Flexible Sensors with a Sandwich Stack Structure of Few-Layer Ti3C2Fx/Polypyrrole Nanowires for Human Motion Detection and Healthcare Monitoring

Flexible wearable sensors with high sensitivity, broad sensing range, and low detection accuracy have great potential applications in human motion online monitoring, human healthcare detection, and human–machine interface. However, high sensitivity and broad sensing range conflict, as the former requires conspicuous structural changes under microstrain while the latter requires complete morphology under large deformation. Herein, we report few-layer 2D Ti3C2Fx and 1D polypyrrole (PPy) nanowires with a sandwich stack structure transfer on polyacrylic acid (PAA) tape based on layer-by-layer (LBL) assemble technology. The 1D PPy nanowires enhance the strain sensor’s interfacial adhesion and electron transmission channel, resulting in high sensitivity and a permissible detection range (0–50%). Under various applied force stimuli, the synergetic effect of Ti3C2Fx nanosheets (4.72 nm thickness) and PPy nanowires (diameter 20–50 nm) endows the stack structure with good electrical–mechanical performance, which is reflected by the sensor’s high sensitivity (GF = 2950, ε = 50%; GF = 475, ε = 10%; GF = 22, ε = 0.1%). Such a flexible sensor with a permissible detection range (up to 50%), a low detection limit (0.1%), and reliable repeatability (>1500 cycles) has potential applications for human motion detection, clinical diagnosis, and healthcare monitoring.