Preparation And Performance Study Of Piezoresistive/Capacitive Paper-Based Flexible Sensors

In the past ten years,flexible wearable sensing devices have attracted the interest of a large number of researchers due to their huge practical application potential.It has always been a challenge to design the conductive microstructure to have excellent performance in the sensitivity and response range of the sensing device.In this paper,paper-based fibers are used as the frame of flexible device sensing materials,and flexible sensors with piezoresistive and capacitive working mechanisms are designed through polystyrene/graphene conductive composite microspheres structure and ion-electronic sensing layer structure.The influence of the component content of the sensing materials on the sensitivity and pressure response range of the device is explored.The research content is as follows:1.Preparation and performance study of paper-based flexible sensor with polystyrene/graphene conductive composite microspheresThrough the combination of heterogeneous aggregation with suction filtration and casting of our research group,that is,according to the basic principle of thermodynamic heterogeneous aggregation,graphene oxide(GO)has a certain degree on the surface of polystyrene(PS)microspheres and paper-based fibers.Regulating the content of the components by distribution and using the method of suction filtration to deposit free graphene oxide nanosheets on the microspheres and fibers,thereby controlling the number distribution of polystyrene/graphene conductive microsphere units,and then changing the sensing performance of the device.The sensor has a sensitivity of 12 k Pa^-1 at an ultra-low pressure value in the response range of 0-24.5 k Pa with good sensing stability.In addition,we have introduced one-dimensional conductive material carbon nanotubes,the response range of the sensor is expanded to 36.75 k Pa,and the sensitivity reaches 10.33 k Pa^-1.The experiments have proved that the device manufacturing is simple and controllable,and the material sources are extensive,which provides a new idea for sensor design.2.Preparation and performance study of ion-electronic capacitive paper-based flexible sensorIonic liquid sensors based on flexible ion electronic sensing mechanisms have been sought after by scholars due to their high sensitivity,low power consumption and high signal-to-noise ratio.When the ionic conductor(solid or liquid)is in contact with the electronic conductor,the charged electronic conductor on the electrode repels the ions of the same charge,at the same time,it attracts the opposite ions from the ionic conductor to the electron/ion interface to form the interface of two electric double layers.Opposite charges on the electrical layer are separated at the nanometer level,giving the sensor ultra-high capacitance.In this thesis,polyvinyl alcohol is used to absorb the ionic liquid and wrap it on the fiber,which gives the conductive sensing unit and increases the elasticity of the paper-based fiber.Graphite powder with conductive properties is coated on the fiber to form an electrode,thereby forming a flexible sensor based on all paper-based materials.The pressure range of the device can reach 98 k Pa,and the sensitivity can reach 93.06 k Pa^-1 under an ultra-low pressure value.Under different compression rates and thousands of cycles,the device still has good sensing performance.At the same time,it can adapt to the change of the ambient temperature within 25-100?,and the?C/?T is only 0.00013 nF/kPa.