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Whether created to serve e-health, fashion or military needs, smart fabrics require energy sources that are often incorporated into clothing. Although electronic component miniaturization helps to make discrete and lightweight integrated devices, engineers today are seeking to “empower” textiles by introducing electronic functions into the fibre. This branch of engineering is called Fibretronics. Researchers at Nottingham Trent University in England explored this approach to create a garment that allows users to charge their small electronic devices while walking in the sun. The technology was developed by the Advanced Textile Research Group, led by Tilak Dias, a professor at the School of Art & Design.
The fabric is equipped with solar cells that produce electrical energy. It can be combined with several types of electronic components in the context of designing solutions for the health, sports, fashion, and other fields. In addition, the technology can offer new functions for applications like monitoring a body’s vital signs (heart rate, blood oxygen and skin temperature) and detecting environmental conditions (light, moisture and ultraviolet rays).
To operate, the garment or accessory must only be exposed to the sun, providing the user a sustainable energy source anytime, anywhere. In this regard, Mr. Dias notes that energy intake has long been the Achilles heel of smart textiles. This technology is also helping to reduce the use of wall outlets.
Manufacturing the Smart Fabric
The aim of the research was to create a manufacturing technique that incorporates solar cells into a textile surface. The solar cells used are photodiodes, semiconductor components that are able to capture light rays and convert them into electrical signals.
The photodiodes were miniaturized and covered with a fibrous sleeve. This created a fabric that behaves like any ordinary textile. The cells are almost invisible to the naked eye; they measure only 3 mm long and 1.5 mm wide. Furthermore, because it is washable, this smart fabric can be made into different types of clothing worn in any circumstance. The photodiodes are encapsulated in transparent resin to protect against water and other potentially damaging factors. Since the electronic behaviour of photodiodes depends on the nature of incoming light coming into contact with the photoactive material, the researchers studied the effect of the fibres and the resin capsule on their operation.
To validate the proper functioning of the technology, the team created a 5 cm square textile. The sample, which included 200 cells, was able to charge a mobile phone and a Fitbit. The researchers estimated that to generate enough energy to charge a smart phone, the fabric had to integrate 2000 photodiodes. Finally, washing tests confirmed that the fibres can withstand several machine wash and drying cycles without altering their performance.
The study co-authored by Achala Satharasinghe, Theodore Hughes-Riley and Tilak Dias, is entitled “Photodiodes embedded within electronic textiles” and was published in Nature Research on November 1, 2018.