From Nature to Engineering – Using Animal Models to Develop Materials

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From Nature to Engineering – Using Animal Models to Develop Materials

please join me in welcoming to the distinctive voices podium dr. David casal asst so my laboratory is called the biomimetics and nanostructured materials lab and it really does reflect what I do I look at organisms that have various structures and functions whether they’re a strong and tough organism or they’re optically diffusing organism and I try and understand what are their properties and struck well first what are their structures from the nano scale up to the macro scale try and understand how those structures relate to their function and then utilize engineering materials to replicate what those organisms are made of to try and enhance the performance and the other half of my lab says well what are these organisms made of and how are they formed so we try and understand the formation of a lot of biological minerals shells teeth bone and utilize strategies that those organisms use to create their architectures to make nano scale materials for energy conversion energy storage so basically solar if you will and batteries and so my research as Jennifer and said I have variety of different kinds of students you know I’m a material scientist don’t tell the chair of my department whose chemical engineer but the group that i have really we have expertise if you will in material science and chemistry but i also rely on collaborations and i think collaborations are really is a very important in order to accelerate your research so all these other tangential areas we utilize some collaborations from all over the world and so as i was mentioning my group has two main thrusts one is can we learn from biologically mineralized organisms and i’m going to talk about this critter a little bit to make impact resistant lightweight materials and actually just came back on sunday from the UK where i did a whirlwind tour of formula 1 racing and some ministry of defense and so who are very interested in this these types of things and as I mentioned the other half of my group says well here’s a biological structure it’s actually the inner lining of a California red abalone it’s otherwise known as mother-of-pearl if you’ve ever seen that this is what its shell structure looks like and we try and understand how that shell grows what’s the mechanism by which it forms and can we use that strategy these are battery materials next-generation lithium-ion battery materials that we want to make fast charging high energy dense batteries that you can take your electric vehicle and drive from here to San Francisco on one charge so that’s kind of the two halves of my group so in my lab we ask different questions and honest I said I’m a bit of a quirky guy but we’ll ask can we learn from mollusks or squid that how what their structures are and how they can make abrasion resistant materials so that we can actually utilize that in engineering application and the other question of course is can we learn from crustaceans this is a crustacean about making impact resistant materials I’m a big sports fan so NFL football there’s obviously a lot of issues with concussions and as I said every time I go to Europe I have to put this in here for impact resistance so we ask why can’t she be more happy so why is she not happy here she’s probably dislocated her shoulder but i’m sure that will heal and she’ll get over that but she just ruined her $3,000 carbon frame bicycle i’m sure she’s not happy about that and so we want to try and address those problems and on a more serious note why can’t we protect our soldiers you know they’re in harm’s way overseas and if you’re a soldier in Afghanistan or Iraq you not only have to wear a kevlar vest you have to wear inserts these are called sapi plates small arms protective inserts and so they will hopefully stop you know high caliber rounds like 30 eight rounds unfortunately it says handle with care what wait this is supposed to you know protect our soldiers what it means if anyone’s in the military you realize that if you’re hit with a round that’s a you know high caliber round it’s a one-off so these will fit they’ll they’ll stop the bullet but after that it’s almost useless if you hit it again with another round it’s not really very protective so what soldiers do is they’ll just drop them in the field I

had a meeting with some Navy SEALs in some abandoned warehouse somewhere in Florida a few months ago and I found out some of the details and in fact these are 31 pounds of extra weight that they’re wearing in the desert and so why would they wear something that’s weighing them down it’s not going to protect them so we try and address those issues why can’t we charge our electric vehicle faster that’s another one out nobody wants to sit at the gas pump or the electric pump for hours at a time and then the last one that I will address is why don’t you want to live near Lance Armstrong so hopefully you’ll start thinking what the heck do I mean by why don’t you I want to live near Lance Armstrong but we’ll get to talking about making clean drinking water okay so how do we solve these problems in my lab we look at nature we try and understand natural systems use them as either examples of high performance or inspiration for making these new materials and there’s a whole different variety of classes of components that could be inspired from from studying these organisms so I’m not going to go through all these but you can imagine just in fact I just had a spider silk meeting right before I came here trying to make high strength materials but there’s all these different types of applications that nature is already provided and the nice thing in our lab is nature has done this for a few hundred million years so we’re essentially stealing from nature’s blueprint makes it life easier so let’s start with this topic can we learn from a mollusk or a giant squid about making abrasion resistant materials I’ll tell you a small story about the squid I won’t talk about them today but we actually went to so doing research is not only in the laboratory you know when you look at natural systems we went to the the Mexico to go deep-sea fishing for these giant Humboldt squid and we were interested in them because you know they’re powerful they can overturn boats and so I brought my postdoc with me and we’re we’re in the ship and we’re pulling one of these guys up on board and he reaches down to pull the hook out of it and it