Highly Strong And Tough Conductive Hydrogels And Their Performances In Flexible Electronic Devices

As the key component of wearable devices,flexible electronic materials have received extensive attention from researchers in recent years and become the focus of functional materials.Due to their unique properties such as softness,elasticity,conductivity,and biocompatibility,conductive hydrogels have been widely studied and applied in flexible electronic devices,especially in bioelectronic devices.However,the limited mechanical performance and anti-freezing ability of hydrogel materials have restricted their applications in flexible electronic devices.Highly strong and tough conductive hydrogels were constructed by controlling the chemical structure,crosslinking points,medium and combining electrospinning technology.The method of preparation and performance control of highly strong and tough conductive hydrogels has been established.The performances of the hydrogels in flexible mechanical sensors and flexible zinc-ion hybrid supercapacitors were investigated,providing a theoretical and technical basis for the research of new gel-based flexible electronic devices.The main results include:（1）Amylopectin（Amy）was introduced into the polyacrylamide（PAM）network crosslinked by poly（ethylene glycol）diacrylate（PEGDA）to construct a PAM/Amy semi-interpenetrating network hydrogel.ZnCl₂ was introduced to prepare PAM/Amy/Zn²⁺hydrogels as conductive components,and their performances in flexible sensors and zinc-ion hybrid supercapacitors were studied.The introduction of Amy improved the mechanical performance,adhesion on various substrates（resin,metal,glass）,and anti-freezing properties of the hydrogels.The flexible strain sensor based on such hydrogel exhibited a sensitivity of up to 1.08,a sensing range of 0-320%,and a response time of 0.12 s.It was further combined with Bluetooth wireless transmission system to realize human motion monitoring.In addition,the hydrogel could be used as an electrolyte for zinc-ion hybrid supercapacitors,achieving excellent cycling stability（>30000cycles）,a specific capacity of 88.3 mAh·g^-1 at a current density of 0.5 A·g^-1,and good flexibility.（2）Poly（acrylic acid）-poly（vinyl alcohol）（PAA-PVA）fibrous mats were prepared using electrospinning technology,and polyaniline（PANI）was introduced via an in-situ polymerization to prepare high-strength conductive organohydrogels with a fibrous structure.The performances of the organohydrogels in flexible sensors were investigated.The effect of PAA content on the fiber structure and mechanical properties of the PAA-PVA organohydrogel was systematically studied.As the PAA content increased,the diameter and breaking strength of the PAA-PVA organohydrogel fibers increased.Further in-situ polymerization introduced polyaniline（PANI）,and the prepared PAA-PVA/PANI fibrous organohydrogel achieved a tensile strength of up to5.06 MPa and a fracture elongation of up to 100%.The strain sensor constructed with the PAA-PVA/PANI organohydrogel exhibited a sensitivity of 1.81,a sensing range of 70%,a low response time of 0.28 s,and high stability（>2500 cycles）.The strain sensor is suitable for various human motion monitoring.（3）Polyacrylamide（PAM）hydrogel networks were introduced into poly（acrylic acid）-poly（vinyl alcohol）（PAA-PVA）fibrous mats by an in-situ polymerization,and multi-scale ionic organohydrogels with a fibrous structure were prepared by immersing into a glycerol-water mixed solution of ZnSO₄.The performance of the hydrogels in flexible electronic devices were investigated.The influence of AM concentration on the mechanical properties of PAA-PVA/PAM/Zn²⁺organohydrogels was systematically studied.Due to their unique structure,PAA-PVA/PAM/Zn²⁺organohydrogels achieved a tensile strength of up to 9.45 MPa,a fracture elongation of 220%,a fracture toughness of 8 MJ·m^-3,and a conductivity of 1.89 mS·cm^-1.The strain sensor constructed with this organohydrogel had a sensitivity（GF）of 0.68,a sensing range of 0-160%,a response time of 0.18 s,and a stable response up to 1000 times.Self-powered battery sensors assembled with PAA-PVA/PAM/Zn²⁺organic hydrogel as electrolyte also achieved high sensitivity（GF=1.12）,low response time（0.28 s）,and high sensing stability（1200 cycles）.In addition,by using PAA-PVA/PAM/Zn²⁺organohydrogels as the electrolyte for zinc-ion hybrid supercapacitors,excellent cycling stability（>8500 cycles）was achieved.The specific capacity reached 40 mAh·g^-1 at a current density of 2 A·g^-1,and the ability to work properly under various temperature and mechanical conditions was also realized.