Engineers in Japan are trying to get robots to imitate that particularly human expression: the smile.
They created a face mask from human skin cells and attached it to robots using a new technique that hides the bond and is flexible enough to transform into a grimace or a soft smile.
The effect is halfway between the terrifying Hannibal Lecter mask and the Gumby claymation figure.
But scientists say the prototypes pave the way for more sophisticated robots, with an outer layer that is elastic and strong enough to protect the machine while making it more human-like.
In addition to expressiveness, the “skin equivalent,” as researchers call it, which is made in the laboratory from living skin cells, can scar and burn and even self-heal, according to a study published June 25 in the journal Cell Reports Physical Science.
“Human-like faces and expressions improve communication and empathy in human-robot interactions, making robots more effective in healthcare, service and companionship roles,” Shoji Takeuchi said in an interview, professor at the University of Tokyo and principal investigator of the study. e-mail.
The research comes at a time when robots are becoming more ubiquitous in factories.
According to the International Federation of Robotics, in 2022 there were 3.9 million industrial robots working on automotive and electronics assembly lines and other work environments.
A subset of the total robot fleet includes so-called humanoids, machines designed with two arms and two legs that allow them to work in environments built for human workers, such as factories, but also in the hospitality, healthcare and education sectors.
Carsten Heer, a spokesperson for the federation, said humanoids were “an exciting area of development” but that mass-market adoption would be complex and could be limited by cost.
However, in October 2023, the Chinese government announced a goal to mass-produce humanoids by 2025, which it predicted would significantly increase its industrial productivity.
For decades, robotics engineers have experimented with different materials, hoping to find something that could protect a robot’s complex mechanisms but was also soft and lightweight enough for a wide range of uses.
If a robot's surface is dented or scratched, it can cause the machine to malfunction, making self-repairing ability a “critical feature” for humanoid robots, the researchers say in the paper.
The new method of attachment to the skin advances the nascent field of “biohybrid” robotics, which integrates mechanical engineering with genetic and tissue engineering, said Kevin Lynch, director of the Center for Robotics and Biosystems at Northwestern University.
“This study represents a groundbreaking contribution to the problem of anchoring artificial skin to the underlying material,” said Professor Lynch, adding that “living skin may help us achieve the holy grail of self-healing skin in biohybrid robots.”
He added that the study does not address how the robots' skin self-heals without external support.
For these robots, the materials challenge extends to lifelikeness: finding ways to give the machine features that make it look and behave more like a human, such as the ability to smile.
Scientists, including Professor Takeuchi and his colleagues at the University of Tokyo, have been working with laboratory-created human skin for years.
In 2022, the research team developed a robotic finger covered in living skin, allowing the machine’s finger to bend like a human finger, giving it the tactility needed to potentially perform more precise tasks.
Professor Takeuchi’s team had tried anchoring the skin with mini-hooks, but these caused tears as the robot moved. So the team decided to mimic ligaments, the small cords of loose tissue that connect bones.
Team members drilled small V-shaped holes into the robot and applied a collagen-containing gel, which plugged the holes and attached the artificial skin to the robot.
“This approach complements traditional rigid robots with soft, biological skins, making them more ‘human-like,’” said Yifan Wang, an assistant professor in the School of Mechanical and Aerospace Engineering at Nanyang Technological University in Singapore who researches “soft robots” that mimic biological creatures.
The skin binding also gives the biohybrid robot the potential to generate sensations, bringing science closer to science fiction and fantasy.
“This could create opportunities for the robot to safely sense and interact with humans,” said Professor Wang.
The faces of the artificially skinned robots in Professor Takeuchi's lab lack the ability to sense touch, temperature changes, or other external stimuli.
Professor Takeuchi said this will be his next research focus.
“Our goal is to create skin that closely mimics the functionality of real skin by gradually building essential components such as blood vessels, nerves, sweat glands, sebaceous glands and hair follicles,” he said.
Instead of neural systems transmitting sensations in a human body, a robot's electronics would need to feed a sensor signal, a development that Professor Wang said would require much more time and research.