| Flexible sensors,especially flexible pressure sensors,will be widely used in health monitoring,wearable electronic devices and electronic skin.Among them,it is still a challenging task to improve the sensitivity and broaden the working range of the sensor by using microstructure.In this paper,aiming at the deficiency of improving sensitivity by reducing microstructure scale in the design of flexible micro-structure pressure sensor,a kind of micro-scale multi-microstructure was designed by using micro-machining technology and PDMS film as flexible material,and a piezoresistive pressure sensor with high sensitivity,wide working range and good cycle stability was obtained.Hydrogels are similar in structure to human skin,and have good flexibility,ductility and biocompatibility.Recently,they have made great progress in the field of sensors.However,due to the extremely high water content,hydrogels are easy to lose water in the air and freeze easily at low temperature,which greatly limits the application of hydrogels in the field of sensors.At the same time,hydrogel as friction power generation material has yet to be developed.In this paper,polyvinyl alcohol/gelatin/glycerin/carbon nanotube(PVA/GE/GL/CNT)composite hydrogel was prepared by freezing-thawing method,and a flexible composite gel sensor with good long-term effect and frost resistance was obtained.The polyvinyl alcohol/polyethyleneimine(PVA/PEI)hydrogel film was prepared by a simple physical crosslinking method,and a self-powered triboelectric sensor with good flexibility was obtained.The specific research work is as follows:With silicon as the template,a dome pyramid-wall-grid microstructure with multiheight hierarchical was designed.The flexible substrate of the pressure sensor with multiple microstructures was prepared by twice molding.Spray gold on the surface of the flexible microstructure substrate to give conductivity to the film and the two flexible substrates were assembled face to face,form a piezoresistive pressure sensor with multiple microstructures.Because of the hierarchical deformation mechanism caused by the unique multiple microstructures of the sensor,it has ultra-high sensitivity when the sensor is pressed in a wide pressure range.The pressure sensor also has excellent bending and twisting strain detection performance,good mechanical durability,low detection limit,and short corresponding time.It can continuously monitor pulse changes,vocal cord vibrations and sound waves generated by speech when the sensor detects human biological signals.Also,a 4×4 sensor array is prepared to realize pixel detection capability.With polyvinyl alcohol/gelatin/glycerin/carbon nanotube(PVA/GE/GL/CNT)composite gel film as the substrate of sensor,a flexible pressure sensor is designed,which has the advantages of detecting slight strain/deformation,excellent lasting effectiveness and good antifreeze properties.PVA/GE/GL/CNT composite gel sensor was prepared by a simple freezing-thawing method.The composite gel sensor has good sensitivity(GF = 1.82),wide strain detection range(350%)and fast response time(250 ms).The combination of gelatin and glycerin makes the sensor have good lasting performance,and the sensor still has good sensing performance after being placed in normal temperature for 60 days.At the same time,the mechanical durability over 500 cycles of the sensor can be obtained.The sensor has good antifreeze properties,so that it can be stored at-18? for a long time without deformation,and still has good flexibility and can respond to external stimuli.The sensor can distinguish various human biological signals and actions with high precision and sensitivity,such as finger bending degree,pulse,arm,knee joint and speak,which realizes the ability of gel sensor to accurately collect the human biological signals.A self-powered triboelectric sensor with good flexibility was designed by using PVA/PEI hydrogel film and PDMS film as two triboelectric layers of the triboelectric sensor.Hydrogel films were prepared by simple physical crosslinking,and the PDMS films were prepared by spin coating.Then the triboelectric sensors were assembled by two films in a face-to-face manner.This sensor can identify different applied forces between 20-100 N in two-electrode working mode,and produce open-circuit voltage of 123 v,short-circuit current of 2.8 ?A and transfer charge of 10 n C.The sensor has good flexibility,and can recognize knocking,bending and twisting.At the same time,the sensor can light up to 20 commercial LED lamps by collecting various mechanical energy in daily life.By preparing a 4×4 sensor array,which shows that the sensor has a good application prospect in the field of self-powered flexible devices. |
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