Chasing the Critical Wetting Transition. An Effective Interface Potential Method

Wettablity is one of the important characteristics defining a given surface. Here we show that the effective interface potential method of determining the wetting temperature, originally proposed by MacDowell and Müller for the surfaces exhibiting the first order wetting transition, can also be used to estimate the wetting temperature of the second order (continuous) wetting transition. Some selected other methods of determination of the wetting temperature are also discussed.

Studies on Surface Tension Influenced Critical Gap in Cantilever Microstructures

ABSTRACTThis note presents an elasto-capillary model of a cantilever subject to capillary stiction during drying process of removing sacrificial layers in MEMS. Similar to the dynamic analysis of the electrostatic pull-in of electrostatic micro actuators, the cantilever beam tends to be pulled down to the substrate due to the nonlinear capillary force with respect to the gap. The critical one-half gap deformation and the corresponding critical wetting area for pulling down a micro cantilever by surface tension are analytically found herein. The instability situation of a generalized critical deformation for power-law surface force with respect to gap is also predicted accordingly. Some prior MEMS works are exemplified to justify this critical one-half gap deformation for capillary stiction.