Nerve agent simulant detection by solidly mounted resonators (SMRs) polymer coated using laser induced forward transfer (LIFT) technique

Novel chemical sensor based on film bulk acoustic resonators (FBARs), in the solidly mounted resonator (SMR) configuration, exploiting three polymer sensitive layers deposited by laser-induced forward transfer (LIFT) are reported. The resonators operate at a frequency of 2 GHz and consist of a piezoelectric aluminium nitride film “sandwiched” between two metal electrodes deposited on a silicon substrate with an acoustic Bragg reflector at the interface to ensure the acoustic insulation. Chemically sensitive polymers, i.e. polyepichlorohydrin (PECH), polyethyleneimine (PEI), and polyisobutylene (PIB), are applied by LIFT onto the SMRs. In order to improve the process efficiency, and to protect the polymer materials from the energetic laser pulses, a triazene polymer, acting as a dynamic release layer (DRL) was used. Upon exposure to different concentrations of dimethyl methyl phosphonate (DMMP) vapour, the polymer coated sensors show fast and reversible responses, with a sensitivity between 239 and 405 Hz/ppm. ndings, i.e. the use of LIFT in conjunction with highly sensitive, robust, and reliable SMR transducers show that this approach is well-suited to implement chemical sensor arrays.