Scientists have developed ultra-thin semiconductor fibres that can be woven into fabrics, turning them into smart wearable electronics.
- Researchers at Nanyang Technological University, Singapore (NTU Singapore) conducted modelling and simulations to understand how stress and instability occur during the manufacturing process. They found that the challenge could be overcome through careful material selection and a specific series of steps taken during fibre production.
- The study, published in the journal Nature, is aligned with the University's commitment to fostering innovation and translating research into practical solutions that benefit society under its NTU2025 five-year strategic plan.
- The researchers are planning to expand the types of materials used for the fibres and come up with semiconductors with different hollow cores, such as rectangular and triangular shapes, to expand their applications.
THE PROBLEM: To create reliably functioning semiconductor fibres, they must be flexible and without defects for stable signal transmission. However, existing manufacturing methods cause stress and instability, leading to cracks and deformities in the semiconductor cores, negatively impacting their performance and limiting their development.
THE WORK: The scientists developed a mechanical design and successfully fabricated hair-thin, defect-free fibres spanning 100 metres, which indicates its market scalability. Importantly the new fibres can be woven into fabrics using existing methods.
- To demonstrate their fibres' high quality and functionality, the team developed prototypes. These included a smart beanie hat to help a visually impaired person cross the road safely through alerts on a mobile phone application; a shirt that receives information and transmits it through an earpiece, like a museum audio guide; and a smartwatch with a strap that functions as a flexible sensor that conforms to the wrist of users for heart rate measurement even during physical activities.
- The team believes that their innovation is a fundamental breakthrough in the development of semiconductor fibres that are ultra-long and durable, meaning they are cost-effective and scalable while offering excellent electrical and optoelectronic (meaning it can sense, transmit and interact with light) performance.
- To develop their defect-free fibres, the NTU-led team selected pairs of common semiconductor material and synthetic material—a silicon semiconductor core with a silica glass tube and a germanium core with an aluminosilicate glass tube. The materials were selected based on their attributes which complemented each other. These included thermal stability, electrical conductivity, and the ability to allow electric current to flow through (resistivity).
- Silicon was selected for its ability to be heated to high temperatures and manipulated without degrading and for its ability to work in the visible light range, making it ideal for use in devices meant for extreme conditions, such as sensors on the protective clothing for fire fighters. Germanium, on the other hand, allows electrons to move through the fibre quickly (carrier mobility) and work in the infrared range, which makes it suitable for applications in wearable or fabric-based (i.e. curtains, tablecloth) sensors that are compatible with indoor Light fidelity ('LiFi') wireless optical networks.
- Next, the scientists inserted the semiconductor material (core) inside the glass tube, heating it at high temperature until the tube and core were soft enough to be pulled into a thin continuous strand.
- Due to the different melting points and thermal expansion rates of their selected materials, the glass functioned like a wine bottle during the heating process, containing the semiconductor material which, like wine, fills the bottle, as it melted.
- The glass is removed once the strand cools and combined with a polymer tube and metal wires. After another round of heating, the materials are pulled to form a hair-thin, flexible thread.
- In lab experiments, the semiconductor fibres showed excellent performance. When subjected to responsivity tests, the fibres could detect the entire visible light range, from ultraviolet to infrared, and robustly transmit signals of up to 350 kilohertz (kHz) bandwidth, making it a top performer of its kind. Moreover, the fibres were 30 times tougher than regular ones.
- The fibres were also evaluated for their washability, in which a cloth woven with semiconductor fibres was cleaned in a washing machine ten times, and results showed no significant drop in the fibre performance.
