Flexible/Bendable Acoustofluidics Based on Thin-Film Surface Acoustic Waves on Thin Aluminum Sheets

Yong Wang; Qian Zhang; Ran Tao; Jin Xie; Pep Canyelles-Pericas; Hamdi Torun; Julien Reboud; Glen McHale; Linzi E Dodd; Xin Yang; Jingting Luo; Qiang Wu; YongQing Fu

doi:10.1021/acsami.0c22576

Flexible/Bendable Acoustofluidics Based on Thin-Film Surface Acoustic Waves on Thin Aluminum Sheets

ACS Appl Mater Interfaces. 2021 Apr 14;13(14):16978-16986. doi: 10.1021/acsami.0c22576. Epub 2021 Apr 4.

Authors

Yong Wang^{1

2

3}, Qian Zhang^{1

2}, Ran Tao^{2

4}, Jin Xie¹, Pep Canyelles-Pericas⁵, Hamdi Torun², Julien Reboud⁶, Glen McHale⁷, Linzi E Dodd², Xin Yang⁸, Jingting Luo⁴, Qiang Wu², YongQing Fu²

Affiliations

¹ The State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Hangzhou 310027, China.
² Faculty of Engineering and Environment, University of Northumbria, Tyne NE1 8ST, U.K.
³ Key Laboratory of 3D Micro/Nano Fabrication and Characterization of Zhejiang Province, School of Engineering, Westlake University, Hangzhou 310024, China.
⁴ Shenzhen Key Laboratory of Advanced Thin Films and Applications, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
⁵ Department of Integrated Devices and Systems, MESA+ Institute, University of Twente, Enschede 7522NH, The Netherlands.
⁶ Division of Biomedical Engineering, James Watt School of Engineering, University of Glasgow, Glasgow G12 8LT, U.K.
⁷ Institute for Multiscale Thermofluids, School of Engineering, University of Edinburgh, Kings Buildings, Edinburgh EH9 3FB, U.K.
⁸ Department of Electrical and Electronic Engineering, School of Engineering, Cardiff University, Cardiff CF24 3AA, U.K.

Abstract

In this paper, we explore the acoustofluidic performance of zinc oxide (ZnO) thin-film surface acoustic wave (SAW) devices fabricated on flexible and bendable thin aluminum (Al) foils/sheets with thicknesses from 50 to 1500 μm. Directional transport of fluids along these flexible/bendable surfaces offers potential applications for the next generation of microfluidic systems, wearable biosensors and soft robotic control. Theoretical calculations indicate that bending under strain levels up to 3000 με causes a small frequency shift and amplitude change (<0.3%) without degrading the acoustofluidic performance. Through systematic investigation of the effects of the Al sheet thickness on the microfluidic actuation performance for the bent devices, we identify the optimum thickness range to both maintain efficient microfluidic actuation and enable significant deformation of the substrate, providing a guide to design such devices. Finally, we demonstrate efficient liquid transportation across a wide range of substrate geometries including inclined, curved, vertical, inverted, and lateral positioned surfaces using a 200 μm thick Al sheet SAW device.

Keywords: ZnO thin films; acoustofluidics; aluminum sheets; flexible devices; surface acoustic waves.