Development of a yarn capable of measuring localised temperature

In this research an electronic temperature sensor (ETS) yarn has been developed by embedding a commercially available thermistor chip into the fibres of a yarn. A polymer resin is used to encapsulate the thermistor creating a micro-pod which protects the thermistor from mechanical and chemical stresses during use, and also allows the ETS yarn to be washed. The thermistor micropod and interconnects were then encased within a warp knitted braid to from the ETS yarn. Temperature is the most widely measured physiological bio-marker in medicine. Temperature changes can indicate underlying pathologies such as wound infections or the formation of ulcers in diabetic patients. A temperature sensor capable of providing remote, continuous and localised (temperature at a given point) temperature measurements could provide clinicians with a powerful tool when handling such complications. Even though there are many flexible temperature sensors they lack true textile characteristics making them unsuitable in many situations. The existing textile-based temperature sensors are incapable of providing localised measurements and can suffer from hysteresis. At the start of the project a geometrical model of the ETS yarn was developed in-order to understand its design parameters. Then the crafting of the ETS yarn was achieved in three key stages. Hardware and software necessary to obtain temperature from the ETS yarn have been developed. Thereafter work has been conducted to characterise the behaviour of the thermistor and understand the design rules for the micro-pod. Theoretical models were created in COMSOL in-order to study the heat flow through the micro-pod and warp knitted braid, and the effect they have on the response and recovery times of the thermistor. The model has been validated using experiments. Results have shown that encapsulating the thermistor in a micro-pod and making it into a yarn has a minimal effect on the thermal time constant and that the resin of the micro-pod and fibres of the warp knitted braid have no significant impact on the accuracy of the temperature readings. The research into calibrating the ETS yarn has shown that the resistance-temperature conversion equation provided by the thermistor manufacturer provided the most accurate temperature measurement with 63 % of the readings being within ± 0.5 °C accuracy. Cyclic tests have been carried out on the ETS yarn to ensure that its performance is not effected by mechanical strain. Thereafter an evaluation of the response of the ETS yarn to operational conditions (ambient temperature, moisture content, wind speed) was studied. Finally, prototype temperature sensing garments have been produced using a network of ETS yarns. The necessary hardware and software to capture the temperature data from these prototypes has been developed. Finally, two prototypes have been created, a temperature sensing sock with five ETS yarn for detecting non-freezing cold injuries and a dressing with 16 ETS yarns to provide a temperature map of a wound. The temperature sensing sock was tested on volunteers. Both the wound dressing and the sock can provide remote, continuous and localised temperature measurements without compromising the textile characteristics of the fabric

Connection techniques of textile wires to the solid and flexible solar cells

In order to make better use of clean energy such as solar energy, textile on earth have the potential to be made into solar textiles. The commercial solar cells can be embedded between the textile layers by laminating to harvest energy for e-textile applications. Research about solar textiles is not mature enough, and many aspects of the problem need to be solved. However, connecting techniques of conductive textile wires to flexible and solid solar cells are not in-deep studied. In addition, solar textile products with these connection technologies must meet washable requirements. To solve the problem of connecting textile wires to flexible and solid solar cells in the production of solar textiles, this study proposes three connection techniques for solar textiles, which are tape, adhesive and stitching based on literature and experimental validation. The feasibility of tape and adhesive methods was analyzed by literature review and the feasibility of stitching method was verified by experiments. The stitching is unapplicable method for solid solar cells that are difficult to penetrate, but applicable for flexible solar cells. The machine-washing durability of solar textile which composed of solar cells with stitch-connected conductive textile wires was verified by experiments. First, the textile wires were joined to flexible solar cells by stitching with the sewing machine and then embedded between fabric layers with TPU-lamination to simulate real set up in e-textile application. The humidity stickers were attached to the surface of solar cells, and it was expected to present solar textile samples with or without water inside. After the machine-washing process is completed, the individual parts of the solar textile sample are disassembled by delamination. For stitching method, after 15 machine wash tests by household washing machines, the performance of the solar cells was hardly affected, and the internal water resistance of the samples was good. The delamination process verifies that the components of the solar textile can be disassembled and have the potential to be recycled. The feasibility of tape connections has been proven by previous studies. Flexible adhesives that have the potential to connect textile wires to solar cells are liste

