CMC/SA/CB/CNT/thermally exfoliated-MXene five-component sponge-structured sensing materials and their enhanced sensitivity and stability

High sensitivity and structural stability are key challenges for sensors. This study introduces a one-step integral assembly method to create a carboxymethyl cellulose/sodium alginate/carbon black/carbon nanotubes/thermally-treated MXene five-component sponge-structured piezoresistive composite (CMC/SA/CB/CNT/T-MXene sponge, CSCCM_T sponge). The multi-scale conductive fillers (zero-dimensional CB, one-dimensional CNT, and two-dimensional (2D) T-MXene) not only reinforce and toughene the sponge structure, greatly improving the structural stability, but also, as conductive fillers, increase the contact sites, significantly improving the sensitivity. Introducing CB transforms the pore wall of the porous composite from a relatively dense 2D structure into a three-dimensional (3D) porous structure. Thermal treatment of MXene not only enhances its conductivity but also makes it easier to exfoliate into nanosheets, resulting in a more uniform distribution of T-MXene within the pore walls. The 3D porous structure improves anti-fatigue stability and promotes contact site variation during deformation, boosting cyclic stability and sensitivity. The lightweight composite exhibits excellent conductivity, mechanical strength (146.7 kPa at 75 % strain), and sensing performance, with high sensitivity (GF = 39.8, S = 1,703 kPa⁻¹), fatigue resistance (24,500 cycles), and fast response (100 ms). These properties enable real-time human motion monitoring and show promise for flexible wearable devices.