A 2-step coating technique for CMUT based chemical sensors

A versatile deposition technology has been developed, which allows a diversity of chemically sensitive materials to readily modify capacitive micromachined ultrasonic transducers (CMUTs) without significant impact on transducer performance. In a 2-step coating process nanoparticles (NPs) and various sensitive materials are deposited onto a CMUT array, which transforms the device into a chemical sensor array. The key feature is a bottom NP layer which modifies the CMUT array in a way that different chemically sensitive materials can be deposited on single CMUT elements in a subsequent step by a simple drop coating technology without any further effort to guaranty localized deposition. Impedance analysis, supported by SEM, reveals that the procedure is reliable and reproducible and the resulting films are uniform and stable. The chemically modified CMUTs have been successfully tested as organic vapor detector.