Microsystems for optical gas sensing incorporating the solvatochromic dye Nile Red

An optical gas sensor has been developed based on the fluorescence emission of the solvatochromic dye, Nile Red, immobilised within various polymers with different physical properties. Microsystems, made either in SU-8/glass or microstructure glass (MSG) substrates, were used to host the environmentally sensitive fluorescent dye within the polymer matrices. The MSG devices have been found to have superior sensitivity to analytes (up to seven times greater) and recovery times (up to 50% faster) than analogous structures made in SU-8. Measurement of the fluorescence at two separate wavelengths confirmed the ability of the MSG sensor array to produce a “fingerprint” response for separate analytes with a high degree of repeatability (the standard deviation of the average response to a given analyte was <1%). Used in conjunction with pattern recognition techniques, the arrays show potential for gas identification and discrimination.