Signals from the electrically conductive hydrogel can clearly distinguish between different facial expressions. Image: 2018 KAUST.
Signals from the electrically conductive hydrogel can clearly distinguish between different facial expressions. Image: 2018 KAUST.

An electrically conductive hydrogel that takes stretchability, self-healing and strain sensitivity to new levels has been developed by researchers at the King Abdullah University of Science & Technology (KAUST) in Saudi Arabia. "Our material outperforms all previously reported hydrogels and introduces new functionalities," says Husam Alshareef, professor of materials science and engineering at KAUST.

Smart materials that flex, sense and stretch like skin have many potential applications involving interaction with the human body. Possibilities range from biodegradable patches that help wounds heal to wearable electronics and touch-sensitive robotic devices.

The new material, described in a paper in Science Advances, is a composite of a water-containing hydrogel and a metal-carbide two-dimensional material known as MXene. As well as being able to stretch by more than 3400%, the material can quickly return to its original form and will adhere to many surfaces, including skin. When cut into pieces, it can quickly mend itself upon reattachment.

"The material's differing sensitivity to stretching and compression is a breakthrough discovery that adds a new dimension to the sensing capability of hydrogels," says first author Yizhou Zhang, a postdoc in Alshareef's lab.

This new dimension may be crucial for applications that involve sensing changes in the skin and converting them into electronic signals. A thin slab of the material attached to a user's forehead, for example, can distinguish between different facial expressions, such as a smile or a frown. This ability could allow patients with extreme paralysis to control electronic equipment and communicate.

In addition, strips of the material attached to the throat have impressive abilities for converting speech into electronic signals, which might allow people with speech difficulties to be clearly heard. "There is real potential for our material in various biosensing and biomedical applications," says co-author Kanghyuck Lee.

More straightforward medical applications include flexible wound coverings that can release drugs to promote healing. These could be applied internally to diseased organs, in addition to adhering externally to skin. The team also envisions developing a smart material that could monitor the volume and shape of an organ and vary drug release according to signals produced, thereby combining medical sensing and therapy.

Other exciting possibilities lie in robotics, where the material could serve in touch-sensitive, finger-like extensions for machinery, for example. There are also anti-counterfeiting possibilities, with slabs of the material with integrated electronics proving highly adept at detecting signatures as they are written.

The KAUST team has a long list of possible applications that can now be further explored and developed. "There is great potential for commercialization," Alshareef concludes.

This story is adapted from material from KAUST, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.