| Benefiting from their good processability,controllable performance,light weight and so on,conductive polymer composites?CPCs?composed of conductive ingredients and insulating polymer matrix have shown tremendous application potentials in various fields including energy sources,electromagnetic shielding,environmental protection and monitoring sensors.Among these applications,CPCs used as sensing materials are prone to perform some response behaviors towards different kinds of external stimuli such as strain,temperature,humidity and gas,attracting lots of researchers'attention.Especially CPC-based sensors with multi-mode strain sensing capacity or multiple stimulus-response abilities,have become a hotspot of current researches.In this paper,we prepared different multifunctional sensing materials based on CPCs,including cylindrical and flaky carbon black?CB?/thermoplastic polyurethane?TPU?aligned composite foams and graphene ink-modified flexible and conductive composite fibers.We put emphasis on the study of the resistance response behaviors towards different modes of strain?compression,tension and bend?and analyzed the inherent relation between the structures and properties of these sensing materials.We also integrated them into sensors and used them to detect diverse human motions in real time.In the meantime,we further investigated their response behaviors towards change of temperature,humidity and gas,and the results showed their promising application prospect in wearable and multifunctional sensing devices.The major research content and conclusions are as follows:1.Study on preparation,compressive sensing behaviors and adsorption properties of CB/TPU aligned composite foamCB/TPU composite foam with a pinnate-veined aligned porous structure was prepared by ultrasonication,unidirectional freeze and freeze-drying process.It had a high porosity of 83.7%,low density of 0.13 g·cm-3,a low percolation threshold of 0.48vol.%,long term resistance stability and nice compressibility.When used as a piezoresistive sensor,it possessed a wide detection range up to 80%strain?corresponding pressure of 584.4 k Pa?,rapid response time of 150 ms and showed good linearity of response with a high maximum gauge factor?GF?of 1.55.In the compression test,it showed excellent discernibility upon different strain amplitudes,superior response stability,reproducibility and nice durability?>10000 cycles?.This compressible foam sensor could steadily detect various human motions in real time and could be integrated into artificial electronic skin with sensor arrays to display the pressure distribution and intensity of different loadings at different pixels,showing enormous application potentials in flexible and wearable sensors or intelligent human-electronics interfaces.Additionally,it showed a high saturated adsorption capacity,excellent adsorption stability and fast oil/water separation ability?35 s?,suggesting its versatility and high application value in adsorption or oil/water separation field.2.Study on tensile sensing behaviors and multifunctional response behaviors of CB/TPU aligned composite foamIn the tensile test,the flaky CB/TPU foam showed nice strain discernibility,fast response time?50 ms?,good response stability and excellent durability?>10000 cycles?.Significantly,it simultaneously reached a wide detection range?up to 170.6%strain?as well as a high maximum GF?775.9?and could respond to bending strain,which was better than many other stretchable strain sensors.After theory analyzing and formula fitting,it was found that the tunneling effect played an important role in the response behaviors of stretch-release process.It could be used to detect motions in different parts of human body and could be integrated into a simple DC circuit containing an LED lamp,converting the lightness signal of LED lamp into strain signal of the foam under stress.Furthermore,this flaky foam sensor could also make responses to the changes of temperature,humidity and organic vapors,showing good discernibility,response stability and repeatability in all these circumstances.Thus,we hold the view that it has a huge potential in motion detection,human-electronics interfaces and multifunctional sensors.3.Study on preparation and multifunctional response behaviors of graphene ink-modified flexible and conductive composite fiberUltrasonication technique was adopted to integrate graphene ink onto the surface of commercial elastic fibers.In the tensile test,the graphene ink-modified flexible and conductive composite fiber showed an ultralow detection limit of 0.1%strain,rapid response and recovery time?33 ms and 35 ms?,superior response stability and durability?>10000 cycles?.In the bending test,it also possessed a low detection limit of 0.5%strain and presented excellent strain discernibility,response stability,reproducibility and durability?>10000 cycles?.It was assembled as a strain sensor to detect human motions of different levels.Furthermore,this flexible and conductive composite fiber could also make a response to humidity,and showed nice humidity discernibility,response stability and repeatability,suggesting its promising application prospect in humidity sensing devices. |
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