Preparation Of Conductive Hydrogels By Biomolecular Template Methods And Study Of Their Strain Sensing Properties

Conductive hydrogels have great application prospects in the field of flexible wearables due to their flexibility,high stretchability,conductivity and biocompatibility.They are ideal candidates for the development of flexible strain sensor.Conductive hydrogels are usually prepared by adding conductive materials into the hydrogel network.But conductive nanomaterials are easy to agitate and difficult to disperse in hydrogels,which severely limit the improvement of mechanical properties,electrical conductivity and strain sensing properties of conductive hydrogels.Therefore,how to achieve uniform distribution of conductive materials in conductive hydrogel matrix,construct reasonable three-dimensional conductive network,and prepare conductive hydrogels with high strength,high conductivity and high strain sensing functions has become an urgent problem to be solved at present.In this paper,the high-performance conductive hydrogels were prepared based on the biopolymer template.The molecular structure of biopolymers has a good affinity for conductive polymers,which can be used as a molecular template to improve the dispersion of conductive polymers,form a three-dimensional conductive network with uniform distribution of conductive polymers,and realize the high strength,high conductivity and strain sensing ability of conductive hydrogels Two kinds of composite conductive hydrogels were successfully prepared based on polyacrylamide-（sodium alginate）（PAAM-SA）hydrogel.In the preparation process,poly-（3,4-ethylenedioxythiophene）-poly（styrene sulfonate）（PEDOT:PSS）and polypyrrole（PPy）doped in hydrogels with sodium alginate as molecular template.The flexible strain sensors were developed based on the conductive hydrogels.The strain sensing performances of the conductive hydrogels were studied systematically,and the applications of the conductive hydrogel strain sensors in human activity monitoring were explored the specific contents are as follows:（1）Polyacrylamide-（sodium alginate）-poly（3,4-ethylenedioxythiophene）（PAAM-SA-PEDOT）conductive double-network hydrogel was prepared by one pot method.SA was used as molecular template to disperse PEDOT,and the SA-PEDOT three-dimensional conductive network was constructed.The mechanical properties,electrical conductivity and adhesion properties of PAAM-SA-PEDOT conductive hydrogels were studied,and the effects of the composition of hydrogels on their mechanical properties and electrical conductivity were systematically studied.PAAM-SA-PEDOT_0.3 hydrogel with excellent mechanical properties,good electrical conductivity and self-adhesion was prepared.The tensile strength of PAAM-SA-PEDOT_0.3 hydrogel was 316 k Pa,the elongation at break was 1410%and the conductivity was 1.17 S·m^-1.The flexible strain sensors were assembled based on PAAM-SA-PEDOT_0.3 conductive hydrogel.It was found that the sensor has a wide detection range of 0-800%and the gauge factor of 5.97in the strain range of 400%-800%.With a response time of 111 ms and good sensing stability,the hydrogel-based sensor could be applied directly to the human skin to monitor human joint movement,swallowing and speaking behaviors.（2）Polyacrylamide-（sodium alginate）-polypyrrole（PAAM-SA-PPy）conductive double-network hydrogels were prepared by in-situ polymerization of PPy using SA as molecular template in PAAM-SA hydrogel.The effects of hydrogel composition on mechanical properties,electrical conductivity,swelling resistance and self-healing properties were also studied.The PAAM-SA-PPy hydrogel has excellent mechanical properties,high electrical conductivity,fatigue resistance,self-healing and biocompatibility.The tensile strength of PAAM-SA_1.5%-PPy_2%hydrogel could reach 560k Pa,elongation at break was 870%,and electrical conductivity was 6.44 S·m^-1.The strain sensors were prepared based on PAAM-SA_1.5%-PPy_2%conductive double-network hydrogel.The sensor has a wide sensing range of 0-800%strain,the gauge factor of sensor is 1.89 for 0-400%strain and 4.53 for 400-800%strain,respectively.With a response time of 103 ms and excellent sensing stability,the hydrogel-based sensor could realize the real-time monitoring of human joint movement,swallowing and speaking.In this paper,PAAM-SA-PEDOT and PAAM-SA-PPy conductive hydrogels were preparation with SA as biopolymer molecular template.Based on the unique structure and excellent performance of conductive hydrogels,the high-performance flexible strain sensors were prepared,and they have broad application prospects in the fields of human motion monitoring,health monitoring,electronic skin,human-computer interaction and soft robot,etc.It provides a reference for the development of flexible strain sensors with high flexibility,high conductivity and high stability.