Preparation Of Carbon-based Composite Conductive Hydrogels And Their Application In Flexible Sensors

Wearable flexible sensor is one of the flexible electronic devices with wide application prospects in human life.However,most sensors are can not be used to detect the multi-scale movement of human body and are vulnerable to damage.In addition,the insensitivity of signal output also limits the development of flexible sensors.To solve the above problems,we prepared a series of composite conductive hydrogels based on two-dimensional carbon materials such as graphene and Mxene,and studied their applications in flexible sensors.1.A dithioester chain transfer agent(CTA)was designed and prepared,and used in reversible addition-fragmentation chain transfer(RAFT)polymerization to obtain two pyrene-functional block copolymers with narrow molecular weight distribution:poly(3-acryloxymethylphenylboronicacid-N,N-dimethylacrylamide),and poly(2-(2,3,4,5,6-pentahydroxyhexaamino)ethyl acrylate-N,N-dimethylacrylamide).They were combined with reduced graphene oxide(r-GO)through?-?coupling and hydrogen bonding.The density functional theory(DFT)was used to optimize the polymer structure and calculate the theoretical distance between planes.The results showed that the distance between the pyrene and the vertical plane of r-GO was about3.46?,which was in line with the distance between planes for?-?coupling.Hydrogels are formed by dynamic borate bonds and hydrogen bonds.The results showed that the hydrogel had controllable structure,good adhesion,self-healing and shape remodeling properties.As a writing sensor,it can recognize and respond to complex writing information of Chinese characters,and has potential applications in piezoresistive sensors.2.A conductive hydrogel composed of poly(N-methylolacrylamide-co-acrylic acid)and MXene was prepared.The hydrogel had super high tensile property(maximum uniaxial tensile strain 1810%),rapid resilience,good electrical conductivity(electrical conductivity 5.41 S/m)and sensitive pressure sensing(sensitivity 39.34).The thixotropic pressure sensor assembled by the hydrogel can realize the sensing of two-way stress,such as the multi-scale human movement and the local micro-pressure change during writing.The results showed that the hydrogel can quickly record pressure signals and output electrical signals,with the fastest response time of 380 ms.It had broad application prospects in human motion monitoring and written information encryption.3.A conductive hydrogel composed of poly(acrylamidohexanoic acid-co-hydroxyethyl acrylate)and MXene was prepared.The hydrogel had good mechanical properties,and its maximum elongation at break was 1661%.Fast self-repair performance was observed,and the rheological test results showed that it can complete an autonomous repair in 6.9 s.In addition,the hydrogel can provide real-time signal feedback on the strength,speed and time interval of continuous finger tapping,and had pressure sensing capabilities after self-repair.Furthermore,the hydrogel had good water retention and retained half of the moisture when placed in an environment of 25 ~oC for 60 days,which may increase its service life when used in sensors.The hydrogel exhibited a potential application in pressure sensors for special populations.