Sodium (Na) metal batteries have attracted recent attention due to low cost and high abundance of Na. However, these batteries face challenges such as dendrite growth, limited cycling stability, and low Coulombic efficiency. These issues have been majorly attributed to formation of a heterogeneous solid electrolyte interphase (SEI) at the anode interface. We study how the electrochemical and structural heterogeneities in SEI influence the reaction distribution and electrodeposition morphology at the Na metal/electrolyte interface. The rate of interfacial growth and onset of failure is determined by the electrochemical and mechanical attributes of the SEI including ionic conductivity, morphology, Young’s modulus and fracture toughness. 

Growth of filaments within the solid electrolyte (SE) remains a major challenge which leads to internal shorts in solid-state batteries (SSBs). Internal stresses and molar volumes of interacting species strongly influence both reaction kinetics at the anode-SE interface and ionic transport within the SE. We are examining the role of mechanics in interfacial stability and optimizing parameters such as molar volumes, shear moduli, applied current density and ionic conductivity for improved battery performance. The stability of the solid-solid interfaces also depends on the cell size and may change if any manufacturing defects are present in the battery. 

Pressure-driven droplet flows through a straight channel are mainly governed by viscous and interfacial forces. The droplet either attains a steady shape, undergoes breakup or fragments into smaller droplets over time. Previous studies have shown that the evolution of droplet depends on various physical parameters such as capillary number, viscosity ratio and drop size. However, the geometry of the constricted channel also heavily influences the droplet shape, flow properties and onset of different multiphase phenomena. The variation in constriction dimensions, such as length and depth, alters the deformation of droplet and can induce breakup/fragmentation. The constriction shape determines the size, velocity and aspect ratio of the droplet as it enters and exits the constriction. 

Design of a reconstructed heart valve for pediatric surgery

Micro-systems Lab, Nanyang Technological University (NTU), Singapore (Summer 2019)