A doctoral student at the Technion – Israel Institute of Technology in Haifa has invented a soft polymer that could be used as a self-healing high-tech “skin.”

Muhammad Khatib’s polymer is elastic and waterproof. It can heal itself if scratched, cut or twisted, or in the event of a disruption to its electrical conductivity and chemical sensing capabilities.

This “e-skin” could be used in a range of applications in the fields of robotics, prosthetics and wearable devices.

Khatib, who conducts his research at the Wolfson Faculty of Chemical Engineering at the Technion under the guidance of Prof. Hossam Haick, presented his innovative inventions in two papers in the journals Advanced Materials and Advanced Functional Materials.

Muhammad Khatib, inventor of e-skin, at the Technion-Israel Institute of Technology. Photo: courtesy

“The e‐skin is empowered with a novel self‐repair capability that consists of an intrinsic mechanism for efficient self‐healing of small‐scale damages as well as an extrinsic mechanism for damage mapping and on‐demand self‐healing of big‐scale damages in designated locations,” writes Khatib.

“The electronic platform lays down the foundation for the development of a new subcategory of self‐healing devices in which electronic circuit design is used for self‐monitoring, healing, and restoring proper device function.”

Inspired by natural mammal skin, scientists have put a great deal of effort into developing artificial electronic materials and devices with similar properties. These types of systems require soft materials whose functioning is not permanently harmed by distortions or tears. This is the problem that motivated Khatib to invent polymers that can heal themselves, just like human skin does after an injury.

Khatib’s self‐healing stretchable conductive pathways were made by embedding silver nanowires or carbon nanotubes into the surface of the polymer.

Self-healing even under water

Khatib’s first project, presented in Advanced Functional Materials, describes the planning, building and implementation of elastomer – elastic and resilient polymer – that is water resistant, strong and capable of stretching to 1,100 percent of its original length without tearing.

It can heal itself, even when soaked in tapwater, seawater, and water with varying levels of acidity. If mechanical damage to the polymer occurs when it is submerged in water, it knows how to heal itself and prevent electrical leakages from the device to the water.

The second project, presented in Advanced Materials, is an e-skin containing a sensory system composed of nanometric materials that selectively and simultaneously monitor environmental variables such as pressure, temperature, and acidity.

Inspired by the healing process of human skin, Khatib included an innovative autonomous self-healing system in the artificial skin. This system consists of neuron-like components that monitor damage to the system’s electronic parts, and other components that accelerate the self-healing process in the damaged places.

This mechanism of self-healing enables the smart electronic systems to self-monitor their activities and repair functional problems caused by mechanical damage.

“The new sensory platform is a universal system that displays stable functioning in both dry and wet environments, and it is capable of containing additional types of chemical and physical (electronic) sensors,” Khatib explained.

“Both projects that were now published pave the way for new paths and new strategies in the development of skin-inspired electronic sensing platforms that can be integrated into wearable devices and electronic skins for advanced robots and artificial organs.”

Khatib’s partners in the research are lab director Walaa Saliba; researcher Orr Zohar, who worked on developing the sensors and their attributes; and Prof. Simcha Srebnik, who worked on molecular simulations that clarify the capabilities of the new polymer.

The research was carried out with the support of the Bill and Melinda Gates Foundation and a grant from the A-Patch project, part of the EU Horizon 2020 program.