Microtribological aspects of the adsorbed water on the LIGA Ni film

摘要

The authors studied the effect of the adhesion of atmospheric water vapor on the movement characteristics of micromachines. For samples they used Ni electrodeposition film created in a process similar to the LIGA process; from adsorption isotherm measurements with crystal oscillator techniques and tip sample inter-surface adhesion measurements, they studied changes in adhesion as related to water coverage rate. The results show that adhesion rose dramatically when the water coverage rate was about 3, regardless of tip radius of curvature. In order to explain this phenomenon, the authors performed thermodynamic analysis of adsorption isotherms and analyzed the distribution of pores on the surface, finding that at a coverage rate of 3, most of the pores of the surface are filled with liquefied water from capillary condensation and that the water condensed in regions in contact between the tip sample where surfaces form a meniscus.