Bimorph material/structure designs for high sensitivity flexible surface acoustic wave temperature sensors.

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??m thick) coated aluminum (Al) foil and Al plate substrates with thicknesses varied from 1 to 1600??m. 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, ?/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 ?/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??m thick), thereby enabling low cost temperature sensor applications to be realized on flexible substrates.

SUBMITTER: Tao R 

PROVIDER: S-EPMC5998018 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature