Abstract
Flexible strain sensors are fabricated by using a simple and low-cost inkjet printing technology of graphene-PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)) conductive ink. The inkjet-printed thin-film resistors on a polyethylene terephthalate (PET) substrate exhibit an excellent optical transmittance of about 90% over a visible wavelength range from 400 to 800 nm. While an external mechanical strain is applied to thin-film resistors as strain sensors, a gauge factor (GF) of the piezoresistive (PR) strain sensors can be evaluated. To improve the GF value of the PR strain sensors, a high resistive (HR) path caused by the phase segregation of the PEDOT:PSS polymer material is, for the first time, proposed to be perpendicular to the PR strain sensing direction. The increase in the GF with the increase in the HR number of the PR strain sensors without a marked hysteresis is found. The result can be explained by the tunneling effect with varied initial tunneling distances and tunneling barriers due to the increase in the number of HR. Finally, a high GF value of approximately 165 of three HR paths is obtained with a linear output signal at the strain range from 0% to 0.33%, further achieving for the inkjet printing of highly sensitive, transparent, and flexible linear PR strain sensors.
Highlights
Flexible strain sensors have recently attracted great interest because of their various potential applications, such as for human motion detection [1], personal health monitoring [2], acoustic vibration detection [3], and human-machine interfaces [4]
To improve the sensitivity of the flexible PR strain sensors, a high resistive (HR) path caused by the phase segregation of the PEDOT:PSS polymer material [21,25] was, for the first time, designed to be perpendicular to the strain sensing direction
The simple and low‐cost inkjet printing of graphene‐PEDOT:PSS conductive ink has been proposed for the fabrication of the flexible PR strain sensors
Summary
Flexible strain sensors have recently attracted great interest because of their various potential applications, such as for human motion detection [1], personal health monitoring [2], acoustic vibration detection [3], and human-machine interfaces [4]. The silicon-based sensor fabrication process requires sophisticated equipment operated in a clean room. These disadvantages confine their application and development for arbitrarily curved surfaces. The inkjet printed strain sensors based on a liquid conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) material has been reported and demonstrated to be a lower GF value of approximately 2.48 [11]. Based on the formation of nanoscale cracks, an ultrahigh sensitive (GF ≈ 2000) strain sensor possesses a nonlinearity PR property [17]. A higher sensitivity is quite important for the flexible PR strain sensors, the requirements that simultaneously satisfy a high optical transparency, a lower hysteresis, and a good linearity are still a grand challenge
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