Researchers innovate scalable robotic fibers with light-emitting, self-healing and magnetic properties

Scalable hydrogel-clad ionoelectronic nickel-core electroluminescent (SHINE) fibers are bendable, emit highly visible light, and self-repair after cutting, restoring nearly 100% of their original brightness. Additionally, fiber optics can be powered wirelessly and physically manipulated using magnetism.

By integrating multiple useful functions into a single device, the fiber has potential applications as light-emitting soft robotic fibers and interactive displays. It can also be woven into smart textiles.

“Most digital information today is primarily transmitted through light-emitting devices. We are very interested in developing sustainable materials that can emit light, and exploring new form factors, such as fibers, that can expand application scenarios, such as smart textiles. A method designed to Continuously emitting devices gives them the ability to self-repair, just like biological tissues such as skin,” said Associate Professor Benjamin Ti, the study’s lead researcher.

The team’s research, conducted in collaboration with the National University of Singapore’s Institute of Health Innovation and Technology (iHealthtech), is published in nature communications December 3, 2024.

Multifunctional innovation in a single device

Luminous fibers have emerged as an emerging field as they have the potential to complement existing technologies in multiple areas, including soft robotics, wearable electronics, and smart textiles. For example, providing functions such as dynamic lighting, interactive displays and optical signals while providing flexibility and adaptability can improve human-computer interaction by making it more sensitive and intuitive.

However, the use of this fiber is often limited by physical fragility and the difficulty of integrating multiple functions into a single device without adding complexity or increasing energy requirements.

The NUS research team’s SHINE fiber solves these challenges by combining light emission, self-healing and magnetic actuation in a scalable device. Compared with existing light-emitting optical fibers on the market that cannot repair themselves after damage and cannot be physically operated, SHINE optical fibers provide a more efficient, durable and versatile alternative.

The fiber is based on a coaxial design that combines a nickel core for magnetic response, a zinc sulfide-based electroluminescent layer for light emission, and a hydrogel electrode for transparency. Using a scalable ion-induced gel process, the team created fibers up to 5.5 meters long that retain functionality even after being stored in the open for nearly a year.

“To ensure clear visibility under bright indoor lighting conditions, a brightness of at least 300 to 500 cd/m2 is generally recommended,” Associate Professor Tee said. “Our SHINE fiber reaches a record brightness of 1068 cd/m2, easily exceeding the threshold and making it clearly visible even in well-lit indoor environments.”

The fiber’s hydrogel layer self-repairs through the reorganization of chemical bonds under ambient conditions, while the nickel core and electroluminescent layer restore structural and functional integrity through thermally induced dipole interactions at 50 degrees Celsius.

“More importantly, the recovery process can restore more than 98% of the fiber’s original brightness, ensuring it can withstand the mechanical stress after repair,” Associate Professor Tee added. “This ability supports the reuse and subsequent self-repair of damaged fibers, making this invention more sustainable in the long term.”

SHINE fibers also feature magnetic actuation enabled by a nickel core. This property allows manipulation of the fibers with external magnets. “This is an interesting property because it enables applications such as light-emitting soft robotic fibers to manipulate small spaces, perform complex movements and emit optical signals in real time,” said Dr. Xuemei Fu, the paper’s first author.

Revealing new human-computer interactions

SHINE fibers can be knitted or woven into smart textiles that light up and easily heal themselves after being cut, adding an element of durability and functionality to wearable technology. With their inherent magnetic drive, the fibers themselves can also act as soft robots, capable of emitting light, self-healing, navigating in confined spaces and emitting optical signals even after being completely severed. In addition, the optical fiber can also be used in interactive displays, and its magnetism can achieve dynamic pattern changes, thereby promoting optical interaction and signal transmission in the dark.

Looking to the future, the team plans to improve the accuracy of the fiber-optic magnetic drive 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 of SHINE fibers.