ELECTRONIC TEXTILE-BASED WIRELESS COMMUNICATION AND SENSING DEVICES

Abstract

Electronic textiles (e-textiles), i.e., the fibers/fabrics with sensing, actuating and communication functionalities, have gained great attentions in wearable applications in recent years. However, the current researches on e-textiles are not suitable for long-term wearing. By way of example, e-textiles with polymer coverages are not air-permeable and can induce errors in measurements; textiles integrated with solid-state battery are not aesthetic for apparel integration and cannot withstand washing and wearing attritions. This thesis proposes new techniques for the design and construction of e-textile materials and devices to achieve the communication and sensing functions used in wireless body area network (WBAN) applications. The thesis specifically focuses on several key aspects that include the functionalization, construction and characterization of the e-textile communication and sensing devices. 1) Conductive yarns are used to construct the antennas and interconnect for WBAN communications systems. Different from traditional metallic wires, the electromagnetic properties of conductive yarns are significantly affected by parasitic elements induced from the micro-structures of the fibers. The parasitic factors of conductive yarns are extracted and characterized in this thesis, and a more accurate model is proposed. Using this new model, the design accuracy of the embroidered inductive coil antenna for Near Field Communication (NFC) is within 5%, as compared to over 20% discrepancy using the traditional Wheeler equation. 2) As wearable devices have to endure different body movements, stretchable and deformation-resilient e-textile structures are also explored. Taking the NFC coil antenna as examples, several geometries and structures are proposed that can maintain stable electrical and EM properties under extreme deformation and elongation caused by stretching and bending. 3) Several functionalization techniques are proposed to construct e-textile sensing devices that are comfortable for long-term wearing, mechanically friendly for apparel integration and electrically stable from ambient variations. The functionalization process uses the pad-dyeing method with graphene oxide (GO) solution, and the GO fabric is further reduced to graphene oxide (rGO) fabric. Based on these techniques, a wool-knitted, rGO-functionalized strain sensor, and a Coolmax-woven, GO-functionalized humidity sensor are introduced. These sensors not only exhibit excellent sensing properties, more specifically, they are also unimodal and are resilient to other modal of ambient variations, i.e., the rGO-based strain sensor is insensitive to heat and moisture from human body; the GO-Coolmax humidity senor is insensitive to external pressure and temperature variations. The outcome from this research will provide guidelines for exploring new e-textile materials and devices, and facilitate the applications of e-textiles for health monitoring, patients/infants caring as well as body movement tracking and logging.

Date of Award	19 Nov 2020
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Yi Li (Main Supervisor), Zhirun Hu (Co Supervisor) & Xuqing Liu (Co Supervisor)