince them to work on the parts the periodic table we want to build something useful like, in this case, a battery.

And so there's a lot of really, I always say it's a great time to be a scientist and engineer because there's so many important problems. You just pick one to work on. And some of them are energy and health care in the environment. And these are significant global issues but to a material scientists they're just huge opportunities. Huge opportunities to try to make an impact in these very large issues. And the way that we've focused on it is at the interface between nanoscience and that nanotechnology. And Sangeeta did a really fabulous job of explaining some of the interesting properties of what happens to material when you shrink it down in size. And we look at that interface between nanoscience and biology or biomaterials.

And basically by taking a large structure, by taking a structure that has many, many different atoms or many of the same atom and making it smaller and smaller and smaller and controlling the surface, controlling the edges of these kinds of materials, you can control the physical properties. Their optical properties, electronic properties, their mechanical properties. And we've been interested in doing that to try to change or control materials for solar cells, batteries for energy storage, CO2 sequestration and storage. In medicine for medical imaging and therapeutics and environmental applications like water purification. And the key to us is controlling the materials. Controlling the shape, controlling where those atoms are and how they respond to a particular kind of environment that we need them to respond to.

And so, if you go back and you think about biology, and again you've seen wonderful examples of biological machines, of the enzymes and proteins. We look at biology and we look at the length scale here of things like proteins a beta pleated sheets in DNA and antibodies, and they're already very small, they're already on the nanometer length scale. So if we could actually harness the potential of these biological molecules to do we want them to do, build a material for a battery, build a material for a solar cell, we figure we have an advantage because we're already starting with something nature gave us. It's very precise, very controlled and now we have to harness it to get it to do something we want to be able to do.

And so here's some examples of some natural biomaterials. This is a coccolithophore, it's a unicellular algae here, it's a one micron link scale. This it the abalone shell and if you fracture it and you look at it, it's made of these stacks of calcium carbonate, basically chalk. These are diatoms made out of silica SiO2. And magnetotactic bacteria make small single domain magnetite, Fe304 that's used in navigation. So those are some examples that nature's already provided us with.

And what's the key? Why can organisms make these materials with exquisite structures and in precise geometries all under environmentally friendly conditions? Well a big key to it is proteins. It's the proteins that these organisms have and they secrete in their cells into their extra cellular spaces and they use those to control and grow their particular materials components. And these proteins are made out of just 20 different amino acids that differ from each other based on its functional group. So it's how the organism puts together these 20 different amino acids in a row and how that structure folds up in a particular shape that allows it to be able to control this the structure that has this shell that is actually 3,000 times tougher than it's geological counterpart for example. And so that to us is very fascinating.

Here's some examples of abalone shells and between these inorganic calcium carbonate tablets are these proteins and these proteins are absolutely key to controlling some of these physical properties. And so basically this works by, in nature, in the example of the shell, the organism has these proteins. In the case of abalone that make the shells, these proteins can be very negatively charged. They're rich in the amino acid's aspartic acid.

And I brought with me periodic tables. I have them made for the incoming class. They say, "Welcome to MIT. Now you're in your element." And you turn them over and it's the amino acids with their PKA's and I'd like to pick up one. When President Obama visited last year I gave it to him. I said "I wanted to give this to you in case you're ever in a bind and need to calculate molecular weight." And he looked at it and he said he would look at it periodically. So I pass these around to a lot of elementary school kids that really get a kick out of carrying them.

So the key is, is these amino acids that make up these proteins grab on to calcium out of the environment and put down calcium carbonate, calcium carbonate and can grow these really nice structures. And so what we said, what I thought about when I first started my lab is what if you had a protein that could bind to any kind of inorganic material that you wanted it to be able to bind to but had never had to opportunity to do this through nature. And we developed this kind of interface. I think as Susan had pointed out in her talk, that she had a hard time with the idea of using yeast for her particular system. When I first wrote my very first proposal grant proposal as a professor, my first review came back that she's insane. When I said I was going to try to develop this genetic link between semiconductoral materials and biology. And obviously it worked out okay.

And so, basically going back to the periodic table, nature mostly uses calcium in the form of calcium carbonate, iron, Fe203, Fe304, silicon in the form of silica, but it doesn't really use this part of the periodic table or this part of the periodic table in terms of materials. You saw earlier a really beautiful talk about how biology and enzymes use ions of manganese and iron, but what we want to do is we wanted to get it to build structures like battery electrodes.

