A monolithic photonic microcantilever device is presented comprising silicon light sources and detectors self-aligned to suspended silicon nitride waveguides all integrated into the same silicon chip. A silicon nitride waveguide optically links a silicon light emitting diode to a detector. Then, the optocoupler releases a localized formation of resist-silicon nitride cantilevers through e-beam lithography, dry etching and precisely controlled wet etching through a special microfluidic set-up. Fine micro-optical sensing functions are performed without the need for any off-chip optics. As the bimaterial microcantilevers are deflected by the stressed polymer film, the disrupted waveguide acts like a photonic switch. Cantilever deflections in the order of 1 Å caused by thickness variations in the order of 0.005 Å are detectable following changes in the physicochemical factors affecting the polymer film thickness. Such factors include the sorption of volatile compounds and through a proper set-up the response to certain vapor concentrations is monitored in real time.