Flexible conductive Ag-CNTs sponge with corrosion resistance for wet condition sensing and human motion detection

Three-dimensional (3D) polyurethane (PU) sponges featuring high mechanical elasticity, compressibility, and durability have emerged as an ideal substrate for building wearable strain sensors. However, the 3D porous structures easily soak up rain, water vapor, sweat, etc., and the constructed sensor's long-term conductivity may be eroded by droplets and experience irreversible damage, rendering the preparation of a wearable flexible sponge sensor with environmental adaptation challenging. Here, by reducing the Ag particles in the carbon nanotube (CNT) suspension, forming a conductive filler Ag-CNTs, and combining with poly (vinylidene fluoride) (PVDF) solution, surface modification with polydimethylsiloxane (PDMS) solution, the PDMS/Ag-CNT-PVDF/PU sponge sensor with 3D conductive network and superhydrophobic structure was fabricated. The results revealed that this modified sponge had a wide strain detection range of 0-80 %, superior conductive sensitivity up to 4.24 kPa-1 in 0-20 kPa, and a fast and stable response time (170 ms) with great reproducibility over 1200 compression-resilience cycles. Furthermore, good superhydrophobicity endows the sensor with remarkable resistance to mechanical wear and chemical corrosion, which can be effectively used to detect human motion in high air humidity environment. This PDMS/Ag-CNTs-PVDF/PU sponge sensor is expected to be used as a practical, flexible wearable sensor and demonstrates potential application prospects in complex environments.