It took a decade, but a Stanford team has developed an artificial, plastic material that mimics the skin’s ability to flex and heal as well as allowing sensory signals like touch, temperature, and pain to be sent to the brain.
It could be a huge leap forward for people with prosthetic limbs.
Zhenan Bao, Ph.D., a professor of chemical engineering at Stanford, worked with a team of 17 scientists to develop the creation, which was revealed today in the journal Science.
Bao’s ultimate goal is to create a flexible electronic fabric embedded with sensors that can cover a prosthetic limb to replicate some of the skin’s sensory functions.
It’s just another step toward her goal of replicating an aspect of touch that enables a person to distinguish the pressure difference between a limp handshake and a firm grip.
“This is the first time a flexible, skin-like material has been able to detect pressure and also transmit a signal to a component of the nervous system,” said Bao.
How Artificial Skin Works
The invention is a two-ply system.
Its top layer collects the sensory input while the bottom transports those signals and translates them into stimuli mimicking nerve cells’ signals.
The team first described how it could work five years ago, saying the plastics and rubbers could be used as pressure sensors by measuring the natural springiness of their molecular structures as they encountered stimuli. They refined that idea by indenting a waffle pattern into the plastic.
Billions of carbon nanotubes were embedded in the waffled plastic. When pressure is applied, the nanotubes squeeze together to create electricity.
The amount of pressure being applied activates a proportional amount of electrical pulses being sent through the mechanism. That is then applied to the circuits to carry pulses of electricity to nerve cells.
In order to make it truly skin-like in that it could bend without breaking, the team worked with researchers from PARC, a Xerox company with a promising technology.
Once the materials were selected and deployed, the team had to determine how to make the signal recognizable by a biological neuron. They bioengineered cells to make them sensitive to different frequencies of light. The light pulses were used to switch the processes inside the cells on and off.
While optogenetics (as the technology is known in research circles) is only used in the experimental phase, other methods are likely to be used in real prosthetic devices, Bao said.
What’s Next in Research
The team hopes to develop different sensors to replicate different tactile sensations. The hope is to help prosthetics discern silk compared to fur, or a glass of water compared to a cup of coffee. Getting to that level, however, is another lengthy process.
“We have a lot of work to take this from experimental to practical applications," Bao said. "But after spending many years in this work, I now see a clear path where we can take our artificial skin.”
Benjamin Tee, a recent doctoral graduate in electrical engineering; Alex Chortos, a doctoral candidate in materials science and engineering; and Andre Berndt, a postdoctoral scholar in bioengineering were the lead authors on the Science paper.
They said the research has been rewarding.
“Working on a project that could impact so many people is great because it really brings people together to work toward a common goal,” Chortos told Healthline. “This was a major factor in the success of the project since there were so many people involved from different labs.”