| Flexible electronics as an emerging research field,has aroused great interest in the issue of how to manufacture flexible electronic materials that maintain durability and high performance under strained conditions.With the advent of human wearable devices and implantable electronic devices,as well as the increasing demand for human-friendly intelligent soft robots,the demand for flexible electronic device has become more complex and diverse.The increasingly diverse needing raised on flexible electronics require a higher deformation capacity,such as bending,twisting,and stretching,in which,the tensile property gains the most challenging.Stretchable transparent electrodes have attracted great concerns as the key component of stretchable transparent devices.At present,the materials including carbon nanomaterials,thin metal films,metal nanomaterials,and conductive polymers are mainly used for stretchable transparent electrodes.However,the conflict between optical transmittance and conductivity has limited the further development for these materials in optoelectronics.The metal grid electrodes can overcome this problem well by adjusting the thickness of the electrodes while maintain the duty ratio constant.Thus,the conductivity of the electrode can be improved with the transmittance unchanged,and thereby realize the independently adjusting of conductivity and visible transmission.The metallic electrodes reveal a low stretchability due to the large Young's modulus.In order to increase the tensile performance of the metal grid,the arrangement of the grid is firstly designed to fabricate stretchable metal mesh grid electrodes.Additionally,we proposed a unique embedded metallic mesh with stretchable structure arrangement to advance the adhesion between the metallic mesh and stretchable substrate during strain process.Thus,we fabricated the stretchable embedded metallic mesh via low-cost and facile laser direct-writing process combined with an electrodepositing method,and systematically characterized the optical,electrical,mechanical and stretchable properties of the produced electrode.Then,the prepared stretchable and transparent electrode based on embedded metal micro-mesh was applied in stretchable transparent heating devices,the as-fabricated device shows excellent heating performance.The main contents of this article are listed as follows1.According to the mechanics theory of materials,simulation and analysis on different metal grid patterns using COMSOL software have been performed.A comprehensive comparison is made according to the Young's modulus of the metal grid,the size of the pattern deformation,and the uniformity of the stress distribution.According to our simulative results,the square structure with a snake shape on the side has the best tensile performance.2.The preparation of the embedded nickel micro-mesh electrode.First,a patterned mask was prepared by laser direct-write lithography;then the patterned micro-grooves with a height of 7 ?m and a line width of 5 ?m on the conductive substrate were obtained through UV-exposure.Following with development subsequently,the dense and uniform distribution Ni mesh on the conductive substrate can be obtained employing selective electrochemical deposition.Finally,the embedded Ni mesh electrode achieved though the solution of PDMS-coated on the free-standing Ni mesh,and then peeled off conductive substrate after curing.The optical transmittance of the electrode at 550nm is 84.3%,and the sheet resistance is only 0.08 ?/sq.3.The performance characterization of the obtained stretchable and transparent Ni micro-mesh electrode.The embedded nickel electrode can be stretched up to 130%,while the sheet resistance has only increased by 17.8%.In the tensile cycle test,the electrode can reach 300 times cycling at 50%strain.And it also can reach 800 times cycling without affecting the optoelectrical performance of the electrode in the cycle stability test,exhibiting good mechanical stability.Additionally,the prepared ultra-thin embedded Ni-mesh electrode can be easily attached to a variety of complex structures,which can be widely used in the wearable electronic devices.4.Application of heating devices based on stretchable and transparent Ni-mesh electrode.When external applied voltage at the both of ends of the Ni-mesh electrode,the temperature of the stretchable electrode was measured using infrared thermal imager.The temperature of the electrode increased rapidly as soon as the input voltage is applied.Lower sheet resistance leads to better heating efficiency,which means a faster heating rate and higher thermal temperature.The whole area of electrode is uniformly heated and meanwhile show strong thermal stability though the distribution image captured by using an infrared camera in bent and tensile state.The stretchable and transparent Ni-mesh electrode with low driving voltage.Good thermal stability,and fast response time can meet the basic requirements for the stretchable and transparent heater. |
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