grabbed onto his arm and he pulled away and there was blood and I said cool he didn’t think it was so cool but he I thought it was cool because if you look at an octopus octopus have suckers on their rings there I took on their on their arms to capture their prey these guys have suckers with teeth in them so they literally compress they’re suckers and the teeth will go into your flesh and grab onto their prey so that’s what happened to my postdoc anyway you left me he left my lab soon after that so maybe there’s a cause and effect so anyway I’ll talk about this mollusk here but before that i’m going to bring you into my material science 101 class so there are a lot of material scientist or should I be afraid to tell you okay all right all right I know there’s one good friend of mine here so if I take a piece of chalk and we don’t use chalk boards anymore there are a few on campus it’s now whiteboards but it tells you how old I am because when i was in school up to college we are still using chalk boards so if i take a piece of chalk and rub it across the chalkboard i’ll deposit the chalk on to the chalkboard and that’s because the chalk is softer than the chalkboard so it wears away it abrades now if i’m a bad student or I didn’t like the grade my professor gave me I’ll go into the room with izle and I’ll take the chisel and if I do the same thing the chisel will actually scratch the chalkboard of course that’s because the material and the chisel is harder than the chalkboard okay so abrasion-resistant hard materials are very important in engineering applications this is actually these are people this is the one of the tunnel boring instruments that was used to go between france and england so abrasion resistant materials oil drilling dental material shaping machining all require hard abrasion resistant materials so this has application can we learn something from nature well let’s go from the engineering world to one of these islands this is actually in Palau so I didn’t go here yet I’m trying to get some funding and hopefully NSF will let me they won’t see right through me so that I want to go and go scuba diving but so I’ll ask a question I’ll ask a question for the audience how do you think this island formed so I’m going to ask the two that said I looked younger I appreciate that how did the silent form most people think it’s erosion from wave action that just a you know cuts undercuts the island but there was a marine biologist named Hans loewenstein back in the 1960s who wanted to investigate this so he went up underneath this rock to take a look a closer look and what he found were these

scratch marks on the rock and near the near these scratch marks he saw this critter called a chiton CH IPO in a chiton is a mollusk it eats algae and in order to get to the algae the algae is growing on the rock but it’s also growing within the rock so the chitin has developed a specialized set of teeth if you can click on that on that slide please maybe one second there we go so with the chitin does these are in our tanks at the University it has a specialized set of teeth here that will go out and scrape away the rock and then as it does this it’s getting access to the algae that it subsequently eats so I’m going to call this snail Martha because I have a friend in the audience named Martha so she’s happy about that I’m sure so so martha has a specialized set of teeth called the radula and it’s basically a long ribbon and the ribbon contains lots of hard mineralized teeth that’s these little pieces right here they’re tricuspid teeth and basically Martha will use that that structure to rashed along the rock and cut away the rock so this is actually what its teeth we did some dentistry on Martha sorry and you can see this is the active region of the regular structure this this belt of teeth so the outer 20 lets teeth or so there’s about 75 rows of teeth here the outermost 20 are actively used in rasping but if you go back into Martha’s mouth you see the teeth go from a black to an orange to yellow to a clear I wish this happened to me what this organism is doing is it’s actively forming new teeth every few days so will literally cut off the last couple of last row every few days and push forward a new row of teeth so it’s forming new teeth I have so many amalgams and me I really wish I could have done this so okay so what do these teeth look like this is actually an electron micrograph that shows that there’s this ribbon structure underneath and then there are these little flexible arms that are made of organic with the fully mineralized teeth sitting on top of them so they literally will just rasp along the rock so we did some investigation we as a scientist we want to know what are these things made of and how are they so hard and abrasion resistant so what we did was or my student did was took the teeth and embedded them in some resin and then section them cut them both at the top here and at the bottom so you can see there’s a trike us one two three here so if you look at the top part of the tooth this is a specialized kind of microscope that while it’s a scanning electron microscope that uses what’s called backscatter that anything that’s brighter here means the atomic number there’s higher atomic number elements in here than there are here so there’s some mineral in here but you can see at the tooth cusp it’s uniform but as you go down into the tooth it actually has a core shell structure much like your own teeth right we have enamel and dentin in our teeth as well but this is not made of calcium phosphate like the teeth that we have so we did this we wanted to find out what exactly are these teeth made of so we ground up the teeth and did what’s called powder x-ray diffraction and we get a diffraction pattern to tell us what these minerals potentially are and we found out there magnetite so these teeth are magnetic they’re made of iron oxide which is cool so they’re they’re roughly about a half a millimeter tall so we drop them on the floor it’s easy to find we just take another magnetic stir bar and pick them up which is pretty cool so what’s so interesting about magnetite well it’s happens to be a very hard biological and geological mineral this is what’s called the nanoindentation map each one of these little pixels here represents a diamond probe that we push into the sample so we took those same section teeth here and you can see that the outline right here pushed in to determine the local mechanical property so the purple here is just the surrounding resin the epoxy so it’s for example its hardness here is very low but if you look at the two of the leading edge of the tooth it actually has quite hard quite a high hardness and the trailing edge of the tooth is softer and we think that design is therefore a self sharpening reason so that as its rasping that the leading edge is going to stay intact but the trailing edge will slowly wear away so it actually is always sharpening but the core contains some other material that