And so, what we decided to do was to do a combinatorial approach, basically do a billion of experiments at a time to see if we could fish out a protein that could control or work with something that we'd like it to be able to work with. And so we decided to borrow an idea from the drug discovery industry and use something called phage display.

So a phage is a virus that-- to a material scientist it's an object that's 880 nanometers in this direction and 6 nanometers in this direction and a single strand of DNA. The DNA codes for the proteins that make up its structure. And by going in and making modifications in genes, basically cutting and pasting additional DNA sequences in here, it codes for additional peptide sequences.

And so you can put a billion different random DNA sequences in here and put a billion different random protein sequences right here. Or also in the major code of the virus. And in doing that you can make a library. Now you can have a billion viruses that are genetically identical to each other but they're going to differ from each other in a small amino acid sequence.

And now you take those and you force them to interact with any kind of material you want. A battery electrode, a solar cell, whatever you're interested in and you're looking for that same kind of protein, amino acid recognition for that inorganic material. Now, if you take a billion possibilities, you may have 1,000 of those billion possibilities that have some affinity for those materials. Everything else gets washed away. Now you take those that have some affinity and they can't replicate themselves to infect them into a bacterial host. The bacterial host acts as a factory, makes a million copies for you. And now you have some population of viruses that have some affinity for this material. And you go through this process, kind of our Darwinian process, five times looking for the survival of the fittest, looking for the one out of a billion that can do it what you want it to be able to do. Grow a battery electrode, make that electrode better as a function of time.

And so the idea is to try to do specificity through evolution and man made fabrication to get something we call the evolved hybrid materials which is materials that are at the living, nonliving interface. And so the applications I always say have never been accused of being focused. The applications that we look at in my lab are battery electrode, we look at materials for displays, we look at solar cells. We look at carbon sequestration and storage, photo catalytic splitting of water, materials for fuel cells, fibers where you could take some of these materials, batteries or solar cells, and integrate them into textiles, nanoelectronics and medical applications.

And so you look at this and you say, well this is a lot, why don't you just focus on one of these things. But going back and thinking about it, to us, everything is a material. What we do to make materials. We put materials together in new ways. Then we try to get a genetic link to that material and then work on an application which could be important to society. And so that's basically what our approach is.

And so here's our toolkit. This virus, with just a couple of genes, and these genes code for the proteins that make it up. There's one protein over here called P3, which is the major coat protein that is encoded by gene three. There's another protein called gene eight and this is a great gene because this gene codes for protein eight which makes up the coat of the virus here. And there's almost 3,000 identical copies of that protein that make up the coat of the viruses. And DNA is negatively charged, these proteins as they get synthesized basically self-assemble around the DNA structure to make this DNA virus, to make this virus here.

Over here are two more genes that are also encoded by the DNA. And again, to a material scientist, one of the things that's really nice about this is it's always the same length. The function of the length of this virus is a function of its DNA. It's always 880 nanometers in length. You make millions and billions of copies of this, they all become the same length. And if you're going to think about using this as a building block say, a tinker toy or a Lego or something like that, every time you manufacture it, it's going to be the same length. So that's another very desirable feature of this particular virus material.

And if you look at it, it's made out of these alpha helix structures. And we're going to actually do now are stick proteins on the ends of these natural alpha helix structures to get them to do something we want to do. If this was an analogy to the abalone shell we would put sequences on there that say grow an abalone shell. Well, we can't compete with an abalone shell in our case, abalone do a wonderful job of making shells. But we say, now grow a solar cell, now grow a battery. Now grow a material for a fuel cell. That's what we want these virus structures to be able to do.

And so, basically what we do is we go in and we modify their genes, modify their proteins and now we get them to build little inorganic shells of nanoparticles around the structure. And again, because the virus is all the same length, because of the length of the virus is a function of its DNA, then all our nanowires are also the length of the DNA. And it's something that should be very, very reproducible.

And here's some examples. These are transmission electron micrographs. These are 50 nanometer scale bars here. In this case we're growing gold nanowires so this virus has the DNA sequence to be able to take gold ions out of a solution and be able to make gold nanowires. We can do so with a very high conversion efficiency, very good yield of these materials. And very good control over the length and the width of these materials. And so again, you learn how to control it through learning how to control the DNA sequence and the protein sequence.

