Fast Vapor Detection by a Micropillar Array-integrated Colorimetric Sensor.

An optofluidic sensor for rapid detection of gasphase analytes from a flowing micro-volume fluid sample towards wearable colorimetric sensing is reported. The sensor is comprised of a metal-insulator-metal (MIM) thin-film structure integrated with a quartz micropillar array for improved delivery of vapor analytes onto the sensing surface. For our proof-ofprinciple demonstration, we utilized a poly(methyl methacrylate) (PMMA) spacer and evaluated its response to ethanol vapors that were delivered in close proximity to the sensing material via the micropillar array. It is demonstrated that the micropillar array reduces the sensor response time from minutes to seconds compared with experiments using a conventional chamber. The sensor's concentration-dependent response also confirms its potential for continuous, compact, and quantitative colorimetric analysis of volatile analytes in low-volume samples.