High-speed optical humidity sensors based on chiral sculptured thin films

摘要

Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA i 6802, USA;Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA i 6802, USA;Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA i 6802, USA;Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA i 6802, USA;Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA i 6802, USA;Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA i 6802, USA;Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA i 6802, USA;Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA i 6802, USA;%A high-speed humidity sensor based on a nanostructured chiral sculptured thin film (CSTF) was fabricated and tested. The sensing principle is based on the shift of the central wavelength of the circular Bragg regime of the CSTF caused by adsorption and desorption of water vapor in the void regions of the CSTF. Spectral changes due to varying relative-humidity (RH) levels in the ambient environment were measured by a spectrometer. The CSTF sensor exhibited excellent reversibility and reproducibility from 40% to 100% RH. Moreover, the adsorption time of the sensor was measured to be as low as ~140ms, making it promising for many high-speed humidity-sensing applications.