Preparation Of Dual-network MXene Hydrogel And Its Multifunctionalization

As a highly regarded type of flexible material,hydrogels possess a unique structure that allows them to hold a large amount of water without being destroyed.Particularly in biological applications,they are inherently soft,highly flexible,stretchable,and possess self-healing properties.However,hydrogels themselves are not conductive.One effective means of enhancing their conductivity is by adding conductive fillers such as carbon nanotubes and graphene.However,these fillers are difficult to disperse and have poor stability in aqueous solutions.In contrast,MXene nanosheets are two-dimensional materials that possess excellent conductivity and hydrophilicity.When combined with hydrogels,they exhibit adaptability and affinity similar to that of biological tissues and organisms,providing hydrogels with conductivity and biocompatibility.Against this background,we have designed a chemically and physically dual-networked conductive hydrogel that combines excellent mechanical strength,efficient electromagnetic and UV shielding effectiveness,and a multifunctional hydrogel-based flexible strain sensor with a wide detection range,superior stretchability,excellent electromagnetic and UV resistance,as well as anti-freeze and moisturizing properties.The specific details are as follows:1、In order to address the issue of the incompatibility between hydrogel’s excellent mechanical strength and efficient electromagnetic and UV shielding effectiveness.In this work,PAAm-PHEMA/PAA-Fe³⁺-MXene hydrogels with double shielding mechanism were prepared by using acrylamide（AAm）copolymer hydroxyethyl methacrylate（HEMA）chemical cross-linking as the first network,and polyacrylic acid（PAA）-Fe³⁺metal ion complexation as the second network,and two dimensional MXene as conductive nanofillers.The presence of MXene and Fe³⁺made the hydrogel possess both electromagnetic and UV shielding properties.The as-prepared double-network hydrogel exhibited high mechanical strength（320.1 k Pa）,high stretchability（1786%）,and good electrical conductivity（3.8 S/m）.In addition,the composite hydrogel also showed excellent UV shielding ability,with transmittances of 0%and 79.2%at characteristic wavelengths of 365 and 550 nm,respectively.At the same time,the composite hydrogel can obtain excellent electromagnetic-interference（EMI）shielding effect of more than 36 d B in the X-band,strong adhesion to various substrates,rapid self-healing performance and high shape adaptability.This work provides a flexible and highly tunable dual-shielding mechanism hydrogel network design and large-scale facile fabrication of new ideas,showing great application prospects in flexible wearable materials.2、Based on the above principles of high stretch deformation and high conductivity hydrogels,a hydrogel-based strain sensor with high measurement coefficient,wide detection range,and multifunctional integration was designed and prepared by further improving the biocompatibility,environmental stability,and overall performance of the hydrogel.In particular,a PAAm-PHEMAA/CMC-Fe³⁺-MXene hydrogel was produced by physically cross-linking carboxymethyl cellulose（CMC）-Fe³⁺as the second network and chemically cross-linking acrylamide（AAm）copolymerized with N-hydroxyethylacrylamide（HEMAA）as the first network.Two-dimensional MXene served as the conductive nanofiller.The hydrogel had good biocompatibility,facile regulation of network composition,and efficient double shielding mechanism with a tensile strength of 347.4 k Pa,a fracture strain of2875%,and a conductivity of 3.6 S/m.Finally,glycerol was added to give the hydrogel anti-freezing and moisturizing properties,improving its stability at room temperature and low temperature,and based on this,a hydrogel-based strain sensor was prepared.The design of dual-network with multiple hydrogen bonds and coordination interactions gave the hydrogel-based human motion sensor rapid rebound and high tensile properties,demonstrating high sensitivity（response time～120 ms,gauge factor～1.62）and a wide detection range（0-700%）,including joint movements and more subtle human movements（facial micro-expression changes and language）.Moreover,due to the synergistic effect of porous structure,moderate conductivity,and ion solution environment,the hydrogel-based strain sensor showed excellent EMI（41 d B,X-band）and UV shielding properties（365 nm,100%,0.5 mm）.In addition,the addition of glycerol made the hydrogel resistant to-30°C without freezing,and it still maintained its tensile properties after being stored at25°C for 7 days.The hydrogel also exhibited strong adhesion（29 k Pa）,high shape adaptability,and self-healing ability.This innovative multifunctional flexible sensor design provides guidance for the development of high-performance and multifunctional wearable materials.