Meniscus-Mode: A Novel Operation Mechanism for Signal Amplification in Capacitive Micromachined Ultrasonic Transducers

Abstract 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.