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A D V A N C E D M A T E R I A L S & P R O C E S S E S | N O V E M B E R / D E C E M B E R 2 0 2 0 2 0 profiles, the array model was reduced to a 4×4 array for calculation efficiency. Twodriving scenarios, singlediaphragm driven and single cell driven, were con- sidered. Figure 9 shows the 4×4 array models for these two driving cases in the crosstalk profile study. In Fig. 9a, diaphragm 4 in cell 1 was driven, and in Fig. 9b the whole cell 1 was driven, and their adjacent di- aphragms were monitored in terms of voltage response. Figure 10 displays the voltage responses of the equally distant diaphragms in the two cases. In Fig. 10a the single diaphragm driven case does not reveal any patterns in the plot, while in Fig. 10b the single cell driven case shows the same volt- age responses of the cells that have the same distances from the driven cell, cell 1. Diaphragm 1 in cell 2 and diaphragm 1 in cell 3 have the same response curves, and diaphragm 3 in cell 2 and diaphragm 2 in cell 3 show the same response plots. Furthermore, the sin- gle cell driven case has less maximum crosstalk, -59.8 dB, than that of the single diaphragm case, -49 dB. The re- sults suggest that the quad diaphragm PMUT cell-based 2D array will be more stable when driven by cells rather than diaphragms. CONCLUSION This article discussed how a FEA approach could improve designs for ro- bust and practical PMUT sensor array construction. PMUT array performance characteristics beyond those discussed in this article can determine: undesir- able PMUT modal distortions; 3D beam profiles, depth of field and sharpness of acoustic wave propagation; and quantitative surface displacement pro- files to ensure uniformity of diaphragm motions. The integration of design op- timization with micro/nano fabrication technologies will have a major impact on the development of PMUT sensor ar- ray technologies for a broad spectrum of industrial and medical applications. ~AM&P For more information: Judith A. Todd, FASM, chair and professor, Department of Engineering Science and Mechanics, The Pennsylvania State University, Uni- versity Park, PA 16802, jtodd@psu.edu . Note: To see animation of the di- aphragm deflections at their centers in the PMUT model simulation from Fig. 3, visit bit.ly/329e1Ch. To see ani- mation of the diaphragm motions and acoustic pressure waves forming and propagating in water from Fig. 7, visit bit.ly/3mPzcRM. References 1. https://www.qualcomm.com/ products/features/fingerprint-sensors. 2. Y. Lu, et al., MUT Fingerprint ID System, U.S. Patent 10,430,631, issued October 1, 2019. 3. https://www.ultrasensesys.com/. 4. H.-Y. Tang, et al., Ultrasonic Touch Feature Extraction, U.S. Patent 10,585,534, issued March 10, 2020. 5. F. Griggio, et al., Micromachined Diaphragm Transducers for Miniatur- ised Ultrasound Arrays, 2012 IEEE International Ultrasonics Symposium, p 1-4, 2012, DOI: 10.1109 ULTSYM. 2012.0503. 6. T. Liu, et al., High-temperature Crystallized Thin-film PZT on Thin Polyimide Substrates, J. Appl. Phys., 122(16), [164103], 2017. DOI: 10.1063/ 1.4990052. 7. C. Cheng, et al., Thin Film PZT- Based PMUT Arrays for Deterministic Particle Manipulation, IEEE Trans- actions on Ultrasonics, Ferroelectrics, and Frequency Control, 66(10), p 1605- 1615, 8753665, 2019, DOI: 10.1109/ TUFFC.2019.2926211. 8. J.N. Kim, et al., 10 MHz Thin- Film PZT-Based Flexible PMUT Array: Finite Element Design and Charac- terization, Sensors, 20(15), 4335, 2020. 9. I.K. Park, et al., Application of Flexible PAUT Probe for Weld Inspection of Piping Elbows, Nondestructive Characterization and Monitoring of Advanced Materials, Aerospace, Civil Infrastructure, and Transportation XIII , 10971, p 109711V, International Society for Optics and Photonics, 2019. 10. H. Zhou, et al., Stretchable Piezo- electric Energy Harvesters and Self- Powered Sensors for Wearable and Implantable Devices, Biosensors and Bioelectronics, 168(112569), 2020. 11. R. Talish and A. Winder, Ultrasound Bandage, U.S. Patent Application 11/ 799,355, filed September 6, 2007. 12. PZFlex 2018 embedded database, OnScale, 770 Marshall St. Suite 200 Redwood City, CA 94063. 13. PI-2600 Series – Low Stress Applica- tion, Product Bulletin, HD Micro-Sys- tems, 250 Cheesequake Road, 703 Parlin, NJ. 14. S. Trolier-McKinstry and P. Muralt, Thin Film Piezoelectrics for MEMS, J. Electroceram., 12(1-2), p 7-17, 2004.