Problems associated with intrinsically destructive sensing mechanisms of organic field-effect transistors constitute one of the main obstacles to using them for the practical applications in sensing and switching. Here we report a smart system, in which a photochromic spiropyran (SP) combined with polymethyl methacrylate (PMMA) is used as a gate dielectric, to develop functional molecular devices capable of photoswitching their electrical conductivity in a noninvasive manner. Significant and reversible capacitance and current transitions in devices are generally demonstrated experimentally when the SP molecules undergo their documented reversible photoisomerization. This concept of conformation-induced capacitive coupling offers attractive new prospects for the development of functional devices by utilizing other stimuli-responsive molecular materials.