Multifunctional Hybrid Fibers With A Core-Shell Segmented Configuration For Flexible Wearable Sensors

With the economic development and social progress for the past few years,people’s health consciousness and health care consciousness have been gradually increasing,prompting people to pay more and more attention to the health monitoring of their family and themselves.As an emerging medical monitoring tool,flexible wearable devices have gained people’s favor due to their intelligent,portable,and real-time advantages.However,most wearable sensors reported in the literature have only a single function,and little consideration is given to the state of daily use and the cost of mass production.In this work,we prepared a multifunctional composite fiber with a core-shell segmented structure using a coaxial needle wet spinning process and demonstrated its application as a flexible wearable strain and temperature sensor.The specific research content is as follows:(1)Preparation of core-shell conductive hydrogel fiber and its performance as a flexible wearable strain sensor: Ionic conductive,electronic conductive,ion and electronic conductive hydrogels were prepared,and their electrical conductivity,relative resistance change and stressstrain relation were compared.The results show that the doped reduced graphene poly(2-acrylamido-2-methyl-1-propanesulfonic acid)hydrogel based on the common conductivity mechanism of ions and electrons has the best conductive properties and strain sensitivity coefficient thus,which has been selected as the core material for conductive hydrogel fibers with core-shell structure.At the same time,the extrusion properties and fast curing properties of several types of thermoplastic elastomers(silicone rubber)have been compared and poly(styrene-isoprene-styrene)has been identified as the fiber’s shell material.On this basis,a coreshell structured conductive hydrogel fiber was prepared by a wet spinning process,and its performance as a strain sensor such as sensitivity,stability,and durability is systematically characterized.The results confirm that the conductive hydrogel fiber not only has excellent strain sensing performance but also can effectively prevents short circuits and volatilization of water in the hydrogel;(2)Preparation of core-shell thermochromic elastomer fiber and its performance as a flexible wearable temperature sensor: The color-changing principle and performance of three thermochromic microcapsules at different temperatures were systematically investigated.Core-shell thermochromic elastomer fiber is mixed at a specific ratio and compounded with a silicone rubber material to prepare a core layer material of a temperature sensing fiber.The core-shell structure thermochromic elastomer fiber is also prepared by the wet-spinning process and poly(styrene-isoprene-styrene)shell material.The results show that this fiber exhibits four distinct colors(purple,brick red,light green,light white)at four different temperatures(0,20,35,55 °C).If we change the weaving method of thermochromic fibers,the patterning of knitted fibers at different temperatures can also be achieved with additional color decoration functions;(3)Preparation of core-shell segmented conductive hydrogel / thermochromic elastomer composite fiber and its performance as a flexible wearable strain and temperature sensor: by using dual-core coaxial needles and wet spinning process to extrude the conductive hydrogel and thermochromic elastomer alternately,we prepare a segmented conductive hydrogel / thermochromic elastomer composite fiber.Because of the large differences between the principles of strain and temperature sensing,prepared segmented fibers do not interfere with their detection signals as strain and temperature sensors.Besides,due to the existence of a segmented structure,a composite fiber can be used as multiple temperature sensors and multiple strain sensors simultaneously,showing very good sensor integration performance.