Capacitive Micromachined Ultrasonic Transducer (CMUT)

Capacitive Micromachined Ultrasonic Transducer (CMUT)

© Fraunhofer IPMS

Ultrasonic sensors are established for low-interference monitoring and analysis of static and dynamic processes in industrial testing and automation technology. Another field of application is medical diagnostics, where ultrasonic sensors are used.

Capacitive micromachined ultrasonic transducers (CMUT) are miniaturised sensor structures whose electrostatic operating principle enables the transmission and detection of ultrasonic waves. This new generation of ultrasonic transducers is manufactured using semiconductor technology processes and thus enables great flexibility in sensor design with high precision and reproducibility in the manufacturing process for single and multi-channel systems.

Features of the CMUTs at Fraunhofer IPMS:

  • wide range of elements with different frequencies (> 400 kHz)
  • high acoustic bandwidth (> 100% in immersion; > 20% in air)
  • high spatial resolution (submillimetre scale)
  • low acoustic losses
  • extreme miniaturisation (≤ 1 mm³). 

In addition, toxic substances (including lead) are not used in the  manufacturing process; the capacitive transducers of Fraunhofer IPMS are therefore RoHS-compliant.

The CMOS-compatible manufacturing process enables a new evolutionary stage in sensor miniaturisation due to the high integration potential with electrical control and evaluation electronics in CMOS technology. In addition, the natural acoustic matching to liquid and gaseous media ensures more efficient sound coupling. The extremely low mechanical coupling between individual sensor channels, in conjunction with the increased acoustic bandwidth, makes greater temporal and spatial resolution accessible. RoHS compliance ensures long-term usability.