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Flexible piezoelectric micromachined ultrasonic transducer (pMUT) for application in brain stimulation

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Abstract

We propose a new flexible piezoelectric micromachined ultrasonic transducer (pMUT) array integrated on flexible polydimethylsiloxane (PDMS) that can be used in studying brain stimulation by ultrasound. To achieve the technical demands of a high sound pressure level and flexibility, a diaphragm-type piezoelectric ultrasound transducer array was manufactured with 55 μm-thick bulk lead zirconate titanate (PZT) that was thinned after bonding with a silicon wafer. The ultrasound transducer array was then strongly bonded onto a PDMS substrate using an oxygen-plasma treatment followed by precise dicing with a fixed pitch to achieve flexibility. The radius of curvature was smaller than 5 mm, which is sufficient for attachment to the surface of a mouse brain. After a thinning process for the PZT layer, we observed that the PZT layer still maintained a high ferroelectric property. The measured remnant polarization (Pr) and coercive field (Ec) were 28.26 μC/cm2 and 79 kV/cm, respectively. The resonant frequencies of fabricated pMUT elements with different membrane sizes of 700, 800, 900, 1200 μm in diameter were measured to be 694.4, 565.4, 430.8, and 289.3 kHz, respectively. By measuring the ultrasound output pressure, a pMUT showed a sound intensity (Isppa) of 44 mW/cm2 at 80 V, which is high enough for low-intensity ultrasound brain stimulation.

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Acknowledgments

This work was supported financially by the KIST Institutional Program (Project No. 2E25590).

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Authors and Affiliations

  1. Center for BioMicrosystems, Korea Institute of Science and Technology (KIST), Hawolgok-dong, Seongbuk-gu, Seoul, 136-791, Republic of Korea

    Jin-Hyung Lee, Il-Joo Cho, Kyungmin Ko, Eui-Sung Yoon & Tae Song Kim

  2. Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 120-749, Republic of Korea

    Jin-Hyung Lee & Hyung-Ho Park

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  1. Jin-Hyung Lee
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  2. Il-Joo Cho
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  3. Kyungmin Ko
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  4. Eui-Sung Yoon
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  5. Hyung-Ho Park
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  6. Tae Song Kim
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Correspondence to Tae Song Kim.

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Lee, JH., Cho, IJ., Ko, K. et al. Flexible piezoelectric micromachined ultrasonic transducer (pMUT) for application in brain stimulation. Microsyst Technol 23, 2321–2328 (2017). https://doi.org/10.1007/s00542-016-2912-5

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