3-D Direct Laser Writing of Capacitive Ultrasonic Transceivers

Ultrasonic probing, testing, and communication are widely used in nondestructive testing, medical applications, and biology. Various technologies for the fabrication of ultrasonic transducers exist: for example, capacitive micromachined ultrasonic transmitters complement commonly used piezoceramic-based systems. Traditionally, capacitive micromachined ultrasonic transducers (CMUTs) are fabricated in a multistep subtractive process mostly leading to silicon-based membranes. Here, we present the additive fabrication of CMUTs with different designs using 3-D direct laser writing (DLW)—a 3-D micro-printing technology. This technology enables design freedoms that go beyond the capabilities of traditional processes. In the present article, we focus on the fabrication of transducers with a center frequency between 500 kHz and 3.5 MHz. The performance (oscillation amplitude, center frequency, bandwidth, and transient response) of thus fabricated transducers is characterized in the air as well as under water and is found to be competitive with traditionally fabricated transducers.