Scientists from Japan have created living human skin that will help in the creation of biohybrid robots, which are made of both living and artificial materials.
The method was presented on June 9 in the journal Matter.
The team was able to give a robotic finger a skin-like texture, as well as water-repellent and self-healing functions.
Shoji Takeuchi is a professor at the University of Tokyo, Japan.
“The finger looks slightly ‘sweaty’ straight out of the culture medium,” Takeuchi says. “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 been consistently trying to make humanoid robots look ‘real,’ especially for those that are developed to interact with humans in healthcare and service industries. By creating a human-like appearance, the communication efficiency and likeability of robotics can be improved.
Limitations of Artificial Silicone Skin
The artificial skin developed for current robots is usually made of silicone, which mimics human appearance. However, it does not achieve realistic delicate textures like wrinkles, and it lacks skin-specific functions. There has also been limited success in fabricating living skin sheets to cover robots. It is very difficult 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,” Takeuchi continues. “To efficiently cover surfaces with skin cells, we established a tissue molding method to directly mold skin tissue around the robot, which resulted in a seamless skin coverage on a robotic finger.”
Constructing the Living Skin
The team first submerged the robotic finger in a cylinder filled with a solution of collagen and human dermal fibroblasts, which are two of the main components that make up human skin’s connective tissues. According to Takeuchi, the method’s success is owed to the natural shrinking tendency of the collagen and fibroblast mixture, which causes it to shrink and conform to the finger.
This layer provides the foundation for the next coat of cells to stick to, and these cells are human epidermal keratinocytes, which make up 90% of the outermost layer of skin. This enables the robot to achieve a skin-like texture and moisture-retaining barrier properties.
The skin demonstrated enough strength and elasticity to allow the robotic finger to curl and stretch, and the outermost layer was thick enough to be lifted with tweezers and repel water. One of the other more interesting aspects of this development is that the crafted skin demonstrated an ability to self-heal, just like human skin.
“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.”
With all of that said, there are still some challenges with this type of living skin. For one, it is weaker than natural skin and requires a constant nutrient supply and waste removal to survive.
The team will now look to overcome these challenges by incorporating sophisticated functional structures with the skin, which could include hair follicles, nails, sensory neurons, 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,” says Takeuchi.