OK so. So I'd like to tell you a little bit about some of the work that we've been doing trying to exploit disorder and the idea here is to design function into mechanical networks and so this has been a project that has been going on for a few years of spearheaded by Andrew you and collaborators at University of Pennsylvania and some people at University of Chicago my student kneedeep Machina and postdoc and our bishop Berger and then some people from the engineering department had Chicago Daniel Reed in one to Pablo and I'll tell you about their work as we go along. So what I want to ask is does disorder matter to the material properties of the system and so what I want to compare for example is what happens for jam glasses in comparison to what you get in a crystal and so up why I'm interested in this is that you know we study glasses all the time but if you know when I was a kid and I was told by a glass was one to the window and knocked on the glass and it was solid just like everything else but they told me this is very different and so when well why is it so different I mean and so well if you go to an X. ray machine and you take X. rays of it you'll see that the structure is different and somehow this was supposed to be so terribly deep and I never understood why I should care if that was the subtle thing that is the difference is just that the particles weren't in organized places. Organized in a Christian way then why is the glass interesting and so the idea here has been to try and find out other ways in which glasses or jam systems are more physis tems are actually different from what you get in the crystals and so there are a couple of things that we know are somewhat different between crystals and glasses and so one thing is. That the exit patients that you get in crystals you know those very well they're the by law for the specific heat at low temperatures T.Q. case it's just saying that the low frequency modes are normal modes of a long wavelength plane waves and what we know is that for. A game systems or glasses that you have many more X. A Taishan particularly at low frequencies and so this is one thing that makes things different between glasses and crystals but are there other things that are special and so what I'm interested in asking Is Ken thought or. Provide some unique functionality that you wouldn't easily be able to get in a crystal and so what are some of the things that we know about well we know that if you have a. You know a glass or amorphous material that there are certain things that it has that is because it doesn't have this. Perfect structure we don't really know what a. Defect is and we have grain boundaries and so this provides certain kind weaknesses for the crystal that you don't necessarily get in the glass and so this is. You know. This water is more forgiving in that way that is you don't have failure due to those kind of modes. Another thing that we know about glasses and jam systems is that your many many quibbling ground states many more than you get in a crystal and so this can lead to. Adaptable features of the system that there are multiple paths for creating a certain kind of function this is the kind of thing I want to explore today and then there's one thing that I just want to mention because it came up in a lot of things that we've heard about during this this conference is that there's a common feature that seems to appear in all sorts of. Disordered systems which is this idea of constraint counter. And so we've seen that in case of the origami that we've heard about we also hear back in faint counting when you talk about jamming or networks or glasses that cetera and so this kind of idea is throughout a lot of disordered systems and so one question is well is this something that you can grab ahold of and therefore make some kind of functionality out of this aspect and so what I want to ask here is can this kind of flexibility that you have in the glass be harnessed in certain ways and so there are two things on the talk about global features and also local features and so these are the two things I want to mention. And so here I want to focus specifically on networks and so I think networks I'm going to talk about are derived from jampacked things and so I don't think this is actually necessary for the. Conclusions I'm going to reach but they are but that is actually what the studies were and so that's what I can tell you about concretely and I think a lot of these things can probably be generalized to more general kinds of disordered materials so how do we make these networks so we take a system of box filled with frictionless shears that are soft that you can squeeze together and so you put these particles in a box randomly and then you let them. Go to their push each other apart because they have repulsive interactions between them until they no longer interact if they can or if the vine is too small then they will end up in some kind of mechanical equilibrium and this mechanical equilibrium will be disordered in so this is what we have on the left hand side here is that these are the spheres that for two dimensional jam packing and then what we do to make this into a network is we. The centers of those fears and we put nodes at those points and wherever there's an overlap that means an interaction between two particles we replace that overlap with an unstretched spring between the two parties and so this is what we get on the right so we are racist for years as fears are no longer there and we have just this network of unstretched Springs between nodes and so that's the system that I want to