Electronically active textiles

Electronically Active Textiles (e-textiles) are a type of textile material that has some form of electronic functionality. This can be achieved by attaching electronics onto the surface of the textile, incorporating electronic components as part of the fabrication of the textile itself, or by integrating electronics into the yarns or fibers that comprises the textile. The addition of electronic components can give textiles a wide range of new functions from lighting or heating to advanced sensing capabilities. As such, e-textiles have provided a platform for developing a range of new novel products in fields, such as healthcare, sports, protection, transport, and communications. The purpose of this volume is to report on the advances in the integration of electronics into textiles, and presents original research in the field of e-textiles as well as a comprehensive review of the evolution of e-Textiles. Topics include the fabrication and illumination of e-textiles and the use of e-textiles for temperature sensing

Light-emitting textiles: Device architectures, working principles, and applications

E-textiles represent an emerging technology aiming toward the development of fabric with augmented functionalities, enabling the integration of displays, sensors, and other electronic components into textiles. Healthcare, protective clothing, fashion, and sports are a few examples application areas of e-textiles. Light-emitting textiles can have different applications: Sensing, fashion, visual communication, light therapy, etc. Light emission can be integrated with textiles in different ways: Fabricating light-emitting fibers and planar light-emitting textiles or employing side-emitting polymer optical fibers (POFs) coupled with light-emitting diodes (LEDs). Different kinds of technology have been investigated: Alternating current electroluminescent devices (ACELs), inorganic and organic LEDs, and light-emitting electrochemical cells (LECs). The different device working principles and architectures are discussed in this review, highlighting the most relevant aspects and the possible approaches for their integration with textiles. Regarding POFs, the methodology to obtain side emissions and the critical aspects for their integration into textiles are discussed in this review. The main applications of light-emitting fabrics are illustrated, demonstrating that LEDs, alone or coupled with POFs, represent the most robust technology. On the other hand, OLEDs (Organic LEDs) are very promising for the future of light-emitting fabrics, but some issues still need to be addressed

THE THERMOELECTRIC, THERMORESISTIVE, AND HYGRORESISTIVE PROPERTIES AND APPLICATIONS OF VAPOR PRINTED PEDOT-CL

Wearable electronics are a valuable tool to increase consumer access to real-time and long-term health care monitoring. The development of these technologies can also lead to major advancements in the field, such as self-charging systems that are completely removed from the electrical grid. However, much of the wearable technology available commercially contain rigid components, use unsustainable synthetic methods, or undesirable materials. The field has thus been moving towards wearables that mimic textiles or use textiles as a substrate. Herein, we discuss the use of oxidative chemical vapor deposition (oCVD) to produce textiles coated with poly(3,4-ethylenedioxythiophene) known as PEDOT-Cl. We evaluate the thermoelectric, thermoresistive, and hygroresistive properties of these PEDOT-Cl fabrics. We also explore the applications of these properties by creating humidity sensors, temperature sensors, and thermoelectric generators integrated with clothing. In general, we discuss the process of designing a wearable to best accommodate the desired application

Flexible Temperature Sensors on Fibers

The aim of this paper is to present research dedicated to the elaboration of novel, miniaturized flexible temperature sensors for textronic applications. Examined sensors were manufactured on a single yarn, which ensures their high flexibility and good compatibility with textiles. Stable and linear characteristics were obtained by special technological process and applied temperature profiles. As a thermo-sensitive materials the innovative polymer compositions filled with multiwalled carbon nanotubes were used. Elaborated material was adapted to printing and dip-coating techniques to produce NTC composites. Nanotube sensors were free from tensometric effect typical for other carbon-polymer sensor, and demonstrated TCR of 0.13%/K. Obtained temperature sensors, compatible with textile structure, can be applied in rapidly developing smart textiles and be used for health and protections purposes

Conformable light emitting modules

As we become increasingly aware that there is more to light than the image it forms on our retina, and as we become more environmentally aware, the value of non-image-forming light increases along with the need for various new light related appliances. In particular, some lighting related applications are emerging which demand conformability (flexibility and stretchability). Well-being, automotive or wearable electronic applications are just a few examples where these trends can be observed. We are finding that conformability could bring various benefits to both users (tactile and optical comfort, optical efficiency, multi-functionality, work/living space savings) as well as manufacturers (heterogeneous integration, light-weight, design freedom, differentiation and less stringent tolerancing). Developed by Ghent University, the SMI (Stretchable Molded Interconnect) technology attempts to address these demands and has been the main focus of this work. With the SMI technology it was possible to design highly conformable circuits using fabrication methods similar to these found in the PCB and FCB industries and standard off-the-shelf electronic components. The goal of this work was to characterize the technology materials in terms of mechanical, optical and reliability performance as well as define a set of design rules to support creation of robust and efficient light modules, also using a set of new, commercially available elastomeric, polymer materials. The developments are illustrated with demonstration devices