| Hydrogels are materials with high water content,deformability,and good biocompatibility.Among them,conductive hydrogels have good electrical conductivity,flexibility and self-adhesion similar to natural biological tissues.The best candidate material for the fabrication of flexible sensors.In recent years,conductive hydrogels with biocompatibility,mechanical flexibility,and fatigue resistance have been extensively studied.Conductive hydrogels can monitor and transmit various physiological and physical signals,which promotes the development of flexible sensors.Flexible sensors have been widely studied in recent years and are an important component of flexible wearable electronic devices.Flexible sensors have wide application prospects in human health monitoring,bioelectronic interface,robotics,and other fields.Flexible sensors have gradually become the main research direction of human-computer interaction technology and artificial intelligence.In this paper,polydopamine modified carbon nanotubes（PDA@CNTs）were used as conductive fillers to increase the conductivity of conductive hydrogels.The double network structure formed by non-covalent bonds between the conductive hydrogel base materials improves the mechanical properties of the conductive hydrogel.In this work,two conductive hydrogels were prepared by combining PDA@CNTs with different hydrogel base materials.The specific research contents are as follows:（1）Polyvinyl alcohol/poly（acrylic acid-co-acrylamide）/polydopamine modified carbon nanotubes（PVA/P（AA-co-AM）/PDA@CNTs）conductive hydrogels were prepared by radical copolymerization and in situ composite methods.PVA and P（AA-co-AM）are connected by non-covalent bonds to form a double network structure and form an efficient energy dissipation mechanism.The addition of PDA@CNTs conductive fillers to PVA/P（AA-co-AM）hydrogels endows PVA/P（AA-co-AM）hydrogels with good electrical properties.The PVA/P（AA-co-AM）/PDA@CNTs conductive hydrogel exhibits excellent tensile strength（1.21±0.04 MPa）,adjustable strain range（221.28±12.04%）,high mechanical strength(the elasticity modulus is 391.91±38.17 k Pa,the toughness is 1.22±0.36 MJm-3)and good electrical conductivity（conductivity is 3.84 S/m）.The PVA/P（AA-co-AM）/PDA@CNTs conductive hydrogel has high sensitivity（sensitivity factor of 1.6）,wide strain sensing range（10%-120%）,and stable electrochemical performance.The PVA/P（AA-co-AM）/PDA@CNTs conductive hydrogel can monitor the movements of fingers,wrists,arms,and knees.Flexible strain sensors based on PVA/P（AA-co-AM）/PDA@CNTs conductive hydrogels can monitor human motion signals and have broad application prospects in the field of flexible wearable electronic devices.（2）The GW-PAM/SA/PDA@CNTs conductive hydrogel was prepared by using sodium alginate（SA）and polyacrylamide（PAM）as substrate materials,glycerin and water as binary solvents,and PDA@CNTs as conductive filler.The GW-PAM/SA/PDA@CNTs conductive hydrogels exhibit super stretching,self-adhesion,and high sensitivity.The double network structure formed by SA and PAM endows the conductive hydrogel with good mechanical properties.The addition of glycerol not only provides the conductive hydrogel with antifreeze and heat resistance,but also improves the mechanical properties of the conductive hydrogel.The GW-PAM/SA/PDA@CNTs conductive hydrogel has excellent mechanical properties,the elongation at break can reach 1000±29.32%,the tensile strength is 170.9±12.41 k Pa,the elastic modulus is 128.66±20.98 k Pa,and the toughness is 702.27±85.93 k Jm-2.The GW-PAM/SA/PDA@CNTs conductive hydrogel also has high sensitivity and wide sensing range,with a sensitivity factor of 2.53 at 360%strain.In addition to this,the GW-PAM/SA/PDA@CNTs conductive hydrogel also possesses antifreeze and heat resistance properties,tissue adhesion,and long-term stability.When the GW-PAM/SA/PDA@CNTs conductive hydrogel is damaged,it can achieve self-healing without any external stimulus.The flexible strain sensor prepared based on GW-PAM/SA/PDA@CNTs conductive hydrogel can realize the monitoring of human ECG signals.In terms of human motion signal monitoring,in addition to monitoring human finger and neck movements,it can also monitor facial micro-expressions.The GW-PAM/SA/PDA@CNTs conductive hydrogel shows its great application potential in flexible strain sensors and provides a new design scheme for the preparation of multifunctional conductive hydrogels. |
