Ultra-thin semiconductor fibers turn fabrics into wearable electronics


Ultra-thin semiconductor fibers turn fabrics into wearable electronics
Ultra-thin semiconductor fibers turn fabrics into wearable electronics

NTU Singapore scientists develop ultra-thin semiconductor fibers that turn fabrics into wearable electronics. Scientists from Nanyang Technological University, Singapore (NTU Singapore) have developed ultra-thin semiconductor fibers that can be woven into fabrics, turning them into intelligent wearable electronics.

To create reliably functioning semiconductor fibers, 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.

NTU scientists conducted modeling and simulations to understand how stress and
instability occur during manufacturing. They found that the challenge could
be overcome through careful material selection and a specific series of steps taken
during fiber production.

They developed a mechanical design and successfully fabricated hair-thin, defect-free
fibers spanning 100 meters, which indicates its market scalability. Notably, the new
fibers can be woven into fabrics using existing methods.

To demonstrate their fibers’ high quality and functionality, the NTU research team
developed prototypes. These included an intelligent beanie hat to help a visually impaired
person crosses 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 fibers 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.

NTU Associate Professor Wei Lei at the School of Electrical and Electronic
Engineering (EEE) and lead-principal investigator of the study 

“The successful fabrication of our high-quality semiconductor fibers is thanks to the
interdisciplinary nature of our team. Semiconductor fiber 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 clear understanding of the mechanisms involved, which ultimately
helped us unlock the door to defect-free threads, overcoming a long-standing
challenge in fiber technology.”

The study, published in the top scientific 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.

Developing semiconductor fiber

To develop their defect-free fibers, 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 allowing 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 firefighters. Germanium, on the other hand, allows electrons to move
through the fiber quickly (carrier mobility) and work in the infrared range, which makes
it is 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 (see image below).

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 melts.

The first author of the study Dr. Wang Zhixun, a Research Fellow in the School of EEE, said, “It took extensive analysis before landing on the right combination of materials
and process to develop our fibers. By exploiting the different 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 another round of heating, the materials are pulled to form a hair-thin,
flexible thread.

In lab experiments, the semiconductor fibers showed excellent performance. When
subjected to responsivity tests, the fibers 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 fibers were 30 times
tougher than regular ones.

The fibers were also evaluated for their washability, in which a cloth is woven with
semiconductor fibers were cleaned in a washing machine ten times, and the results
showed no significant drop in fiber performance.

Co-principal investigator, Distinguished University Professor Gao Huajian, who
completed the study while he was at NTU, said, “Silicon and germanium are two widely
used semiconductors, which are usually considered highly brittle and prone to fracture.
The fabrication of ultra-long semiconductor fiber demonstrates the possibility and
feasibility of making flexible components using silicon and germanium, providing
extensive space for the development of flexible wearable devices of various forms.
Next, our team will work collaboratively to apply the fiber manufacturing method to
other challenging materials and to discover more scenarios where the fibers play key

Compatibility with the industry’s production methods hints at easy adoption.

To demonstrate the feasibility of use in real-life applications, the team built smart
wearable electronics using their newly created semiconductor fibers. These include a
beanie, a sweater, and a watch that can detect and process signals.

To create a device that assists the visually impaired in crossing busy roads, the NTU
team wove fibers into a beanie hat and an interface board. When tested
experimentally outdoors, light signals received by the beanie were sent to a mobile
phone application, triggering an alert.

A shirt woven with the fibers, meanwhile, functioned as a ‘smart top,’ which could be
worn at a museum or art gallery to receive information about exhibits and feed it into
an earpiece as the wearer walked around the rooms.

A smartwatch with a wristband integrated with the fibers functioned as a flexible and
conformal sensor to measure heart rate, as opposed to traditional designs where a
rigid sensor is installed on the body of the smartwatch, which may not be reliable in
circumstances when users are very active and the sensor is not in contact with the
skin. Moreover, the fibers replaced bulky sensors in the body of the smartwatch,
saving space and freeing up design opportunities for slimmer watch designs.

Co-author Dr Li Dong, a Research Fellow in the School of Mechanical and
Aerospace Engineering said, “Our fiber fabrication method is versatile and easily
adopted by industry. The fiber is also compatible with current textile industry
machinery, meaning it has the potential for large-scale production. By demonstrating
the fibers’ use in everyday wearable items like a beanie and a watch, we prove that
our research findings can serve as a guide to creating functional semiconductor fibers
in the future.”

For their next steps, the researchers are planning to expand the types of materials
used for the fibers and come up with semiconductors with different hollow cores, such
as rectangular and triangular shapes, to expand their applications..

Ultra-thin semiconductor fibers turn fabrics into wearable electronics: Original Article. 

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