Mechanical and sensing properties of three-dimensional, high-strength superflexible CMC/SA/MXene/CNT aerogels

Abstract

Developing pressure sensors that combine high sensitivity, a wide response range, and a stable signal output is a great challenge. Due to the insufficiently robust structure of the sensor's skeleton, the sensor's skeleton will not only cause irreversible damage under repetitive pressure but will also produce uncontrollable deformation in the contact area between the skeletons, thus affecting the sensor's detection range, sensitivity, and the stability of the signal output. In this study, carboxymethyl cellulose/sodium alginate/MXene/carbon nanotube (CMC/SA/MXene/CNT) aerogels are prepared by directional freezing–freeze drying. The aerogel has a three-dimensional isotropic porous structure with two-dimensional faces as the supporting skeleton in the X, Y, and Z dimensions. Moreover, conductive CNTs and MXene are embedded in the skeleton to form a leaf-vein structure, which enhances the strength and toughness of the skeleton. The aerogel has a light weight, high conductivity, excellent mechanical properties (compressive strength of up to 148.78 kPa at 80% strain), and exceptional compression resilience. Assembling it into a piezoresistive sensor, it is characterized by its high sensitivity (GF = 7.6, S = 894.8 kPa⁻¹), excellent fatigue resistance (retaining stability after at least 10 000 uninterrupted cycles), and rapid response time (0.16 s). The sensor is used for real-time monitoring of human movement and physiological activities and as a signal transmission device, indicating its broad application prospects in the field of flexible smart wearables and signal transmission devices.