Now this is something that we're really excited about right now. But this is just a kind of a cartoon, well it's actually kind of a cartoon that we drew, it's also based on crystal structures. But the idea of being able to go from a DNA sequence to control a protein sequence to a functional device.

Towards the end, if I have time, I'll talk about a new material recently, from going from a DNA to a device, to be able to grow a solar cell that increases the efficiency of the solar cell by about 2 1/2 or 3%. Just based on a very small amount of protein. Engineer the virus to be able to grab onto a good conducting material which is a carbon nanotube, engineer the virus to be able to grow an inorganic material, titanium inorganic material around the virus structure, incorporate it into an already existing solar cell and basically be able to increase your electron collection efficiency and increase the efficiency of your solar cell.

We've been working in energy storage for a couple of years now and one of the particular areas we've been working in are lithium ion batteries. It's something that everyone in this room is probably using and is carrying several lithium ion batteries right now. And MIT's an absolutely wonderful place to work in the battery field. And we've been thinking about how do you make biological batteries? How do you basically take a structure, this would be a structure of a lithium ion battery. There's two electrodes, there's a negative electrode, the anode, a cathode over here. And then there's lithium ions that are going back and forth between these structures. And here you can see the lithium ions are stored in this graphite structure on the side of the battery. And they have to be able to cross over and then be able to interact with the electrode on this side of the battery.

And so because we wanted to see if we could build biological batteries. Because biology is so wonderful at packaging things. Think about how DNA is packaged in your cells. We thought about, let's see if biology can help us package inorganic material in a more effective way to make batteries. So we set about to do this.

And so how do you give genetic information to a battery? We wanted to be able to make anodes and cathodes materials, interface them with new kinds of electrolytes. We thought that we could make materials that would be ultra thin and light weight, that would have a higher energy density, and also be flexible, conformable, textile integratable, and synthesize at room temperature. Because just like the abalone chooses to use a manufacturing approach which is environmentally friendly, everything we do in our group we try to do in an environment friendly way. If you're growing bacteria and you're growing viruses or yeast in an environment that's toxic to them they're not going to be that useful to you anyway. And so we try to convince our organisms to work in a way to build these structures in environmentally friendly as possible.

And this work was done in collaboration with a Paula Hammond who is a fantastic collaborator of mine. She's in chemical engineering. And Professor Yet-Ming Chiang is also a fantastic collaborator. So the three of us worked along with our students to make flexible, conformable, room temperature synthesis biological batteries.

The answer for us is usually a virus. And so we were able to select a virus that could grow a material called cobalt oxide which could be a material that is used as a battery electrode. They key for why biology could do it in this case is we're able to make very small nanoparticles with very controlled size. And that was useful for our applications. And then we're going to take advantage of viruses to be able to self-assemble, which I don't have time to talk about today, to self-assemble into a battery electrode and be able to test that. And this is work that was done by a fantastic student of mine, Ki Tae Nam, who's now faculty in Korea.

And then we're going to take advantage of the idea of how biology can tweak things a little more and a little more to try to make them better and better as a function of time. And this is one of things that I like about using biology to make materials because if you can get biology to make a material but the material is not very good, it doesn't have very good characteristics, you have the ability of genetics and you have the ability of evolution to try to make it better and better. And so if we can get any function out of it at first we're happy because we know we have the possibility of trying to manipulate it to make it better.

And so my really brilliant student, Ki Tae, he had the idea to engineer a virus with two genes. One to grow cobalt oxide, the material that's going to be a good ionic conductor. To be able to interact with a lithium. And one that's a good electrical conductor to get the electrons in or out of the system. So it's a two gene system. One virus has two genes to be a good electrical conductor and a good ionic conductor. And he was right.

In this case, this is a transmission electron micrograph here of a single virus, it has two genes. He gives it gold and it grows little gold nanoparticles. And I hope you can see the little gold dense particles here and all the spaces in between. The spaces in between is where it has proteins not to grow gold but it has proteins to grow cobalt oxide. Now he gives it cobalt oxide, or actually cobalt. And then it makes cobalt oxide.

