The Effect Of Medium' Modulus On Resistance-strain Behaviour Of Flexible Conductive Composites And Performance Adjustment

Highly flexible conductive composites have great prospects in the field of new flexible electronic components,such as force sensitive/piezoresistive resistance sensors,stretchable electrodes and retractable circuits,et al.,exhibiting great commercial value.Significantly,the resistance-strain behavior as the core parameter for evaluating the performance of conductive composites for flexible electronics and its application,which can be divided into sensitivity and non-sensitivity.To date,the conductive network design,composite structure design and other methods are adopted by researchers to adjust performance.However,few researches have focused on the intrinsic modulus of conductive medium effect on resistance-strain properties.Especially,the discrepancy of co-deformation ability between conductive medium and flexible matrix,resulting in the change of the microscopic morphology of medium,irreversible damage of the conductive network/structure and other factors on the resistance-strain behaviors,which have become a technical bottleneck for the preparation of high-precision,high-elastic flexible electronic conductive composites.Therefore,This work focus on the difference of modulus between high modulus medium and matrix,application of low modulus medium,the interfacial force between low modulus medium and matrix,and influence of intrinsic phase characteristics of low modulus medium,which effect on resistance-strain behavior and its Performance regulation.High-elastic modulus(E,10¹¹ Pa)of gold and a three-dimensional?3D?porous structure with high elasticity PU?E,10⁶ Pa?were used as the conductive medium and elastic network,respectively,and 3D Au@PU was constructed by atomic sputtering.A straight-through crack structure of the spider leg was prepared by compression on the Au@PU skeleton,which depedent on the modulus difference between gold film and PU?about 10⁵ Pa?.By modulus difference effect on the high modulus medium of microscopic morphology,the crack tends to be saturated when the deformation is higher than 90%,and the crack density is about 0.85?m^-1.The independent gold conductive elements separated by straight-through cracks in the 3D Au@PU compression strain,the inner skeletons of conductive mechanism rely on conductive overlaps,the conductive unit of outer skeleton is the tunnel current conduction converted to the insulating state.Therefore,the sensitivity is increased from 0 to 1.09 in the 0-23%small deformation region.In the 23%-60%,the sensitivity is up to 4.43 by contact strain under the bending of the skeleton.This novel crack design simultaneously achieves small deformation and large deformation motion monitoring requirements,fast response?9 ms?,ultra-low detection limit?0.568 Pa?,and cycle stability over 1000 times.The micro-cracks of high-modulus conductive medium are inevitably generated during the co-deformation process with the matrix,liquid EGSInSn?E,0-10 Pa?with low Young's modulus and PDMS?E,10⁶ Pa?were used as the conductive medium and the elastic matrix,respectively.The highly elastic EGaInSn/PDMS fibers were prepared by combining the PDMS fibers composed the hollow channel structure and the incompatible between the flexible matrix and EGaInSn.A mechanism that the resistance-strain performance regulated by volumetric resistance variation of the medium is realized.The results show that low modulus of EGaInSn makes it consistent with the inner diameter variation of the PDMS fiber.The small change in the inner diameter of the flow channel?0.3%?is sufficient to cause volume resistance change??R?0.15%?.The resistance-strain response is found to be linear function relationship.The inner diameter variation of circular flow channel can reduce the hysteresis effect,the larger the inner diameter,the smaller the hysteresis effect.When the inner diameter is 750?m,the hysteresis is only 0.11%,the response time is 9 ms,and the working range is 0.3%-140%.In order to solve the technical difficulty of poor compatibility between the low modulus EGaInSn conductive medium and the flexible substrate,by using the hydrophilicity of liquid metal microspheres interface,the polymerization of ethyl-cyanoacrylate monomer is initiated by interfacial water to achieve strong infiltration of liquid EGaInSn onto polyacrylate film?PA?.The adhesion between EGaInSn and poly?ethyl-cyanoacrylate?is increased from 0.45?N to 9.0?N,a 20-fold increase.When the monomer concentration is 0.6 g/cm²,the contact angle between GaInSn and PA from superhydrophobic turn into hydrophilic,and the adhesion stability is optimal.The maximum strain value of the unchanged resistance is 60%.When the elongation is 120%,the?R/R₀ is only increased by 230%,and the hysteresis effect was as low as 11.4%.Under 60%deformation,?R/R₀ was also maintained at 0.12 under 500 cycles at a frequency of 0.01 Hz.The prepared EGaInSn@PA conductive film can effectively achieve reliable bonding during the stretching process,and its resistance-strain shows insensitive characteristics.The physical properties of low modulus liquid metal are not conducive to the application of flexible electronic components.Nickel?Ni?doping and heat treatment processes are used to prepare a liquid-solid two-phase structure with high stability of GaInNi alloy.Nickel doping has found that GaInNi can still maintain low-cost,easy-to-process liquid metal forming technology.Phase studies have found that Ni,Ga,and In undergo an intermetallic chemical reaction during low temperature heat treatment to form crystalline compounds of Gallium-Nickel compound and Indium-Nickel compound,and the proportion of crystalline phase in liquid GaIn is achieved by regulating the atomic ratio of Ga,In,and Ni.It is found that GaInNi not only has the conductivity and stable morphology of solid conductive medium,but also has intrinsic stretchability.Resistance-strain behavior study found that the GaInNi@PA film was cycled at 100%strain for 1000 times,and the?R/R₀ was increased only 0.25 when n _Ga:n _In:n_Ni=5:1:4.And GaInNi exhibits good mechanical stability,alkali resistance and stretchability in a stretchable electronic circuit.