A flexible and highly sensitive capacitive pressure sensor based on conductive fibers with a microporous dielectric for wearable electronics

Abstract

In this study, a flexible and highly sensitive capacitive pressure sensor has been fabricated by coating a microporous polydimethylsiloxane (PDMS) elastomeric dielectric onto conductive fibers. Conductive fibers were prepared by depositing silver nanoparticles (AgNPs) in poly(styrene-block-butadiene-styrene) (SBS) polymer on the surface of Twaron fibers. The configuration obtained by cross-stacking of two microporous PDMS-coated fibers imitates a capacitive sensor, which responds to compressive stress by increasing the contact area and decreasing the separation between the fiber electrodes. Moreover, the gradual closure of micropores under pressure increases the effective permittivity of the dielectric, thereby enhancing the sensitivity of the sensor. A relatively high sensitivity of 0.278 kPa⁻¹ for a low pressure region (<2 kPa), negligible hysteresis of 6.3%, a dynamic response time in the millisecond range (∼340 ms), a low detection limit of 38.82 Pa and an excellent repeatability of over 10 000 cycles were achieved. Finally, the practicality of the sensor was also demonstrated by loading small objects (∼9.4 mg) and gentle finger touches (<10 kPa). By virtue of its excellent sensitivity, low pressure detection and cost-effective fabrication process, our sensor is applicable for next-generation advanced touch panels with a more human-friendly interface, non-invasive health monitoring systems, and artificial robot arms.