| In this paper,metamaterials absorbers were designed to convert electromagnetic wave into electric energy wireless through thermal energy.We used the resonant structure of metamaterials to form local hot spots on the surface of metamaterial.The influence of surface metal thickness on the surface temperature distribution of the metamaterials was investigated,and a utilization scheme of hotspot was proposed.(1)A metamaterials absorber has been designed,properties of waveabsorbing,depletion and surface temperature have been researched via simulation and experiment.Absorption efficiency about 0.99 at 2.433 GHz was obtained on the optimism structure from simulation analysis.Energy loss predominantly focused on the field enhancement region,it indicates that the electromagnetic energy is absorbed through dielectric loss then converts to thermal energy.Further analysis of the temperature distribution shows the temperature reached about 55.0oC when electromagnetic wave radiation with 0.086W·cm-2 at 2.433 GHz.Based on the above simulation results,we prepared the samples and test their wave absorbing properties and the surface temperature distribution.The numerical calculation was acceptable agreement with experimental results.We used the samples and thermoelectric module to realize energy wireless transmission,which could be used to control temperature wirelessly,to make the electromagnetic wave be converted to thermal energy and/or electric energy.(2)We firstly studied electric-LC(ELC)and split ring resonator(SRR)structures,and the simulation results of the electromagnetic characteristics and surface temperature indicated that local hot spots were formed on the surface of the sample.Experiment results showed the hot spot temperature reached by SRR was as high as 180.7oC when the incident electromagnetic wave power of 6W.Combining the local electric field enhancement effect of the resonant structure with high lossy dielectric in the metamaterial,the electromagnetic wave could be efficiently collected and converted into heat radiation by forming a hot spot,which expected to be used in non-linear and energy harvesting fields.(3)Secondly,the influence of the copper film thickness on the temperature distribution and hot spot temperature of the SRR surface was simulated.With the thickness of copper film continuous decrease,the ohmic loss of the SRR gradually increase,while the change of dielectric loss was unobvious.Under the same powerful of electromagnetic,with the decrease of thickness,the temperature of hot spot becomes higher and the profile of copper becomes increasingly lighter.When the thickness reached 0.001 mm,the temperature of hot spot as high as 167.0oC.The thickness has a great influence on the surface temperature distribution of the material.Not the micro-structure of the metamaterials,but also the thickness of the metal film could be changed to different heat distribution.(4)Finaly,a utilization scheme of hot spots generated by SRR was proposed through combining the thermoelectric material of Bi2Te3 with the SRR.Using the temperature difference formed by the hot spots,the electromagnetic was converted into electrical energy by Bi2Te3.The resonance characteristics,surface electric field,loss and surface temperature distribution of SRR/Bi2Te3 composite structures were simulated.Experiment results showed temperature difference of Bi2Te3 was as high as149.8oC when the incident electromagnetic wave power of 7W.The C-V curve of the SRR/Bi2Te3 under different incident power of electric field waves indicated the open circuit voltage of a single SRR/Bi2Te3 as high as 27 mV. |
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