Transcript

Nano-exploration for the Development of Sustainable Materials | Cristina Ruiz Agudo | TEDxKonstanz

so good afternoon everybody now i today i'm going to talk to you about exploration but from an exceptional perspective which is the nano scale perspective so the prefix nano is the greek word for dwarf and is used to refer to something that is really really small so for instance when we talk about nano sizes we use the term nanometer which refers to uh which is one billionth of a meter so 10 to the power of minus 9 meters something really really small so imagine for instance that you have a one meter ruler to take this ruler and then you cut into a thousand pieces this ruler you have one millimeter everyone is familiar with this with this unit then we get this one millimeter and then we cut it again into a thousand pieces then we have one micrometer and then this one micrometer again cutting if we will be able to cut it with the c source in a thousand pieces then we will reach a nano uh meter but to put the nano scale in a more understandable perspective you have to think you can think for instance of a water molecule a water molecule has a size of 0.3 nanometers so this molecule is as big about as big in comparison to a tennis ball as the tennis ball is to planet earth and if we have a look into this regime of really a small object actually we can set the many entities that you are all familiar with so for instance at the very end we have atoms or molecules at the smaller sizes if we move forward we find dna strands then a sizes of about 100 nanometer corresponds to the corona barrel size um if we enter the micrometer regime uh we this is the typical size for bacteria that we have seen already in some of the other presentations today and then going further we reach the size the diameter of one of your hairs which corresponds to 100 microns and i this limit is really important of 100 microns because because it limits the uh of the sizes that you can see with your naked eyes to the sizes that you cannot see and to be able to explore this regime below 100 micrometers we need to use some tools that help us to do that and the exploration of the nano and the microwave became feasible due to the advancement in the development of instruments that allowed us to see these objects that we were not able to see before so one of the most important inventions was the invention of the electro microscope so an electron microscope is just a normal microscope that use electrons instead of light that you usually use in an optical microscope and you use electrons because they allow you to see things that you cannot resolve with your naked eye or with an optical microscope and then you can imagine uh you are a material scientist and suddenly you are given this a new tool to play around so what do you do you start exploring everything that is around you and one of the most attractive kind of materials are the biological materials so these materials are really interesting because they have because they're structural functionality and also because they are organized at different length scales and for instance you can see here this is an electron microscopy image there in the corner you can see the scale bar two microns pretty small and this is the outer path of a mouse tooth this is so called enamel and this material has three levels of organization at different length scales so we can see these nanofibers here these nanofibers are made of a material a crystalline material called hydroxyapatite one compound these nanofibers are embedded in a within a protein matrix and then they are all bundled together forming these microfibers that you can see here of about two micro micrometer size and then these fibers also are sharing some of them the same orientation which is the third level of organization so all in all um the result all in all this results in a material that has incredible properties and that allows you to eat the food every day and this is a interplay between the composition of the material this crystalline hydroxyapatite and also of these levels of organization at different length scales i already mentioned the word crystalline and the word crystal but what is a crystal so a crystal is a solid material that uh is composed of a range building units that can be atoms ions or molecules so if you go to your kitchen you can find several crystalline materials one of them one of them is the cooking salt so the cooking salt is formed by the regular arrangement of sodium and chloride into a cubic structure but actually we don't need to go really far to find crystalline materials because in our own body we are able to produce many crystalline substances that are essential for the proper functioning of our organism so we are able as we saw to chew food or we are able to stand up straight or even to keep our balance thanks to some crystalline materials that we are producing ourselves but also crystalline materials are industrially relevant such as pharmaceutical compounds or construction materials such as gypsum and cement and it's important to study the nanostructure of those materials but not only the nano structure but what deals to this nano structure and we can think about the formation of crystalline materials so called crystallization as playing with lego bricks so imagine that you have uh at the beginning all the lego bricks they are disorder and they are swimming around in in a liquid media then at the end you have your lego structure which is composed of these lego bricks that are arranged in order so the process of crystallization is how do we is the process from which we go from the disorder swimming bricks to the final or the uh structure and this process has been understood for more than a 100 years within the classical view of crystallization so in brief this theory claims that crystallization starts by the lego bricks colliding with each other then eventually you will form a small crystal that is order and then this when this crystal reach a certain size is it will grow by the addition of building uni of single lego building units to form the final macrocrystalline material but as i said due to the development of instruments that allowed us to study these processes and this nanostructure then there were some experimental evidence for many systems that could not be really understood within the classical view of crystallization this means that there were some stages here involved between the disorder lego bricks and the final order structure that could not be well explained within this theory and i will show you one specific case the case of calcium carbonate so calcium carbonate is the main component of inorganic component of the eggshell and it has been shown for the formation of this crystalline material that first you form some assemblies of lego bricks that they are still swimming around in your solution then they aggregate and they densify forming some let's call it liquid nano droplets you can imagine them as regions on your