I’ll show you in a second that actually allows the tooth to survive against some catastrophic it won’t break completely in half so this is just a little map of that so if we compare this is what’s called an Ashby plot so i can compare different classes of materials compare their hardness with their modulus is another word for stiffness how stiff are they and so does anyone surf in here I I did when I would warm water but I won’t in California too cold so anyway ABS is the primary component of a lot of surfboards so it’s a saw it’s a polymer so these are all polymers here but if you go up this slope here you can see as you get increased stiffness or increased hardness you get metal alloys steals zirconium oxide of ceramic materials one of my friend in the audience is an expert in ceramics I have to tread lightly aluminum nitride silicon nitride and tungsten carbide materials that are used in tools tooling drill bits so why did I show this here is your tooth on this map tooth enamel so what it means is based on my lecture that I gave you about rubbing chalk on the chalkboard the chisel it means that you shouldn’t go in home and chew on your stainless steel pot okay you won’t fare very well don’t do that you probably shouldn’t try these anyway but anyway so that’s the hardness of tooth enamel and an abalone shell I also show so where does the chitin the material properties of the chitin light this is a log-log plot so we’re talking order of magnitude between these and so it’s significantly harder and also stiffer than human teeth and and what biology has done here is it selected the materials the material components that are accessible to it because biology doesn’t have access to tungsten carbide ok so there’s iron dissolved in the ocean that it can actually sequester using specialized proteins called ferret ins that will then pump in this material in for the teeth okay so now there’s engineers I heard in this room so there’s going to be a quiz after this and here’s what the quiz will be based on if I take two materials of high stiffness and low stiffness and I put them in a periodic array next to each other in a composite and I place this material under tension I pull on it and put a crack in it one of two things can happen that crack can either propagate through completely or the crack can deflect if you take a ceramic plate you know if your dinner plate you drop it on the floor what happens it fractures catastrophic alee but composite materials where you have a high and low modulus if and this is what the quiz will be about right here if the difference basically it boils down to if the difference of the stiffness matters or is greater than a factor of four we would expect to get cracks deflecting at interfaces so what biology does is they’ll assemble materials in a hierarchical structure with these interfaces so that a crack propagating will not go right through it will have to be deflected and there’s a lot of energy absorption or toughening that occurs due to this and so if we look at these teeth here’s the core of the tooth here’s the shell of here’s the stiffness if I do my basic math it is greater than a factor of four we would expect cracks to be deflected right and so here we see a crack that’s in the core of the tooth it propagates but it’s deflected by the shell so this just shows this interface this is one way that biology uses its structures to toughen its components so we go to these nano indents that I’ve made remember I push that little diamond probe and I got that little map with all those dots so these are the little dots if you look up close this would be for example the core of the tooth so because it’s a softer material the probe goes in deeper on the outside it’s a harder material the probe does not penetrate as deeply but we interestingly found that their cracks that all are along the side of the tooth these cracks are going along the tooth they don’t propagate into the tooth so I asked the question why I can take credit for probably one picture on this whole presentation that’s this one where I fractured the tooth and I went into the microscope because I couldn’t wait for my grad student so i was up at two in the morning and i said i want to try this so this is actually the tooth fractured and on the shell of the tooth you can see it’s actually made of these little nanostructures nano rods of magnetic material these are the nanorods right here that are all aligned parallel to the long axis of the tooth that give the tooth incredible hardness but also some strength along its long axis this is actually more evidence these are the the nanorods that we actually see these magnetic nanorods there’s actually organic surrounding each nanorod so not only is it a hierarchical structure from the core and the shell of the tooth but

even within the shell it’s hierarchically assembled such that each little nanorod is surrounded by something less stiff so you have a lot of deflection through these nano rods as well and by the way this organic here is responsible for assembling and growing this mineral as well so we take advantage of that when we make nano scale materials so where are we going with this while we’re now making abrasion resistant coatings thin film materials but now not we’re not making them out of magnet we’re making them out of a material that actually is self-cleaning as well so we’re trying to take multiple components something that’s hard that we learned from a design from nature of making these hard nanorods but using instead of a magnetic material using some semiconducting material that’s actually self-cleaning so that’s the direction we’re going with that okay I want to jump into one of my favorite topics and we have about 15 of these guys in our lab and they’re called the mantis shrimp so what’s the motivation behind this study again I just came back from all these aerospace and automotive meetings in the UK where they’re interested in making lightweight materials that are both strong stiff and tough but getting something that stiff and tough is very challenging for engineers and the components that engineers that we use will