Meniscus-mode: A novel operation mechanism for signal amplification in capacitive micromachined ultrasonic transducers

• Published in: Sensors and actuators. A. Physical. Vol. 319; p. 112549
• Main Authors: Tawfik, Hani H., Singh, Navpreet, Elsayed, Mohannad Y., Nabki, Frederic, El-Gamal, Mourad N.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.03.2021; Elsevier BV
• Subjects: Amplification; Capacitive; CMUT; Contact angle; Elongation; Finite element analysis; Microelectromechanical systems (MEMS); Micromachined; Micromachining; Probes; Signal processing; Signal strength; Simulation; Surface tension; Transducers; Ultrasonic scanners; Ultrasonic technology; Ultrasonic testing; Ultrasonic transducers; Ultrasonics; Water circulation; CMUT; Microelectromechanical systems (MEMS); Surface tension; Contact angle; Capacitive; Micromachined; Ultrasonics
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2021.112549

•A novel operation mode for CMUTs that employs the meniscus formed by the surface tension of the water for signal amplification is presented.•Finite element simulations were presented to model the phenomenon.•A fabricated CMUT tested in a pulse-echo setup was used to demonstrate the phenomenon experimentally.•Amplification ratios that reach up to ∼2.24× compared to the traditional full-immersion operation case are reported. This paper presents a novel operation mechanism for ultrasonic testing in-water. The mechanism employs the surface-tension forces between the water and ultrasonic probe surfaces to cause an elongation (meniscus) of the water column and thus focuses the ultrasonic beam. The proposed meniscus-mode operation mechanism exploits this phenomenon to amplify the ultrasonic signal in comparison to the traditional fully-immersed setup. The visualization of the proposed mechanism is presented with the aid of finite-element simulations. In addition, the ultrasonic signal amplification due to operation in meniscus-mode is demonstrated experimentally using a capacitive micromachined ultrasonic transducer (CMUT) fabricated in PolyMUMPs technology. A factor of ∼2.24× improvement in the ultrasonic signal strength is measured.