Wearable sensors can output various external stimuli(such as pressure,temperature,and humidity)as electrical signals,and are receiving attention in fields such as health monitoring,disease diagnosis,and artificial intelligence.Among sensor materials,hydrogels are widely used because of their excellent flexibility and stretchability.However,most hydrogels cannot meet the requirements of high mechanical strength and high electrical conductivity at the same time,which hinders their development to some extent.Textiles have good flexibility,tensile strength and tensile recovery,and are suitable substrates for the preparation of strain sensors.Compared with traditional rigid sensors,flexible conductive fabric-based sensors prepared with the combination of hydrogel and conductive fabrics are soft,thin,ductile,sensitive and able to fit the human body movement,which can effectively enhance the mechanical properties and sensitivity of the hydrogel,make the detection more accurate and convenient,and provide a new way for solving this problem.Flexible sensors prepared with fabric as a substrate require the selection of a suitable conductive material.The bond between the metal-based conductive material and the polymer fiber layer is usually poor and easily detached due to mechanical deformation.After the carbon-based conductive material is bonded to the fabric,the fabric-based strain sensors obtained have poor conductivity and cannot monitor small deformations during application due to the lack of a continuous contact conductive mechanism.Therefore,it is necessary to select a conductive material that can be firmly bonded with the fabric substrate and has excellent electrical conductivity,so as to develop a fabric-based flexible sensor with high sensitivity and large strain range.The introduction of conductive polymers into fabrics results in conductive fabric sensors with human motion monitoring functions.Common conductive polymers include polypyrrole(Ppy),polyaniline(PANI),and poly(3,4-ethylenedioxythiophene)(PEDOT),among which PANI is widely used in the field of fabric-based flexible sensors due to its advantages of good stability,simple synthesis process,and high conductivity.In this paper,a high-strength and high-fatigue-resistant polyester-spandex blend fabric(containing 92％polyester and 8％spandex)was used as the substrate material for the flexible sensor,and PANI was polymerized on the surface of the fabric by in-situ polymerization to prepare a PANI conductive fabric.Then the multifunctional hydrogel(PAC hydrogel)prepared by blending PVA,CaCl2 and CS solution was coated on its surface to obtain the PANI conductive fabric-enhanced multifunctional hydrogel sensor.The prepared conductive hydrogel fabrics were analyzed for scanning electron microscopy,mechanical properties,frost resistance,water retention,swelling,antimicrobial and sensing properties.The results showed that the best performance of the prepared 13％-PAC conductive hydrogel fabrics was achieved when the mass fraction of PVA was 13％,and its mechanical strength was as high as 8.2 MPa,which was about 4.56 times of that of pure hydrogels.Under 100％tensile strain,the 13％-PAC conductive fabric-based hydrogel showed recoverable energy dissipation and high fatigue resistance.The hydrogen bond formed between PVA,EG and water molecules hindered the evaporation of water molecules,so that the hydrogel exhibited excellent frost resistance and water retention,respectively,and did not undergo a phase transition at-70 ℃,and the residual mass ratio reached 68.69％after 7 days of placing.The 13％-PAC conductive fabric-based hydrogels showed good water swelling properties at different temperatures(20 ℃,30℃and 40 ℃)and good swelling-shrinkage reversibility at different pH(pH=4 and pH=10)buffers.The incorporation of CS gave the 13％-PAC hydrogels strong antimicrobial properties against Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus),with bactericidal rates as high as 92.55％and 99.49％,respectively.In addition,the 13％-PAC sensing fabric exhibited high sensitivity(GF=0.461),stability and fast response to different strains.When monitoring human movement,the 13％-PAC sensing fabric can monitor human facial micro-expressions and movement states,showing different resistivity changes for different movement amplitudes and realizing a graded response.The technology based on the combination of conductive fabric-based hydrogel flexible sensors and electronic information is expected to provide new ideas for the development of a new generation of smart textiles in the field of wearable electronics such as medical diagnostic and health monitoring devices.
flexible wearable sensorsin-situ polymerizationPANI composite conductive fabrichydrogelhuman movement monitoring
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