Scientists from Nanyang Technological University, Singapore (NTU Singapore) have developed ultra-thin semiconductor fibres that will be woven into fabrics, turning them into smart wearable electronics.
To create reliably functioning semiconductor fibres, they have to be flexible and without defects for stable signal transmission. Nevertheless, existing manufacturing methods cause stress and instability, resulting in cracks and deformities within the semiconductor cores, negatively impacting their performance and limiting their development.
NTU scientists conducted modelling and simulations to grasp how stress and instability occur in the course of the manufacturing process. They found that the challenge might be overcome through careful material selection and a selected series of steps taken during fibre production.
They developed a mechanical design and successfully fabricated hair-thin, defect-free fibres spanning 100 metres, which indicates its market scalability. Importantly the brand new fibres will be woven into fabrics using existing methods.
To exhibit their fibres’ prime quality and functionality, the NTU research team developed prototypes. These included a wise beanie hat to assist a visually impaired person cross the road safely through alerts on a cell 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 versatile 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 event of semiconductor fibres which are ultra-long and sturdy, meaning they’re cost-effective and scalable while offering excellent electrical and optoelectronic (meaning it could actually sense, transmit and interact with light) performance.
NTU Associate Professor Wei Lei on the School of Electrical and Electronic Engineering (EEE) and lead-principal investigator of the study said, “The successful fabrication of our high-quality semiconductor fibres is because of the interdisciplinary nature of our team. Semiconductor fibre fabrication is a highly complex process, requiring know-how from materials science, mechanical, and electrical engineering experts at different stages of the study. The collaborative team effort allowed us a transparent understanding of the mechanisms involved, which ultimately helped us unlock the door to defect-free threads, overcoming a long-standing challenge in fibre technology.”
The study, published in the highest scientific journal Nature, is aligned with the University’s commitment to fostering innovation and translating research into practical solutions that profit society under its NTU2025 five-year strategic plan.
Developing semiconductor fibre
To develop their defect-free fibres, the NTU-led team chosen pairs of common semiconductor material and artificial material — a silicon semiconductor core with a silica glass tube and a germanium core with an aluminosilicate glass tube. The materials were chosen based on their attributes which complemented one another. These included thermal stability, electrical conductivity, and the power to permit electric current to flow through (resistivity).
Silicon was chosen for its ability to be heated to high temperatures and manipulated without degrading and for its ability to work within the visible light range, making it ideal to be used in devices meant for extreme conditions, reminiscent of sensors on the protective clothing for fire fighters. Germanium, alternatively, allows electrons to maneuver through the fibre quickly (carrier mobility) and work within the infrared range, which makes it suitable for applications in wearable or fabric-based (i.e. curtains, tablecloth) sensors which are compatible with indoor Light fidelity (‘LiFi’) wireless optical networks.
Next, the scientists inserted the semiconductor material (core) contained in the glass tube, heating it at hot temperature until the tube and core were soft enough to be pulled right into a thin continuous strand.
As a result of the several melting points and thermal expansion rates of their chosen materials, the glass functioned like a wine bottle in the course of the heating process, containing the semiconductor material which, like wine, fills the bottle, because it melted.
First writer of the study Dr Wang Zhixun, Research Fellow within the School of EEE, said, “It took extensive evaluation before landing on the fitting combination of materials and process to develop our fibres. By exploiting the several melting points and thermal expansion rates of our chosen materials, we successfully pulled the semiconductor materials into long threads as they entered and exited the heating furnace while avoiding defects.”
The glass is removed once the strand cools and combined with a polymer tube and metal wires. After one other 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 whole visible light range, from ultraviolet to infrared, and robustly transmit signals of as much as 350 kilohertz (kHz) bandwidth, making it a top performer of its kind. Furthermore, the fibres were 30 times tougher than regular ones.
The fibres were also evaluated for his or her washability, by which a cloth woven with semiconductor fibres was cleaned in a washer ten times, and results showed no significant drop within the fibre performance.
Co-principal investigator, Distinguished University Professor Gao Huajian, who accomplished the study while he was at NTU, said, “Silicon and germanium are two widely used semiconductors which are often considered highly brittle and liable to fracture. The fabrication of ultra-long semiconductor fibre demonstrates the chance and feasibility of creating flexible components using silicon and germanium, providing extensive space for the event of flexible wearable devices of varied forms. Next, our team will work collaboratively to use the fibre manufacturing method to other difficult materials and to find more scenarios where the fibres play key roles.”
Compatibility with industry’s production methods hints at easy adoption
To exhibit the feasibility of use in real-life applications, the team built smart wearable electronics using their newly created semiconductor fibres. These include a beanie, a sweater, and a watch that may detect and process signals.
To create a tool that assists the visually impaired in crossing busy roads, the NTU team wove fibres right into a beanie hat, together with an interface board. When tested experimentally outdoors, light signals received by the beanie were sent to a cell phone application, triggering an alert.
A shirt woven with the fibres, meanwhile, functioned as a ‘smart top’, which might be worn at a museum or art gallery to receive details about exhibits and feed it into an earpiece because the wearer walked across the rooms.
A smartwatch with a wrist band integrated with the fibres functioned as a versatile and conformal sensor to measure heart rate, versus traditional designs where a rigid sensor is installed on the body of the smartwatch, which will not be reliable in circumstances when users are very lively, and the sensor will not be in touch with the skin. Furthermore, the fibres replaced bulky sensors within the body of the smartwatch, saving space and freeing up design opportunities for slimmer watch designs.
Co-author Dr Li Dong, a Research Fellow within the School of Mechanical and Aerospace Engineering, said, “Our fibre fabrication method is flexible and simply adopted by industry. The fibre can be compatible with current textile industry machinery, meaning it has the potential for large-scale production. By demonstrating the fibres’ use in on a regular basis wearable items like a beanie and a watch, we prove that our research findings can function a guide to creating functional semiconductor fibres in the long run.”
For his or her next steps, the researchers are planning to expand the varieties of materials used for the fibres and give you semiconductors with different hole cores, reminiscent of rectangular and triangular shapes, to expand their applications.
