(484i) Nonequilibrium Self-Assembly and Aniosotropic Effects

This research is focused on understanding the fundamental implications of having anisotropic temperature as well as implementing nonequilibrium self-assembly (NESA) systems in practice. In terms of theory and modeling, multiscale simulations that bridge the gap between the molecular (or nano) scale of the nonequilibrium agitating particles moving anisotropically, and the larger particles that are being agitated has been performed. During the simulations, agglomeration tests by measuring the orientational ordering (to probe and quantify the structure of the growing assemblies) has been conducted. Also, energies and entropies at various stages of NESA and compare the results with those of nonequilibrium coarse-grained field theories has been calculated.  Simultaneously, several system in laboratory practice has been implemented– these systems will be based on larger assembly components being surrounded by smaller magnetic particles that can be anisotropically “jiggled” by time-varying external fields. These magnetic particles are the non-Brownian particles effectively creating an anisotropic temperature field experienced by the larger particles. The ultimate objective – and, indeed, great hope – of our work, is that we will be able to engineer self-assembling structures of arbitrary shapes and properties by designing appropriate agitation “schedules”. Of course, magnetic agitation is but the first step in these directions, and we also envision other classes of systems based on acoustic or pressure waves, and also on rapidly varying external temperature gradients. This work will create a novel experimental test-bed for studying non-equilibrium self-assembly under well-defined conditions. It can also lead to practical development in designing efficient bottom-up micro- and nanomanufacturing schemes.
Molecular dynamics simulation has employed to test the above hypothesis. Several simulations with various settings were performed including change of the long-range interactions between the beads, changing the density of the system, relative diameters. The anisotropy in temperature would act as an external field that can form various patterns of self-assembled (SA) structures including hexagonal and rod shaped considering hydrodynamic and friction effects. It is found that different agitation modes play crucial form in obtaining different SA patterns. These patterns are found in DNA-coated particles, colloids, polymers, and supercooled fluids.