High toughness and low modulus MXene organogel for wearable strain sensors

Abstract

High strength, high toughness, low hysteresis, and low modulus properties are crucial for conductive hydrogels to enhance their reliability in flexible sensing applications. However, achieving these seemingly conflicting properties simultaneously remains a significant challenge. This paper reports on an ultrasensitive hydrogel sensor constructed through a one-pot polymerization process involving acrylamide (AM) and dimethylaminoethyl methacrylate (DMAEMA), with cellulose nanocrystals (CNC) serving as the reinforcing phase and two-dimensional conductive material MXene as the conductive component. The electrostatic interaction between the tertiary amine group of DMAEMA and the cellulose nanocrystals, coupled with the hydrogen bonding among the surface functional groups of MXene, confers high tensile strength (325 kPa), high tensile strain (3058%), high toughness (4.9 MJ m⁻³), low modulus (50 kPa), and low hysteresis (<12%) to the hydrogel. Furthermore, after a resting period of 10 minutes, the maximum stress of the hydrogel can recover to 98.9%. The incorporation of MXene nanosheets significantly enhances the electrical conductivity of the hydrogel, providing it with short response (150 ms) and recovery times (150 ms). When designed as a wearable sensor, the hydrogel can accurately monitor large strains and subtle movements of the human body. More importantly, this hydrogel sensor can also be employed for information encryption and decryption, simulating Morse code for communication, thereby further expanding its practical applications in intelligent sensors.