talk about today and see what we can what kind of functionality we can have in that case. So as I said I want to talk about two things global response and the local response and so the global response I want to just talk about the module lie of the system so the bulk modulus and the sheer margin so want to remind you briefly about what those are so the bulk modulus is if I take a system of the bulk system the bulk modulus is I squeeze it in all directions equally and that cost a certain amount of energy to do that the energy cost to squeeze is a measure of the book market should book on just as a measure of the energy cost to squeeze this thing compressed in all directions so that's one of the modulus the other modulus is the sheer modules that I want to talk about and so this is I take this system and I. Find shear it in this case it's just simple sheer and again moving it in this direction is going to cost some energy and that energy one way of characterizing the energy is that your Majesty math the energy it takes to give it a unit here in that direction so these are the two kinds of modular life that we're interested in in this case and one of the things that you should. Think is well how big are these two modules I. And the two module I are typically in crystals comparable to one another and why is that well simply that I have to if I look at the microscopic I have two atoms and I'm pushing them together this way well they have to come up against potentials of their nearest neighbors and so that one energy scale the other thing is if I do it your mind just will maybe I'm coming at this direction instead and while still going up against that same potential between the two particles so it's going to be the same order of magnitude it may be off by a cosigned theta I don't care about or close on data here the direction which I'm moving these things that's of order unity so that your module and bulk of crystals are typically comparable to one another and so this is the. What we typically get for Crystal and behavior and then I've been talking about these two things because the one thing that we heard about. In the first day was the side DIA of the possums ratio until I just want to remind you what the possums ratio is possums ratio is a measure of you know if I take a material and an ordinary material and I pull it in one direction it gets narrower in the direction just as you showed us on. Wednesday and so this is the normal material and so this has a positive possums ratio I pulled in this direction and it squeezes down in the other two directions and in the ideal case it would be incompressible that is the volume of this thing would not change in that particular case now. That is what you have for normal materials and then the word I learned from Martin was that the other end of this is weird right that was your characterization of. A negative plus on ratio of materials and so this is the case of negative possums racial material I call it in one direction and it expands equally in all these other directions so OK and so material that does that is not common and we found I mean this is so it's a weird material and one of the things is could we make materials like that and it would that be something generic that you could find in if you could make this in three dimensions this could be a. Something that you could say well we can actually begin to make materials that are not normal. And so typically if you think about it what materials that you do you have that are. Negative plus one ratio and. There are probably only two that you're commonly familiar with one is. It's only barely negative which would be cork that you have for your wine bottles and so you don't want something that has a. Positive ratio which puts a cork in and it breaks the neck of the bottle and you don't want with native POS on ratio because then as you know if you. You know push in from the bottom it squeeze in from the sides and it will go out too easily so you you want something that has essentially zero Possum's ratio and so cork is very good it has zero near zero percent ratio the other thing that you may know that has negative parts of ratio if you complicate a paper and you couple of paper and this as you have in Him Paul you pull in one direction and somehow expands in all these other directions and so this is the two materials that you typically see there you go if you raise it up high so we can all see that look at that brilliant. Experimentalist. Par Excellence OK. Now I raise this regard. To the well of the module I of the system because in elasticities. There's a one to one relationship between the Possum's ratio and this. Ratio of the bloke and it's your module so if you have a very very low value of shear compared to the bulk of the shear of essentially goes to zero compared to the bulk then you have a normal material and so it's easy to shear the same hard to compress it and so this is. Something which would have a normal positive Possum's ratio and if you go to the other regime where this your module is much much much much greater than the bulk modulus then you go into this organic case the negative passant ratio you did and so that's what I want to explore. It so what I want to ask now if one of these networks is I've measured the bulk monitors I've measured the shear modulus and now what I want to ask you suppose I go in to this network and I grab a bond at random and I pull it out of the system. What's going to happen to the module well. It will change by a small amount because there's one Bond missing now so there will be a delta be. Labeled I for that bond there