By Will Soutter
Scientists and Engineers at University of Michigan have used computerized simulations to demonstrate that entropy, mostly considered as disorder, could lead to formation of ordered nanostructures.
The findings have implications for synthesizing materials with capabilities such as shape-shifting skins for camouflage purposes. The desired material properties could form the basis of design of such materials which could then be realized using nanoparticles.
A major challenge is in making nanoparticles form the targeted structures. Findings from recent studies by the team demonstrated that this challenge could be overcome by employing specific particle shapes which can spontaneously form desired structures when they are crowded together. This also prompted the team to explore the number of structures possible from a particular shape.
The team carried out thousands of simulated experiments to study 145 different shapes under various levels of crowding. Drifting particles form the arrangement with the highest entropy. Entropy could be considered as disorder if there is space between the particles, resulting in random orientations. However, if the particles are crowded tightly, entropy would cause the particles to form ordered crystal-like structures that atoms form. Simulated findings demonstrate that 70%of tested shapes formed three types of crystal structures under the influence of entropy. The types were liquid crystals similar to those in flat-screen TVs, crystals akin to salt and plastic crystals. It is possible to predict the structures that would be formed by studying the particle shape and group behavior prior to crystallization.
The team is now attempting to study why the 30% resisted order.