Development of highly sensitive/durable porous carbon nanotube–polydimethylsiloxane sponge electrode for wearable human motion monitoring sensor

Herein, we present a novel approach for fabricating porous carbon nanotube–polydimethylsiloxane (CNT–PDMS) sponge electrodes for piezoelectric/piezoresistive sensing. Using a combination of sugar template methods and dip-coating techniques, we synthesize porous CNT–PDMS sponge electrodes via a straightforward manufacturing process. The electrical properties and mechanical strength of the electrodes can be adjusted finely by varying the concentration of the carbon nanotube (CNT) solution and immersing time. Through an analysis of the wetting behavior, compression tests, and electrical durability assessments, the optimal conditions for electrode production are identified. Although no significant changes in the water droplet contact angles are observed based on the CNT coating conditions, the CNT solution concentrations increased and the immersion times prolonged, which are correlated with enhanced mechanical robustness and electrical resilience. Furthermore, the porous CNT–PDMS sponge electrodes exhibit distinct sensitivity to compression displacement owing to variations in their pore structures. Additionally, these electrodes demonstrate consistent and stable piezoelectric/piezoresistive properties across various compression speeds while showing minimal sensitivity to the compression speed. The porous CNT–PDMS sponge electrode fabricated under the 3 wt%-60 min conditions demonstrates significant potential as a highly effective piezoelectric/piezoresistive sensor for human motion detection.