By Beatriz Valero de Urquia

Researchers at the University of Tokyo have developed a method to cover a robotic finger with living human cells.

In Japan, a team of scientists has pushed forward the field of robotics, by crafting living human skin on robots.

With the aim of making robots more human-like, the researchers from the University of Tokyo submerged a robotic finger in a cylinder filled with a solution of collagen and human dermal fibroblasts, the two main components that make up the skin’s connective tissues.

Due to the natural shrinking tendency of this collagen and fibroblast mixture, the solution adapted to the shape of the robotic finger, providing a uniform foundation for the next coat of cells — human epidermal keratinocytes — to stick to. These cells make up 90 per cent of the outermost layer of skin, giving the robot a skin-like texture and moisture-retaining barrier properties. 

The results, described in the journal Matter, not only gave a robotic finger skin-like texture, but also water-repellent and self-healing functions.

Researchers cover robotic finger with living human skin/Elsevier

“The finger looks slightly ‘sweaty’ straight out of the culture medium,” said Shoji Takeuchi, a professor at the University of Tokyo, Japan. “Since the finger is driven by an electric motor, it is also interesting to hear the clicking sounds of the motor in harmony with a finger that looks just like a real one.”

Scientists have strived to make robots appear more human-like, particularly those intended to interact with people, as  human-like appearance can improve communication efficiency and evoke likeability.

However, while the current method of using silicone to cover robots can mimic the human appearance, it lacks skin-specific functions. Attempts at fabricating living skin sheets to cover robots have also had limited success since it’s challenging to conform them to dynamic objects with uneven surfaces.

“With that method, you have to have the hands of a skilled artisan who can cut and tailor the skin sheets,” said Takeuchi. “To efficiently cover surfaces with skin cells, we established a tissue-moulding method to directly mould skin tissue around the robot, which resulted in a seamless skin coverage on a robotic finger.”

The skin developed by Takeuchi’s team has enough strength and elasticity to bear the dynamic movements as the robotic finger curled and stretched.

In experiments, the team proved that the outermost layer was thick enough to be lifted with tweezers and repelled water, which is vital for use cases such as packaging, in which robots wild need to handle electrostatically charged tiny polystyrene foam. When wounded, the crafted skin could also self-heal with the help of a collagen bandage, which gradually morphed into the skin and withstood repeated joint movements.

“We are surprised by how well the skin tissue conforms to the robot's surface,” said Takeuchi. “But this work is just the first step toward creating robots covered with living skin.”

Despite the advances, the developed skin is still too weak to be used commercially, as it requires constant nutrient supply and waste removal. Takeuchi and his team plan to work on addressing those issues and incorporating more sophisticated functional structures within the skin, such as sensory neurons, hair follicles, nails, and sweat glands.

“I think living skin is the ultimate solution to give robots the look and touch of living creatures since it is exactly the same material that covers animal bodies,” said Takeuchi.

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