Capacitive micromachined ultrasonic transducers for biochemical detection with flexible high sensitivity

In this paper, we have designed and fabricated the capacitive micromachined ultrasonic transducers (CMUTs) by low temperature bonding process under 350 °C. And the electrospinning technology is innovatively applied as a coating method for the functionalization of CMUTs' top membrane to achieve a uniform fiber structure, which is beneficial to absorbing and releasing the biochemical gas, that is to say, it can be applied to recycling use. It was further demonstrated that the mass effect on functionalized CMUTs' resonant frequency has been distinctly intensified with the increase of direct current (DC) bias voltage V
_bias
between the top and bottom electrodes from 10V to 30V, the resonant frequency changes from 1.787 MHz to 1.664 MHz. Simultaneously volume sensitivity was calculated from 200.000 ppb/Hz to 78.125 ppb/Hz with the concentration of sulfur dioxide (SO
₂
) from 100 ppm to 333 ppm. By applying appropriate V
_bias
, not only the volume sensitivity can be flexibly guaranteed, but also the energy consumption will be reduced.