Preparation Of Tough,Self-Healing Conductive Double-Network Hydrogel And Its Application In Flexible Sensors

Conductive hydrogels combine the flexibility of traditional gels with the electrochemical properties of conductive fillers（conductive polymers,carbon-based materials,conductive ions）,and have broad applications in wearable flexible sensors,artificial electronic skin,and human-computer interaction in recent years.However,the currently reported conductive hydrogels often suffer from poor mechanical properties and lack of self-healing properties,which severely limit the practical application.Therefore,this thesis focuses on the preparation of high strength and toughness,self-healing conductive double network hydrogel,and explores its application in flexible sensors,carrying out the following research work.Specifically,the research content of this thesis includes the following two aspects.（1）Preparation of tough,self-adhesive Li⁺/agar/p HEAA conductive double-network hydrogel and its application in flexible strain sensor.In this chapter,Novel Li⁺ions doped agar/（N-poly（hydroxyethyl）acrylamide）（p HEAA）conductive double-network hydrogels（Li⁺/agar/p HEAA DN hydrogels）were synthesized and assembled as strain sensors for human motion monitoring.The incorporation of Li⁺not only endowed the hydrogel with high electrical conductivity,but also enhanced the interaction between the agar and the p HEAA network,thereby enhancing its mechanical proprerties.At proper content of Li⁺（0.8 wt%）,transparent Li⁺/agar/p HEAA DN hydrogels with excellent mechanical perfomances（fracture stress of 1.18 MPa and fracture strain of 860%）,good self-recovery and self-repairing properties were obtained.Ascribe to the plenty of amide and hydroxyl functional groups in p HEAA networks,the as-prepared hydrogels displayed strong self-adhesiveness on various nonporous solid surfaces（e.g.,aluminum,glass,titanium,and stainless steel）with high interfacial toughness of 920-1130J/m² due to the multiple hydrogen bonding between the hydrogels and substrates.Based on Li⁺/agar/p HEAA DN hydrogels with excellent toughness,surface adhesiveness,and electrical conductivity,they can be assembled into strain sensors for monitoring human joint motion and tiny vocal cord vibrations.The Li⁺/agar/p HEAA DN hydrogel strain sensor has broad application prospects in healthcare management,disease diagnosis,and artificial electronic skin.（2）Preparation of high-strength and fast self-healing conductive hydrogel and its application in flexible strain sensorIn this chapter,by incorporating Sb₂S₃@PPy-DA nanocomposites with photothermal conversion properties into PVA/p HEAA dual-network hydrogels,a near-infrared photoinduced fast self-healing conductive hydrogel strain sensor was constructed for human health monitoring.Firstly,Sb₂S₃ nanomaterials were synthesized by using the hydrothermal method.In order to enhance the electrical conductivity,the Sb₂S₃nanomaterials were coated with polypyrrole（PPy）and modified with dopamine（DA）to obtain Sb₂S₃@PPy-DA nanocomposites.The synthesized Sb₂S₃@PPy-DA was introduced into the boric acid-crosslinked polyvinyl alcohol as the crosslinker and conductive filler as the first network,the physically crosslinked poly（N-hydroxyacrylamide）as the second network,and the glycerol-water mixed solvent as dispersion medium to construct near-infrared photoinduced fast self-healing conductive hydrogels（SPOH）.Under optimized conditions,SPOH exhibited excellent mechanical properties（fracture stress 1.25 MPa,fracture strain 620%）,and the introduction of Sb₂S₃@PPy-DA not only endowed high conductivity of the hydrogels,but also enabled the hydrogel with the photothermal conversion effect.Meanwhile,the SPOH displayed excellent anti-freezing properties（no freezing at-20°C）,self-adhesive（interfacial toughness up to 257.8 N/m on glass）,and excellent strain response gauge factor（GF=4.97）,which are applied in strain sensors and biopotential electrodes for precise monitoring of human physiological signals.In addition,a self-powered sensor capable of efficiently harvesting energy was obtained by composing a sandwich-like device between the hydrogel and two layers of viscous Ecoflex silicone rubber,with short-circuit current of 6.4μA,the open-circuit voltage of 282.2 V,and short-circuit transfer charge of 110 n C.These outstanding advantages highlight the great potential of the SPOH in wearable flexible strain sensors,bioelectrodes,and health care management.