Full-laminating Flexible Strain Sensor Based On Graphene

A sensor is a device that can sense a specified parameter and convert it into measurable signals according to certain rules and it is vital to realize automatic detection and automatic control.With the increasing demand for sensors and more in-depth research,shortcomings are gradually exposed as(1)Sensors,in past,mainly use silicon as the substrate,which have the disadvantages of rigidity,brittleness and fragility;(2)The flexible sensor substrate can't being fully fitted onto skin;(3)The tensile property of the sensor is usually poor,causing the instability of the device,which the repetition rate and the sensitivity are both problematic.With the development of flexible sensors,the current research also faces several problems.(1)The smooth surface of the flexible sensor substrate and the rough surface of the skin can not be closely attached to each other;(2)The sensor has weak signal sensing ability and cannot effectively induct human joints;(3)The stability of the flexible sensor is poor.In this thesis,a flexible strain sensor by using graphene as the sensing material and polyvinyl alcohol film as substrates,is proposed.During the experiment,the flexible sensor has shown stable performance,improved repetition rate and high sensitivity,and can be seamlessly attached to the skin.Lastly,a practical application of the flexible strain sensor is illustrated.The main work and results of this thesis are listed as follows:(1)A novel method to prepare graphene was proposed with graphite sheet as anode and Pt as cathode.TEM and SEM characterizations were carried out and the honeycomb structure of graphene and the stacking structure of graphene have been observed.(2)For preparation of the sensor substrate,a scheme of transferring the sensing material graphene twice to the sensor substrate was proposed with the intermediate material PDMS.(3)Through the characterization of the flexible sensor substrate,it has been found that a thinner graphene film possessed higher conductivity.Meanwhile,by adjusting the thickness of the film,the optical transmittance substrate reached 90%.The surface morphology of the substrate is observed via SEM,and the peel strength of the substrate was measured.It showed that the sensor and the skin can be closely attached with a peel strength of 28.6 N/m.(4)By using a tensioner and semiconductor characteristic parameter analyzer,the sensitivity,repeatability and stability of the sensor were evaluated.Results showed that the sensitivity of the sensor was high and the strain coefficient range was up to 62~138,which is higher than most of previous results.The repeatability coefficient of the flexible strain sensor was 1.3% and the hysteresis coefficient downed to2.07%,indicating that the sensor behaved excellent performance and strong stability.(5)Finally,in order to replace the traditional remote control unit,a wireless system based on STM32 and the novel flexible sensor is made to control the action of a car model via finger movements.