Capacitive micromachined ultrasonic transducer: transmission performance evaluation under different driving parameters a
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TECHNICAL PAPER
Capacitive micromachined ultrasonic transducer: transmission performance evaluation under different driving parameters and membrane stress for underwater imaging applications Abdullah ˙Irfan Yas¸ar1 • Fikret Yıldız2 • Osman Erog˘ul1 Received: 18 February 2020 / Accepted: 25 March 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Transmission performance of a CMUT element in terms of output pressure and displacements was evaluated. A SIMULINK model of single CMUT element based on mechanical model of MEMS capacitor was used and the analyses were performed under different ac and dc conditions. 2.6 lm thick Si, Poly-Si and Si3Ni4 membranes with a radius 60 lm were used to obtain results for underwater imaging application. Relation between membrane stress and outputs of CMUT was also investigated using SIMULINK model for commonly used CMUT membrane made of Si3Ni4 and polysilicon membrane under different electrical driving parameters. It was observed that different ac signal inputs (sine, square and sawtooth) showed different effects on CMUTs pressure and displacement characteristics. Our results indicated that the maximum output pressure and displacement were obtained in a square waveform. In addition, although stress on membrane increases the displacement and pressure of CMUT membrane made of Poly-Si, quality factor inversely proportional to stress on membrane. Membrane stress has adverse effect on Si3Ni4 membrane transmission outputs. The used model in this study might enable to determine optimum driving electrical inputs and stress on membrane to control CMUT outputs in terms of output pressure, displacement, quality factor and bandwitdh.
1 Introduction Capacitive Micromachined Ultrasonic Transducers (CMUTs) are MEMS based structures that can be used to generate and detect ultrasonic acoustic signals (Goyal and Mohan 2018). CMUT is a new concept and has many advantages compared to piezoelectric transducers. Small size, mass production, compatibility with 2-dimensional geometry, ability to work in a wider bandwith and higher frequency, reliable work at high temperatures are some of mostly mentioned superiorities of CMUT in literature (Oralkan et al. 2002; Olcum et al. 2005; Wygant et al. 2005; Wang et al. 2014; Fouan and Bouakaz 2016; Greenlay and Zemp 2017). Furthermore, it is easier to integrate CMUT array with electronic with the help of
& Fikret Yıldız [email protected] 1
Biomedical Engineering Department, TOBB University, Ankara, Turkey
2
Electrical and Electronics Engineering Department, Hakkari University, Hakkari, Turkey
advanced silicon technology for diffeerent application in air and water medium (Wygant et al. 2005). As shown in Fig. 1, the CMUT array consist of several similar elements, which has two electrodes, the bottom electrode is fixed and the top electrode is placed on a vibrating membrane. Most commonly piston (Fig. 1c) and clamped (Fig. 1d) model of CMUT are used to analyses CMUT transmit and r
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