Photoactuation of micromechanical devices by photochromic molecules

Spiropyran doped P(VDF-TrFE) nanocomposite films were spray-coated onto silicon micro-cantilevers. We show that switching the molecules from the closed- to the open-ring form by UV light gives rise to a downward bending of the cantilever as well as to a decrease of its resonance frequency. This photoactuation is reversible by means of heating and simultaneous visible light irradiation. From the flexural bending and resonance data, we extracted the actuation strain (0.13 ± 0.03%), stress (4 ± 1 MPa) and elastic energy density (2.3 ± 1 mJ cm−3) associated with the photoisomerization of spiropyran molecules in the composite films.