Proof of concept of an air-coupled electrostatic ultrasonic transducer based on lateral motion

• Published in: Sensors and actuators. A. Physical. 2022-10, Vol.345, p.113813, Article 113813
• Main Authors: Monsalve, Jorge M., Melnikov, Anton, Stolz, Michael, Mrosk, Andreas, Jongmanns, Marcel, Wall, Franziska, Langa, Sergiu, Marica-Bercu, Ioana, Brändel, Tim, Kircher, Marco, Schenk, Hermann A.G., Kaiser, Bert, Schenk, Harald
• Format: Article
• Language: English
• Subjects: Coulomb-actuated microbeam; Damping; Electrostatic transduction; Frequency ranges; Micromachined ultrasonic transducer; Micromachining; Noise; Noise levels; Radio frequency; Radio frequency interference; Range finders; Sound; Sound pressure; Transducers; Ultrasonic transducers
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2022.113813

An alternative implementation of an electrostatic MUT (Micromachined Ultrasonic Transducer), relying on multiple beams that displace along the chip’s surface instead of a single membrane displacing perpendicular to it, is presented in this work. With this approach, a design requiring a low bias voltage (24 V) and occupying a small area (3.3 ×3.3 mm², 2D/λ≈0.77) was shown to generate a sound pressure level of 82 dB (re. 20 µPa-rms) at 40 kHz and a distance of 8.9 cm. The high level of damping allows this transducer to operate in a wide frequency range (35–63 kHz). The operation of this device as an ultrasonic receiver was also proven. An implementation of this transducer as a rangefinder requires a strong reduction in the noise level, particularly coming from radio-frequency interference, in order to increase its detection range. [Display omitted] •A transducer concept based on lateral motion (instead of vertical) is used for transmitting and receiving airborne ultrasound.•A high fluidic damping was observed, enabling a transmission bandwidth of nearly an octave (35–65 kHz).•This electrostatic device is based on an array of microbeams and has a sidelength smaller than half a wavelength.