Piezoelectric Micromachined Ultrasonic Transducers: Design and Applications

Piezoelectric micromachined ultrasonic transducers (PMUTs) harness the direct and inverse piezoelectric effects in thin-film materials deposited on micromachined silicon substrates to generate and detect ultrasound with high efficiency and minimal power consumption. Typical designs comprise a suspended diaphragm or membrane incorporating a piezoelectric layer—commonly aluminium nitride, scandium-doped aluminium nitride, zinc oxide or lead zirconate titanate—electrically biased and driven to flexural vibration modes. Precision microfabrication techniques, including surface and bulk micromachining, wafer bonding and release etching, yield devices with resonant frequencies ranging from hundreds of kilohertz to tens of megahertz, tailored by membrane geometry and material properties. Key performance metrics such as electromechanical coupling coefficient, bandwidth, fill-factor and sensitivity are optimised through material selection, electrode patterning and cavity design. Integration with complementary metal–oxide–semiconductor circuitry at the wafer level reduces parasitics and enhances signal-to-noise ratio, enabling compact, monolithic solutions. PMUT arrays find application across healthcare imaging, intrabody communication, biometric sensing, non-destructive industrial evaluation and robotics. Advances in high-order resonance exploitation, large-density packing and novel piezoelectric compounds have broadened the functional bandwidth and spatial resolution of PMUT systems, supporting real-time diagnostics, continuous patient monitoring and wearable or implantable devices of global significance.

Research from Nature Portfolio

Recent studies have demonstrated lithium niobate PMUT arrays for intrabody wireless communication, exploiting multiple flexural modes to merge resonances and achieve a combined bandwidth of up to 400 kHz. A 225-element array, confined within a 3 × 3 mm footprint, has delivered data-rates of 800 kbit/s through tissue phantoms at distances from 3.5 cm to 13.5 cm. This work underscores the potential of high-bandwidth PMUT links for continuous monitoring and telemetry of implanted medical devices.

Piezoelectric Micromachined Ultrasonic Transducers: Design and Applications publication trend

The graph below shows the total number of articles in piezoelectric micromachined ultrasonic transducers: design and applications across all publications each year (not limited to Nature Index journals).

Technical terms

Piezoelectric effect: Generation of electric charge in certain crystalline materials when subjected to mechanical stress, and vice versa.
Micromachined ultrasonic transducer (MUT): Miniaturised ultrasound emitter and receiver fabricated by microelectromechanical system techniques.
Flexural mode: Bending vibration of a thin diaphragm that produces ultrasonic waves.
Electromechanical coupling coefficient: Dimensionless measure of efficiency in converting electrical energy to mechanical motion and back.
Bandwidth: Frequency range over which a transducer operates effectively, influencing resolution and data-rate capacity.

References

1. Thin-film PMUTs: a review of over 40 years of research. Microsystems & Nanoengineering (2023).
2. Lithium Niobate Piezoelectric Micromachined Ultrasonic Transducers for high data-rate intrabody communication. Nature Communications (2022).
3. Beyond fundamental resonance mode: high-order multi-band ALN PMUT for in vivo photoacoustic imaging. Microsystems & Nanoengineering (2022).
4. Development of a High-Density Piezoelectric Micromachined Ultrasonic Transducer Array Based on Patterned Aluminum Nitride Thin Film. Micromachines (2020).
5. Monolithic Single PMUT-on-CMOS Ultrasound System With +17 dB SNR for Imaging Applications. IEEE Access (2020).