The Development and Testing of an Experimental Apparatus Used to Explore the Evolution of Soap Films Formed and Detached from Novel Silicon Wafer Frames Having Patterned Boundaries.*

Motivation for the apparatus described in this poster stems from fundamental questions regarding along-the-edge instabilities of retracting liquid sheets: Instead of using a wire frame on which to form and detach soap films, is it possible to use a microfabricated silicon wafer allowing for the micropatterning of the frame edge to induce disturbances of known spatial wavelength onto the liquid film edge? Using this novel approach, can the growth and evolution of these modulated disturbances on the detached film edge be measured? Here we document the development and testing of an apparatus to answer these questions. The work was completed by three undergraduate student research teams. Our results show that 200 um thick silicon wafers can be fabricated via traditional semiconductor processing techniques to form frames with electrically conductive patterned edges. Secured using 3D printed holders, the wafers can be repeatably withdrawn from a bath to form soap films whose thickness can be measured locally and globally. Detachment of the films is caused by Joule heating of the frame edge, with synchronized cameras capturing the evolution of the detached film. Future work using this apparatus will address fundamental scientific questions.