Research On Passive Wireless Flexible Pressure Sensor Based On LC Resonance Principle

Flexible pressure sensors have broad application prospects in research fields such as electronic skin,human-computer interaction,and medical detection due to their good portability and high conformality.However,compared to wired flexible pressure sensors,passive wireless flexible pressure sensors have become a research hotspot in recent years because of their characteristics that do not require power supply and wireless transmission,especially in the fields of medical health and sports monitoring.So far,the research work has made great progress,but there are still many problems that need to be further solved,such as the relatively complicated preparation method,and the limited research on the optimization of the material and structure of the sensitive dielectric layer.Based on the basic principle of LC resonance,this paper designs a passive wireless flexible pressure sensor structure,using three different dielectric layer materials,namely Polydimethylsiloxane(PDMS)porous material dielectric layer,Multi-walled carbon nanotubes(MWCNTs)/PDMS porous composite media layer and Carbon black(CB)/PDMS porous composite media layer.The three kinds of sensors prepared were tested for sensing performance,analyzed the microscopic mechanism and verified the application scenarios.The specific research content is as follows:(1)Designing a passive wireless flexible pressure sensor structure,using HFSS software to simulate and analyze the change of the sensor resonance frequency by changing the capacitance.The results show that the proposed sensor structure design is reasonable and feasible.Optimize the test coupling distance by varying the height of the readout coil.(2)A passive wireless flexible pressure sensor with PDMS porous material as the dielectric layer was prepared,and the effect of different ammonium bicarbonate doping concentrations on the performance of the sensor was studied.(3)Under the condition of the doping concentration of ammonium bicarbonate is2:3(mass ratio of PDMS curing agent),a passive wireless flexible pressure sensor with MWCNTs/PDMS composite porous material as the dielectric layer was prepared,and the influence of MWCNTs doping concentration on the performance of the sensor was studied.The test results found that compared with pure PDMS porous media,the introduction of MWCNTs can effectively improve the overall performance of the sensor.(4)Under the condition that the doping concentration of ammonium bicarbonate is 2:3,a passive wireless flexible pressure sensor with the CB/PDMS composite porous material as the dielectric layer was prepared,and the performance of the CB with different doping concentrations was explored.Impact.The results show that compared with pure PDMS porous media,the introduction of CB can effectively improve the overall performance of the sensor.In summary,three sensor structures with different medium layers were prepared in this paper.By analyzing the different mass ratios of ammonium bicarbonate,MWCNTs and CB,the performance of the sensor was tested and analyzed.When the doping concentration of ammonium bicarbonate was 2:3,the porous structure prepared was the best for improving the performance of the sensor.However,the doping of MWCNTs and CB can further improve the performance of the sensor,and the sensor has the best comprehensive performance when the concentration(mass ratio of PDMS curing agent to PDMS)is 50:100.The preparation method is simple,the cost is low,and it can clearly distinguish the movement process of human limbs,so it has a potential application prospect in the field of intelligent wearable.