Ultralow-Cost, Highly Sensitive, and Flexible Pressure Sensors Based on Carbon Black and Airlaid Paper for Wearable Electronics

Flexible pressure sensors have attracted considerable attention because of their potential applications in healthcare monitoring and human-machine interactions. However, the complicated fabrication process and the cos of sensing materials limit their widespread applications in practice. Herein, a flexible pressure sensor with outstanding performances is presented through an extremely simple and cost-efficient fabrication process. The sensing materials of the sensor are based on low-cost carbon black (CB)@airlaid paper (AP) composites, which are just prepared by drop-casting CB solutions onto APs. Through simply stacking multiple CB@APs with an irregular surface and a fiber-network structure, the obtained pressure sensor demonstrates an ultrahigh sensitivity of 51.23 kPa-1 and an ultralow detection limit of 1 Pa. Additionally, the sensor exhibits fast response time, wide working range, good stability, as well as excellent flexibility and biocompatibility. All the comprehensive and superior performances endow the sensor with abilities to precisely detect weak air flow, wrist pulse, phonation, and wrist bending in real time. In addition, an array electronic skin integrated with multiple CB@AP sensors has been designed to identify spatial pressure distribution and pressure magnitude. Through a biomimetic structure inspired by blooming flowers, a sensor with the open-petal structure has been designed to recognize the wind direction. Therefore, our study, which demonstrates a flexible pressure sensor with low cost, simple preparation, and superior performances, will open up for the exploration of cost-efficient pressure sensors in wearable devices.