Preparation Of The Aramid-based Elastic Conductive Material And Its Strain Sensing Performance

In recent years,with the rapid development of the smart wear field,electronic products have gradually developed toward flexibility and scalability.Elastic conductive materials have attracted massive attention due to their excellent scalability,strain sensitivity,and good electrical conductivity under different strain conditions.Among them,elastic polymers sued as matrixes and introducing conductive fillers,such as conductive polymers,nano-metal materials,and carbon materials,have become an important research direction.As an important application of elastic conductive materials in the field of smart wearable device,elastic strain sensors play a decisive role in smart medical care through directly installing on human skin or compounding into clothing to monitor human health and activities.In this paper,a dense and uniform PVA/Ag nanoparticles network was deposited on the surface of Kevlar fiber bundles by aqueous solution in-situ reduction method.The optimal preparation conditions of conductive Kevlar fibers were determined by comparing different Ag precursor solution concentration,reducing agent concentration,reduction time and reduction temperature.The conductive network structure was characterized by scanning electron microscopy and EDS elemental analysis.Meanwhile,the Ag nanoparticles content of conductive Kevlar fibers with different treatment layers were analyzed by thermogravimetric analysis.What's more,the conductivity of conductive Kevlar fibers was characterized by digital multimeter.A flexible SEBS protective layer was applied to the surface of conductive Kevlar fibers with the purpose of protecting its conductive network.Aramid elastic braided wires were prepared by using SEBS elastic rubber as the core and Kevlar fiber bundles as the woven material.Based on the optimal conditions for preparing conductive Kevlar fibers,the effects of ultrasonic pretreatment time,postultrasonic soaking time and reduction time on the properties of SEBS/Kevlar/PVA/Ag NPs elastic conductive materials were further explored.The conductive network structure and element content of elastic conductive materials were studied by scanning electron microscopy and EDS elemental analysis,which showed that a dense porous structure of Ag nanoparticles was formed in the Kevlar woven structure.In addition,the elastic conductive material exhibited ultra-high conductivity(40466 S/m),wide strain range(>200%),controllable sensitivity(GF=1.85-8.14),fast corresponding time(75 ms)and super high durability(>10000).In order to further clarify the strain-resistance change mechanism,we introduce a finite element simulation analysis,and combined the contact point equivalent stress and the change of braid structure to propose a novel interpretation mechanism,which perfectly examined the mechanism of resistance change with strain.Based on elastic conductive materials,elastic strain sensors with different sensitivities were prepared by a simple and inexpensive method.The elastic strain sensors were attached to the knee joints,fingers,wrists,face,and throat to monitor activities of different degrees and frequencies of the human body.The elastic strain sensors' monitoring signals reveal high reproducibility and stability,showing a huge application prospect in the field of flexible wearable devices.