Micromachined ultrasound transducer array for cell stimulation with high spatial resolution

In this work, we present a piezoelectric micromachined ultrasonic transducer (pMUT) array for local stimulation on cultured cells with a high spatial resolution for the first time. We used a bulk piezoelectric film that has a higher piezoelectric coefficient (d₃₁) than that of the thin film materials to achieve high acoustic power within a small membrane. The 500-μm-wide and 55-μm-thick transducer membrane exhibits a resonant frequency of 780 kHz, which is within the effective frequency range for stimulating cells. We also demonstrate successful in vitro experiments by stimulating cells using the fabricated pMUT array and verifying the stimulation using fluorescence calcium imaging. Using fluorescence imaging, we observed an increase in Ca²⁺ level of TRPA1 expressing HEK293T cells under ultrasound sonication, which confirms that TRPA1 channel in HEK293T cells was activated by ultrasound.