High-speed optoelectronic semiconductor devices, such as light-emitting diodes (LEDs) and diode photodetectors have now been embedded into fibres, which could be woven into wearable fabrics, as reported in Nature News & Comment. The full report was published in Nature, a scientific journal, on July 8 and represents the latest achievement in “smart” fabrics ― clothing with soft electronic devices that can optically communicate with other devices, which could have numerous potential applications in both telecommunications and healthcare, for example, monitoring someone’s heart rate.
Semiconductors are the basic building block of today’s digital electronics, and until now have been the missing component for making wearable fabrics with various complex functions. This discovery could rapidly progress the capabilities of optoelectrical fibres. A key advantage of this study is that the electronic components are based on existing commercially available high-performance devices ― ready-made, high-quality optoelectronic components only a few micrometres in size, referred to as chips.
Former Massachusetts Institute of Technology (MIT) graduate Michael Rein, Prof. Yoel Fink, professor of materials science and electrical engineering at MIT and CEO of AFFOA (Advanced Functional Fabrics of America), along with their MIT colleagues teamed up with AFFOA, Inman Mills in South Carolina, École Polytechnique Fédérale de Lausanne, Switzerland, and MIT’s Lincoln Laboratory, to develop the novel electronic devices.
The technology may sound simple but making the devices work and in a form that can be reliably manufactured in large quantities turned out to be quite a difficult process. To achieve this feat, the tiny light-emitting semiconductor diodes were connected to a pair of copper wires thinner than the width of human hair. One of the biggest challenges was ensuring these chips, as well as the conducting wires, could be protected from water and other environmental conditions. But by embedding the chips in a transparent polymer, they were protected from the elements and were also able to emit and detect light. The resulting soft devices are long polymer fibres with diodes lined along the centre connected by the copper wires, which can be sewn into various textiles.
One interesting possibility is the potential of transmitting information by optical means between fabrics. In other words, pulses of light emitted by a fabric can be sensed by another fabric close by, thus establishing an optical communication link. Rein and colleagues also showed that the intensity of light collected by the light-detecting fibre varies based on a person’s heart rate, therefore, by simply pressing a finger against the light-emitting fibre, the fabric could potentially act as a very basic heart rate monitor.
The findings are only preliminary and further optimisation is still required before these devices can be used effectively in real-world applications. In saying that, the first commercial products using this technology could be available as soon as next year, however, as with any new technology, economic factors will also be a deciding factor as to whether or not the technology is adopted.
(1) Rein, M. et al. Diode fibres for fabric-based optical communications. Nature (2018). DOI: 10.1038/s41586-018-0390-x