Research On Flexible Pressure Sensor Based On Microstructured PDMS Composite Dielectric Layer

With the rapid development of Internet of Things technology,flexible electronic products have shown great potential and broad application prospects in many fields.Among them,capacitive pressure sensors have been favored by many scholars in the field of flexible sensing at home and abroad because of their simple structure,insensitivity to temperature and humidity,low power consumption and other advantages,and have become one of the current research hotspots.However,the sensitivity,production cost,stability and integration of large-area sensing arrays are still key factors limiting the practical application of this type of sensor.The research on capacitive flexible pressure sensors is focused on enhancing sensitivity,improving the sensor fabrication process and optimising the structure of the sensing array,combining microstructures,composite dielectric layers and new flexible electrodes.The main points of this paper include the following three areas:（1）A capacitive flexible pressure sensor based on a sandpaper microstructured dielectric layer and flexible microelectronic printed electrodes was prepared.The dielectric layer of the sensor uses sandpaper as a template and PDMS as a substrate for the flexible dielectric layer,replicating the surface microstructure of the sandpaper to improve the sensitivity of the sensor.The conductive ink is printed on PET as a flexible electrode by a flexible microelectronic printer,which realizes the unification of the encapsulation layer and the electrode layer,simplifies the structure of the sensor,and effectively reduces the problem of electrode shedding and fracture.After testing the performance of the sensor,the sensor had a sensitivity of 0.175 k Pa^-1 over a pressure range of 3 k Pa,still had a good capacitive response over a pressure range of 80 k Pa and passed 1000 cycles at a pressure of 6 k Pa.（2）A new capacitive flexible pressure sensor based on a graphene/polystyrene microsphere/PDMS composite dielectric layer and activated carbon non-woven electrodes was prepared.The sensor uses PDMS as the substrate for the flexible dielectric layer and uses the self-assembly properties of polystyrene microspheres to build a more uniform microdome structure on the surface of the dielectric layer,while doping graphene as a conductive filler into the dielectric layer,effectively improving the dielectric constant of the dielectric layer.In addition to this,an ultra-thin dielectric layer film of 70μm has been achieved using photoresist as a sacrificial layer.Activated carbon non-woven electrodes have been prepared by depositing carbon nanotubes into activated carbon non-woven fabrics,which have the advantage of a conductive filler that is not easily dislodged and high strength compared to other fabric electrodes.After the performance test of the sensor,the sensor has the advantages of high sensitivity(0.209 k Pa^-1),wide detection range（150 k Pa）,high stability（3500 cycles）and fast response recovery（<40 ms）.The sensor was tested for further applications.It can detect bending,mouse double click,muscle contraction and pressure changes of the front and rear swing arms,and has great potential in the field of wearable electronics and dynamic monitoring.（3）A 3×3 flexible pressure sensing array was constructed on the basis of a prepared flexible sensing unit with a graphene/polystyrene microsphere/PDMS dielectric layer and an activated carbon non-woven electrode.Different from the traditional flexible capacitive sensor array with upper and lower electrodes,the sensing units of the sensor array are connected by“S”shaped bending,which increases the amount of stretching and reduces the risk of electrode fracture.The application test shows that it can identify strip,ring,cylinder and bending angle,which has certain practical value.