For millennia, the thought of mechanical humans has captivated and terrified us, from Talos, the enormous bronze robot that guarded the princess Europa in ancient Greek stories, through Cylons and Terminators.
With the creation of live robot skin, we're closer than ever to developing a robot that looks remarkably like a person. This slimy material is water resistant, self-healing, and has a texture similar to our own skin.
It's formed of human skin cells, after all.
"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 Shoji Takeuchi, a tissue engineer at the University of Tokyo.
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," Takeuchi comments. "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."
Attempts to graft skin onto robotic surfaces have proven difficult in the past, but Michio Kawai and colleagues at the University of Tokyo devised a method that allows the skin to shape itself to the device.
"It is difficult to cut, glue, or suture the endpoints of skin equivalent without damaging the soft, fragile tissue," Kawai and colleagues write in their research.
Instead, scientists submerged 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 connective tissue of the skin.
They next applied epidermal cells (keratinocytes), the major component of our outermost skin layer, to this primer layer. The material would not have the same level of water repellence as mammals if it didn't have this additional layer.
The electrostatically charged polystyrene bead adheres to the finger without an epidermis in the video below, making it difficult for the finger to handle.
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 content in the first solution, as well as increased cell maturation, according to the researchers, might help.
Surprisingly, the artificial skin may be repaired with a collagen bandage, which the live cells absorb and incorporate into their system to help repair the damage.
While the results are impressive, the availability of lab-grown tissue is currently restricted. It won't stay long outside of its nutritional solution because, like our skin, it needs a steady supply of water to avoid drying up, but the artificial skin layers lack the intricate components of the circulatory and sweat gland systems that provide this hydration.
"Building perfusion channels within and beneath the dermis equivalent to mimic blood vessels to supply water, as well as the integration of sweating glands in the skin equivalent, are important directions for future research," Kawai and colleagues add.
They also propose attaching 'nerves' and sensors to lab-made skin so that it may be multi-talented like our own, acting as both a protective barrier and a sensory organ.
"We are surprised by how well the skin tissue conforms to the robot's surface," says Takeuchi. "But this work is just the first step toward creating robots covered with living skin."
Researchers think that by making robots seem more human, we will be able to better relate to and enjoy them, allowing them to better engage with people in the medical, care, and service industries. (Of course, this assumes we can advance artificial humanoids beyond the uncanny valley.)
"These findings show the potential of a paradigm shift from traditional robotics to the new scheme of biohybrid robotics that leverage the advantages of both living materials and artificial materials," the researchers write.
