Gas sensing using polymer-functionalized deformable Fabry–Perot interferometers

We report a chemical vapor sensor in which polymer swelling, upon analyte absorption, is used to deform an on-chip silicon Fabry–Perot interferometer (FPI). The magnitude of the deformation, recorded through the resonance wavelength shift, is proportional to the analyte concentration in accordance with a simplified analytical model and with finite element simulations. Conventional and phenyl-doped polydimethylsiloxane (PDMS) polymers are used to functionalize different interferometers, which are tested for the detection of two volatile organic compounds, i.e. m-xylene and cyclohexane. The detection of m-xylene concentrations down to 34 ppm—limited by our flow-meter setup—is achieved experimentally. Based on the sensitivities and the noise characteristics of the devices, limits of detection (LODs) of 1.6 ppm m-xylene and 6.3 ppm cyclohexane are expected.