Preparation Of PVA-based Conductive Composite Hydrogels And Their Applications In Flexible Sensors

Based on the excellent mechanical flexibility,biocompatibility and skin-matching adaptation of hydrogels,conductive hydrogels can realize the acquisition and transmission of human physiological signals,and have a very broad application potential in the field of flexible wearable sensors.However,the deficiencies in the conductivity and mechanical properties of hydrogels have been the key to their sensor applications,and thus this study focuses on the enhancement of conductivity and mechanical properties as well as the development of sensor applications for in-depth study.The ionic conductive hydrogel was prepared by using polyvinyl alcohol and gelatin as the main backbone of the composite hydrogel.By adding Li Cl,the conductivity could reach2.67 S m^-1.The composite hydrogel had good mechanical flexibility and the tensile deformation up to 200%.The composite hydrogel was encapsulated as a flexible sensor for application testing.In the test,the sensor performed well with sensitive signal transmission（response time of 370ms,recovery time of 260 ms）,stable acquisition,and accurate and timely transmission of both large and small amplitude mechanical signals.In order to improve the mechanical properties of the hydrogel and sensor response speed,an electronically conductive hydrogel was constructed with reduced graphene oxide as the conductive medium,polydopamine and polyvinyl alcohol composite preparation.The composite hydrogel has excellent sensing sensitivity（GF of 2.78）,response time of 370ms,recovery time of 260 ms,conductivity up to 2.2 S m^-1 and tensile deformation of 220%.In application tests,the sensor has stable signal acquisition and accurate and timely transmission of small movements and even weak signals such as vocal cord vocalization.Polyvinyl alcohol and polyacrylic acid form a three-dimensional structured hydrogel with a semi-interpenetrating structure under the action of a cross-linking agent,and ionic hydrogels are prepared by immersion in Li Cl solution.On the basis of maintaining the good electrical conductivity of the hydrogel,molybdenum disulfide with photosensitive properties is added.Molybdenum disulfide can absorb photons under light and generates photoelectrons,which give the hydrogel a response to infrared laser signals.The hydrogel has superior mechanical properties（tensile deformation up to 600%）,high conductivity(2.92S m^-1),high sensitivity（GF of 1.17）,optimal interval of 20%-50%for compressive deformation detection,and ultra-fast response time and recovery time of 330 ms and 550 ms,respectively.The resistance value of the sensor decreases after the absorption of infrared light.As a flexible sensor for application testing,it can accurately translate mechanical signals into electrical signals with special peak levels and achieve translation and interpretation of signals.