In Japan, engineers 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 with a new technique that conceals the bond and is flexible enough to transform into a grimace or a squishy smile.
The effect is somewhere between the terrifying mask of Hannibal Lecter and the plasticine figure Gumby.
But scientists say the prototypes pave the way for more sophisticated robots, with an outer layer that is both elastic and durable enough to protect the machine while making it appear more human.
Beyond expressiveness, the “skin equivalent,” as researchers call it, which is made from living skin cells in the laboratory, can scar and burn, but also self-heal, according to a study published on 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,” said Shoji Takeuchi, professor at the University of Tokyo and principal investigator of the study, in an email.
This research comes as robots become increasingly ubiquitous in factories.
There was 3.9 million industrial robots working on automotive and electronics assembly lines and in other work environments by 2022, according to the International Federation of Robotics.
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 designed for human workers, such as factories, but also in the hospitality, healthcare and education.
Carsten Heer, a spokesman for the federation, said humanoids were “an exciting area of development” but mass market adoption would be complex and could be limited by cost.
Yet in October 2023, the Chinese government announced a target of mass producing humanoids by 2025, which it says would significantly increase its industrial productivity.
For decades, Robotic engineers experimented with materialshoping to find something that could both protect a robot’s complex machinery while also being flexible and lightweight enough for a wide range of uses.
If a robot’s surface is scratched or scratched, it can cause the machine to malfunction, making the ability to self-repair a “critical feature” for humanoid robots, the researchers said in the paper.
The new skin-attachment method advances the nascent field of “biohybrid” robotics, which integrates mechanical engineering with genetic and tissue engineering, said Kevin Lynch, director of Northwestern University’s Center for Robotics and Biosystems.
“This study is a novel contribution to the problem of anchoring artificial skin to the underlying material,” said Professor Lynch, adding that “living skin could 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 such robots, the materials challenge extends to verisimilitude: finding ways to imbue the machine with features that make it appear 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 human skin made in the laboratory 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 to potentially perform more precise tasks.
Professor Takeuchi’s team had tried to anchor the skin with mini-hooks, but these caused tears when the robot moved. So the team decided to mimic ligaments, the tiny strings of loose tissue that connect bones.
Team members drilled small V-shaped holes into the robot and applied a gel containing collagen, which plugged the holes and attached the artificial skin to the robot.
“This approach integrates 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 studies “soft robots” that mimic biological creatures.
Skin bonding also gives a biohybrid robot the potential for sensation, bringing science closer to science fiction fantasy.
“This could give the robot the ability to detect humans and safely interact with them,” Professor Wang said.
The faces of the artificial-skinned robots in Professor Takeuchi’s lab do not have the ability to detect touch, temperature changes, or other external stimuli.
Professor Takeuchi said this was his next research goal.
“We aim to create skin that faithfully 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 the neural systems that transmit 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.
