Porous Three-dimensional Gelatin Fiber-based Flexible Capacitive Sensors By Electrospinning

In recent years,the rapid development of the Internet of Things(IoT)technology,Sensors are receiving a lot of attention as a key part of the process.Capacitive sensors are one of the common types of pressure sensors,and their working principle is to convert external stimuli into capacitive signal change output.High porosity and low density three-dimensional elastic materials as the dielectric layer of capacitive pressure sensors can further enhance the sensitivity and detection range of the sensors,but the proposed three-dimensional porous elastic materials at this stage still have difficulties in further reducing their density limits while ensuring high sensitivity and compressibility.Compared with the traditional twodimensional lamellar fiber membranes,electrostatically spun three-dimensional puffy fiber membranes have further improved specific surface area and porosity,and are easy to prepare three-dimensional porous structures with very low density.This thesis focuses on a fully flexible capacitive pressure sensor based on a threedimensional gelatin fiber membrane dielectric layer prepared by electrostatic spinning technology.In this paper,the molding mechanism of three-dimensional electrostatic spinning is studied,and it is concluded that the fluffiness of the fiber film during deposition has a linear correlation with the specific resistance of the fiber surface.And it is shown that the addition of surfactant CTAB to gelatin can effectively improve the electrical conductivity of spinning solution and reduce the fiber surface specific resistance.In this study,spinning liquor with different concentrations and mass ratios of gelatin and CTAB were prepared for electrostatic spinning,and the microscopic morphology and physicochemical properties of the fiber films were analyzed,and the results showed that the 40-100(%)gelatin fiber films had the largest fiber diameter,the lowest density,and the best mechanical properties.The 40-100(%)gelatin fiber film was used as the dielectric layer of the flexible capacitive sensor,and PEDOT:PSS was selected as the flexible electrode material to assemble the fully flexible capacitive sensor with the flexible PDMS film as the substrate.The sensitivity,stability,and detection limit of the sensor were tested,and the results showed that the sensor exhibited high sensitivity with a value of 0.769 k Pa-1.In the pressure fatigue test,the sensor was able to maintain consistent and stable sensing performance under 1600 repeated pressure actions.Due to the excellent pressure sensitivity of the fiber membrane,the sensor also achieves a capacitive response to small pressures of up to 1 Pa.Also,the sensor can quickly respond and provide feedback to pressure changes in different human movement states.