Capacitive ultrasonic transducers with a new vibrating structure

In this work an electrostatic micromachined ultrasonic transducer using a new vibrating structure is described. The basic idea is to use a single thin plate suspended by means of a regular grid of small diameter columns. We show that this structure is able to vibrate, all in phase. The new transducer shows many potential advantages over the typical electrostatic cMUT: better transmission efficiency and reception sensitivity because the inactive area used by the column constraints is about 30% less than that used by the rails of the cMUT cells; for the same reason also a better reflection coefficient is expected. Because the virtual micro-cells of the device are not separated from each other there is no need to operate one or more holes to evacuate the micro-cells as in the typical cMUT technology; this means a better spatial uniformity of the mechanical characteristics of the vibrating plate and, in turn, less spurious vibration modes and improved mechanical reliability.