Collaborative Research: Reversible and Triggerable Self-Assembly of Photoresponsive Catanionic Vesicles

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

CBET-0829182 Chmelka When a liquid displaces another fluid on a solid surface, the angle that it subtends with the solid is called the dynamic contact angle. It provides a measure of the force on the solid and is used to understand the limits of the feasibility of the process. This limit arises when the displaced fluid gets entrained. These features are observed in coating flows as in making of photographic films, in displacement of one fluid by another in a pore which is of importance in the recovery of crude petroleum oil by displacement with another fluid, and in microelectronic devices where pools of liquid or liquid in a continuous form is moved from one region to another. Intellectual Merit. In the modeling studies proposed here, the P.I. will approximate the contact line region a liquid wedge of this dynamic contact angle displacing a second fluid following earlier successful models. The momentum balance equations will be solved correct to order of Re,(Reynolds number) and viscous dissipation will be calculated for the whole system. This is equated to the rate of surface work done, again following earlier successful model. Final solution will be in the form of the angle as a function of Ca, (capillary number) and Re. The novel features are (a) correlations at large the angle will be established, (b) correlations for liquid-liquid system will be established (c) the onset of entrainment at the angle = 180° (or at 0°), and the reasons why it may vary from one system geometry to another will be established. A simpler problem of entrainment in a receding contact line will also be studied separately under a different formulation. The P.I. will also perform experiments to obtain experimental data for the above systems and ranges of operation. Broader Impact. These results would allow one to set windows of operation where a coating process is feasible, assuming that the process fails at entrainment. Dynamic contact angles also provide estimates of force balances in the systems. Consequently, the above correlations provide a very good basis for sound process design in systems that are in the cutting edge in emerging technologies. The basic theory is straightforward and the progress that would be made can also be incorporated into teaching either in a course on interfacial phenomena or transport, both of which are taught by the P.I. in form of technical electives. Both undergraduates and graduate students will be employed in the laboratory.