3D direct laser writing of capacitive ultrasonic transceivers

Ultrasonic probing, testing and communication is widely used in non-destructive testing, medical applications and biology. Various technologies for fabrication of ultrasonic transducers exist: For example, capacitive micromachined ultrasonic transmitters complement commonly used piezoceramic-based systems. Traditionally, capacitive micromachined ultrasonic transducers are fabricated in a multi-step subtractive process mostly leading to silicon-based membranes. Here, we present additive fabrication of capacitive micromachined ultrasonic transducers with different designs using 3D direct laser writing - a 3D micro-printing technology. This technology enables design freedoms that go beyond the capabilities of traditional processes. In the present paper, 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, transient response) of thus fabricated transducers is characterized in air as well as under water and is found to be competitive with traditionally fabricated transducers.