The Research On Capacitive Flexible Pressure Sensor Based On PDMS Composite Dielectric Layer

In recent years,the application of flexible electronic devices in electronic skin,health monitoring,pressure sensing and so on,has received more and more attention,and then led to more innovative experiments and in-depth understanding of researchers.The flexible capacitive pressure sensor converts the external physical factors it feels into electrical signal output,so that people can intuitively observe the influence of external factors on our life production,and thus help people to carry out more accurate and effective practice activities.Different pressure changes are important means for sensing external information.For flexible pressure sensors,the improvement of their sensitivity is a focus in recent years.According to different sensing principles and various materials,scholars at home and abroad have successfully developed flexible pressure sensors,which improve the dielectric properties of the dielectric layer and the microstructure of the dielectric layer to increase the sensitivity of the sensor.But these sensors have some limitations.In order to design a device with good performance and low cost,In this paper,a flexible pressure sensor based on changing the properties and structure of the dielectric layer is proposed and studied in depth.1.In order to achieve the compressibility of the pressure sensor,electrodes selection is very important.After comparison of several electrodes and limitationsofexperimentconditions,theITO/PET?indiumtin oxide/polyethylene terephthalate?conductive film was used as the upper and lower layer electrodes.After experiments,the stability of the ITO/PET electrode and the sensor was proved.Due to the special flexibility requirements,the choice of sensor dielectric is also very important,it must have a certain degree of flexibility and compressibility,so polydimethylsiloxane?PDMS?which has the small Young's modulus and chemical stability of is precisely better choice.However,due to its low dielectric constant,PDMS,which is a flexible dielectric layer,results in a small capacitance variation and a limited range of capacitance.To solve this problem,in this paper,PDMS was doped with conductive particles of acetylene black,and composite materials with both PDMS chemical stability and softness characteristics and good dielectric properties of acetylene black could be prepared,so that the dielectric properties of the composite were improved by using the percolation theory,and the sensitivity of the sensor was improved.When the mass fraction of acetylene black was 2.5 wt%,the sensitivity reached 0.73 kPa^-1,and at the same time,the viscosity of the film was reduced,and the overall performance of the flexible device was also improved.In addition,the sensor had excellent performance in the detection of small forces and the response speed and the recovery performance was better.2.In order to further solve the stickiness problem of the film and use the microstructure to improve the sensitivity of the sensor,this paper first used the template method to dissolve and obtained the pores.The sodium chloride?NaCl?particles were mixed in PDMS.Since the NaCl particles were easily dissolved in water,the mixed film was cleaned and had a microporous structure.We studied pressure sensor performance of porous structure sensors.The sensitivity of the sensor reached 0.76 kPa^-1,and a series of performance tests found that NaCl-porous thin-film sensors have good results in testing dynamic response and hysteresis characteristics.3.This paper also used the template method-the gas pores to improve the sensitivity of the sensor.In the PDMS,sodium bicarbonate?NaHCO₃?particles were mixed,and the cured films were respectively reacted with hydrochloric acid and the film was heated to decompose to produce gas,and then the by-products were continuously dissolved out.Contrast with the effect of making pores,a method for making pores was selected by heat decomposition and gas generation.Comparing the meathod of dissolved NaCl particles,due to the gas generated and led to the presence of pores inside the film,the sensor was more easily compressed,the sensitivity reached 0.98 kPa^-11 when 20 wt%NaHCO₃particles were mixed,and could feel a pressure of 10.15 Pa.Besides,the response time is less than 180 ms and hysteresis is small.Both methods of making pores make the sensor more easily deformable than a pure PDMS sensor at the same pressure,which in turn increases the sensitivity of the flexible pressure sensor.However,the gas pore-forming method has a higher sensitivity,so the gas pore-forming method is used in subsequent optimization experiments.4.Pores are formed inside the C/PDMS composite film doped with 2.5wt%acetylene black,which made the sensor's sensitivity continue to increase to1.1 kPa^-11 through the microstructure and the film had good dielectric properties.The dynamic response test was better than C/PDMS composite thin film sensors and microstructure sensors,which showed that the interaction of conductive particles and microstructures greatly improved the overall performance of the sensor.