Abstract

Humidity-sensitive polymer, namely poly(vinyl alcohol-co-vinyl acetal), was deposited on a flexible poly(ethylene terephthalate) (PET) substrate pre-covered with a sputtered Au:Pd thin layer in order to develop an optical flexible humidity sensor. The spin-coating method was applied for the thin polymer film deposition. The optical and sensing properties of the device were studied after repeated bending deformation in the range of 25−1000 times. Transmittance measurements at different levels of relative humidity were conducted in order to examine the sensing properties of the probed flexible sample. The influence of the number of bending deformations on the performance of the sensor is studied, and the possibility for its successful application is demonstrated and discussed.

Highlights

  • Various types of materials have been considerably studied in order to develop humidity sensors with high sensitivity and stability, broad operating humidity range, and prompt response time

  • poly(ethylene terephthalate) (PET) flexible substrate and borosilicate glass were pre-covered with Au:Pd sublayer of gold/palladium, ratio of 80:20 and thickness of 30 nm

  • Thin metal films were deposited on all substrates by cathode sputtering of gold/palladium target (Quorum Technologies, Lewes, UK) for 60 s under vacuum 4 × 10−2 mbar by using Mini Sputter Coater SC7620 system (Quorum Technologies, Lewes, UK)

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Summary

Introduction

Various types of materials have been considerably studied in order to develop humidity sensors with high sensitivity and stability, broad operating humidity range, and prompt response time. The requirement of a low-cost humidity sensor with high performance is hard to achieve, and its development faces multiple challenges such as compatible materials and substrates, suitable manufacturing techniques, etc. A variety of materials can be used [1,2,3], but polymers stand out due to their easy deposition in the form of thin films, relatively low cost, tailored functionality, and fast response [4]. The influence of the number of bending deformations (range 25–1000) on the performance of the sensor and on the optical characteristics was investigated

Materials and Methods
Conclusions

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