Complex Regional Pain Syndrome Medicine

Soft, stretchable electronic skin could reconstruct the sense of touch

This post originally appeared on StatNews.

The largest organ in the body is a wonder. Skin is soft, flexible, and sensitive to every imaginable stimuli, and seamlessly plugs into the nervous system. This makes it extremely difficult to replicate — but that hasn’t stopped a team of Stanford researchers from trying.

“We hope in the future, prosthetic devices can not only give the functionality but also the appearance of our natural body,” said Weichen Wang, an engineering Ph.D. and first author on a paper on electronic skin published Thursday in Science. 


Electronic skin, or “e-skin,” is not a new concept. Scientists have been dreaming of human-machine interfaces that mimic the sense of touch, healing patients with paralysis or lost limbs, since at least the 1960s. Researchers across the world are working on different iterations, with some that focus on tactile sensing and others that are built for health monitoring, some built from hard, inorganic materials made flexible and others created with soft, organic materials that are flexible from the start. 

A soft e-skin system is preferable in that it’s easier to apply to normal skin. But getting a device built out of entirely soft materials to produce the strong electronic signals needed to sense touch is a challenge. In the paper, the Stanford team demonstrates that it’s possible to use a soft, stretchable e-skin to trigger a nerve response. When applying more pressure or a higher temperature to the skin, the nerve-like electronic pulses moved faster. The research team, led by Zhenan Bao, tested the material on a rat, applying different pressures to the sensor on the e-skin. Nerve cells started firing in the rat’s brain, triggering leg twitches. 

“The most exciting part of this work is that we are able to use all soft materials to fabricate everything, from sensors to the circuits,” Wang said. 


The team also succeeded in making their e-skin run on low voltage. Placing high-voltage electrical devices on skin is dangerous, so building a low-voltage device that still produces the appropriate electric response is crucial. 

Experts, including Wang, told STAT that bringing this technology to the clinic is still a distant reality. So far, most e-skin researchers are simply trying to prove that it’s possible to build a skin sensing system at all, validating the safety and efficacy of the electronic materials. That alone has taken 30 years. 

“You can validate proof of concept into animal models, but that doesn’t mean it’s going to be implemented very quickly in humans,” said Stéphanie Lacour, a neuroengineer working on stretchable biomaterials at the Swiss Federal Institute of Technology.

Still, outside experts are impressed by the Stanford team’s progress in proving the viability of a soft skin device. Tsuyoshi Sekitani, an engineer at Osaka University, emphasized how hard it is to build a sensory feedback loop using only stretchable electronics. It helps move us toward a world where “the boundary between living organisms and machines is disappearing,” he said. 

He noted that it’s unclear how well the system would hold up when integrated with the human body. The Stanford system is built from organic materials, which are more vulnerable to damage from water, oxygen, and high humidity. Withstanding wear and tear caused by the air or human skin will be key. 

“The defense and rejection reactions of living tissues are extremely delicate, and as yet, the long-term stability of the interface between engineered materials and living tissues is far from satisfactory,” Sekitani wrote in an email to STAT. “Further development of biocompatible materials is essential.”

In addition to testing for durability, Wang hopes to incorporate more sensors into the e-skin in the future. They’ve tested the skin only with a pressure and temperature sensor so far. Scaling up to include more sensors and more circuits will create a more accurate dupe for real human skin — perhaps someday gifting prosthetic devices all the subtleties of touch.

This post originally appeared on StatNews.