use metals and integrate them with ceramics or polymers to try and make a composite material some mixture of these materials but you notice that we can’t really get the best trade-off of stiffness and toughness there’s always some loss somewhere and as engineers we try and build things that are so strong when they fail they fail catastrophically and nature does something different which I’ll show in a second so what does nature do so nature provides not just hierarchical construction of minerals and organics to make strong lightweight tough and stiff materials they incorporate multifunctionality their self-healing abilities right you yourselves are able to self heal you have bones right if you fracture your bone they heal you have sensing elements incorporated into your structures so somehow the aircraft industry would love this right is to make lightweight fuselages with sensing elements in corporate self-healing elements incorporated into it nature does this very well so what does nature use I mentioned those chitin teeth are formed using some organic and mineral nature only has access to certain types of proteins and polysaccharides are basically just complex sugars you know so Ellis is one of those chitin kato-san is found in the exoskeletons of crab which hopefully my wife and I will eat tonight and minerals so we have minerals of calcium carbonate basically chalk calcium phosphate that’s what your bone mineral is bio silicon iron oxide would be another one I would add to this so that’s the material selection that nature has available to it it doesn’t have like I said tungsten carbide or something like this or our carbon nanotubes so nature does something different they take stiff components like calcium phosphate found in your bone and protein but they assemble it at this really intricate hierarchical structure that yields materials or composite materials that do have a good trade-off with stiffness and toughness and so the area of research that we focus in this region in our laboratory we look for materials that are both stiff and tough so let’s get to what an example of a stiff tough organism if I ok there we go so this is a mantis shrimp mantis shrimp is not a shrimp mantis shrimp is a crustacean and it has a similar body plan of a shrimp and the front it looks like a praying mantis that’s where it gets its name so let’s see I’m going to use my friend Martha again Martha have may have some PhD students that don’t come into the lab all the time I have some of that problem too so what do I do or Martha does maybe this will be the student and this will be Martha she’s angry she pushes them against the rock and says hey get to work but what the Mantis is really doing here it’s feeding so it’s eating a snail and how it actually gets to the snails meat because the snail goes back inside when it’s attacked it has to crack open this shell and for decades this structure the shell structure i showed you that layered structure earlier i said it’s the abalone that was considered the gold standard of biological inspiration for making next generation tough composites and yet the mantis shrimp eats those guys for breakfast right so we said that’s pretty cool so what does the Mantis do well it uses these structures they’re called dactyl clubs and the dactyl club will underwater accelerate faster than a

22 caliber bullet so it’s one of the fastest striking organisms on the planet underwater and so if we look at this it’s able to generate forces the mantas are only about four inches long and by the way we don’t put them in glass tanks in my lab for a reason we keep them in plastic tanks and guess what just a few days ago I like to play in the lab and new students that come in have to get their pan put into the tank now then just we don’t do that but but now they’re cracking the acrylic tanks as well they’re incredibly powerful and they’re aggressive in their territorial so you would never put two of them in the same tank together I’ve made that mistake when I started studying these in 2007 I put them in went to the restroom and came back one was floating so so they’re territorial but they get impact with incredible amounts of force and because they’re accelerating crew water with incredible rate they’re literally shearing the water and creating capitation bubbles they’re boiling the water around them and you go excuse me you can actually see this let me see if I can show you that video can you click on that please there you go so there it is impacting the snail and that flash right there or right there that’s a cavitation event so they’re poor pray not only have to put up with a punch they also have implosion zuv these bubbles hitting on the imploding on them and they can do this tens of thousands of times the Mantis can do this tens of thousands of times without breaking its own fist so you know obviously I ask my students to try and hit a wall they’re not going to do that because they’re going to break their hand right away so how does it what is this material made of and how is it architected that makes it so tough and impact resistant so I’ll talk a bit more about the science behind it so we did a CT scan this is the body plan of the Mantis this is its carapace its exoskeleton but here’s its club and by the way the Mantis evolved 500 million years ago they originally were spear fisherman or women and they would spear fish soft-bodied prey so they would use this there’s actually a vestige right here this little pointy Mike so there were spearing types of mantas but over the next hundred million years those soft bodied organisms developed exoskeletons crab clam things like this so the Mantis try to eat those two and it couldn’t with its sphere so it’s tried to use its its elbow it’s really its elbow not its fist and the well-endowed elbowed mantis split off into the smashing kind so there still exists a spearing kind and a smashing kind so this is the smashing kind where study so we’ve taken this club if this is what’s its dactyl Club and we’ve cut it in half and basically looked at its microstructure the outside of the club this is again this backscattered electron microscope micrograph that we’re anything that’s a heavier element will show up brighter so this is a brighter region this is where it’s impacting its prey behind this there is this periodic region and then there’s this other region on the side and I’ll explain what those are so again this is just an optical micrograph showing that the there are crystals inside this impact region and those crystals are oriented in some specific direction