Scientists at the National University of Singapore have been inspired by the jellyfish and other marine invertebrates to create an electronic, skin-like material. The transparent, stretchable, touch-sensitive, and self-healing material can work underwater and might be used in water-resistant touch screens and so-called soft robots. [Cao, Y., et al., Nature Electronics (2019) 2(2), 75: DOI: 10.1038/s41928-019-0206-5]
NUS's Benjamin Tee worked with collaborators from Tsinghua University and the University of California Riverside on the invention. "Tee has been working on self-healing materials for many years and is well aware of the problems that have to be overcome in developing such systems."One of the challenges with many self-healing materials today is that they are not transparent and they do not work efficiently when wet," he explains. "These drawbacks make them less useful for electronic applications such as touch screens which often need to be used in wet weather conditions." Tee adds that "With this idea in mind, we began to look at jellyfishes - they are transparent, and able to sense the wet environment. We wondered how we could make an artificial material that could mimic the water-resistant nature of jellyfishes and yet also be touch sensitive."
In a proof of principle, the team created a gel consisting of a fluorocarbon-based polymer with a fluorine-rich ionic liquid. The polymer network interacts with the ionic liquid via highly reversible ion-dipole interactions, which the team explains give it the ability to self-heal. Moreover, unlike other conductive hydrogels, this material does not swell in water nor does it dry out when left in the air. The novel material retains its properties and structure in both wet and dry conditions. The team adds that it functions well even in sea water, acidic, and alkaline environments.
The team made their electronic skin by printing it into an electronic circuit. As it is soft and stretchable, its electrical properties change when it is put under strain, simply touched or pressed. "We can then measure this change, and convert it into readable electrical signals to create a vast array of different sensor applications," Tee explains. Indeed, it should be possible to 3D print completely transparent and fully functional circuits from this material.
With such a substance to hand it could be possible to construct soft robots and soft electronics devices that can mimic biological tissues and perhaps even organs and make them more compliant to human-machine interaction. But, perhaps one of the more immediate applications that would benefit anyone who has dropped their smart phone, is a touch screen that can repair itself!