Preparation And Sensing Properties Of Gelatin-based Conductive Network Hydrogels

Due to its excellent flexibility and excellent conductivity,conductive hydrogels have been widely used in flexible electronic fields such as intelligent wearable devices,human motion detection,human-machine interface and electronic skin.Among them,gelatine-based conductive hydrogels have excellent flexibility and biocompatibility,and are considered as one of the ideal materials for flexible electronic devices in the future.However,gelatine-based conductive hydrogels have weak mechanical strength and poor electrical conductivity,which greatly limits their application as flexible strain sensor substrates.In addition,the preparation process of most gelatin-based conducting hydrogels is complex,the reaction system is pH limited,and requires the use of toxic chemical crosslinkers.Therefore,it is of great significance to develop gelatine-based conductive hydrogels with high strength,good stretchability,strong conductivity,anti-freezing,moisturizing and self-healing ability by using simple process,low cost and green preparation method,which is of great significance to improve the wide application of gelatine-based conductive hydrogels in flexible sensors.In this paper,the purpose of constructing high strength and stretchable gelatin based conductive hydrogels is to prepare gelatin based conductive hydrogels with biocompatibility and good mechanical and conductive properties.Broaden its potential application value in wearable flexible sensor,intelligent robot,artificial electronic skin and so on.(1)Based on the tensile properties,electrical conductivity and anti-freezing and moisturizing properties,gelatin(Gel)content,graphene(GR)content and binary(water/glycerin)solvent ratio was optimized by single factor.The results showed that the optimal ratio of the components of the graphene/gelatin(GR/Gel)conducting hydrogel was 10%Gel,0.8%GR,V(water):V(glycerol)=82:18,the GR/Gel conductive hydrogel was prepared with tensile strength of 114.63 KPa,elongation of 157.85%,conductivity of 6.68×10-3 S/m,anti-freezing,moisturizing and adhesion.(2)The effects of the content of microfiber cellulose(MFC)on the tensile properties,swelling properties,electrical conductivity and adhesion properties of graphene/microfiber cellulose/gelatin(GR/MFC/Gel)conducting hydrogel and the interaction mechanism between MFC and Gel were investigated.The results of FTIR showed that the addition of MFC did not destroy the characteristic structure of Gel,and the physical cross-linking network structure of MFC and Gel was formed through strong hydrogen bonding.SEM also confirmed the existence of hydrogel network structure.The tensile test results showed that when the content of MFC was 4.5%,the tensile strength was 329.61 KPa,which was 3.03 times of that without MFC.The elongation is 203.75%,1.35 times of that without MFC.The swelling test showed that when the content of MFC was 6%,the swelling rate of GR/MFC/Gel conductive hydrogel was reduced to 431%,and the complete shape of GR/MFC/Gel could be maintained after soaking in binary solvent for 150 h.The conductivity test results showed that the addition of MFC could improve the conductivity of GR/MFC/Gel hydrogel.When the content of MFC was 6%,the conductivity of GR/MFC/Gel hydrogel was 7.25×10-3 S/m.GR/MFC/Gel conductive hydrogel has good anti-freezing,moisturizing and self-healing properties.(3)The sensor performance test results show that the GR/MFC/Gel conductive hydrogel sensor has excellent sensitivity(GF=2.77),rapid response(response time is 0.2s,recovery time is 0.3s)and excellent cyclic stability.It can be used as a smart wearable material for real-time monitoring of human activities such as finger,elbow and wrist bending,as well as tiny facial expressions such as smiling,opening mouth,frowning and blinking.In addition,it can be used as an electronic pen to recognize complex handwriting and convert mechanical signals of the human body into real-time electrical signals.GR/MFC/Gel conducting hydrogels have broad prospects in applications such as smart wearable electronics,personalized health monitoring and human-machine interfaces.Meanwhile,the GR/MFC/Gel hydrogel sensor can adapt to low temperature environment and maintain good sensing performance in the cold environment of minus 20℃.