TY - JOUR
T1 - Bimorph material/structure designs for high sensitivity flexible surface acoustic wave temperature sensors
AU - Tao, R.
AU - Hasan, S.A.
AU - Wang, H.Z.
AU - Zhou, J.
AU - Luo, J.T.
AU - McHale, G.
AU - Gibson, D.
AU - Canyelles-Pericas, P.
AU - Cooke, M.D.
AU - Wood, D.
AU - Liu, Y.
AU - Wu, Q.
AU - Ng, W.P.
AU - Franke, T.
AU - Fu, Y.Q.
N1 - Funding Information:
The authors acknowledge the financial support from the National Key Research and Development Program of China (Grant no. 2016YFB0402705) and a Basic Research Program of Shenzhen (Grant no. JCYJ20170817100658231); NSFC under project No. 61774028, and Fundamental Research Funds for the Central Universities under project No. ZYGX2016Z007; UK Engineering and Physical Sciences Research Council (EPSRC) grants EP/L026899/1 and EP/P018998/1, a Knowledge Transfer Partnership No KTP010548, a Newton Mobility Grant (IE161019) from the Royal Society and the National Natural Science Foundation of China, and Royal Academy of Engineering UK-Research Exchange with China and India, NSFC (Grant no. 11704261) and NSFC (Grant no. 51605485). We acknowledged Dr. Julien Reboud for his discussions, suggestions and experimental support.
Publisher Copyright:
© 2018 The Author(s).
PY - 2018/12/1
Y1 - 2018/12/1
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85048497817&partnerID=8YFLogxK
U2 - 10.1038/s41598-018-27324-1
DO - 10.1038/s41598-018-27324-1
M3 - Article
C2 - 29899347
AN - SCOPUS:85048497817
VL - 8
JO - Scientific reports
JF - Scientific reports
SN - 2045-2322
IS - 1
M1 - 9052
ER -