t=1.25ns

1. Multi-Scale Study of Coupled Reaction and Wetting Dynamics in Droplet SpreadingYing Sun, Drexel University, DMR 1104835 t=1.25ns The goal of this project is to examine coupled reaction and wetting dynamics in droplet spreading, with special attention on the effect of intermetallic compound formation on drop wetting kinetics, contact line advancement, and evolution of the solid-liquid interface. Using molecular dynamics (MD) simulations of a cylindrical Al drop spreading on Ni(111) and Ni(100) substrates slightly above the melting point of Al but below melting for Ni3Al, we directly observe for the first time the coupled wetting, dissolution, and crystallization processes. The results show that the formation of the B2 NiAl phase on Ni(111) substrate suppresses the wetting kinetics. t=2.50ns t=6.25ns Snapshots of MD simulation of Al(l) wetting on Ni(111) at 1200K. Lay 1 Al Lay 2 Al wetting kinetics t=7.5ns t=1.25ns t=0 interface t=0 interface density at drop center

2. Multi-Scale Study of Coupled Reaction and Wetting Dynamics in Droplet SpreadingYing Sun, Drexel University, DMR 1104835 We study the mechanism and application of UV tunable, nanopatterned ZnO or TiO2 surfaces for two-phase heat transfer. Jaymeen Shah, junior ME major works on nanostructured, stimuli responsive surfaces for wetting control and enhanced heat transfer. w/o UV t = 25 ps with UV t = 0 Wetting control by tuning density of ZnO nanorods. Commencement for Gang Qiu (MS, right) and Viral Chhasatia (PhD, middle) in June 2012. w/o UV with UV t = 25 ps t = 0 ps • Publications: • Qiu, G. et al., J Power Sour 219 (2012) 223. • Hu, H. and Sun, Y., J Appl Phys, DOI: 10.1063/1.4749393, 2012. • Tian, Z. and Sun, Y., Int J Heat Mass Transfer, 2012 (submitted). • Sun, Y. and Webb, E.B., Script Mater, 2012 (submitted). H2O ZnO t = 0 Molecular dynamics simulation with reactive force field – ReaxFF for bond breaking and bond forming.