Scalable fibers with light-emitting, self-healing and magnetic properties could enhance human-robot interactions

A team has developed flexible fibers with self-healing, light-emitting and magnetic properties. The scalable hydrogel-clad ionotronic nickel-core electroluminescent (SHINE) fiber is bendable, emits highly visible light, and can automatically repair itself after being cut, regaining nearly 100% of its original brightness. In addition, the fiber can be powered wirelessly and manipulated physically using magnetic forces.

With multiple useful features incorporated into a single device, the fiber finds potential applications as light-emitting soft robotic fibers and interactive displays. It can also be woven into smart textiles.

The team’s research was published in Nature Communications on 3 December 2024. The researchers include interdisciplinary scientists from the Department of Materials Science and Engineering under the College of Design and Engineering at the National University of Singapore (NUS) who collaborated with the Institute for Health Innovation & Technology (iHealthtech) at NUS.

“Most digital information today is transmitted largely through light-emissive devices. We are very interested in developing sustainable materials that can emit light and explore new form factors, such as fibers, that could extend application scenarios, for example, smart textiles. One way to engineer sustainable light-emitting devices is to make them self-healable, just like biological tissues such as skin,” said Associate Professor Benjamin Tee, the lead researcher for this study.

Multifunctional innovation in a single device

Light-emitting fibers have become an area of burgeoning interest owing to their potential to complement existing technologies in multiple domains, including soft robotics, wearable electronics and smart textiles. For instance, providing functionalities like dynamic lighting, interactive displays and optical signaling, all while offering flexibility and adaptability, could improve human-robot interactions by making them more responsive and intuitive.

However, the use of such fibers is often limited by physical fragility and the difficulty of integrating multiple features into one single device without adding complexity or increasing energy demands.

The NUS research team’s SHINE fiber addresses these challenges by combining light emission, self-healing and magnetic actuation in a single, scalable device. In contrast to existing light-emitting fibers on the market, which cannot self-repair after damage or be physically manipulated, the SHINE fiber offers a more efficient, durable and versatile alternative.

The fiber is based on a coaxial design combining a nickel core for magnetic responsiveness, a zinc sulfide-based electroluminescent layer for light emission and a hydrogel electrode for transparency. Using a scalable ion-induced gelation process, the team fabricated fibers up to 5.5 meters long that retained functionality even after nearly a year of open-air storage.

“To ensure clear visibility in bright indoor lighting conditions, a luminance of at least 300 to 500 cd/m² is typically recommended,” said Assoc Prof Tee. “Our SHINE fiber has a record luminance of 1,068 cd/m², comfortably exceeding the threshold, making it highly visible even in well-lit indoor environments.”

The fiber’s hydrogel layer self-heals through chemical bond reformation under ambient conditions, while the nickel core and electroluminescent layer restore structural and functional integrity through heat-induced dipole interactions at 50 degrees Celsius.

“More importantly, the recovery process restores over 98% of the fiber’s original brightness, ensuring it can endure mechanical stresses post-repair,” added Assoc Prof Tee. “This capability supports the reuse of damaged and subsequently self-repaired fibers, making the invention much more sustainable in the long term.”

The SHINE fiber also features magnetic actuation enabled by its nickel core. This property allows the fiber to be manipulated with external magnets.

“This is an interesting property as it enables applications like light-emitting soft robotic fibers capable of maneuvering tight spaces, performing complicated motions and signaling optically in real-time,” said Dr. Fu Xuemei, the first author of the paper.

Unraveling new human-robot interactions

The SHINE fiber can be knitted or woven into smart textiles that emit light and easily self-heal after being cut, adding an element of durability and functionality to wearable technology.

With its intrinsic magnetic actuation, the fiber itself can also function as a soft robot, capable of emitting light, self-healing, navigating confined spaces and signaling optically even after being completely severed. Additionally, the fiber can be used in interactive displays, where its magnetism allows for dynamic pattern changes that facilitate optical interaction and signaling in the dark.

Looking ahead, the team plans to refine the precision of the fiber’s magnetic actuation to support more dexterous robotic applications. They are also exploring the possibility of weaving sensing capabilities—such as the ability to detect temperature and humidity—into light-emitting textiles made entirely from SHINE fibers.