Thermally Drawn Multi-Material Fibers for Electronic Textiles

Advanced functionalities integrated within fibers and fabrics are at the heart of the technological developments for electronic textiles. While functionalities are often added to the fibers or textiles via different deposition strategies, an emerging alternative approach relies in integrating materials and devices within the individual fibers. The thermal drawing process in particular, the technique used to fabricate telecommunication optical fibers, have experienced a series of materials and processing breakthroughs that have significantly expand the kind of materials and architectures that can be integrated into fibers. Flexible and even stretchable polymer fibers have been demonstrated to integrate metallic electrode arrays, electrically addressed semiconducting and piezoelectric domains, micro-channels, or textured surfaces with nanometer feature sizes. This provides fibers with novel advanced optical but also electronic and optoelectronic functionalities, with intriguing opportunities in energy harvesting and storage, fiber probes and optprobes, sensing, bioengineering and advanced e-textiles. In this presentation, we would like to introduce the vibrant field of multi-material fibers and highlight the several opportunities for the electronic textiles community. We will in particular present the fabrication approach, materials and achievable architectures offered by this process leading to novel electronic fibers and textiles (Adv. Materials 31, 1802348 (2019) (review paper from our group)). We will then discuss several recent results from our group starting with a first design that allows for the detection and localization of pressure along the fiber axis (J. Phys. D: Appl. Phys. 50, 144001 (2017)). We will then move to new designs based on the thermal drawing of thermoplastic elastomers, that enables to realize soft and deformable fibers (Adv. Mat. 30, 1707251 (2018)). We will show in particular electronic fibers and e-textiles that integrate conducting nano-composites (Adv. Funct. Mat. 30, 1904274 (2019)), and an innovative design where several liquid metal electrodes are co-drawn within an elastomeric cladding, forming distributed sensors based on transmission line principles (Nature Electronics 3, 316 (2020)). The achieved combination of pressure points localization and textile stretching enabled with only two contact points at a fiber end is unprecedented. We will also demonstrate similar soft fiber architectures and textile adapted for self-powered sensors and energy harvesters relying on the triboelectric effects (Nature Communications. 11, 3537 (2020)). We will conclude with the recent demonstration of the drawing of metallic glasses we could achieve, with feature sizes down to a few nanometers within a flexible fibers (Nature Nanotechnology 15, 875 (2020)), paving the way towards novel opportunities for fibers and textiles in bioengineering, sensing, electrochemistry (ACS Appl. Mat. and Int. 13, 43356 (2021)), and fabrics for the composite industry (Adv. Mat. Technologies 6, 2000957 (2021)).