and that plays a very important role there’s this periodic region and here this this side region called the striated region so we did some analysis on this impact region and what this is we went to Brookhaven National Lab in up in New York and did what’s called synchrotron x-ray this x-ray is about a hundred million times more intense than a chest x-ray so you probably wouldn’t want to stand in front of this beam and what we did with this beam was we interrogated what the material components were and how they were oriented and we found that the outer region that you saw on the other micrograph that was white this is a highly crystalline and oriented calcium phosphate and specifically the same mineral that’s found in your bone so there’s a bone like mineral that’s highly oriented made at room temperature and stronger than an engineering ceramic that’s famous for being you know quite strong silicon carbide so it’s quite impressive the inside of the club also consists of calcium phosphate and calcium carbonate other minerals but it’s amorphous there’s no periodic arrangement of atoms with in the structure okay the side region this is what I called the striated region it’s located here in green what that is these are fibers so that I show here they’re mineralized fibers that are literally just like these beads that I’m wearing on my wrist they’re literally wrapping around the entire club circumferentially and they keep the club under compression so you see Manny Pacquiao wraps tape around his fist there before a fight and that’s because when he punches there’s a tendency for the fist to expand laterally while ceramic materials don’t do well when they’re pulled in tension so by keeping

things under compression there’s a less there’s a less like likelihood of cracks propagating and failing so this band of fibers that wraps around the club keeps everything compressed and then I mentioned about the earlier mantis the 500 million year old mantis was a spear fisherman this is the spear fisherman right here it also has these fibers wrapped around it but it has it wrapped around its its spike and we think those those fibers wrap there on the spike keep the spike from torquing during a penetration event much like these guy wires keep this tower standing up straight ok so this is the what we find is one of the most exciting regions of the club is this interior which we call the periodic region so when we first made that or when we first analyzed this club we polished it flat when you notice all these cracks and these cracks have this this see pattern to them what’s going on where are cracks forming and where do they go so we fractured open the club and when we did in this region here when we did that we see the structure so this structure is called a bull again structure or a helicoid so all the helicoid the schematic shows it very well is you’ve got uni-directional fibers that are oriented let’s say in zero degrees the next layer that’s stacked on top of it is stacked at some small angle let’s say two or three degrees then there’s another at six degrees and nine degrees etc until each there’s a complete 180 180 degree rotation of these fibers and then it will repeat itself over and over again so why is this structure so important what does it do for toughening the club so what we found was the club after about ten thousand impacts I didn’t have a grad student counting the impacts of course but we get estimated it based on the fact that a mantis every three to six months will basically mult it will shed its Club and form a new one so based on our feeding habits we asked them in and knowing that between molt’s it can impact from ten to fifty thousand times this was somewhere ten to 20,000 impacts so notice so what this is this is a section of the club we cut it in half and this is this backscatter image where you see the brighter mineral this is the periodic region this periodic region has a lot of these are nano cracks so how we got this is we basically put this club under a microscope an electron microscope and we let the beam just sit there and charge and so anytime you have some high surface area material it tends to charge up the electrical the electricity essentially can’t escape out of the club so it charges up so all these little wire looking structures are cracks so I mentioned earlier that engineers build things so strong that when they fail they fail catastrophically biology has a different strategy it says well let’s build it strong enough there will be cracking here but none of these cracks leave the club so it stays intact and remember this is after tens of thousands of times of impacts so the structure that bollagan structure what we found was then a little bit of engineering here is that it’s not just those deflections remember we were talking about the teeth where there’s a if you have a modulus stiffness difference of greater than four you have this deflection of cracks you also have this twisting of cracks and that provides a significant amount of toughening for these composites so what do we do well we wanted to figure out what that angle of pitch was we went back to the x-ray and determine what that angle was it was really small less than two degrees per layer of rotation and well that takes a lot of effort so we said well why don’t we try and mimic this structure so we went back to the Mantis we knew what its design was we knew that this is made of calcium phosphate and some sugar based fibers some five material well that’s great but if we want to make one of these types of materials we’d probably want to use an engineered material so we we swapped out some of these materials for carbon fiber and resin epoxy resin which is found in your typical aircraft and we used a strategy that aircraft industry or processing method that aircraft industry uses to make its composites and we said let’s make all these different rotational angle composites and compare it to an aircraft standard which is this one kwasi isotropic and let’s see how they show against each other so this is actually just a section through one of these composites and I actually brought I brought some with me here so I’ll leave them in the bag because there are some fibers in here and you might not want to hold on to them but there’s three different types of panels in here I’ve got one made of glass fiber the middle one the yellow one is Kevlar and the back one is is carbon fiber so if somebody wouldn’t mind taking that so this is if it says Kwazii I so it means it’s the aircraft standard yep and then yes please and then this one the other

