Colorimetric porous photonic bandgap sensors with integrated CMOS color detectors

In this paper, the development of a novel colorimetric sensor system based on the integration of complementary metal-oxide-semiconductor (CMOS) color detectors with a modified porous polymeric photonic bandgap sensor is reported. The color detector integrated circuit (IC) is implemented with AMI (AMI Semiconductor) 1.5 mu m technology, a standard CMOS fabrication process available at MOSIS (http://www.mosis.org). The color detectors are based on the spectral responses of buried double junctions (BDJs) and stacked triple junctions (STJs); the ratio of the photocurrents at the junctions provides spectral information. Both types of color detectors are characterized with a monochromator, and the results are compared. The BDJ color detector is used with a porous photonic bandgap reflection grating whose reflection spectra shifts as a function of the concentration of vapor analyte present. The experimental results verify that the color change of the photonic crystal can be detected and correlated to the change in analyte concentration. The entire system is compact and low power.