Abstract

A fundamental challenge for surface acoustic wave (SAW) temperature sensors is the detection of small temperature changes on non-planar, often curved, surfaces. In this work, we present a new design methodology for SAW devices based on flexible substrate and bimorph material/structures, which can maximize the temperature coefficient of frequency (TCF). We performed finite element analysis simulations and obtained theoretical TCF values for SAW sensors made of ZnO thin films (~5 μm thick) coated aluminum (Al) foil and Al plate substrates with thicknesses varied from 1 to 1600 μm. Based on the simulation results, SAW devices with selected Al foil or plate thicknesses were fabricated. The experimentally measured TCF values were in excellent agreements with the simulation results. A normalized wavelength parameter (e.g., the ratio between wavelength and sample thickness, λ/h) was applied to successfully describe changes in the TCF values, and the TCF readings of the ZnO/Al SAW devices showed dramatic increases when the normalized wavelength λ/h was larger than 1. Using this design approach, we obtained the highest reported TCF value of −760 ppm/K for a SAW device made of ZnO thin film coated on Al foils (50 μm thick), thereby enabling low cost temperature sensor applications to be realized on flexible substrates.

Details

Title
Bimorph material/structure designs for high sensitivity flexible surface acoustic wave temperature sensors
Author
Tao, R 1   VIAFID ORCID Logo  ; Hasan, S A 1   VIAFID ORCID Logo  ; Wang, H Z 2 ; Zhou, J 3 ; Luo, J T 4 ; McHale, G 1   VIAFID ORCID Logo  ; Gibson, D 5 ; Canyelles-Pericas, P 1 ; Cooke, M D 6 ; Wood, D 1 ; Liu, Y 7 ; Q Wu 1 ; Ng, W P 1   VIAFID ORCID Logo  ; Franke, T 8 ; Fu, Y Q 1 

1  Faculty of Engineering and Environment, Northumbria University, Newcastle upon Tyne, UK 
2  Faculty of Engineering and Environment, Northumbria University, Newcastle upon Tyne, UK; State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, P.R. China 
3  College of Intelligent Science and Engineering, National University of Defense Technology, Changsha, HuNan, P.R. China 
4  Faculty of Engineering and Environment, Northumbria University, Newcastle upon Tyne, UK; Shenzhen Key Laboratory of Advanced Thin Films and Applications, College of Physics and Energy, Shenzhen University, Shenzhen, P.R. China 
5  Institute of Thin Films, Sensors & Imaging, University of the West of Scotland, Scottish Universities Physics Alliance, Paisley, UK 
6  Department of Engineering, Durham University, Durham, UK 
7  State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, P.R. China 
8  Biomedical Engineering, University of Glasgow, Glasgow, UK 
Pages
1-9
Publication year
2018
Publication date
Jun 2018
Publisher
Nature Publishing Group
e-ISSN
20452322
Source type
Scholarly Journal
Language of publication
English
DOI
https://doi.org/10.1038/s41598-018-27324-1
ProQuest document ID
2054867502
Copyright
© 2018. This work is published under http://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.