Polymer Skins With Switchable Roughness

Polyvinyl alcohol (PVA) films with embedded electrically-responsive liquid crystal (LC) ellipsoids were fabricated to develop a membrane coating featuring tunable roughness. Membranes (∼30 microns thick) were placed between opposing pieces of indium-tin oxide (ITO) glass, creating electrodes for creation of a uniform electric field. Applied voltages ranged from 0V–350 V, as films were observed using an optical microscope. Thin-film interference patterns were observed in various regions of each film and were measured. Contour plots of film displacement were created and showed elevations across the observed region. The area of the first dark fringe regions, assumed to be in contact with the top glass surface, were measured as a function of applied voltage. The maximum displacement of the film was estimated to reach 1.5 microns and the area in contacted with the top glass surface increased 127% between 0–350 V. Finite element modelling results illustrate the influence of polarity on the roughness of the film surface.