Preparation Of Cryogenic Gel And Its Application In Sensors And Supercapacitors

Benefiting from the excellent flexibility,favorable mechanical recoverability,remarkable ionic conductivity,and ultrahigh strain sensitivity,conductive hydrogels could be employed not only as flexible strain sensors but also as the desirable electrolytes of flexible supercapacitors.Up to present,various novel conductive hydrogels have been widely designed and studied in sensors,flexible supercapacitors,and other fields.However,conventional hydrogels have exhibit poor low-temperature tolerant capabilities,which are usually hard and broken by freezing,resulting in the loss of their structural integrity,flexibility and conductivity.Therefore,the practical applications in extremely cold environment are significantly hindered.At present,despite significant progress has been made in the design of hydrogels,achieving the low temperature tolerance of hydrogel still remains a tremendous challenge.The preparation of gels with freezing resistance and studying their application prospects as flexible sensors and supercapacitors in low temperature environment are of great practical significance.Furthermore,the long term stable hydrogel based flexible sensor also requires excellent flexibility,sensitivity,anti-drying ability,self-healing performance and stability in underwater and organic environment.These properties ensure that the sensor can be used in a variety of harsh environments.Therefore,we have prepared the anti-freezing hydrogel with self-healing performance,anti-drying ability,and underwater and organic environmental tolerance and applied it to flexible sensors.The sensors possess excellent sensitivity and stability,and can realize sensing detection in harsh environment(low temperature,underwater and organic reagent).In addition,the anti-freezing active organic hydrogel was prepared by adding organic solvents and active substances into the hydrogel,and the specific capacitance and energy density of the supercapacitors fabricated by the gel were improved.At the same time,the organic hydrogel can also be assembled into flexible sensors to monitor the movement of human body.The results are as follows:1.An extraordinary stretchable(1769%),toughened(0.46 MPa),self-healing,water-retaining(78%after 8 days),anti-freezing(below-40°C),and anti-swelling(in water/organic solvents)conductive hydrogel is designed and prepared by simultaneously introducing zwitterionic proline,metal ions,and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)into vinyl hybrid silica nanoparticles cross-linked polyacrylic acid networks.Based on this hydrogel,the fabricated strain sensor exhibits excellent strain sensitivity(GF=3.07),wide sensing range(from 5 to 700%),reliable stability(800 cycles at 200%strain),and accurate human motion detection ability along two opposite directions(bend down or bend up).In particular,it can not only withstand outstanding mechanical damages but also maintain stable sensing performances in water/organic solvent environments and freezing condition of-40°C.More interestingly,under Fe Cl₃-EG(ethylene glycol)and ascorbic acid-EG solution external stimuli,the resultant hydrogels also display the significant shape memory behaviors and information recording/erasing capabilities even at an extremely cold environment(-40°C).These remarkable performances greatly expand the application fields of hydrogels in harsh environments.2.A novel long-term anti-freezing and mechanically tough conductive active organohydrogel is designed and prepared by simultaneously introducing poly(vinyl alcohol)(PVA),alizarin red(ARS),and H₂SO₄ into a H₂O/ethylene glycol(EG)binary solvent.Benefiting from the low temperature tolerance capability of H₂O/EG and extra pseudocapacitance contribution of ARS active molecules,even at the temperature as low as-37°C,the flexible supercapacitor assembled by the active organohydrogel still demonstrates a large electrode specific capacitance(240 F/g),high energy density(21Wh/kg),and superior durability(97%capacitance retention after stored for 50 days).Impressively,owing to the excellent strain sensitivity(GF=2.18)and significant repeatability,the active organohydrogel based anti-freezing strain sensor can not only precisely monitor the large-scale and subtle human movements but also efficiently distinguish the directions of the movements under RT or-37°C.Overall,investigation of long-term low temperature tolerant active organohydrogels provides a versatile strategy to exploit flexible energy storage devices and strain sensors applied in extremely cold environments.