one that says helicoid is what we mimicked from the mantis shrimp so this is the composite that we made for the Mantis so the composites on passing around are the same thickness the same weight but the different architecture here and then we said well how do they perform so we used an aircraft standard test method that Boeing uses to test its composites so we took one of those panels and put it in this device here this impact our it basically drops down slams down on to this panel and we can determine how much impact it can take I also use it as a scare tactic for my students to say if you don’t can you put hit this video so we put their hand in here the students hand it clamps down and then this thing will oh you need to play the audio there you go maybe you play that with sound it’s more intimidating for the students right if you can carry there you go yeah so it’s an incredible amount of force so again the aircraft industry uses this to determine how much damage occurs in their their composites so this is actually the the composite from the Boeing 787 if you flown one of their beautiful but the puncture this is the back side of the panel that impactor went through this panel and there’s lots of damage to it but most importantly that the puncture goes through if we compared to the Mantis the puncture doesn’t go through there is damage but it hasn’t catastrophic alee failed just some splits and delaminations we call them so if we compare this what the aircraft industry will do is look at how deep the dent from that impactor goes in so the quazy isotropic which is our aircraft industry went in 1.2 5 millimeters the Mantis mimic went in forty-nine percent of that same weight same material same process pretty cool the aircraft industry also does does an additional test they say well how strong let’s say the wing took some impact well how strong is it after impact so we have to mount these composites in some specialized machine and we measure how much residual strength here is the residual strength of your aircraft standard and then the mantis mimics are almost twenty percent stronger after impact yes oh ok so Riverside Riverside is out in the desert almost if you drive 30 more minutes east no one cares what you do I think so I know so because no one found out about this until I told people so I have a student he has he’s in the military he owns a whole cachet of weapons so I’m very nice to that student i don’t want himshowing up at my office one day so we actually built these composite materials out of carbon fiber and took the same round that’s in the semi-automatic ar-15 you know on a serious note this is the same weapon that the folks in San Bernardino had used and the bullet rips right through this panel but when we change the material instead of using stiff carbon fiber we changed more elastic fibers and now we’re trying to mimic spider self to to do this the bullets and you can see multiple rounds go in these panels but they don’t come out the other side an equally important if you if you know any police officers they want something that’s not going to not only going to save their life and stop a bullet they want that bullet to not penetrate so far through that it breaks the rib cage which often happens so this penetration this this depth behind it is only less than a millimeter which is quite impressive so we’ve grabbed a lot of attention from a lot of people okay and because we’re in the desert oh and by the way I have my students hold the panels do you trust your engineering yes or no right and so then we also built an IED and improvised explosive device can you click on this please and put it on top this is not the proper way to test IEDs we’re working with army research labs to do this if you can click on this thank you and turn up the volume it’s always fun so this is one of our panels it’s five millimeters thick and click area see okay so this is the panel afterwards that’s where the IED sat most of the blast was not directed at the panel which is why I say we’re working with army research labs where we can add proper IED testing but the bottom line is it’s a lightweight material there is damage here and we think it can hold and no shrapnel we think it can hold damage so now we’re making thinner composites these are 1.5 millimeter so you can see my hand behind here and doing different types of ballistics testing ok now we’re also making you know looking at the mammoth the Manta structure you have its inner core this energy absorbing region which we put in helmets which I made one here I’ll just show it so this is one of the helmets we made so not only do we make flat panels we can make curved composites and now we put ceramic coatings on the outside to

make them hard abrasion resistant and also if you think about military applications you can flatten a flattened around with this we’re also looking at flexible materials not just the fibers but the material that goes between the fibers called the matrix so there’s Nick and Steven in my lab testing these the old-fashioned way and they’re quite strong both of the guys but the current technology is we use these fibers that are given to us from different companies that make carbon fiber or another you know glass fiber and those fibers are about one-twentieth the thickness of your hair about 5 micrometers so we said well that’s great that’s going to give us a certain thickness composite what if we can make the fibers thinner could we make thinner composites so I’m using a process called the electrospinning where you basically take a polymer put it in this little syringe I just did this yesterday I wanted to get in the lab and do something instead of being at my computer so you put this polymer in here you apply a potential from this needle to this circulating device and basically it spits out these fibers and so now we’re making the same polit we’re using the same polymer that’s used to make carbon fiber this is the polymer that we’ve spun after we heat it up to form carbon we can make fibers that are about a hundred nanometers thick so that’s about one one thousandth the thickness of your hair so imagine putting those layers in a composite if something is 50 times thinner than what that has for the same number of rotations so they’re they’re obvious you know advantages for this so that’s where we’re going with that and so we’re making next-gen materials this is hay-soos Rivera one of my star new PhD students he took it on his own self to go and buy an NFL helmet and then take the shell off and put a carbon carbon fiber