1-D polymeric photonic crystals as spectroscopic zero-power humidity sensors

In the present study, a one dimensional polymeric photonic crystal is designed, fabricated and evaluated as a humidity sensor. The polymeric photonic crystal is consisted of a multilayer stack of sequential hydrophobic and hydrophilic layers applied using conventional photolithographic steps: spin-coating and DUV exposure. During exposure in a humidity environment, the hydrophilic layers of the sensor swell, hence growing its optical path and giving a red-shift of the reflectance peak and consequently a different color of the device. The spectroscopic humidity sensor does not require external power since its sensing ability is based on the reflectance peak shift of the photonic crystal in the visible spectrum (color change of the sensor). The design, fabrication, evaluation and characterization of the device and its evaluation as humidity sensor is presented.