High sound pressure piezoelectric micromachined ultrasonic transducers using sputtered potassium sodium niobate

Fan Xia; Yande Peng; Wei Yue; Mingze Luo; Megan Teng; Chun-Ming Chen; Sedat Pala; Xiaoyang Yu; Yuanzheng Ma; Megha Acharya; Ryuichi Arakawa; Lane W Martin; Liwei Lin

doi:10.1038/s41378-024-00841-y

High sound pressure piezoelectric micromachined ultrasonic transducers using sputtered potassium sodium niobate

Microsyst Nanoeng. 2024 Dec 27;10(1):205. doi: 10.1038/s41378-024-00841-y.

Authors

Fan Xia^#¹, Yande Peng^#¹, Wei Yue¹, Mingze Luo², Megan Teng¹, Chun-Ming Chen¹, Sedat Pala¹, Xiaoyang Yu³, Yuanzheng Ma⁴, Megha Acharya⁵, Ryuichi Arakawa⁶, Lane W Martin^{5

7}, Liwei Lin⁸

Affiliations

¹ Department of Mechanical Engineering, University of California, Berkeley, CA, 94720, USA.
² School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu, 210096, China.
³ Bioengineering and Biomedical Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, 710049, China.
⁴ Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, China.
⁵ Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA.
⁶ Scientific Research Laboratory Div., Niterra Co., Ltd, Nagoya, 461-0005, Japan.
⁷ Departments of Materials Science and NanoEngineering, Chemistry, and Physics and Astronomy and the Rice Advanced Materials Institute, Rice University, Houston, TX, 77005, USA.
⁸ Department of Mechanical Engineering, University of California, Berkeley, CA, 94720, USA. lwlin@berkeley.edu.

^# Contributed equally.

PMID: 39725681
DOI: 10.1038/s41378-024-00841-y

Abstract

This work presents air-coupled piezoelectric micromachined ultrasonic transducers (pMUTs) with high sound pressure level (SPL) under low-driving voltages by utilizing sputtered potassium sodium niobate K_0.34Na_0.66NbO₃ (KNN) films. A prototype single KNN pMUT has been tested to show a resonant frequency at 106.3 kHz under 4 V_p-p with outstanding characteristics: (1) a large vibration amplitude of 3.74 μm/V, and (2) a high acoustic root mean square (RMS) sound pressure level of 105.5 dB/V at 10 cm, which is 5-10 times higher than those of AlN-based pMUTs at a similar frequency. There are various potential sensing and actuating applications, such as fingerprint sensing, touch point, and gesture recognition. In this work, we present demonstrations in three fields: haptics, loudspeakers, and rangefinders. For haptics, an array of 15 × 15 KNN pMUTs is used as a non-contact actuator to provide a focal pressure of around 160.3 dB RMS SPL at a distance of 15 mm. This represents the highest output pressure achieved by an airborne pMUT for haptic sensation on human palms. When used as a loudspeaker, a single pMUT element with a resonant frequency close to the audible range at 22.8 kHz is characterized. It is shown to be able to generate a uniform acoustic output with an amplitude modulation scheme. In the rangefinder application, pulse-echo measurements using a single pMUT element demonstrate good transceiving results, capable of detecting objects up to 2.82 m away. As such, this new class of high-SPL and low-driving-voltage pMUTs could be further extended to other applications requiring high acoustic pressure and a small form factor.

Grants and funding

ECCS- 2128311/National Science Foundation (NSF)