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

Pang, H.-F. et al. (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, 128336. (doi: 10.1016/j.surfcoat.2022.128336)

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Abstract

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:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Reboud, Dr Julien
Creator Roles:
Reboud, J.Data curation, Validation, Writing – review and editing
Authors: Pang, H.-F., Tao, R., Luo, J., Zhou, X., Zhou, J., McHale, G., Reboud, J., Torun, H., Gibson, D., Tao, K., Chang, H., and Fu, Y.-Q.
College/School:College of Science and Engineering > School of Engineering > Biomedical Engineering
Journal Name:Surface and Coatings Technology
Publisher:Elsevier
ISSN:0257-8972
ISSN (Online):1879-3347
Published Online:04 March 2022
Copyright Holders:Copyright © 2022 Elsevier B.V.
First Published:First published in Surface and Coatings Technology 442: 128336
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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