Investigation On Induced Growth Fe₃O₄ Nanowires On Flexible Fabrics And Its Sensing Behavior

Design of traditional textiles is becoming more difficult to meet consumer demand for apparel functionality.Under the dual influence of technological factors and consumer market stimulus,smart flexible fabrics gradually started and developed.As a source of information,flexible sensors play an indispensable and important part in information systems,especially the development of sensing sensitive materials.One-dimensional?1-D?Fe₃O₄ NWs is one of the ideal sensitive materials for smart flexible fabrics with the characteristics of single crystal,environmental friendliness and high sensitivity.However,the in situ growth of Fe₃O₄ NWs over their orientation and morphology on a wide range of low heat-resistant fabric is still a challenge,which limits its practical application.This thesis mainly focuses on using irradiation graft modification to achieve the stable and directional growth of 1-D Fe₃O₄ NW arrays on the surface of fabrics?PP nonwoven fabrics and PET knitted fabrics?,and build smart flexible metals?Ag or Ni?/Fe₃O₄ NWs functional fabric material.Then,the performance and mechanism of smart flexible fabrics in terms of Temperature sensitive response,humidity response and strain response were investigated.The specific research work is as follows:1)A method was put forwarded for the in situ formation of Fe₃O₄ NW arrays on the surface of polymer substrate by the radiation-induced graft polymerization of acrylonitrile and subsequent amidoximation of the grafting chains,followed by a simple coprecipitation process.XPS proved that Fe₃O₄ NWs and the substrate are connected by N-O-Fe and Fe-N chemical bonds.SEM and TEM observation found that a layer of Fe₃O₄ NW arrays is observed on the surface of the flexible substrate?length:diameter ratio?10?.Flexible Fe₃O₄ NWs-PP nonwoven fabric showed good durability,saturation magnetization,superparamagnetic properties and excellent UV-vis absorption capacity.2)Smart flexible Ag/Fe₃O₄ NWs fabric with a sandwichlike structure were formed through the modified silver mirror reaction?electroless silver plating?,designed by layer-by-layer assembly on the surface of the Fe₃O₄ NWs-PP nonwoven fabric.Due to the capture and catalysis of silver ions by Fe₃O₄ NWs,fish-scale-like Ag flakes were only deposited on the upper and lower layers of the fabric and served as electrode layers?about 100?m?,while a small amount of silver ions diffused into the inside to form the sensing layer of Fe₃O₄ NWs@Ag?about 700?m?.The results showed that smart flexible Ag/Fe₃O₄ NWs nonwoven fabric had good flexibility and stability,and can be arbitrarily cut without affecting the sensor structure.This sensor can also be tailored into various shapes and stitched into other textiles or existing electronic systems.3)The electrical conductivity of the smart flexible Ag/Fe₃O₄ NWs nonwoven fabric decreases first and then increases rapidly as the temperature rises,transforming from electrical insulation to conductor.The sensor provides a real-time monitoring strategy for early warning fire detection?below 100°C?,and can be converted into electrical conductors as fire alarm fabrics in case of fire.Its response time is 2 s and sustained detection time exceeds 15 min.After cutting,sewing or embroidering,the smart flexible Ag/Fe₃O₄ NWs nonwoven fabric can be used as a water molecule concentration?humidity?sensor.Smart flexible Ag/Fe₃O₄ NWs nonwoven fabric can monitor the user's health status,including humidity response,breath monitoring,skin moisture measurement and exercise monitoring.Moreover,the sandwichlike design provides a reliable strategy to modify household fabric items to provide a fire warning function,and as a humidity response and health monitoring sensor.4)High conductivity PET strain sensors were fabricated by radiation-induced graft polymerization and co-precipitation method,in-situ formation of Fe₃O₄,and subsequent electroless deposition of nickel?Ni?on a polyester fabric.Fe₃O₄ acted as a joint component by improving the adhesion of the conductive Ni layer to the PET support and enhancing the magnetic properties of the Ni metal layer,endowing the strain sensor excellent robustness.The strain sensor exhibited reveals a distinctive negative resistance variation the increase in strain,and has a fast,stable and repeatable signal response?stretching range 0-40%,working frequency 0.05-1 Hz?.The sensor can be sewed directly onto clothes for motion monitoring and electromagnetic interference shielding,and can also be used as a magnetic response switch.