Preparation And Research Of Flexible Strain Sensors Based On Graphite Nanoplatelets

In recent years,with the rapid development of science and technology,computer technology has increasingly developed,in pursuit of faster,more intelligent,but also in pursuit of the volume of computers,applications and portability of higher requirements.Therefore,intelligent wearable equipment has attracted more and more interest.Most of the traditional smart wearer is limited to the monitoring of a small number of healthy physical signs,such as heartbeat,step number,based on three axis accelerator and the need to update the algorithm to obtain the human condition.However,for the various parts of the body,for example,how the pressure skin suffer is,and what the bending state of joints are and so on.The force can not be monitored in real time,so it is necessary for a wearable device to monitor the motion information of all parts of the body in real time.It is different from the traditional three axis accelerator.The graphite nanoplatelet based sensor can realize the sensing of different parts of the human body,and will become the core device in the next generation intelligent sensing devices.Therefore,it is very important to create a new flexible stress sensor.Based on graphite nanoplatelet,polyurethane,rubber and other materials,a thin film sensor with sandwich structure and a fiber sensor with shell core structure have been prepared.First,the thin film sensors with sandwich structure are prepared.Because of the graphite nanoplatelet is difficult to distribute evenly in the polymer system,this study compares the different polymers during the selection of polymer filler.To obtain sensors with high flexibility and high conductivity,and compared the carboxymethyl cellulose(CMC),polyurethane(PU),silicon acrylic emulsion(Si-Acr),the ultimate mechanical properties and electrical properties determine that polyurethane(PU)is the best polymer filler.In addition,because of the large number of polyurethane brands,when selecting the suitable polyurethane brand,the thin film sensor with high flexibility is necessary.So the flexibility of the film sensor under selection is focused on.The film sensor was obtained by dip-coating process,it is difficult to perform sensing performance test because its high flexibility and sensitivity,in addition,because it is used in wearable equipment,surface dustproof and anti-oxidation are the factors to be considered when designing thin film sensors,so the film surface needs a layer of protective layer,so the polydimethylsiloxane(PDMS)is used as a protective layer to seal thin film sensor with sandwich structure.The test of thin film sensor with sandwich structure is followed by pressure,tension,bending,impulse and response of sound vibration.It is found that deformation caused resistance changing is the mechanism of the sensor.Secondly,the fiber sensor with shell core structure is prepared by roll to roll process,based on the experience of thin film sensor.The fiber sensor with shell core structure is dipped within graphite nanoplatelet and polyurethane.Through the method of dip coating,a conductive layer on the surface of rubber fiber is obtained,with a thickness of about 20 ?m.During the roll to roll process,the surface of the fiber sensor formed micro crack,and the fiber sensor of the shell core structure with micro cracks is obtained.The performance of the fiber sensor is tested,including tension,strain and cyclic performance.The deep application of the wearable electric field is verified,and the fiber sensor has been set in the circuit,in which the corresponding chip is designed and developed.By converting the resistance changes of the fiber sensor into the electrical signal,the robot hand is controlled and a series of real-time control actions are completed,and the leap from a single sensor to a complete device is truly realized.