we moved a delta G. The change in the bulk money in the sheer amount just due to that one bomb being removed so there's a delta G. and there's a Delta B. for that one bond and so I want to measure what those that is for that bond but now want to put those that bond back and I want to now take another bond at random out of this network pull that one out and I do the same thing I measure what is Delta be for that bond and Delta G. for that bond and now I do this for all the bonds in the system and I now am going to get a distribution of. How many bonds. How many. Bonds will give a contribution Delta B I how many bonds will give a contribution to the G.I. and so to see how this works I want to start off by looking at what you would get if you had a crystal. And so a crystal is really a very boring system that is I have a unit cell which I repeat in term an ability over and over and over again in all directions and if I think of the very simplest case of a crystal so I'm going to have one and impune itself then it's a very simple thing that is what does the distribution of these B I's and geodes look like well it'll just be a delta function that is if I take this bond out it'll have a value of Dell to be I I put it back and because his next Bond that I choose is identical to the first one I take it away it will also have that same contribution to the book munchers for this year modules so all module I own the all bonds contributes to the bulk modulus and sure modules in an identical way and so what I have is this is distribution of B. eyes here still to be eyes will just be a delta function everything will do the same thing Bill nothing will do more nothing will do less. OK And so what I want to ask is Well what happens to this property of a material when I make it disordered and so typically what I would have thought is that if I. Go and I make a make the same disorder I put disorder into mine a material that I would get a blurring out of that delta function that it would just spread out a little bit and you know some bonds will create a little more time with create a little bit different less change to the July but it will be basically. Centered around that average value. And so what I want to ask now is well what happens if I do this for. Or a jam system so something that's fully disordered and. As disorders as I can make it OK And so what you're going to see here is now I'm going to show you this distribution function for the bulk of my just if your mind to light of this thing for these this. These distribution function for Delta beyond but the first thing you're going to see is this dirty work at the foot because the axes are going to change from linear axes to log axes which means something funny is happening OK and so themselves this is not what disorder does and it this is the distribution functions that we get and so what you see about this is that first of all the actually says changelog axes so that means that I have an incredibly broad distribution of how a bond will affect either the book knowledge of the few modules and that's one thing it goes all the way it's very broad it goes all the way it's continuous It goes all the way down to as low a value as we can find in our simulations and so this goes all the way down to zero as close as we can get. The other thing about this is that it's basically universal that it's the same distribution here for Delta B I N for Delta G.I. both have the same behavior so it's. Still something is you know kind of universal about this and. What of. Then you'll have post-doc was able to show is that this distribution function which is sweeping something under the rug here about how universal it is it's not exactly universal to begin with but after a few pruning things it becomes universal for the bookmark to so once you've done that then this distribution function has this simple form of a power law cut off by this exponential and so this is something we can show where the. This country and so we have these distributions that are broad and continuous and universal OK So now having gotten this far what I want to ask you is well you know if you have a bond over at the right hand side so. You don't have a point there but. Of Days of well of two I take the side way over here OK and. Well I thought you can give me your arm is going to use your arm to the point. So if I take this pond here and that was a bond that made a very big difference to the both modulus I would have guessed that that would have had a very big effect on the shear margin says Well that is if it's an important bond to the system is that important bond to the system but what we find is that that's not true at all that is these. Distributions are nearly completely uncorrelated with one another so the distribution of what you get for the shear module and for the bulk on July are less than one percent correlated so they're completely uncorrelated So if I took this pond away for the bulk month list. Its contribution to this year much is could have come from anywhere in this distribution it doesn't matter what its value was to the book modules and so this is. These two properties are somehow very different from what I would have expected from a crystal and this is what I want to use now in. In order to do things and so what I want to do is first go back to something that Martin did. Way back in two thousand and nine which was if you took a. Network of the kind that I mention and I reach in and pull a bond out at random I can ask well what does it do to the bulk margins and what does it do this year modulus and. Basically if I keep doing this taking bombs