(6bj) Solid-State Self-Assembly : Fundamentals and Applications

Nanoscale science and technologies has been developed tremendously during the last two decades, introducing a variety of nanomaterials with unique properties. However, incorporation of the properties into macroscale functional applications has been limited. An essential challenge is the integration of such unique properties into assemblies for micro- and macroscale devices and discovering appropriate conditions under which this can be accomplished. Here I explore the self-assembly of nanoparticles (NPs) in solid-state under external stress for discovering fundamental understandings of mechanisms and dynamics for various engineering applications. 1. Yoonseob Kim et al. Nature, 2013, 500, 59-63 first demonstrated an example of excellent stretchable conductors from self-assembly of spherical NPs in solid-state. Free-standing stretchable conductors were assembled by layer-by-layer assembly. High conductivity and stretchability were observed and the properties originated from dynamic self-organization of NPs under stress. Modified percolation theory to incorporate the self-assembly of NPs gave excellent match with experimental data. 2. The current study demonstrated the chiroptical activities of NPs in solid-state for the applications of biosensing devices and optoelectronics. Unconventional transfer of macroscale stresses shaped nanoscale assemblies with handedness. Chiroptical responses were reversibly tunable by controlled stresses. Computational simulation supported the chiroptical properties originated from self-assembly of NPs in solid-state.

Based on my past experience, I will develop a research plan that includes, but are not limited to, more fundamental studies about 1) initiation force and main driving force of self-assembly, 2) relation between nanoparticles and external stresses, 3) form of probable assemblies not only in chain and cell but for higher dimensionality, and 4) optimization to the commercially available materials. Understanding the fundamentals has great potentials to lead to improved material designs for advanced applications. Specific objectives include the following: 1) stretchable semiconducting nanoparticle composites for reversibly tunable photocurrent with discovery of unique pathways, 2) electro-tunable mechanical properties of angioplasty balloons with enhanced performance including in-vivo experiments, 3) reversibly stretchable Li-ion batteries with high performance during many repeating cycles of huge mechanical stress.

 

The works were funded, in part, by Rackham Predoctoral Fellowship, University of Michigan, STX foundation, Seoul, Korea, and US Air Force Office of Scientific Research.