An apparatus for measuring a material's photomechanical response

This paper describes a simple and inexpensive apparatus for measuring the light-induced shape change of a material, which can be implemented in a high school or undergraduate laboratory. The key components of the apparatus are a laser pointer to actuate the material, a force sensor from an inexpensive jeweler's balance to measure the response, an Arduino for data acquisition, and a means for mechanically mounting the setup. The apparatus described here was used by high school students and teachers in a summer program to characterize liquid crystal elastomer samples. The theory of photomechanical response is used to interpret the gathered data, from which material parameters related to this theory are determined. (C) 2018 American Association of Physics Teachers.