out over and over again I'm just doing rigidity percolation And at that point I know that both the two mothers and the both modules are going to drop in tandem with one another and so the ratio of G. over B. remains constant and so nothing much happens when I take the. Things at random but notice that what I'm plotting here is the ratio of this year to the book modules and I just told you that I have a broad distribution of both your module and contributions so I can reach in and pull out a bond that has a very big effect on one modules but not on the other or vice versa and so this is what I want to do now and I'm going to take out the bond which has the largest contribution to the vault much less so I know what all the bonds are I can ask the computer to tell me which Bond if I take it away has the largest effect on the book modulus I go in and I pulled up on the way what that's going to do is it's going to make B. drop as fast as it can because I've taken the way the bond that created it was most important for that whereas modulus is just going to drop by an average amount and as I do this I do this over and over and over again so I'm starting up here at. The disease just measuring how many bonds extra over rigidity threshold that I have so out here I have a lot of extra bonds in the system and now I take them away one time and that means that Delta Z. is dropping so I start here and I take away one bond and move up one little bit here I keep doing it over and over and over again and this thing just continues to increase G. over be increases dramatically and this is now again a log scale and so this Geo would be is up to ten to the ten I mean so ten orders of magnitude in that case. Now I can do. Something else I could have gone and asked So let's prune the bonds that has a minimum effect on the book modulus Now if I do that. Going to. Be will not change at all but Delta G. is going to change by its average amount each time and so that means this ratio of G. over B. is going to drop so I start from the same point for the same network and I just keep pruning in that way and now. Will be dropped and this goes down to about ten minus four and so just by pruning. A few percent of the bonds in the system I can tune this shear to the bulk modulus by something like fourteen orders of magnitude and so that's a large change and what that's telling me is I can go from something that's completely or exact that is with a possible ratio of negative one all the way to one is completely incompressible which is Possum's ratio in well in three D. would be cause for issue of plus a half in to do you be a plus one. OK And so this is what we could do fight pruning the Delta B.S. I could have also done the same thing by pruning on the shear Montreux I instead of the book my choice and here again I get another set of. Curves that I can go I can make something or that it by putting a minimum value of Delta G.I. or make it incompatible by tuning the maximum value Delta G. Od so I have all these different ways of getting to the end point that I want. OK So this is. These different algorithms produce different kind of pruning. Behavior and so I get different lattices I can get the same. Possums ratio by tuning in. Riding of ways as a many many ways of achieving this the desired property of the system the Possum's ratio by pruning. In many different ways I can get the same thing. OK And so then what we try to do with we want to make these things in the laboratory and so we go in and so we can do this either in two dimensions and so in two dimensions we take a sheet of rubber and we take it to a laser cutter and we cut out everything that doesn't look like a network and that's what we have on the left and on the right we can do the see in three dimensions by building this up by three D. printer and so we print these things in three D. in two you can make. Systems that are three D. or two D.. And so this is. One way that we test whether we're actually doing something correct in the system now. What I'm not going to show you the behavior for the. Organic networks here are five shows something in the. For the local thing in a minute so having said that with making these things in the laboratory of now I want to ask what else can we do with these networks and so the question is can we make. Other things that are on a more local scale so I told you about the bulk module the bulk module I were the only things that happened I would be kind of interesting but it would be somewhat limited and so what we want to do is take a lesson from biology and ask about what do what does biology do in biology makes use of proteins in a way that is very. Very important to the biology in this is what's called protein Alistair E. and so here this is. Pulled from the biology website and so you take. A protein and what this idea of Alistair does is that if you have one side on the protein where you. Add your bind to something here then. At a site way over on the other side of the protein it now has the ability to bind this substrate over here whereas if you didn't have this. Bond here it would lose the ability to find something far away and so this is an important way of the proteins control their behavior their dynamics and so what we wanted to ask is well can we do the same thing in the case of. Of our networks or mechanical networks and so here is what we were doing in so we take so the idea is I ask you please come up to this network that we've just made this network and. I ask you to please choose at random Your choice of where you want to source and so this was where you happen to choose a source