liquid where you have more concentration of lego obliques then from these nano droplets we expel the water out and then we form a solid material but the solid material is still disorder so there is no order within the lego bricks and then from this disorder material our other lego structure emerge and this strato can grow to give the final macro structure by adding single lego bricks but also larger entities and i'm a scientist and i work in research of the studying the crystallization mechanism of many different crystalline materials some of them are industrially relevant but other are biologically and relevant and i'm especially interesting interested in studying what happened when we add foreign legal bricks to the media so when we add some additives in the media what happened with these stages in this formation process and why do we care about that why do we care about this knowledge at all or why do i care about that this knowledge at all this fundamental knowledge that i gather so for instance for the calcium carbonate system this is a system i have been studying for many years and then what i do is to apply this knowledge to design some uh strategies to solve daily problems so for instance in this case we were using calcium carbonate for us at the contaminating agent so as an uh we were putting in into water that had a high concentration of heavy metals to be able to trap those metals into water and therefore study the feasibility of this compound to be used as a contaminant also other problems i have to i work with are actually i want to avoid the formation of this crystalline material i want to avoid that the lego bricks come together and form that crystalline material because these materials can provoke problems in industrial processes and also because actually can provoke problems in your own body so in this case down down here in the corner you can see calcium oxalate crystals and these crystals are formed are the main component of kidney stones so deformation is detrimental for your body and in that case we were studying how these crystals are formed and how could we inhibit or delay its formation deformation so all in all it's really important to understand i hope you got that it's important to understand the path the different steps involved in the formation of crystalline materials to be able to come up with means of controlling those processes and now i wanted to introduce you one material that actually doesn't need introduction which is cement so i'm pretty sure that all of you are familiar with it but um cement is actually not so before this talk probably you all heard about nanotechnology and nanoscience but i'm pretty sure that when we talk about nanomaterials cement or concrete are not material that comes to your mind because they are so bulky they are so um old they are known for centuries and they are so gray and ugly that no one will think about that when we talk about nano materials so cement is the main component of concrete so concrete we make it by simply mixing water with cement and some stones then you let this mixture harden and then it end up in this material that is fundamental in our society for housing and infrastructure so as an impressive fact concrete is the most consumed material after water but even if this material has been known already for for centuries there is still the seek for technological innovation and this is due to the footprint to the co2 footprint associated to the main component of concrete which is a cement so the production of cement accounts for approximately eight percent of the total anthropogenic co2 emissions so this is a really huge number and therefore the uh we there is some um now some urgent need of developing materials with a lower co2 footprint and if we look at uh cement at the nanoscale it looks like this so cement is the nano glue that is keeping together all of the rest of the components so here we have the unreacted grain and then from the surface of them we have this a hydrated cement so this disorder network that they meet with each other keeping together all the rest of the components and it has been shown in the last in the last years that these disordered networks they are we can distinguish some subunits so some mini bricks there that have those dimensions but they are disorder and they are not arranged in another way and also the role that they play on the uh the role that they play on the formation of the networks or even though this even if these networks are an aggregation-based based process is elusive for scientists and the important the important thing to understand here is that the binding ability of cement-based material emerge from the nanostructure so therefore if we are able to create an structure that is beneficial for us this will result in superior mechanical properties and in this sense of material with superior mechanical properties of course nato has done already some incredible achievements so you can see here an acre so naked is composed 95 percent of calcium carbonate five percent of some protein and organics and is five times tougher than the crystalline material that is a hundred percent calcium carbonate and why is this why are those uh meccan superior mechanical properties emerging the the answer of that uh we can find it if we look at the nanostructure so we have a brick and mortar structure where we have some calcium carbonate platelets that they are arranged in this brick and mortar structure and this calcium carbonate gives um it's a hard but brittle material so it gives a strength to the to naked but then also we have this organic membrane that is the responsible for the flexibility and also it inhibits carrack uh propagation all in all resulting in these amazing mechanical properties so the same concept could be applied to cement so we have these plateds that they have been identified so if we are able to order them in a specific way then we can we could achieve superior mechanical properties if we achieve superior mechanical properties this translates into less cement needed for having the same mechanical performance and this will translate in lower the co2 emission associated to cement-based materials but as you can imagine this is a really ambitious goal and a lot of research needs to be done in order to identify all of these little steps involved in the crystallization process of cement if we want to come up with means of controlling this process so what i wanted to show you today is that ordinary materials such as cement on acre when we look at them at the nanoscale they are actually quite amazing and in this sense the the nanobot is as you saw upon us it cannot be questioned or denied and also its exploration is really important because it can help us not only to understand the world that is surrounding us but also to develop new strategies new advanced materials that can help us to improve our world and to tackle the problems of the current and future problems that we that we face thank you very much [Applause] you