Preparation And Properties Of Anti-freeze And Conductive Hydrogel Based On Polyvinyl Alcohol

Recently,conductive hydrogels with good flexibility and stretchability have provided potential alternatives for flexible sensors,personal health monitoring devices,and smart wearable devices.However,most conductive hydrogels are often hindered by problems such as poor mechanical property and biocompatibility,non-reusability and narrow operating temperature range.Hence,it is necessary to prepare a hydrogel with excellent mechanical properties,remoldability,anti-freezing and conductivity.In this paper,anti-freeze and conductive hydrogels were successful prepared by adding polyvinyl alcohol and gelatin.In this system,glycerin and sodium chloride were introduced into the PVA/gelatin hydrogel.Due to the salting out effect of sodium chloride,the hydrogen bond between glycerin and PVA and between PVA and PVA are enhanced,which greatly improve mechanical properties of the gels(fracture stress of 1044 k Pa,fracture strain of 715%,Young's modulus of 157 k Pa and toughness of3605 k J/m~3).In addition,owing to the presence of sodium chloride,the gels have good conductivity and exhibit outstanding strain sensitive electric behavior as biosensors to monitor routine movement signals of human body.In particular,the gels with low temperature tolerance can maintain good conductivity and flexibility at-20oC.Interestingly,there are only non-valence interactions,the gels are capable of being recovered and reused by heating injection,cooling molding and freezing-thawing cycles.Then,we synthesized another anti-freeze and conductive hydrogel using polyvinyl alcohol and sodium alginate.Firstly,Sodium chloride was used to induce sodium alginate into sodium alginate fibers.Then,PVA and glycerin were added into sodium alginate fibers to prepared hydrogel.There are multiple hydrogen bonds between sodium alginate fiber and PVA,so the gels exhibit extraordinary mechanical properties,such as h igh tensile/compressive strength(1.19 MPa,4.5 MPa),high toughness(2.58 MJ/m~3),anti-fatigue-fracture ability and remodeling.In addition,the gels show sensory capability toward stress and strain,and are considered as sensors to monitor various movements of human body.In particular,the gels demonstrate temperture tolerance ranging from-20°C to 40°C and non-drying for 6 day at 25°C.The anti-freeze and conductive hydrogel based on PVA was synthesized by this simple strategy.It was foreseen that this hydrogel might be widely used in multiple areas such as artificial intelligence,electric skin and smart wearable devices.