that I ask you to come back in please choose another place on this network that you want to be the target and so you chose this thing far away to be on the target so this is totally random is your choice and then I ask you Do you want this target when I pull the source apart so I want to target to pull apart or do I want to go together so it's your choice precisely where you source where the target and what you want the active action to be and so the question is can we can we tune the same to that case and so we using the same idea and this is what I wanted to be able to show you if we had had the. Overhead projector of so this is the idea so here we have a. View so the This Is It OK so you can see it and so what you actually see here is are two separate networks there's one on top of the other. What if I pull them apart you'll see that these two networks really were almost identical and what I can show you here because I don't have four hands but is that if I pull on the source I can make in one case the target come apart and the case of how you come together and so I will show that to you if anyone's interested they DID WE CAN I can show that you. Directly but but this actually works OK and so. This kind of behavior so this is. We didn't know you could do this and now the fact that you can do this and you can do this with nearly one hundred percent. Success rate is something that we didn't expect to be so easy to do and so this kind of work has also done by two other groups who ran the same time so I met you group and. See TO SEE THE has also done some related work in the same the same general ideas. Can you design out a star response. So what. I want to ask now was well how complicated can that task be that is. What I told it beginning is we have one source and one target could I'm now ask you to have one source but more target so the sources over at the upper left and I have three things which I've asked the system to. Create So if I pull on the source I want those three other targets to move in the direction and with the amplitude that I've put right there and the question is can you do that and the answer is yes and. What we're showing here is at the on the bottom left is how many targets can I. Have. The the function that I prescribe at random how what's the probability of being able to get all of those to work and so what you see here. Is. So for a system the size of an In this case with a size eight system what we can do with you can have asked will see if I can tune one yes I can tune one can or two to yes I can tune to but pretty soon I can tune that many because I only have eight particles in the system but if I make the system bigger and bigger YOU SEE THAT CAN TOO MANY MANY MANY sites here many targets with that one source so the complexity of the task is increasing so there's a number of targets I'm asking system to tune and each different color is for a system of a different size and so if I make the system larger and larger and larger I can tune many many many more sites almost uniformly so there is a probability of success and so I can get nearly one hundred percent success of with many many targets if if I make the system large and the question is Well how does a number of targets increase with the number of nodes I have in the system and at least the present behavior is the algorithm that we have is a little bit sub linear it still says that if I have an infinite system I can prune an infinite I can to an infinite number of sites but it doesn't scale with the size of the system so it says that in the infinite size limit I can tune zero percentage of the sides but still be an infinite number but. But this is depends on the algorithm that we're choosing to tune this thing in so that we may be able to do better than that. OK but it also tells us one other thing which is that what how many ways could I have two and one. Site right that is and well since I can tune any of them and T. of them then the number of ways of getting that one function. Is going to be some exponential. You know it's a. Whatever that thing is called the. The Benefactor Oriel thing with a factor of me that's lots so it's not one and. So. What it's saying is that this is really a very easy thing to to create five minutes OK so. And so this is the. Kind of showing the power of the said is. We started with asking what. Was biology doing and could we mimic it and then what we found out was very easy to do it and part of the reason so easy to do it is that there are so many different ways in which you can do it and that's what this is basically telling us. Until now I just want to end with one last thing which is talking about aging. Behavior and so this is now a little bit different that is what I'm thinking about is suppose I have a sand pile you know and so it's a big heap of sand and down in the middle of the sense of it's feeling the weight from everything on top of it and so these particles are under a lot of force between the grains of sand. So what's going to happen here is well the grains that are under the most force they're going to do form plastically over time not a lot but over time a long enough time you will see that these grains are no longer going to be nice little fears they'll be little flat top guides and so they're going to distort over time. And so the bonds that are the under the most stress most force are going to form faster than those that are under less force and so this is the idea so it's a little bit different from the pruning that is this is a weaker form of pruning I'm just allowing the system to evolve under its own steam it's measuring