An in situ polymerized polypyrrole/halloysite nanotube–silver nanoflower based flexible wearable pressure sensor with a large measurement range and high sensitivity

Abstract

Flexible wearable sensors have attracted a lot of attention because of their great potential for application in wearable medical health detection, human activity detection, and artificial electronic skin. However, achieving both high sensitivity and a large measurement range on a single sensor remains a serious challenge. Here, we prepared piezoresistive sensors by dip-coating polypyrrole-coated halloysite nanotube (PPy/HNT)–silver nanoflower (AgNF) composite conductive materials on polyurethane sponges. The fabrication process is simple and reproducible on a large scale. The assembled sensor has a large sensing range (0–400 kPa), high sensitivity (3.97 kPa⁻¹), ultra-fast response/recovery time (40 ms/50 ms), and reliable repeatability (12 000 s of cyclic testing). In addition, halloysite nanotubes greatly increase the measurement range of the piezoresistive sensor. The synergy of the crack sensing mechanism and the contact sensing mechanism allows the sensor to maintain high sensitivity over a large strain range while also detecting different levels of human motion. What's more, it has shown outstanding performance in acting as an artificial electronic skin to quantify the magnitude of external pressure distribution and in wireless motion detection in real time. It has potential application in the next generation of artificial electronic skin, medical health detection, and real-time detection of motion signals.