CFN Colloquium

My group studies the spatiotemporal heterogeneity of materials and addresses the associated science and technological questions of how to image it, quantify it, understand it, and engineer it for new properties, from the finest atomic scale to the particle assembly and composite scale. Specifically, we adapt a suite of electron videography methods (e.g., liquid-phase TEM, electron tomography, 4D-STEM) and machine-learning based data-mining to synthetic soft, biological, and energy related systems. In the first direction, we focus on the synthesis and phase behaviors of colloidal nanoparticles. We image the crystallization pathways in solution, where the discreteness and multi-scale coupling effects complicate the free energy landscape. Single particle tracking and simulations combined unravel a series of interesting dynamics at this length scale, such as non-classical nucleation, size-dependent crystal growth habits, and moiré patterning, enabling advanced crystal engineering. In the second direction, we study membrane proteins in their native lipid and liquid environment at the nanometer resolution. The proteins exhibit real-time "fingering" fluctuations, which we attribute to dynamic rearrangement of lipid molecules wrapping the proteins. The conformational coordinates of protein transformation obtained from the movies are used as inputs in our molecular dynamics simulations, to derive lipid-protein interactions. In the third direction, we further push direct imaging to separation membranes formed from interfacial polymerization as well as multivalent ion batteries, where microstructure heterogeneity leads to morphogenesis and distinct charge transport properties. Our studies on these systems reveal unified presence and importance of spatiotemporal heterogeneity in morphology, composition, structure, and functionality. Our suite of "electron videography" tools serve as the basis for imaging and manipulating materials in space and time at the nanoscale.