The Fabrication And Application Of Flexible Conductive Materials And Sensors

With the rapid development of information technology in 21st century,flexible conductive materials and sensors draw the attention of researchers because of its great potential application in wearable intelligent equipments,implantable medical devices,real-time monitoring of human physiological signals and flexible foldable display.Among them,piezoresistive flexible pressure sensors and relevant flexible conductive materials become the research hotspot for its excellent sensing performance,simple preparation process and other superior comprehensive performances.Due to the current ordinary piezoresistive flexible pressure sensors still cannot meet the actual demand in the mechanical properties and sensing performance,designing special microstructure of sensors to enhance the response performance has becoming one of the hotspots for researchers at home and abroad in recent years.However,traditional manufacturing process generally involves using extremely expensive instruments such as lithography machine,in order to simplify the procedure and cut down the cost,researchers try to take their inspiration from nature and use some special microstructure found in nature to prepare flexible conductive materials and relevant flexible and wearable pressure sensors.In the study of this paper,on the one hand,flexible conductive graphene porous material with three dimensional spongy microstructure is prepared inspired by spongy structure from nature;on the other hand,the templates from nature with special microarray structure such as leaves and abrasive papers are used to prepare flexible wearable pressure sensors.The main research contents are as follows:1. Flexible conductive graphene porous material with three dimensional spongy microstructure:In this study,polystyrene?PS?microspheres are used to prepare the flexible conductive graphene porous material with three dimensional porous microstructure inspired by spongy structure from nature.During the experiment,PS microspheres are synthesized firstly by dispersion polymerization and mix with graphene paste?GP?in a certain proportion to prepare the composite system of GP/PS,then the PS microspheres are removed by heating at elevated temperatures to obtain the graphene porous material with three dimensional spongy microstructure,and the last step is pouring PDMS as the polymer flexible substrates to prepare flexible conductive graphene spongy material with three dimensional porous microstructure.The results of experiment show the flexible conductive graphene material has a porous microstructure and get the best microstructure and sensing performance when the mass ratio of GP and PS is 1:25.2. Flexible wearble pressure piezoresistive sensor with the surface microstructure of the chinese redbud leaf:In this study,polydimethylsiloxane?PDMS?films with the surface microstructure of the chinese redbud leaf are prepared through twice cloning attempts inspired by bionics.Then the PDMS films covered with reduced graphene oxide?r GO?on the surface are prepared surface through modification,electrostatic self-assembly,and reduction reaction,on this basis,a kind of flexible piezoresistive pressure sensor with the surface microstructure of the chinese redbud leaf is prepared.Through the analysis of PDMS films covered with r GO,it's demonstrated that there are microstructure on the surface of the chinese redbud leaf and r GO conductive layer on the surface of PDMS films.Then the performances of flexible pressure piezoresistive sensor were systematically tested,the results show that the sensitivity of the sensor is 4.0463 k Pa^-1,the detection limit of the sensor is less than or equal to 0.84 Pa,and the sensor has good cyclic stability under 2000 cycles.The mouse tapping experiment and wrist movement experiment of the flexible piezoresistive sensor are processed,and the results show that this type of flexible wearble piezoresistive sensor can be applied to motion detection.3. Flexible wearble pressure piezoresistive sensor with the stochastic distribution surface microstructure of abrasive paper:In this study,inspired on the bionics,abrasive papers which have similar surface microstructure to the human epidermis are used as models to prepare thermoplastic polyurethane?TPU?flims with the stochastic distribution surface microstructure of abrasive paper.on this basis,a kind of flexible piezoresistive pressure sensor with the stochastic distribution surface microstructure of abrasive paper is prepared.Through the analysis of TPU films,it's demonstrated that there are stochastic distribution surface microstructure of the abrasive papaer on the TPU films.Then the performances of flexible pressure piezoresistive sensor were systematically tested,and the results show that the sensitivity of the sensor is 2.2425k Pa^-1,the response time of the sensor is 2 ms,the detection limit of the sensor is less than or equal to 0.72 Pa,in addition,this sensor has great real-time response characteristics and excellent cyclic stability under 5000 cycles.The pulse and vocal cord vibration tests using this type of flexible piezoresistive sensor are carried out and the the experimental results indicated that the flexible wearble piezoresistive sensor can be applied to real-time monitoring of human physiological signals and speech recognition.