Damping characteristics of a micromachined piezoelectric diaphragm-based pressure sensor for underwater applications

This paper reports on the underwater damping characteristics of a micromachined piezoelectric pressure sensor packaged using liquid crystal polymer (LCP) and polydimethylsiloxane (PDMS). In water, its sensitivity is flat about 6 dB (ref. 1 V/Pa) from 20 to 400 Hz while its bandwidth is 1.2 kHz. In air, its sensitivity is about -33 dB (ref. 1 V/Pa) at low frequency and increases significantly after 4 kHz. The damped response in water can be attributed to the introduction of additional mass and damping elements to the sensor structure, which reduces the quality factor of the diaphragm. The larger sensitivity in water is due to higher pressure as a result of the denser water environment.