And now over here you have a hybrid material that's cobalt oxide and gold. And now you can go test this as a battery. And so there's different functions you look at or properties you look at in batteries. This is capacity, this is related to how much lithium that it can store. And these are rechargeable batteries. You're going to be able to charge, discharge, charge, discharge these materials.

And so all I want you to look at is this is our first generation battery. One gene here. And this is our second generation battery, two genes. And you can see the improvement in the capacity between these. And so after this point, we started realizing, wow, if we can get one virus to have two genes or one virus to have three genes, what we want it to do- maybe that's a good way to start increasing device performance of these materials.

But then working with our collaborator Paula Hammond, she works a lot on polymer systems. She works on something called layer by layer assembly where you have basically a beaker of positively charged polymers and a bigger negatively charged polymers. And you can take a slide like-- and this is the way I always say it is. My students say it's nothing like it really works. I don't actually even have the code to get into the machine they use but the slide they dip it between positive, negative, positive, negative, positive, negative. And they can build up these little layers that are going to be layers of electrolyte.

And so then we engineered our virus to like her polymer. So we could build up this little polymer, dip it into our virus, our virus now likes her polymer and it lines up on the surface of this polymer. And now you dip it into a third beaker and you now start nucleating or growing a battery electrode material.

And you pull it out like this. This is a transparent electrode material that's self-assembled by a virus. So it kind of looks like Saran wrap. It's flexible. And you can test that as a battery electrode. And these are what the viruses look like, all lined up on that material.

You can do other really fun things like this because it's all solution based process. You could make a stamp. You make thousands of battery electrodes on a stamp and stamp it onto a surface and transport it on it's surface. So these are a bunch of really small micron-size virus battery electrodes that are stamped onto a surface again because it's all made at room temperature at the bench top.

And so we were excited about this and we published this in science and we went to our review for the funding agency and they said, well that's good but you only have half a battery. Where's the other half of the battery? And so it took us a while to get to this point.

So I went back to my students, because I can't actually make anything myself, and I said, where's the other half of the battery? And so they worked really, really hard and it ends up that the positive electrode material is much more difficult to make than the negative electrode material. And part of the reason is the high voltage material. Part of the reason is that you even have to have a better electrical conducting material connected with your ionic conducting material. So I had a fantastic team of students who worked on trying to basically increase electrical conductivity in some of these ionic conducting materials.

And here's part of my dream team here. This is Yun Jung Lee who just took a faculty in Korea as well. And Hyunjung Yi who's getting ready to graduate in a couple months. And here was their idea. Let's engineer a virus to pick up single walled carbon nanotubes. Such a good electrical conducting materials. These materials are very, very small. These materials are like one nanometer in diameter.

And so they engineered these viruses to have a sequence to pick these up and then the engineered the virus to have another sequence that said now grow the rest of the electrode material on top of it. So they were growing iron phosphate material which is a nice material for being environment friendly. And I show this mostly because I always say the best day of my life was the day my kids were born but this is really close next to it because this is the day that we had a genetic sequence, DNA sequence, that was directly related to the quality of the device basically.

So the one particular DNA sequence gave us a high powered battery that was a really fantastic battery. And that's what my group had been working on. That was the whole principle that we were working on is if you have the right DNA sequence, you have the right protein sequence, you can really have state of the art materials and state of the art devices. And so I had to show that because that was a happy day in our lives.

And so then they engineered them to basically pick up single wall carbon nanotubes and they form this percolating network with the good electrical conducting materials interspersed with the rest of the electoral materials. And this is just for fun, this is actually looking at four nanometers link scale. These are single wall carbon nanotubes here on the tip of a virus. This is the tip of virus here and it goes all the way up here would be the rest of the virus. And it's showing the interface between the iron phosphate and the single walled carbon nanotubes. So two different proteins bring these together to bring together these two materials.

And I have four seconds. And basically we're able to make very high rate capability batteries out of these and high powered batteries out of these. This is fun because this is a one gene system, a better one gene system and a two gene system here. We're actually able to get high power battery that were very, very state of the art.

We were able to show these to President Obama when he came to visit. And these batteries, there's actually quite a few of these at different science museums around the country. These high powered batteries that are better, in this case are just lighting up an LED but are made biologically.

