Research And Application Of Wearable Capacitive Pressure Sensor

In recent years,flexible pressure sensors have received increasing attention due to their wide range of applications,such as wearable electronics for electronic skin and health monitoring.Among them,capacitive flexible pressure sensors stand out due to their unique features such as energy saving,simple device structure and low manufacturing cost.Capacitive pressure sensors basically consist of two parallel electrodes and one dielectric layer,and their sensitivity can be improved by adjusting the microstructure of the dielectric layer or electrodes,or be improved by adding new materials to the dielectric layer to form a composite dielectric layer.To date,great achievements have been made in the development of capacitive pressure sensors with high sensitivity.However,in order to achieve practical applications,capacitive pressure sensors must not only exhibit high sensitivity,but also possess other performance,such as low detection limit,high stability,and fast response time.Therefore,trade-offs between unique characteristic and the overall performance of flexible capacitive pressure sensors is a major challenge.In addition,most of the wearable pressure sensors reported are fabricated based on impermeable elastic dielectric layers and electrode films,and the devices as a whole do not have breathability,which limits their comfort for long-term wear.To address the above problems,this paper designs two porous dielectric materials based on low-cost porous structure preparation methods,which not only improve the traditional sensor performance such as sensitivity,response time and stability,but also have unique characteristics such as breathability and low crosstalk.They are expected to adapt to various environments.In view of the electrical,mechanical properties of materials and the demand for high sensitivity,stability,two types of porous dielectric materials are designed in this paper.The research work is as follows:（1）Porous dielectric material with permeability,low compression modulus,and high dielectric constant（the relative permittivity reached 107.8,dielectric loss was 0.07）was prepared with the sacrificial template method introducing the CCTO（giant dielectric constant material）and rGO into PDMS（low dielectric constant elastomer）.This method technically has the superiority of low fabrication cost and simple process.In addition,the porous CCTO/rGO/PDMS foam has a low compression modulus（0.007 MPa）and a compressionally variable dielectric constant,which can effectively improve the sensitivity of the pressure sensor.Breathable dielectric and electrodes were prepared to form a capacitive pressure sensor with high sensitivity(3.277 k Pa^-1),fast response time（<48 ms）,fast recovery time（<48 ms）,excellent cycle stability durability（11,000cycles）and high breathability(13 mg·cm^-2·h^-1).Furthermore,they can be used to form a wearable monitoring devices.Patterned electrodes were prepared by spraying method to form sensor array which demonstrates high xy resolution and high sensitivity.（2）A ultra-thin porous dielectric material with permeability and large dynamic response range was prepared by the breath-figure method.High elastic modulus TPU（1000 MPa）,GMWCNTs,and CCTO were used as the substrate,conductive material,and filler material to form a CCTO/GMWCNTs/TPU dielectric layer with a thickness of 90.6μm and a dielectric constant of 50.4.The porous ultra-thin dielectric elastomer also has a relatively high water vapor transmission of 8 mg·cm^-2·h^-1.The porous Ag NW/TPU conductive membrane（4.7μm）and the microstructured ternary composite membrane were laminated to prepare a capacitive pressure sensor with a sensitivity of 0.731 k Pa^-1,which is wearable,breathable(7 mg·cm^-2·h^-1)and ultra-thin（100μm）,with a large dynamic monitoring range（100 kPa）.