The robots can be covered in living skin grown from real human cells, which will make them look like humans, writes New Scientist.

As jobs increasingly take on the roles of nurses, caregivers, teachers, and other people who involve close personal contact, it is important to make them more human so that we are comfortable communicating with them, says Shoji Takeuchi of the University of Tokyo in Japan. At this time, the robots are sometimes coated in silicone rubber to give them a fleshy look, but the rubber lacks the texture of human skin, he says.

To make the skin more realistic, Takeuchi and his colleagues bathed a plastic robot’s finger for three days in a soup of collagen and human skin cells called fibroblasts. Collagen and fibroblasts stuck to the finger and formed a layer similar to the dermis, which is the second top layer of human skin.

Next, they gently poured other human skin cells called keratinocytes onto the finger to recreate the upper layer of human skin, called the epidermis.

The resulting skin 1.5 millimeters thick could be stretched and compressed when the finger was bent back and forth. Takeuchi says it wrinkled like normal skin during that time. “It’s much more realistic than silicone.”

The skin of the robot could also be healed when it was cut by grafting a collagen sheet on the wound. However, after a while, the skin began to dry out because it did not have blood vessels to fill it with moisture.

In the future, it may be possible to include artificial blood vessels in the skin to keep it hydrated, as well as sweat glands and hair follicles to make it more realistic, Takeuchi said. It should also be possible to make the skin different colors by adding melanocytes, he says.

Now researchers plan to try to cover the whole robot with live skin. “But since this research field has the potential to build a new relationship between humans and robots, we need to carefully consider the risks and benefits of making it too realistic,” Takeuchi said.