This work has demonstrated the possibility of unlocking the potential of Capacitive Micromachined Ultrasonic Transducers (CMUTs) for highly precise force measurement. The innovative approach is based on translating mechanical stress directly into a shift in the resonance frequency. In contrast to conventional methods, we use this frequency change as a highly sensitive measurement variable. The underlying physical principle is that an applied force on a bending beam induces strain in the CMUT, which measurably alters its oscillation behavior. This technological advancement will be presented at the IEEE Sensors Conference in October 2026.

The theoretical foundation of this work is a comprehensive methodological investigation that combines analytical approaches with detailed numerical simulations in COMSOL. To accurately describe the system, a model based on the 6-element Butterworth–Van Dyke equivalent circuit was developed. The experimental validation of the results shows an impressive agreement between modeling and measurement. In addition to the modeling, the sensor was thoroughly characterized to validate the highly sensitive frequency shift under real-world conditions.

It is particularly noteworthy that the CMUT already proves to be a competitive alternative to the industrial gold standard, the strain gauge. Despite its significantly smaller size, the CMUT matches conventional sensors in terms of sensitivity and, moreover, offers substantial potential for further optimization. Thanks to its high level of integrability and sensitivity, it opens up entirely new application areas where space constraints are critical.

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