We were able to share this actually in other science museums and we had 600 visitors. Paula Hammond and I had 600 visitors and we had 100 kids make battery electrode materials at the science museum. It was very, very fun. They had very good time doing that.

And then we transitioned this to an undergraduate teaching lab. This is 2109. It's a junior level teaching lab where the students are trying to make better and better batteries which is also very, very fun.

This year, we're going to make solar cells in this clas. So the technology-- although I always say the viruses do all the work. The students say, oh, no. That's not true. We find the viruses that do all the work. Once you get them to be able to manufacture these materials in a high quality way then it's not too difficult to transition that technology.

I was going to talk about photocatalytics [INAUDIBLE] in water but that was not very realistic in terms of how much time I had. So I gave you one example of things that we're working on, and I'm over. I thank you.

PRESENTER: Don't go anywhere.

BELCHER: Okay.

PRESENTER: Thank you, Angie. Questions?

AUDIENCE: I was just taken by your comment, or maybe it was your student's comment, we find the viruses to do the work and maybe you explained this but I'm a mathematician so I might need a little extra explanation. How do you find the viruses to do the work?

BELCHER: That's a good question, I kind of zoomed over that point. Basically we start with a billion possibilities. The way that we used to do it in the old days is we start out with a billion possibilities. We take those billion possibilities and we say, of these, can any of them grow the material that we're interested in growing. And a small population will be able to grow those materials that we're interested in growing.

And so in about a ten microliter sample. Or maybe, I haven't done this myself in a long time. Maybe it's a hundred microliter sample. In a small sample, you can have a billion different viruses. You pipette them out and you force them to interact with the kind of material you want them to be. Is it a semiconductor material? Is it a battery material?

And they're going to be in the solution and they're going to be interacting with that surface. And we're looking for the ones that are the good fits. We're looking for the ones that bind and don't let go. Then we change the conditions under which the semiconductor and the virus are interacting.

So we can basically get rid of anything that didn't stick. And anything that had any affinity for that material at all, we can fish it back out again. We don't know what it's sequence is, at this point we don't care. We say you guys are the winners. You did a good first job.

Now we take it and we say okay, now interact but now we're going to make it harder. We're going to change the pH, we're going to change conditions so now it's even more difficult. Now get rid of all those. And you keep going through that until you find one that's decent. Now we actually, because we've done this for almost 10 years now, we have an idea of what works and what doesn't and now we can do rational design in combination with kind of combinatorial to come up with the best kinds of approaches. Thanks for the question clarification.

AUDIENCE: Hi I've heard you speak a couple of times and you're amazing. I'm wondering the timeline for some of these technologies to become commercially available.

BELCHER: That's a great question. So they have founded two companies and the one company is in transparent conductors for touch screens. And that one doesn't have any biology in it. The ideas were based on biology and that actually has commercial products that can be purchased now.

I have a second company that's in the catalyst in heterogeneous catalysis and that actually is kind of in the earlier stages. Some of the materials I've talked about today are in prototyping with different companies around the world. And none of those are commercially available but they're in about prototyping stage. We're excited about a lot of the technologies. Basically I'll leave it at that.

But we can go from idea to a good working prototype in about a year. Year, year and a half. I'd like to take credit for it but it really is my fantastic students who get in there until it's done. And then it gets harder because you have to think about all kinds of, how to you integrate it in, how do you fit it in with current tooling technologies? How do you scale it? How are you going to put in a rooftop and in every house in America and things like that.

So there are all kinds of things to think about. But we're pretty pleased with the progress right now. I don't want to take away from anymore time.

PRESENTER: Thank you Angie.

So our next speaker is Christina Ortiz. She's a professor of Material Science and Engineering and MIT's Dean for Graduate Education. Professor Ortiz is the leader of MIT's bio nanomechanics laboratory. She received her BS from Rensselaer Polytechnic Institute in 1992 and then both her Master's and PhD from Cornell University. All of her degrees are in the field of material science and engineering.

Professor Ortiz came to MIT and joined the ranks of the faculty in 1999. She focuses her research on the structure and mechanics of biological materials. Her scholarly and leadership achievements at MIT and in her profession have been recognized by her peers and in many awards, including the National Science Foundation Presidential Early Career Award for scientists and engineers and the National Security Science and Engineering Faculty Fellow Award from the Department of Defense. In 2009 Dr. Ortiz received a Dr. Martin Luther King Jr. Leadership Award for recognition of her service reflecting the late civil rights leader's ideals and vision. Her talk today is entitled Biological Structural Materials, Interdisciplinary Convergence of Engineering, Architecture, and Evolutionary Biology. Professor Ortiz.

