Unlike artificial skin that is commonly used when building robots, this skin is alive, said lead study author Shoji Takeuchi, project professor in the department of mechanical and biofunctional systems at the Institute of Industrial Science at the University of Tokyo.
“Living skin is the ultimate solution to give robots the look and touch of living creatures,” Takeuchi said.
His research team chose a robotic finger for the experiment because this mechanism is well studied and a critical part of a robot, he said.
Building the skin
The humanlike skin is made using the same building blocks as human skin, Takeuchi said.
The robotic finger was first submerged in a solution of collagen, which is a fibrous protein, and human dermal fibroblasts, the two major components that make up human skin. Dermal fibroblasts are the primary cell type in the connective tissue of the skin.
After the solution conformed around the finger, Takeuchi applied human epidermal keratinocytes to the outside. A keratinocyte is the main type of cell that makes up the human epidermis, the outermost layer of skin, he said.
In the trials, the elastic human skin moved freely while the finger made different motions, Takeuchi said. His team put a collagen bandage on a part of the finger that had been inflicted with a wound to mend it, and the robot was able to move freely after the protein repaired the skin.
Collagen is a major component of human skin and has healing properties, according to a 2021 study.
The skin could also repel water, which expanded what tasks the robot could perform.
When researchers used a robot with wet surface material, polystyrene foam beads stuck to it, according to the study. These beads are commonly used as filler material in products such as beanbags and some stuffed animals.
When the scientists tried the same experiment with the water-repellent humanlike skin, the robotic finger could flick the foam beads away without them sticking, the authors said.
Designing robots in our own image
Humanoids are robots that perform tasks that involve interacting with humans in settings such as the medical, nursing care and service industries, according to the study.
It’s important to have humanlike robots when they are in places humans commonly frequent, said Pulkit Agrawal, Steven and Renee Finn career development professor and assistant professor in the department of electrical engineering and computer sciences at the Massachusetts Institute of Technology in Cambridge. He was not involved in the study.
“Humans design spaces around them, so having a humanlike robot is useful in those scenarios,” Agrawal said.
For example, robots that may one day be in a household need to be able to pick up items and move around the way a person does, he said.
If a robot were to be made of metal, it would need to be extremely precise to pick up another hard object such as a mug, Agrawal said. There would be a small amount of contact between the two objects since neither is flexible.
If the hand were soft like human skin, the robot could be less precise since more surface area on the mug would be covered as the soft skin conforms to the handle, he said.
A step in the right direction
The discovery is an important one, Agrawal said, but development of the humanlike skin still has a long way to go.
Skin is a living organism, so it needs to sustain itself by being constantly nourished while removing waste, Takeuchi said.
Unfortunately, the current skin that was grown does not have that ability built in, so it cannot sustain itself, he said.
Takeuchi is interested in adding a vascular system, the way blood is circulated throughout our body, to help shuttle nutrients to and from the cells and keep the skin alive. He also wishes to develop additional details for the skin such as hair follicles, nails and sweat glands.
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