Functional electronic textiles for light emitting and colour changing applications

Smart fabrics, or electronic-textiles (e-textiles), concern the addition of electronic functionality to standard textiles. Textiles are a ubiquitous material available in many forms and used in a huge range of applications from clothing to technical textiles that are applied in, for example, creative industries and medicine. This proposal addresses the fabrication of light emitting films on textiles and their application to achieve textile displays and colour-changing fabrics through research into electronically functional inks and using spray coating, inkjet and screen printing. Textiles are demanding substrates for device printing due to their rough surface topology, porosity and the constraints they impose on processing temperatures. The achievement of suitable functional materials along with reliable, consistent fabrication processes will have a huge impact in the textile, garment and creative industries. The ability to control the appearance of textiles through selective illumination and colour change will produce a step change in e-textile capability that will add value, function and product differentiation.

In particular, this programme of research will investigate the fabrication of textile organic light emitting electrochemical cells (OLECs) operating at visible and UV wavelengths. OLECs have the attractions of being electrochemically stable in air, require a low turn on voltage (~3V) and demonstrate a high luminance level (>800 cd/m2) allowing them to be clearly visible in everyday lighting. The OLEC structure requires only a single functional layer which makes it relatively straightforward to fabricate compared to, for example, OLED's. The ability to selectively emit different wavelengths of light will produce a step change in e-textile capability. Visible wavelength OLECs can be used to produce variable, controllable, light emitting patterns on the textile, which can be used in high visibility clothing or fashion applications. UV wavelength OLECs will enable a textile to perform ultraviolet germicidal irradiation (UVGI), which is a disinfection method that uses short wavelength UVC light at 222 or 254 nm. Textile based UVGI can be incorporated into medical applications such as smart bandages to treat/prevent infection and reduce reliance on antibiotics. UV-OLECs can also be combined with additional printed photochromic layers to realise non-light emitting colour changing textiles. When exposed to UV light, photochromic materials change from transparent to opaque and this can produce significant changes in colour. This approach can control the textile appearance without emitting light or requiring the OLEC to be continuously switched on

The research will include the formulation of custom designed enhanced organic molecules with enhanced emission efficiency compared to the state of the art. These will be formulated into printable materials and combined with printable conductive materials. Device architectures and fabrication processes (spray coating, inkjet and screen printing) will also be explored. The research will address the key processing challenges in order to realise reliable and robust thin films and devices on textiles.

E-textiles in general will enable a huge range of new textile products that will revolutionise the textile industry and industries that use e-textiles such as fashion, defence, healthcare/medical, automotive, interior design and workwear. All these industries will benefit from a low cost, low power practical technology for illuminating textiles. For example, workwear applications will benefit from garments that both emit and reflect light making workers more visible and safer. The ability to change the appearance of fabrics will impact upon the fashion and defence industries by enabling a step change in the ability of clothing to vary in appearance. This will enable a new class of fashion related products and, for defence applications, improved camouflage will make personnel harder to detect and observe. The interest of Dstl in this project testifies to this. The automotive industry could exploit the technology in car interiors as an alternative approach for lighting simplifying wiring and providing product differentiation. Applications of the UV light emitting textile will impact upon the healthcare sector by providing a convenient and practical platform for treating wound infections and reducing the reliance on antibiotics. This could improve patient care and potentially reduce treatment times. Project partner URGO are well placed to exploit the research results in this area.

The number of applications of light emitting textiles means a successful technology will impact directly upon the textiles industry. This project should provide a mass manufacturable route for low cost, low power light emitting textiles that will add a competitive advantage for companies that develop the research into practical manufacturing processes. Project partners Carrington Textiles have the expertise and facilities to do this. Such a new class of textile products will provide a new market for the raw materials involved impacting upon chemical companies such as Merck.

The potential for impact of the research is very significant and the project partners represent the supply chain and end users providing an excellent opportunity for generating impact. Other routes for impact will also be pursued as described in the Pathways to Impact.