Lightweight, flexible and highly sensitive segregated microcellular nanocomposite piezoresistive sensors for human motion detection

Lightweight, flexible and highly sensitive piezoresistive sensors are promising for future generations of wearable electronics, artificial intelligence, human-computer interaction and soft robotics. Herein, segregated microcellular nanocomposites based on the microcellular poly(ether-block-amide) beads coated with silver (microcellular Pebax@Ag beads) are fabricated by the scalable and feasible supercritical CO₂ foaming combined with dip-coating and curing approach. The segregated microcellular nanocomposites show low mass density (0.6 g/cm³), good flexibility (60% compressibility) and high electrical conductivity (0.64 S/m) with ultralow percolation threshold (0.28 vol%) benefiting from the simultaneous incorporation of segregated structures and microcellular structures. The resultant segregated microcellular nanocomposite piezoresistive sensors exhibit superior piezoresistive performances including improved relative resistance changes and higher sensitivity upon the externally applied compression strains owing to the synergistic effect of multiple mechanisms: higher local effective MWCNT contents due to the excluded-volume effect, construction of more effective 3D MWCNT/Ag conductive networks and rapid response due to the highly-resilient microcellular Pebax beads. Furthermore, the segregated microcellular nanocomposite piezoresistive sensors show outstanding long-term durability and working stability upon the repeated compression strains. Practical applications of the segregated microcellular nanocomposite piezoresistive sensors in functional sole materials have been verified for human motion detection during walking, implying their outstanding potential for burgeoning applications such as wearable electronics, artificial intelligence, human-computer interaction and soft robotics.