Fully Printed PEDOT:PSS-based Temperature Sensor with High Humidity Stability for Wireless Healthcare Monitoring

Abstract

, takeo Shiba, takao nishikawa & Shizuo tokito * facile fabrication and high ambient stability are strongly desired for the practical application of temperautre sensor in real-time wearable healthcare. Herein, a fully printed flexible temperature sensor based on cross-linked poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was developed. By introducing the crosslinker of (3-glycidyloxypropyl)trimethoxysilane (GOPS) and the fluorinated polymer passivation (CYTOP), significant enhancements in humidity stability and temperature sensitivity of PEDOT:PSS based film were achieved. The prepared sensor exhibited excellent stability in environmental humidity ranged from 30% RH to 80% RH, and high sensitivity of −0.77% °C −1 for temperature sensing between 25 °C and 50 °C. Moreover, a wireless temperature sensing platform was obtained by integrating the printed sensor to a printed flexible hybrid circuit, which performed a stable real-time healthcare monitoring. Body temperature is an essential vital parameter reflecting the physiological activities. Monitoring of body temperature provides insight into human health conditions, such as cardiovascular condition, wound healing, pulmonological diagnostics, and syndromes prediction 1-4. Therefore, the flexible temperature sensor is highly desired to realize personal healthcare devices, which enable real-time monitoring of an individual's health state 5,6. Many efforts have been made to develop flexible temperature sensors, which mainly contain three types: pyroelectric detectors 7,8 , resistive temperature detectors (RTDs) 9,10 , and thermistors 11. Among them, the thermistor which relies on the thermo-resistive effect of sensing material is widely used, due to its simple device structure, fast response, and wide sensing range 12,13. Various thermistor materials have been developed and investigated, including composites of conductive filler with polymer, and temperature sensing conductive materials such as silver nanowire (AgNW) 14,15 , carbon nanotubes (CNTs) 16 , reduced graphene oxide (rGO) 17,18 , and poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) 19,20. However, most of these studies focused on improving the sensitivity and mechanical performance of temperature sensors, while their ambient stability, especially humidity stability, has rarely been considered. Additionally, the development of wearable temperature sensors via simple fabrication still a big challenge. Since the use of wearable devices inevitably exposed to ambient humidity, it is of great interest to develop a facile fabricated humidity-resistant temperature sensor. In contrast to its counterparts, PEDOT:PSS has been proven as a promising candidate for the wearable temperature sensor, not only owing to its outstanding mechanical properties and turntable electrical characteristics, but also the superior in simple, patternable, and high reproducible fabrication, such as printing 21,22. However, as a water-soluble polymer, the resistance of PEDOT:PSS also be easily affecte...

Tailoring the Self‐Healing Properties of Conducting Polymer Films

“…[16,35] A higher amount of GOPS likely leads to the formation of more cross-linking bonds surrounding PSS shells, hindering the water uptake of PSS and restricting the volume expansion upon water uptake. [47] The , leading to the conformational change of PEDOT chains. [35,[38][39][40] decrease of swelling upon GOPS addition also affects the waterenabled healing ability of PEDOT:PSS by creating barriers for the propagation of PSS and PEDOT to the cut area after water drops, leading to prolonged healing time and thus lowering healing efficiency.…”

Microporous Induced Fully Printed Pressure Sensor for Wearable Soft Robotics Machine Interfaces

“…Next, PEDOT:PSS was printed on the planarization layer using the dispenser system (350PC, Musashi Engineering) to form the electrodes. [ 24 ] The interelectrode distance was 1 mm. The electrode was annealed at 150 °C for 30 min and had a thickness of ≈500 nm.…”

Printed Soft Sensor with Passivation Layers for the Detection of Object Slippage by a Robotic Gripper

“…A cross-linkable poly(4-vinyl-phenol) (PVP) (436224, Sigma-Aldrich) solution consisting of a mixture of PVP and melamine resin (418560, Sigma-Aldrich) was spin-coated onto the PEN film as the planarization layer using 1-methoxy-2-propyl acetate (01948-00, Kanto Chemicals) as the solvent. An 800 nm thick lower electrode made from poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) (Clevios SV4 STAB, Heraeus) was screen printed onto the planarization layer and annealed at 150 °C for 30 min [ 24 ]. Further, a 8000 nm thick layer of poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) (FC-25, Piezotech, VDF:TrFE molar ratio of 75:25) dissolved in trimethylphosphate (TMP) at a concentration of 12 wt.% was formed by blade printing and annealed at 145 °C for 1 h. The upper sensor electrode consisted of screen printed PEDOT:PSS and was annealed at 145 °C for 30 min.…”