Japanese scientists have created “sweaty” organic skin for robots that can heal itself.

A team at the University of Tokyo has crafted living human skin on robots, not only giving a robotic finger skin-like texture, but also water-repellent and self-healing functions.

The team placed a robotic finger in a solution of collagen and human dermal fibroblasts; the two main components that make up human skin’s connective tissues.

This initial layer of ‘skin’ shrank naturally to wrap the finger, and acts like an undercoat for the next layer 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 finger looks slightly ‘sweaty’ straight out of the culture medium,” says first author Dr Shoji Takeuchi. 

“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.”

Looking human is a major goal for the designers of humanoid robots, as it can improve communication efficiency and evoke likability. 

While current silicone skin made for robots can mimic human appearance, it falls short when it comes to delicate textures like wrinkles and lacks skin-specific functions. Attempts at fabricating living skin sheets to cover robots have also had limited success, since it is 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,” says Dr 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 crafted skin has enough strength and elasticity to bear the dynamic movements as the robotic finger is curled and stretched. 

The outermost layer is thick enough to be lifted with tweezers and repels water, which provides various advantages in performing specific tasks like handling electrostatically charged tiny polystyrene foam, a material often used in packaging. 

When wounded, the crafted skin could even self-heal like humans’ 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,” says Dr Takeuchi. 

“But this work is just the first step toward creating robots covered with living skin.” 

The developed skin is much weaker than natural skin and cannot survive long without constant nutrient supply and waste removal. 

Next, Dr Takeuchi and his team plan to address those issues and incorporate 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,” he says.

More details are accessible here.