Jean Hakuzimana

A study on the morphology of thin copper films on para-aramid yarns and their influence on the yarn’s electro-conductive and mechanical properties

The latest technological advances in new materials and devices enabled wearable systems to be created by utilizing textile solutions. These solutions require electro-conductive yarns as a basic component. Although the production of electro-conductive yarn is widely reported, research is still necessary to characterize them to advance their electro-conductive and mechanical properties. Hence, we served this need and characterized copper-coated para-aramid yarns produced by an in-house developed electroless deposition method. In this paper we present our investigation on the yarn’s copper layer characteristics after deposition. Furthermore, we looked, in depth, at the yarn’s electro-conductive properties before and after washing as well as their mechanical properties before and after copper deposition. We found a dependency of the copper layer morphology on its deposition time. This is directly correlated to the resulting layer thickness and hence to the yarn’s electro-conductive properties, demonstrating the autocatalytic nature of the coating process. Above that, the electro-conductive properties of the coated yarn linearly decrease with washing cycles. Furthermore, the copper coating impairs the yarn’s mechanical properties decreasing its specific stress at break by 30%.

Steps Towards a Textile-Based Transistor: Development of the Gate and Insulating Layer

During recent years, intensive research has been carried out in the area of electronic textiles. There is an emerging trend to create garments that host electronic components embedded in the textile substrate, as well as electronic textiles made from yarns or fibers already possessing electronic properties. The creation of passive devices, such as textile electrodes that measure body parameters, has proved successful. However, there is a great need for the development of textiles possessing additional active functions. Accordingly, we investigated the possibility of developing a textile substrate possessing integrated switching and amplification functions by depositing parts of an organic thin-film transistor on fibrous substrates of varying geometries and origins. This article relates the initial steps we employed to develop a textile-based thin-film transistor. It reports the development of a gate layer from the deposition of electroless copper, as well as the deposition of a polyimide dielectric layer using dip coating. Further, it discusses the layer’s properties in terms of thickness and electrical characteristics. A copper layer of 350 nm thickness deposited on polyester tape and polyamide fibers displayed excellent electro-conductive properties. A smooth gate dielectric layer was achieved with a polyimide concentration of 15 w% and a withdrawal speed of 50 mm/min. As a result, optimum conditions for producing thin functional gate and dielectric layers were found. The transistor properties, the deposition of a semiconductive layer, and the production of drain and source electrodes remain the focus of future work.

How to Equip Para-aramide Yarns with Electro-conductive Properties

Electro-conductive textiles are increasingly demanded in our today’s technology-driven world as they combine functionalities with high wearing comfort. Thus, they are, for instance, very suitable for being applied as electrodes integrated in clothing to measure biomedical parameters of a person. For this purpose they need to be modified to provide reliable electro-conductive properties. This can be achieved by depositing metals on the textile surface. Copper and gold are good materials to be used for this purpose because of their outstanding electro-conductive properties and possibility to deposit them in form of a thin layer on the surface of a fiber. In this work preference was given to copper. Hence, a thin layer of copper was deposited on synthetic yarns by means of an electroless deposition. This paper states the coating method for the copper deposition on para-aramide yarns. Further, it reports the first results on the characterization of the copper layer and the performance of the resulting yarns.

Gold Coated Polyester Yarn

Textiles are increasingly studied to use them as sensing and measuring devices of body parameters. For this purpose they need to be modified to provide on the one hand reliable and stable electroconductive properties and on the other they should be biocompatible. This can be achieved by depositing electroconductive materials such as metals on the textile surface. Gold is an ideal material to use as it offers the aforementioned criteria and can be applied as a thin coating on the surface of a fibre, yarn or fabric. We developed gold coated yarns that are highly electrically conductive, skin-friendly and stable. In this presentation, we describe the gold coating method and show first results of the characterisation of the coated yarns. A commercially available polyester yarn was coated with a thin layer of gold by using an electroless plating method. The plating solution was optimised towards the concentration of each component, the working temperature and pH. The quantitative analysis of the surface coverage of gold with EDAX and cyclic voltammetry showed in both cases a surface coverage of more than 95%. For the future, research will be continued to characterise the longterm behaviour of the yarns.