Abstract
Porous polytetrafluoroethylene (PTFE) is physically flexible, thermally and chemically stable, relatively inexpensive, and commercially available. It is attractive for various flexible sensors. This paper has studied flexible capacitive humidity sensors fabricated on porous PTFE substrates. Graphene oxide (GO) was used as a sensing material, both hydrophobic and hydrophilic porous PTFE as the substrates, and interdigitated electrodes on the PTFE substrates were screen-printed. SEM and Raman spectrum were utilized to characterize GO and PTFE. An ethanol soak process is developed to increase the yield of the humidity sensors based on hydrophobic porous PTFE substrates. Static and dynamic properties of these sensors are tested and analyzed. It demonstrates that the flexible capacitive humidity sensors fabricated on the ethanol-treated hydrophobic PTFE exhibit high sensitivity, small hysteresis, and fast response/recovery time.
Highlights
Humidity Sensors Based on GrapheneFlexible humidity sensors have recently gained attention in various applications including respiratory devices, incubators, sterilization processes, medicine production, and storage [1,2]
At low RH levels (
The response/recovery time of sensors based on bare hydrophobic PTFE and ethanol-treated hydrophobic PTFE substrate are still similar, which are s/5 s and s/6 s, respectively
Summary
Flexible humidity sensors have recently gained attention in various applications including respiratory devices, incubators, sterilization processes, medicine production, and storage [1,2] The sensors with both cost-effective fabrication processes and high performance such as high sensitivity and linearity, low hysteresis, and fast response time are essential to meet the requirements of the emerging application areas. To address this need, the humidity sensors based on flexible substrates such as polyimide (PI), polydimethylsiloxane (PDMS), polyester (PES), polyethylene naphtholate (PEN), polyethylene terephthalate (PET), cellulose, and paper have been developed [2]. Compared with the traditional hydrophobic and hydrophilic PTFE substrates, the ethanol-treated porous hydrophobic PTFE substrate increases both yield and performances of the flexible capacitive humidity sensors
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