ORTIZ: Thank you so much I'm happy to be here today. Thank you very much for the invitation it's been a wonderful conference. I'm honored actually to give this talk today. So I'm going to talk about my research today in biological tissues and I'll give you a little bit of my timeline of my research and also where it's going, where it's been and some of our, sort of new areas that we're getting into.

I just wanted to start with, I'll start with the students since they really have done all the work. This is just a listing of some of my current and former students and postdocs that have contributed to the work. And also three of my closest collaborators, Alan Grodzinsky, Mary Boyce, and Subra Suresh who have really inspired me and I've collaborated with them throughout my time at MIT. And so today a lot of the work I'm going to talk about is in conjunction with Professor Mary Boyce who's in our mechanical engineering department and so you'll see a lot of this collaboration between us.

So structural biological materials basically are materials in biology that serve some sort of mechanical function. And this could be load bearing, penetration resistant, lubrication, et cetera. And these materials are highly complex as you also heard from Angie Belcher's talk, that they're generally composite materials with many components and levels of structure that have been sort of designed throughout the evolutionary process for specific mechanical functions. And so, our sort of research has focused on, in the last sort of 15 years, there have been many new methodologies developed where you can probe the structure and properties of materials in general at very, very high resolution. So at unprecedented levels. So down to the single molecule level or the single molecular structure level.

And so with all of these sort of technologies that have become advancing it's been great not only for the field of material science and the discipline of material science, but as I'll show you today, really in the field of also biomaterials and also how this can link to the fields of architecture and evolutionary biology. And hopefully by the end of the talk I'll show you that I think there's great potential for combining a lot of these methodologies from material science with these other fields.

And so generally we work on sort of two classes of materials, musculoskeletal and exoskeleton. Musculoskeletal are those internal to the body and exoskeletons are obviously external to the body. And although they may sound very different, generally they're made out of the same fundamental constituents. Biopolymers, minerals, ceramic minerals, et cetera. And so there's a lot of commonalities between the two of them.

So musculoskeletal includes cartilage, bone, intervertebral discs, et cetera. And then for the exoskeleton work we have sort of three subprograms involved in flexible armor on exoskeletons of animals, transparent armor, and then what we call sort of extreme armor where animals have developed armor that resists very harsh conditions. And this includes things like blasts, underwater volcanoes, high temperatures, high pressures, et cetera.

And on the musculoskeletal side we really are looking at what are the molecular origins of degradation of the tissue with age, disease, and injury. And so our work sort of looking at the structure and properties of these materials really has a medical application in terms of facilitating the development of diagnostics, clinical treatments for disease, and tissue engineering, tissue regeneration. On the exoskeleton side, all of this is really, initially, through funding agencies was, the motivation was really to look at these for inspiration in providing protective systems for defense, military, and other applications. And actually, if you look at it, it is sort of applicable to structural applications in general.

And so I'm just going to briefly touch on the first one. Well first I'll start with this. So basically, our work has really focused-- so as you heard I'm trained as a material scientist and I came to MIT in 1999 after doing a postdoc in Europe. I was on an NSF NATO postdoc fellowship in Holland and at that time many of the new instruments were just starting to be developed and it turned out that this laboratory in Holland actually had a whole array of these new instruments that I could learn and play with. And so I went there for about two years and just learned how to use them, all of them were coming out, it was a really exciting time. And then when I came here I really had an interest in biological materials and because of the complexity and beauty of the structures and the way that they're designed. And so we applied basically-- we developed all these methods.

And the large part of my career here has been really, even though I would consider it interdisciplinary because it involves many different engineering disciplines, material science, you know, mechanical engineering, biological engineering, even electrical engineering because many of these molecules are charged, I would say that it really focused on high resolution structure property relationships which is the classic sort of paradigm for material science and engineering. And as we move forward in the last year or so, or two years, when we look at these systems we realize that the design in them goes way beyond this what we call sort of inherent materiality. And that this inherent materiality works with design principles that exceed and go beyond my discipline.

