Stretchable, self-healing material lights up

A new stretchable material, when used in light-emitting capacitor devices, enables highly visible illumination at low operating voltages, and is also resilient to damage due to its self-healing properties. This innovation, called the HELIOS (Healable, Low-field Illuminating Optoelectronic Stretchable) device, was achieved by researchers at the National University of Singapore (NUS) and has been described in the journal Nature Materials.

“Conventional stretchable optoelectronic materials require high voltage and high frequencies to achieve visible brightness, which limits portability and operating lifetimes,” said Assistant Professor Benjamin Tee. “Such materials are also difficult to apply safely and quietly on human-machine interfaces.”

To overcome these challenges, Asst Prof Tee and his team began studying and experimenting with possible solutions in 2018, and eventually developed HELIOS after a year.

In order to lower the electronic operating conditions of stretchable optoelectronic materials, the team developed a material which has very high dielectric permittivity and self-healing properties. The material is a transparent, elastic rubber sheet made up of a blend of fluoroelastomer and surfactant. The high dielectric permittivity enables it to store more electronic charges at lower voltages, enabling a higher brightness when used in a light-emitting capacitor device.

Unlike existing stretchable light-emitting capacitors, a HELIOS-enabled device can turn on at voltages that are four times lower and achieve illumination that is more than 20 times brighter. It also achieved an illumination of 1460 cd/m² at 2.5 V/µm, the brightest attained by stretchable light-emitting capacitors to date, and is now comparable to the brightness of mobile phone screens. Due to the low power consumption, HELIOS can achieve a longer operating lifetime, be utilised safely in human-machine interfaces and be powered wirelessly to improve portability.

HELIOS is also resistant to tears and punctures. The reversible bonds between the molecules of the material can be broken and reformed, thereby allowing the material to self-heal under ambient environmental conditions.

Describing the potential impact of HELIOS, Asst Prof Tee said, “Light is an essential mode of communication between humans and machines. As humans become increasingly dependent on machines and robots, there is huge value in using HELIOS to create ‘invincible’ light-emitting devices or displays that are not only durable but also energy efficient. This could generate long-term cost savings for manufacturers and consumers, reduce electronic waste and energy consumption and, in turn, enable advanced display technologies to become both wallet and environmentally friendly.”

For example, HELIOS can be used to fabricate long-lasting wireless displays that are damage-proof. It can also function as an illuminating electronic skin for autonomous soft robots to be deployed for smart indoor farming, space missions or disaster zones. Having a low-power, self-repairing illuminating skin will provide safety lighting for the robot to manoeuvre in the dark while remaining operational for prolonged periods.

The NUS team has filed for a patent for the new material and is looking to scale up the technology for specialty packaging, safety lights, wearable devices, and automotive and robotics applications.

Image caption: The NUS research team behind the novel electronic material is led by Assistant Professor Benjamin Tee (centre). With him are two team members: Wang Guanxiang (left), who is holding a sample of the illuminated material, and Dr Tan Yu Jun (right). Image credit: National University of Singapore.

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