P(VDF-TrFE)/carbon black composite thin film based flexible piezoresistive pressure sensor with high sensitivity for low-pressure detection

Abstract

• The P(VDF-TrFE)/carbon black (CB) composite film, fabricated via spin coating, demonstrates a highly sensitive, flexible, and tunable piezoresistive sensor. • The incorporation of 0.75 wt% CB enhances the sensor’s properties, achieving an average sensitivity of 5.63 kPa −1 , a maximum sensitivity of 314 kPa −1 , and a remarkable gauge factor (GF) of 4.5 × 101⁰. • The sensor exhibits a rapid response time of 20 ms, detecting pressure changes as small as 0.5 Pa. • A proposed model explains the ultra-high sensitivity by considering factors such as surface contact area, tunneling barrier thickness, and electrostatic charge redistribution in the CB/P(VDF-TrFE) composite. • The sensor’s high sensitivity and flexibility make it ideal for real-time monitoring of human physiological movements, including finger pressing, bending, and walking. Flexible piezoresistive sensors have attracted considerable attention in wearable devices, e-textiles, and robotic intelligent applications for their simple structure, biocompatibility, and real-time health monitoring. However, high-performance piezoresistive pressure sensors with tunable characteristics and a simple fabrication process are essential to support these diverse applications. Here, we propose an ultrathin Poly(vinylidene fluoride-co-trifluoro ethylene) (P(VDF-TrFE))/carbon black (CB) composite film (∼4 µm thick) based, highly sensitive, flexible, and tunable piezoresistive sensor, realized through percolation of CB NPs in a piezoelectric P(VDF-TrFE) material. At 0.75 wt% CB, the sensor achieves a high average sensitivity of 5.63 kPa −1 , over a 0−250 Pa range, with a maximum sensitivity of 314 kPa −1 at 0.5 Pa. The pressure sensor has a fast response time of 20 ms and detects a low-pressure change as low as 0.5 Pa, where a maximum gauge factor(GF) of 4.5 × 10 10 was estimated. A physical model, considering changes in surface contact area, tunneling barrier thickness, and electrostatic charge redistribution in the CB/piezoelectric matrix, has been proposed to explain the ultra-high sensitivity observed. The sensor was successfully used for real-time monitoring of human physiological movements, such as finger pressing, finger bending, and wrist bending.