material around its twenty percent lighter now we’re doing impact testing to see how how strong it is I have a really good set of cim guys that work with me and gals we’ve done we’ve actually spun off a startup company Chris just got his PhD he’s leading this effort so okay I only have ten minutes maybe so what do we also learn about biology for nanomaterials so we actually like I said we understand how nature is architected but how does nature build things and can we use that to make nano materials biology uses your bone is made at room temperature or 37 degrees so and it uses solution based processing not your you’re not made in a CVD reactor and it uses organics you have collagen fibers in your bone that guide the growth of the calcium phosphate that’s sitting inside your bone if you didn’t have that calcium phosphate you wouldn’t be standing so provides support and obviously over millions of years you know there’s optimization of structure to have some type of function versus traditional engineering materials often use high temperature environmentally unfriendly methods now that doesn’t mean we can always use bio-based methods because some materials really require high temperature methods that’s just the nature of it so these are just examples of beautiful structures found in biology where we get inspiration I already talked about the abalone this is a brittle star brittle stars this organism that has arms and in its arms it has the single crystal arrays of mineral with neurons underneath it and when there’s a predator that comes by over above it it can detect my new differences in intensity of light it knows something’s there and it can scuttle away these are sponges made of glass found off the coast of Santa Barbara their 99% porous and yet they’re mechanically very robust and these are radiolarians they just look cool they look like medieval helmet so I like that okay all right so if I look at a biologically formed calcium carbonate this is what it would look like in the shell if i look at geological calcium carbonate this is what it looks like so biology really gives you this control of size and shape and orientation of crystals so how it does this if we look inside the shell we see that it contains between those plates layers of organic and it’s organic that first self-assembles and then a gel of mineral gets in filled into these spaces and crystallizes and as it crystallizes you basically the crystallization is blocked by this by this organic layer and so it controls again the size and the shape so we say let’s use a strategy like that let’s control the growth of crystals using organics and the like so we’re not trying to make the next generation of solar cells by putting a bologna Zhaan our house and hoping they work we’re trying to understand how the abalone grows and use that strategy to making nanomaterials for solar applications we use convergent technologies for either you know solar or making purified water batteries or structural materials which I talked about already so I’m going to go through a little bit because I think I’m I’ve talked to so I get too involved and excited about my research but you know we try and address this this is really not true anymore is it but it

will be true again at some point gas prices will go up but regardless we’re burning fossil fuels and we’re polluting our atmosphere we’re also polluting our waters and so you know could we make solar devices that you know would be able to avoid using this these fossil fuels and I like this well you know more energy hits the surface of the earth in one hour than all the energy used by the world in one year so you know it’s pretty obvious but you know I won’t talk about lobbyists in Congress okay all right so you know there was one thing that was mentioned our calculation that was done that said for example if you could build a 50 mile long by 50 mile wide solar panel with the current technology in the u.s. pick ax square state where nobody lives you could power the United States that’s neat so why isn’t this happening well but what happens when the Sun Goes Down we have to store that energy somewhere so in our lab we’re also interested in making lithium-ion batteries that can store this energy okay and so or we’re interested in making cars that can charge fast or drive long distances we use the same material that’s found in the Chevy Volt in its cathode there’s cathode and an anode in a battery and this material is readily available making it inexpensive and it’s also environmentally friendly which is great unlike what’s in your cell phone it’s usually a lithium cobalt oxide which is a toxic material so you wouldn’t want this so this is what the crystal structure looks like it contains the iron and oxygen that are in this certain environment called an octahedra with these phosphate tetrahedra and because there are strong bonds between the iron and oxygen and phosphorus and oxygen and makes it really thermally stable versus what’s in your cell phone material and it also makes it chemically stable which gives it a long life cycle but because of those strong bonds it has poor electronic conductivity and in order to operate a lithium ion better you have to get an electron out to power whatever you’re trying to power so it has to be electrically conductive so what people do is they often will grind up sugars and and an anneal or heat your battery material to make some conductive coating and also this has a very low diffusion rate what it means is lithium ions take a long time to go in and a long time to go out of your batteries so could you make the size of the battery smaller so the pathway that that lithium ion goes in is shorter so in our lab we use this bio inspiration we say here’s the shell the shell is controlled has controlled growth by using organic so here’s a little organic molecule and it uses this to or could we use something like this to guide the growth of these battery materials and so we do this by taking these organics and during the growth of our crystals for the batteries we hope that these organics will bind to these structures and control their growth to give us something that might look like this and so this is what I wanted to show I’m going to skip the next few slides but essentially we’re making the same this these are all the same materials that are in the lithium ion battery if you looked inside the Chevy Volt the cathode particles about 5 micrometers spherical structure again about one-twentieth the thickness of a human hair that’s boulders in our world so we want to make materials for