A High-Performance Flexible Piezoresistive Sensor Based on a Nanocellulose/Carbon-Nanotube/Polyvinyl-Alcohol Composite With a Wrinkled Microstructure

Flexible pressure sensors have received extensive attention from researchers due to their wide applications in wearable electronics. Fabricating microstructures is the key to improving the sensing performance of flexible sensors, and the morphology and conductivity of the microstructure has a critical influence on the sensing performance of flexible sensors. In this study, conductive composite films using cellulose nanofiber, carbon nanotubes, and Poly(vinyl alcohol), were fabricated using a pre-stretching method to produce a low-cost, adjustable microstructure morphology of a flexible pressure sensor. The relationship between the morphology and conductivity of the microstructure with the sensing performance of the sensor was revealed. A sensor with the best overall performance was fabricated by regulating the above factors. The sensor exhibits good sensitivity in both the low-pressure range and the medium to high-pressure ranges (S $=$ 67.59 kPa $^{\mathbf {-1}}$ over $0-2$ kPa and S $=$ 5.05 kPa $^{\mathbf {-1}}$ over $2-20$ kPa), a very low lower detection limit (approximately 6 Pa). In addition, the addition of CNF and PVA gives the conductive microstructure good flexibility, thus resulting in the sensor excellent cycling properties. Finally, the sensor has been shown to detect wrist pulses and limb movements, indicating its potential application in human physiological signal monitoring