Flexible and green electronics made from silk

A research group from the Technical University of Denmark (DTU) is developing a new class of flexible, eco-friendly thin-film electronics, which they call ‘fleco-ionics’.

The team utilised cocoons, woven by silkworms, to extract silk — one of the strongest materials in nature, and one that is cheap, readily available and biodegradable. In addition, it is an ionic conductor — a material that can conduct electricity mainly through the passage of ions.

Ionic conductors have been utilised to yield flexible Li-ion batteries, stretchable display devices, transparent touch screens, loudspeakers and actuators, but they still present drawbacks. Notably, most of them have been made of synthetic materials, which are potentially hazardous for humans and the environment. Therefore, research towards eco-friendly alternatives is essential — and silk could be the answer.

“We need to think simple,” said Professor Alireza Dolatshahi-Pirouz, head of the DTU research group. “Why do we want to do old, complicated chemical syntheses that take months and years to optimise when we can be smart and look into nature?”

The team has now transformed this natural polymer into an ionic material with stable performance in both aqueous and chemically active environments, enabling a wide range of applications within the field of flexible and wearable electronics. They have already used it to develop a small motion sensor, made from silk and nano-sized clay.

As explained in the journal Advanced Science, the production process for the sensor is extremely simple, with the two main components simply mixed together in water; the product is thus easy to upscale. It is also low cost ($0.62/unit), maintains its high electrical sensitivity even after 2000 bending cycles and can be recycled again and again. The technology is thus suitable for mass production without compromising the environment.

Applications for the flexible motion sensors vary from pressure-sensitive displays to motion-sensing gloves, with the team already developing their own E-glove equipped with the sensors. Supported by DTU’s Proof of Concept funding, the first prototype of their E-glove should be ready in about 10 months, which could help surgeons to perform better in operations, translate sign language or even help golfers improve their technique.

The scientists are also working on flexible sensing systems that readily conform to the curvatures of the body and can measure motions without any discomfort to the user. This would address a number of drawbacks that current motion capture imaging technologies are suffering, including their limited measuring range, low sensitivity and impractical measuring scenarios.

Image credit: ©stock.adobe.com/au/lily

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