Detection of sarin gas by chemoselective polymers transferred by laser induced forward transfer

The possibility to apply Laser Induced Forward Transfer (LIFT) for printing chemoselective polymer pixels on Surface Acoustic Waves sensors (SAW) for warfare agent detection is presented in this study. 2-port resonator SAW devices operating at approximately 392 MHz were fabricated and then coated with different chemoselective polymers, i.e. polyepichlorhydrine (PECH), polyisobutylene (PIB) and polyethylenimine (PEI). The three polymers were deposited by LIFT as well defined rectangular pixels on the interdigital electrodes region of very sensitive SAW resonators. The performances: i.e. insertion loss and Q factor degradation of the laser printed electroacoustic devices was evaluated, at the Network Analyzer, after a detailed optimization of the polymer coating process, as sensitive film coating thickness, homogeneity and area are concerned. This allowed optimizing the SAW based resonator sensors to be included into the electronic conditioning circuits to provide a reliable and low noise frequency output signal. Tests with a chemical warfare agent (sarin) on the SAW sensor arrays with the laser printed polymers revealed very good device performances; in particular it was demonstrated a very high sensitivity to this gas up to concentrations in the range of a few ppm.