Interfacial and Surface Phenomena
1. Remobilizing Surfactants and Their Application to Enhancing the Thermocapillary Migration of Bubbles in a Microgravity Environment
Bubbles rising in an aqueous phase move as if they had a solid surface rather than a mobile fluid interface. The solidification of the surface is due to the adsorption of surfactant impurities which rigidifies the bubble interface. We have identified surfactants that adsorb to form a mobile monolayer, allowing a bubble to move hydrodynamically as if it had a clean fluid surface. In collaboration with NASA, we are using these surfactants to enhance the thermocapillary migration of bubbles in microgravity.
2. Gas/Liquid Phase Co-existence of Soluble Surfactants at the Air/Aqueous Interface
Surfactants are used to rapidly reduce the interfacial tension when a new interface is created. Relaxations in tension usually exhibit an initial induction of high tension that can limit the technological use of surfactants in high-speed interfacial processes. Our molecular level understanding of the induction period allows us to design surfactants that condense more easily and have reduced induction times.
3. Nanoscience Engineering
The goal is to design surfaces that can selectively template the heterogeneous nucleation of one polymorph of a crystalline material that exists in several different forms. This is done by fabricating nano- island domains of one chemical functionality surrounded by a continuous matrix of a second on a solid surface by using the phase separation of self assembling monolayers. We are currently using these islands as vestibules for the crystallization of nanoplatelets and for the adhesion of proteo-liposomes for surfaces for molecular recognition and sensing.