And this includes things like geometry. As we start to expand into well, how does it work with geometry, and how does it work together to create a functional structure? Now we realize that there are approaches in other fields beyond the engineering field that really can contribute and are essential to understanding and learning.

And conversely, a lot of the interesting things that we've done here can expand these other fields. And this includes, so this is mechanical engineering, material science and engineering. But evolutionary biology I'll talk about their quantitative 2D/3D methods for quantifying shape. And I'll show you also how what we can bring in engineering to the field of evolutionary biology as well as architecture. So we've had two architects in my group. Collaborating with a new architecture professor Neri Oxman on creating new bio inspired designs based on biological structures. And I'll show you a little bit of prototyping that we've done that.

So our work started sort of in the field in collaboration with Alan Grodzinsky who's a professor in three departments, three different departments. And basically we spent a lot of time looking at, so cartilage is this thin tissue at the ends of long bones in your knee joints. And this tiny little strip of tissue can have an enormous impact on the quality of life if it doesn't work properly.

And so my background before I came to MIT was polymer physics, polymer mechanics, polymer synthesis, even, for two years. And so this was a purely polymeric system. It's a charged polymer polyelectrolyte system. It's a fiber composite system. And so we started to think about how to translate some of those ideas from the field of polymer physics to understanding the charged polymer systems. Beautiful polymers, I should say, in the joint which have a direct mechanical function. And so we were able to go through and use a whole array of methodologies to probe down to the single molecule level for the first time. Basically directly visualizing these single molecules in the tissue that are responsible for the function of the tissue and also for the degradation of the tissue when you have an injury or during osteoarthritis and connect these, the molecular structure, basically to sort of the function of the joint in terms of this. So it turns out that the negative charges, the electrostatics, between these molecules give you the stiffness that you need in your joint and the lubrication your joints.

Furthermore, in addition to these high resolution imaging, we were to then go on and actually to measure forces between individual molecules. And how do those forces translate into your stiffness in your joints. Into your modulus, or your stiffness. So we worked both at single molecule level, we've worked at the single cell level, these tiny little areas around cells, what is going on there when you synthesize? When cells are input in scaffolds and synthesize a tissue, what does it really look like?

And then I mean we basically took what was in the fields of classical mechanics of whole tissue. You take out a chunk of whole tissue, you do a mechanical tests on it, and you understand the stiffness at the macro level. So macroscopic means basically you can see the tissue and we basically brought it down to the molecular level. So this is an experiment where we apply a dynamic oscillatory load.

And if you look at the displacement, it's basically one to three nanometers. And so we could basically go down to the molecular level. And this is exactly analogous to decades of experiments that were done at the macroscopic level. And so what we did really was link the molecular level to the macroscopic function and open this sort of area up with the whole suite of new methodologies. And I should say many of these I learned myself when the instruments had just become available in the '90s. And you know the first instruments had come out and learned from scratch just in the lab actually when I was in Holland.

So I'm going to move to exoskeletons. So this is the musculoskeletal. And the rest of my talk's going to be on exoskeleton. So this is our first foray-- well we've worked on other types of animals. We have a lab full of live exotic animals now. Mostly marine aquariums. And this is one of our favorites who unfortunately passed away recently.

This is Polypterus senegalus. It's an armored fish, one of the few fish that still maintains a robust exoskeleton from 500 million years ago. You can see he's quite flexible from Africa, from Senegal. And full exoskeleton suit. You can't see it really but the exoskeleton is underneath the scales. The scales are mineralized. Basically they're 95% ceramic in the outer layers. So it has a full exoskeleton suit.

And yet it's incredibly fast, incredibly flexible. It's amazing, the path that my career has taken at MIT because there's been so many serendipitous twists and turns that I could have never imagined the point I am now to where I actually started when I first arrived here. And this fish actually arrived, basically one of my students had gone to a museum in France and brought back a sample that he had been talking to curators in the museum. And we started looking at it and it was just amazing and has led to all kinds of different research for us.

So as I said before, we first started out looking at the inherent material structure of this. And the things that emerged from studying the structure of this guy were pretty amazing. It had the armor basically was designed to resist penetration. It has a multi-layered structure that has the exact layer thicknesses and sequences in order to resist penetration. Has interfaces that were reinforced. It has its crystallography axis in the right directions.