Rayleigh and shear-horizontal surface acoustic waves simultaneously generated in inclined ZnO films for acoustofluidic lab-on-a-chip

Pang, Huafeng, Tao, Ran, Luo, Jingting, Zhou, Xiaosong, Zhou, Jian, McHale, Glen, Reboud, Julien, Torun, Hamdi, Gibson, Desmond, Tao, Kai, Chang, Honglong and Fu, Yong Qing (2022) Rayleigh and shear-horizontal surface acoustic waves simultaneously generated in inclined ZnO films for acoustofluidic lab-on-a-chip. Surface and Coatings Technology, 442. p. 128336. ISSN 0257-8972

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Official URL: https://doi.org/10.1016/j.surfcoat.2022.128336


There are significant challenges in controlling uniformity of crystal inclination angles, growth orientations and film thicknesses to generate dual-mode surface acoustic waves (e.g., Rayleigh ones and shear-horizontal ones) for lab-on-a-chip applications. In this study, we demonstrate large area (up to three inches) and uniformly inclined piezoelectric ZnO films, sputtering-deposited on silicon using a glancing angle deposition method. Characterization using X-ray diffraction showed that the inclined ZnO films have an average crystal inclination angle of 29.0°, apart from the vertical (0002) orientation, at a substrate tilting angle of 30o. Reflection signals of ZnO/Si surface acoustic wave devices clearly show the generations of both shear horizontal surface acoustic waves and Rayleigh waves. The Rayleigh waves enable efficient acoustofluidic functions including streaming and transportation of sessile droplets. Excitation direction of Rayleigh waves on the acoustofluidics versus the inclined angle direction has apparent influences on the acoustofluidic performance due to the anisotropic microstructures of the inclined films. The same device has been used to demonstrate biosensing of biotin/streptavidin interactions in a liquid environment using the shear-horizontal surface acoustic waves, to demonstrate its potential for integration into a complete lab-on-a-chip device.

Item Type: Article
Additional Information: Funding information: This work was financially supported by the UK Engineering, and Physical Sciences Research Council (EPSRC) grants EP/P018998/1, EPSRC NetworkPlus in Digitalised Surface Manufacturing EP/S036180/1, and Special Interests Group of Acoustofluidics under the EPSRC-funded UK Fluidic Network (EP/N032861/1). We also appreciate the support from EPSRC Centre for Doctoral Training in Renewable Energy Northeast Universities (ReNU) for funding through grant EP/S023836/1, the National Natural Science Foundation of China (NSFC 11504291, 12074309, 52075162, 61274037, 12104320), International Exchange Grant (IEC/NSFC/201078) through Royal Society and the NSFC, the Key Research Project of Hunan Province (2019GK2111), Innovation Leading Program of New and High-tech Industry of Hunan Province(2020GK2015), the Key Research Project of Guangdong Province (2020B0101040002) and the Natural Science Foundation of Changsha (kq2007026). This work was also financially supported by Key Research and Development Program of Guangdong Province (Grant No. 2020B0101040002), Special Projects in Key Fields of Colleges in Guangdong Province (2020ZDZX2097), Research Project in Fundamental and Application Fields of Guangdong Province (2020A1515110561) and Shenzhen Science & Technology Project (Grant no. JCYJ20180507182106754, JCYJ20180507182439574, RCBS20200714114918249, GJHZ20200073109583010). Experimental supports from Dr. Zhefeng Lei, Prof. Xingang Luan, Dr. Chao Zhao, Dr. Yuanjun Guo and Dr. Pep Canyelles Pericas are acknowledged.
Uncontrolled Keywords: ZnO film, c-axis inclined orientation, shear horizontal-SAW, acoustofluidics
Subjects: F200 Materials Science
F300 Physics
H600 Electronic and Electrical Engineering
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: John Coen
Date Deposited: 22 Feb 2022 15:10
Last Modified: 04 Mar 2023 08:00
URI: https://nrl.northumbria.ac.uk/id/eprint/48519

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