Surface Morphology Construction And Strain Sensing Response Of Graphene-based Conductive Fabrics

The fabric flexible strain sensor use fabric as the base material and can convert external tensile strain stimuli into visual resistance signals.It can be applied to many fields such as human movement recognition,safety protection system and medical rehabilitation training.With the in-depth study of conductive nanomaterials,the performance of fabric flexible strain sensors has been improved,and its application range has become more diversified.Among them,reduced graphene oxide(RGO)has stable mechanical properties and a large surface area,ensuring electron transmission under large strains.And it becomes a preferred nanomaterial for the construction of conductive network on fabric surface.However,it is difficult for a single conductive component to meet the conditions of high sensitivity and large sensing range at the same time,and different conductive network morphologies mean different sensing mechanisms.Therefore,studying the construction of surface conductive network is of great significance to improve graphene-based conductive fabrics’ strain sensing performance.The subject use highly elastic polyester-spandex knitted fabric as the flexible substrate.Based on the preparation of two-dimensional sheet reduced graphene oxide(RGO)by the dipping-drying method,the conductive polymers polyaniline(PANI)and polypyrrole(PPy)are respectively assembled with RGO to form different conductive networks.In addition,by adjusting the morphology of PANI and PPy through different dopants,four graphene-based conductive fabrics with different surface conductive network morphologies were constructed.We also deeply explored the strain sensing performance and response mechanism of fabrics with different conductive network morphologies.For the graphene-based conductive fabric with excellent comprehensive performance,the application in human joint monitoring was explored.The main work and content are as follows:Firstly,the construction of 2D-1D conductive network in RGO/PANI fabric and the strain sensing response characteristics are studied.The polyester-spandex knitted fabric is used as substrate,and the 2D sheet-shaped RGO conductive layer is attached to the fabric by dippingdrying method.Then in situ polymerize PANI on the RGO fabric.Afterwards,sodium dodecylbenzene sulfonate(SDBS)and hydrochloric acid(HCl)are used as dopants to adjust the aspect ratio of PANI in the 1D direction.Thus,nanowire-shaped and nanorod-shaped PANI are obtained.In addition,the sensitivity,stain range,stability,resolution and other sensor performance indicators of the two fabrics were explored.The results show that the sheetnanorod-shaped RGO/PANI fabric doped with SDBS/HCl at a concentration ratio of 1:90 has excellent conductivity,and the square resistance is 0.228 KΩ/sq.Its maximum strain range is100 %.Compared with the sheet-nanowire-shaped RGO/PANI fabric doping HCl,the sheetnanorod-shaped RGO/PANI fabric performs better in terms of repeatability,sensitivity and resolution.Secondly,we explored the construction of different dimensional conductive network in PDA-RGO/PPy fabric and the strain sensing response characteristics.In order to solve the problem of conductive layer shedding,polydopamine(PDA)is used as the adhesive to enhance the bonding fastness between the conductive layer and the fabric.From the perspective of optimizing the morphology of the conductive network,PPy is selected to construct different conductive network morphology with RGO to further improve the maximum strain range and sensitivity of conductive fabrics.Then,using cetyltrimethylammonium bromide(CTAB)as a soft template.By adjusting the ratio,0D nanoparticles-shaped and 1D nanoribbon-shaped PPy are obtained,which respectively form conductive network with RGO.The results show that the fastness of the conductive layer in the PDA-RGO/PPy fabric is significantly improved after PDA modification,and the square resistance is as low as 0.08 KΩ/sq.Both types of conductive networks form "island bridge structure" when subjected to strain stimulation.Compared with the sheet-nanoparticles-shaped PDA-RGO/PPy fabric,the strain sensitivity of sheetnanoribbon-shaped PDA-RGO/PPy(CTAB)fabric is 10.8 when the maximum strain sensing range reaches 130%.And the PDA-RGO/PPy(CTAB)fabric can distinguish 1% stretching changes.It also has better resolution when stretched in a larger range.Finally,the graphene-based conductive fabric strain sensor was prepared and the human joint monitoring experiment was carried out.By building a human joint motion sensing system and using 3D human body scanning system to measure the strain of human joint skin,sheetnanoribbon PDA-RGO/PPy(CTAB)fabric is used as a sensing element to monitor finger joints,wrist joints,elbow joints,and elbow joints.The mechanism of conductive network changes in different joint motions is also explored further.The experimental results show that the sensing mechanism of the fabric sensor is mainly the disconnection mechanism and crack propagation.It can realize the monitoring of different joint motions according to the resistance change curve,so it has a wide range of application prospects.