Future robots could be enveloped in lifelike skin that not only appears more human but also has the ability to repair itself, much like human skin, thanks to an innovative approach using cultured skin cells.
This advanced skin will also have a more natural appearance due to a novel method of attaching it to the robot’s skeleton, as well as its ability to self-repair from cuts or scrapes, according to researchers.
Their findings were published on June 25 in the journal Cell Reports Physical Science.
Artificial skin has long been seen as a way to make robots more human-like, with cultured skin offering a more realistic look compared to synthetic materials like latex.
However, one of the challenges has been finding the right adhesive method to prevent the skin from sagging or slipping off the robot’s frame, which can be visually unsettling.
Previously, robotics researchers tried to address this issue by using “anchors”—hooked or mushroom-shaped structures—to secure the artificial skin to the metallic frame. While this method prevented the skin from shifting, it often resulted in unsightly lumps, compromising the skin’s human-like appearance.
In this new study, researchers developed a technique where the robot’s skeleton is designed with tiny holes. Into these holes, the artificially grown skin extends V-shaped hooks, known as “perforation-type anchors.” These anchors securely attach the skin to the robot while maintaining a smooth and flexible surface.
Making Robotic Skin More Lifelike
The artificial skin is applied to a robot that has been treated with a water-vapor plasma, making it hydrophilic, or more attractive to liquids. This treatment allows the cultured skin’s gel to penetrate deeper into the holes, ensuring a tighter bond with the robot’s surface.
One significant advantage of this new skin is its potential to allow robots to operate alongside humans without experiencing excessive wear and tear. Small tears or damage to the skin could self-repair without the need for manual intervention, according to the research team. However, the study did not measure the speed at which the artificial skin heals after being damaged.
In a demonstration, researchers replicated how skin changes when a human smiles. They attached the artificial skin to a robotic face with a sliding layer of silicone underneath, which created the effect of “inflating cheeks” as the muscles contracted, pushing the skin up at the corners of the mouth. Thanks to the perforation anchors, the skin could seamlessly conform to the 3D contours of the face without any protruding bolts or hooks.
The researchers also compared the performance of the artificial skin on surfaces with and without the perforation-based anchors. On anchorless surfaces, the skin shrank by as much as 84.5% over seven days, while on surfaces with 0.04-inch (1 millimeter) anchors, the shrinkage was reduced to 33.6%.
Skin contraction on a robot could cause it to separate from the robot’s inner frame, ruining its lifelike appearance and potentially damaging the skin layer. Larger anchors of 0.1-inch (3 mm) and 0.2-inch (5 mm) further reduced shrinkage to 26.4% and 32.2%, respectively.
The Path to Humanlike Androids
Shoji Takeuchi, a researcher involved in the study at the Institute of Industrial Science (IIS), University of Tokyo, explained that several steps remain before robots can be equipped with skin using the team’s methods.
“Firstly, we need to enhance the durability and longevity of the cultured skin when applied to robots, particularly by addressing issues related to nutrient and moisture supply,” Takeuchi said. “This could involve developing integrated blood vessels or other perfusion systems within the skin.”
“Secondly, improving the mechanical strength of the skin to match that of natural human skin is crucial. This involves optimizing the collagen structure and concentration within the cultured skin.”
Takeuchi also pointed out that for artificial skin to be truly functional, it must eventually be able to convey sensory information, such as temperature and touch, to the robot wearing it, and be resistant to biological contamination.
The researchers believe that advancements in this field could enhance our understanding of how facial muscles convey emotions, potentially leading to breakthroughs in treatments for conditions like facial paralysis, as well as expanding the capabilities of cosmetic and orthopedic surgery. Additionally, improved skin adhesion techniques might eliminate the need for V-shaped holes in future robotic designs.
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