With the creation of living robot skin, we're closer than ever to developing a robot that looks remarkably like a person. Because it's formed of human skin cells, this substance is water repellent, self-healing, and has a texture similar to our own skin.

"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," University of Tokyo tissue engineer Shoji Takeuchi said.

A prototype of this lab-grown skin has been successfully coated onto a three-jointed, working robot finger.

"The finger looks slightly 'sweaty' straight out of the culture medium," says 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."

Previous attempts to graft skin onto robotic surfaces failed, but Michio Kawai, a tissue engineer at the University of Tokyo, and colleagues created a different way that allows the skin to form itself onto the device.

Instead, they immersed the robotic structure in a collagen and dermal fibroblast solution - cells that generate the proteins that make up our skin's structural matrix. These are the primary components of the skin's connective tissue.

They next applied epidermal cells (keratinocytes), the major component of our outermost skin layer, to this primer layer. Without this extra layer, the material would lack water repellence similar to that of animals.

While the gooey substance could withstand the robotic finger's repetitive stretching and contracting actions, it is still far weaker than human skin. A higher collagen concentration in the first solution, as well as increased cell maturation, according to the researchers, could help.

Surprisingly, the artificial skin may be repaired with a collagen bandage, which the living cells absorb and integrate into their system to help repair the damage.

While the results are impressive, lab-grown tissue is still quite limited. It cannot survive long outside of its nourishing solution because, like our skin, it requires a steady supply of water to avoid drying up, but the artificial skin layers lack the complex components of circulatory and sweat gland systems that provide such hydration.

They also propose attaching 'nerves' and sensors to lab-made skin so that it can function as both a protective and a sensory organ like ours.

The researchers hope that making robots appear more human will help humans relate to and like them more, allowing them to communicate with us more effectively.

Their research was published in Matter.