Construction Of Conductive Networks In Polymers And Their Application To Sensors

Sensors,a type of detection device that can sense external information and convert the perceived information into electrical signals,have gained wide applications in industrial production,medical equipment,daily life,defense science and technology,aerospace,and many other fields.However,traditional sensors suffer from insufficient flexibility,low response,etc.while flexible sensors developed in recent years are limited by the trade-off between sensitivity and working range;therewith the sensors still have very large development space.In this paper,a series of their structures and properties were characterized as well.The concrete research content are as follows:1.Because flexible sensors with multi-modal responses are essential for applications in the complex environment of wearable products,a unique carbon nanotube（CNT）hollow-sphere scaffold is fabricated using self-assembling of polystyrene（PS）microspheres and microwave irradiation to achieve flexible strain,pressure,and laser sensors.The CNT hollow-sphere scaffold comprising intertwined CNTs has a sophisticated conductive network,and the polydimethylsiloxane（PDMS）as the matrix has good accommodation and can withstand large tensile and compressive deformations.Therefore,the fabricated CNT hollow spheres/PDMS composite sensors showed good responses to the applied strain（gauge factor are 1247,20166,55438 in the strain regions of 0-65%,65-96%,96-107%,respectively,27 ms response time,and over 20000 cycles durability at40%strain）and pressure(gauge factor from 0.07 to 3.15 k Pa^-1,beyond the pressure sensing range of 248 k Pa).Also,due to the intrinsic photothermoelectric nature of CNTs,the sensor can show non-negligible sensitivity to laser light(the sensitivity is 0.066 s^-1 at 5 s of 532nm laser irradiation).In addition,their uses in body movement detection,healthcare,tactile perception,and colloid concentration detection are demonstrated.It is believed that the CNT hollow spheres/PDMS composite sensors will pave the way for practical applications for future wearable electronic devices,which could recognize human motion as well as sense air quality and disease diagnosis.2.Polymer hydrogels have the advantage of being flexible sensors,but at present,functional polymer hydrogels exhibit some shortcomings in terms of the high-cost monomer,complicated synthetic routes,and so on.Therefore,it is of practical interest to develop simple and low-cost smart hydrogels to expand the utility and functionalities of polymer hydrogels in areas of the sensor.In this work,a bilayer intelligent composite hydrogel was developed using thermoresponsive poly（N-isopropyl acrylamide）（PNIPAM）hydrogel and solvent-responsive poly（sodium acrylate）（PSA）hydrogel,which showed multimode response to external stimuli including solvent,temperature,and strain.In solvent,the different swelling ratios of the PNIPAM and PSA make the bilayer hydrogel bend to be used in the fields of grasping and releasing objects in solvents,liquid level monitoring,information encryption,etc.Thanks to the temperature responsiveness of PNIPAM,the hydrogel can be applied to monitor the temperature of a flammable solvent area.Also,the good electrical conductivity coupled with the high stretchability（strain range over 591%,sensitivity over the entire strain range of 1.34,linear relationship≥0.996,and response time of 116.6 ms）make the hydrogel useful as a strain sensor,which can be used for the identification of body movements such as fingers,wrists,elbows,and knees.It is believed that the hydrogel reported here possess great potential to be employed as high-performance flexible sensor towards low-cost,facile fabrication and multimode response.