example this is a nano belt that’s 20 nanometers thick that’s significantly thinner than 5 microns where the lithium ions will go in and out and can get into that structure faster so we do this using bio-inspired processing so because of time limitations I think I’m going to skip these next slides because it actually shows how these particles form so I assume that’s okay with our our directors upstairs I want to get to the last topic and that’s this so why don’t you want to live near Lance Armstrong why not what did Lance do he’s famous he won a bunch of Tour de France’s and then we found out why he cheated right you steroids so bless you why don’t you want to live near Lance because if you’re taking hormone based drugs endocrine disrupting compounds you will including birth control and other types of even ibuprofen your body will process about fifty percent of that chemical you pee out the rest where does that go don’t say the ocean goes to waste water treatment plant waste water treatment plant is not capable of handling a lot of these hormone based drugs so if you live near Lance you might have this happening at your dinner table so could we use some technology to get around this by the way this is this is some study that was done in the waters of comparing wastewater or hormones in wastewater so these are birth control drugs there are high concentrations in the wastewater so people are flushing these down the toilet they end up in surface water so we water our lawns with this the water percolates and ends up in aquifers good time for me to take a

drink hope this is purified otherwise I might growing growing something that I shouldn’t be and they’re finding these hormones in drinking water which is a big problem and if you look at the different technologies that are used in wastewater treatment powder activated carbon chlorination they’re really not effective for a lot of these hormone based drugs but there is a technology that is and it’s called photocatalysis what this is is you take sunlight or light you shine it on a material in this case it’s a semiconducting material called titanium dioxide it’s found in sunscreens and when you do this in the presence of water you generate radicals and these radicals can destroy any carbon structure and break it down essentially into co2 and water great so can we do this well the key here is making the materials in the right way to make them highly active so what we do is we engineer material by controlling its molecular structure where we can basically guide which type of titanium dioxide forms which gives it its maximum activity and so we’ve tested these materials and what we’ve done is so this is a plot where I’ve taken a certain organic contaminant and I put it in our water with our reaction are catalysts are titanium dioxide catalyst and we put light on it and we measured how fast it can degrade our organic contaminate so a hundred percent is the organic is gone so we compared an industrial photocatalyst this this company makes this catalyst so it takes about 30 minutes for this industrial catalyst to degrade that organic the materials that we’re making using this bio-inspired process are degrading it in about 18 minutes so that’s great can we do something more with this and why isn’t this technology and current wastewater treatment systems cost what is so expensive about this process I have to take these nanoparticles put the Miss in this reactor send them down these two banks shine light on it that lights going to cause that reaction to occur to degrade the organic but then what do I want to drink nanoparticles I hope not so in this case you have to recollection them back in here that takes time and money so it’s not really used in current wastewater treatment systems so we came up with a strategy to get around this we added a polymer to this reagent that I showed that diagram of its chemical structure put it in these reactors these reactors are called bombs by the way and I never put that an email i call them autoclaves anyway so we mix these two together and we get we get tater tots so these tater tots what they are is polymer here’s a little schematic of it that is embedded with these little nanoparticles of titanium dioxide and then we take these tater tots and we can slice them up into little thin disks so let me count how many are here so I make sure I get them back okay six can I ask you to sew these so what we’re doing now so what we’re doing now is we’re taking those materials sorry oh okay please so we’re taking these materials that have your tater tot we slice them up into thin little discs which I’m passing around now we heat it up and when we do this we burn out the polymer those little particles of this catalyst fuse together but when they do they leave behind pores holes so now what we’re doing is taking these membranes and putting it into a one-step process where you can flow waste water through shine light on it and hopefully outcomes clean water so that’s what we’re moving towards we’re trying to get desalination that’s a big challenge because right now the pores are about 5 nanometers that’s really small but two separate salts we need really small you know a tenth less than a tenth of that so I talked too long because I always talk too much I don’t like to read slides I just like to say we learn from nature both on the structural aspect as well as we learn how nature makes its materials to produce next generation materials I haven’t done much of the work this is the group that did all the work i have really talented postdocs dongsaeng is a Pacific Northwest National Lab James is at Harvard michiko is in Tokyo as a professor les’s at USC as a teaching and I’ve got a good group of grad students I have an army of undergrads I love undergrads because they’re so excited and motivated but as I said I don’t do all this work the mechanics is really Pablo zvati area Purdue he’s a mechanician he did a lot of the analysis and also these other collaborators but we always have to thank the organisms right this is the right so the Mantis is

over here this is the the rasping chitin and this is the abalone and then I of course i have to thank the funding because grad students are expensed so the research is fun if anybody wants to join my lab come up it can be frustrating right because he do this the Mantis with seven years of research that finally led to our breakthrough but at the end my mom and I get to eat these organisms so it’s a lot of fun to just study this so anyway so I’ll thank you for your attention sorry I went a little over