its own. As on it and then responding with a memory of what it. Learned about. From all the weight that's been on top of it so that it has memory in it it's also a greedy algorithm so in the sense that. What it's doing is it's no longer asking pulling the bond away asking which Bond was the most important I'm just asking which Bond has most stress on it and that's something that the system just knows and it responds to what that stress is so it's a very greedy algorithm it's not having to do any complicated computations and it just goes down hill and so this is the results that we def of this so the idea here is that. The bonds are in the most stress to form classically faster than those with less stress and so what I mean by that so the energy of this pile is the sum of the energies of each of the bombs separately minus a lot a lot is the unstretched length and I'm going to let the unstretched length relax very slowly depending on how much force there is on that actually and so L. I zero changes slowly in time and we feed that back in and this is what the ageing of the system does and what you see is well the bulk modest drops this year modulus doesn't do very much and so after time in two dimensions or three dimensions you get that the ratio of geo be it gets larger and larger and you get some of this really it drives itself towards inorganic behavior automatically on its own and so this is something called directed ageing that is you usually think of ageing is just some bad thing that happens you don't typically think of aging into this directed in one pathway to a particular place and this is a ageing that you somehow knows it wants to make a weird material items. OK And so that's where I basically want to end so I just want to. Conclude that. Designing function into disordered networks there is what I've tried to present here is a new paradigm for designing punctual materials based on the idea of using the disorder in the material to make it possible to design the functionality I've shown that you can do this globally and you can select the passant ratio you can. Do locally and get action at a distance Alistair effect in the system. But as I've said many times before no good talk is really finished until you have the both feet line and so this is a bullshit line so everything above this line I hope you believe in I mean I think that's all facts everything below the bullshit line you have to believe it all OK And so this is what I want to. See them the picture if you will and so what I've tried to show here is that there's a new principle for disordered matter and this principle is that this independent of Bond level response that you have these very broad distributions for the Delta bialys in the Delta G.I. they're very very broad They go all the way down to zero and these distributions are uncorrelated with each other and this allows a new kind of functionality to be tuned into disordered materials that is not available for their order can't counterpart the second thing that I want to make is OK so what does this have to do with real things and so can you do this in situ and so on in our lab we're working on doing this in situ those we're trying to figure out whether we can actually measure without going to the computer which Panjandrum most stress and then flip them and make the systems do do stuff on their own so that's one thing could we do this microscopically so that you go down into. Design interactions between particles at the microscopic scale which you could then if they're under stress a laser could. Come in and zap them those bonds that are in distress where as it would leave the other ones alone that would be a different kind of thing that you could you could do and so this would be so that we can dream of happening one thing is biology which is you know we started with the South stuff having to do with biology but what does it really part about biology that's kind of. You know those great you bristle on our part to think that what we have to say has anything to do with biology but you can at least say that well since it's so easy to do in these mechanical networks perhaps that's why biology can make use of it so easily and so that was one idea that of how we can return to biology something that we took from biology to begin with and finally you know the idea is that you might be able to use this stuff in architecture I'm so buildings no longer have to have rectilinear walls I mean we have you know you look at a Frank Gehry building and they are all doing all sorts of things and what this allows you to do is OK so you have this disordered structure and so if my colleague across the way pisses me off what I want to be able to do is go to my window push it a little bit and have the window fall out OK And so this would be how I could get even with. The. People in mind but my my last OK with that I thank you very much I should just say want to hear all the people who did all the work and so and really who was involved in all of this and then Goodrich started this work out on the organic materials and they. Took that over improve all these various things about it Jason rocks has done the work on the Alice Terry and then you'll read in one the Pablo from engineering group. Has applied this to actually show how you can add on bendy constraints into these materials and then the machine and Berger did the making the. In the lab and then Elaine it headed for E N N Rick run Ellen Fitch who did the work on many you know how many different ways you can. Create the same kind of how complex your function can be without Thank you very much thank you.