| In recent years,stretchable conductors have attracted great attention due to their potential applications in various wearable electronic devices such as personalized health monitoring,smart displays,and smart clothing.These electronic devices need to fit tightly to the curved surface and be able to withstand large deformations.Thus the stretchable conductors need to have high stretchability and high conductivity at the same time,which can ensure stable electrical performance under large strains.For the traditional blending method of preparing stretchable conductors,the contact between conductive fillers decreases obviously during the stretching process,resulting in a sudden decrease in conductivity.Therefore,researchers tried to introduce wrinkles,waves,spirals,kirigami and other stretchable structures in the composites of flexible substrate and conductive filler to ensure stable electrical connection under large deformation.Among all these methods,the formation of wrinkled structure by prestretching-and-releasing strain method is a typical representative of the development of stretchable conductors due to its high controllability and simple preparation process.Based on this method,this paper deposited a wrinkled conductive coating on the elastic fibers prepared by electrospinning,and prepared a composite film with multifunctional integration of stretchable electromagnetic shielding and photo/electro-thermal conversion.The main works are as follows:(1)A stretchable TPU/MXene composite film with a wrinkled structure was obtained by spraying MXene on the uniaxially pre-stretched thermoplastic polyurethane(TPU)electrospun fiber membrane and releasing the strain.The morphology evolution of the composite films during dynamic stretching was observed by scanning electron microscopy(SEM).The result shows that the wrinkled structure stores a large amount of stretchable area to assume most of the deformation during stretching,thus achieving the stable connection of the MXene conductive network.The good strain-invariant conductivity of the composite satisfies the application of stretchable electromagnetic shielding,which shows a stable electromagnetic shielding effectiveness of approximately 30 d B under 50%tensile strain.In addition,owing to the localized surface plasmon resonance effect and high electrical conductivity of the MXene layer,the composite film exhibits excellent photo/electro-thermal conversion performance,and can reach a steady-state temperature of 54.4 ~oC under 1 solar intensity irradiation.The performance does not decrease significantly in the uniaxial strain range from 0 to 100%.In addition,due to the good conductive of the composite,it can quickly reach a steady-state temperature of 108 ~oC at 5 V operating voltage.(2)A stretchable TPU-PDMS/Ag NWs/MXene composite film with a biaxially wrinkled structure was prepared by a biaxial prestretch-release and spraying method,which overcomes the problem that the conductive layer will crack with the expansion of transverse width in the uniaxial prestretch-release process.Moreover,the conductive network of MXene and Ag NWs provides higher electrical conductivity for the composite film,and solves the problems of poor adhesion of Ag NWs to the substrate,avoiding the easily bending or peeling during stretching.The composite film maintains an electromagnetic shielding efficiency of more than 40 d B in the uniaxial strain range of 0-50%,and still has a shielding efficiency of 39 d B at 50%biaxial tension(125%plane strain).At the same time,the wrinkle texture of the composite film can effectively inhibit the light reflection and significantly improves its photo-thermal conversion performance,which can reach a steady-state temperature of 59 ~oC under the irradiation of 1 solar intensity.In addition,the composite film also has good electro-thermal conversion,can reach a steady-state temperature of 109 ~oC at 4 V operating voltage,and shows good reliability,repeatability and cycling stability. |
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