Caltech Young Investigators Forum

Thursday April 21, 2022 12:00 PM
Location: Online Event

Mechanistic Understanding of Metal-coordination Bond Dissociation in Biological and Synthetic Materials for Tunable Mechanical Properties

Abstract: Incorporating dynamic metal-coordination bonds as loadbearing crosslinks into synthetic materials, including hydrogels, has become increasingly attractive not only to improve self-healing and toughness of materials, but also due to the ease of tuning metal-coordination bond stability. However, a priori determination of kinetic behavior of metal-coordination complexes, especially important in the rational design of metal-coordinated materials with prescribed properties, is missing.

This lecture presents computational modelling and physical experiments of imidazole and histidine-Ni2+ metal-coordination complexes to elucidate how they affect bulk mechanical properties of metal- coordinated protein and polymers. First, I report an empirical relationship between the energy landscape of metal-coordination bonds, simulated via metadynamics modeling, and resulting macroscopic viscoelastic properties in ideal metal-coordinated hydrogels, measured as network relaxation time. Then, I discuss how clusters of metal-coordination complexes affect protein mechanical properties. Altogether, this work contributes design criteria for metal-coordination chemistry in materials design.

Bio: Eesha Khare is a PhD Candidate in Materials Science and Engineering and NSF Graduate Research Fellow under the mentorship of Professors Markus Buehler and Niels Holten-Andersen. Her research focuses on studying self-healing materials with tailored mechanical properties using computation and experiment. In addition to her science research experience, Eesha has also worked at the California Energy Commission, QuantumScape, and was named in Forbes 30 under 30 in Energy. Eesha holds a BS from Harvard University and MPhil from University of Cambridge Trinity College and is originally from California.

Velocity Fields of a Non-Equilibrium High Reynolds Number Turbulent Boundary Layer Over Rough and Smooth Surfaces

Abstract: Turbulent boundary layers (TBLs) are thin regions of fluid near a surface with highly viscous and shear-driven forces that contain chaotic and random vortical structures of varying size and energy content. Vehicle surfaces are rarely considered hydrodynamically smooth, due to macroscopic defects in the finishes or from build-up of naturally occurring roughness. This can negatively impact the performance of the vehicle. Roughness effects rarely occur in isolation from external perturbations or compounding flow histories such as changing pressure gradients which occur due to variations of surface curvature or freestream blockage. Comprehension of these flow behaviors is integral to further data-driven modeling necessary to improve vehicle design and performance. Research has shown that the effect of a bi-directional pressure gradient is to impact the boundary layer parameters such that the local flow behaviors respond to both the local and upstream pressure gradient conditions. This talk will focus on the experimental investigations of velocity field behavior of a turbulent boundary layer over rough and smooth walls in a complex, yet functionally driven, pressure gradient field.

Bio: Vidya Vishwanathan is a PhD candidate advised by Prof. William Devenport and Prof. Todd Lowe at the Center for Renewable Energy and Aero/Hydrodynamic Technology (CREATe) at Virginia Tech. She received her B.S. degree in Aerospace Engineering from Virginia Tech. As an experimentalist she conducts her research in the Virginia Tech Stability Wind Tunnel in which she measures and observes the behavior of non-equilibrium turbulent velocity fields using particle image velocimetry (PIV). She is a recipient of the National Defense Science and Engineering Graduate Fellowship. Her research interests are in turbulence, wind tunnel testing, and flow diagnostic techniques.

This talk is part of the Caltech Young Investigators Lecture Series, sponsored by the Division of Engineering and Applied Science.

Series Caltech Young Investigators Lecture Series