University of Tokyo researchers have found a way to bind engineered skin tissue to the complex forms of humanoid robots, taking inspiration from human skin ligaments.

In addition to better lifelike appearance, potential benefits to robotic platforms include increased mobility, self-healing abilities, and embedded sensing capabilities, according to Professor Shoji Takeuchi of the University of Tokyo in a statement. Their research could also be useful in the cosmetics industry and to help train plastic surgeons.

Binding skin to complex structures

Takeuchi is a pioneer in the field of biohybrid robotics, where biology and mechanical engineering meet. So far, his Biohybrid Systems Laboratory has created mini robots that walk using biological muscle tissue with 3D-printed lab-grown meat and engineered skin that can heal.

“By mimicking human skin-ligament structures and by using specially made V-shaped perforations in solid materials, we found a way to bind the skin to complex structures. The natural flexibility of the skin and the strong method of adhesion mean the skin can move with the mechanical components of the robot without tearing or peeling away,” Takeuchi said.

Any shape of the surface can have living skin applied to it—think of the possibilities

Previous methods to attach skin tissue to solid surfaces involved things like mini anchors or hooks, but these limited the kinds of surfaces that could receive skin coatings and could cause damage during motion. By carefully engineering small perforations instead, essentially any surface shape can have skin applied to it.

The trick: use a special collagen gel for adhesion, which is naturally viscous so difficult to feed into the minuscule perforations. But using a common technique for plastic adhesion called plasma treatment, they managed to coax the collagen into the fine structures of the perforations while also holding the skin close to the surface in question.

Imagine super-self-healing robots with humanlike dexterity and realistic skin

“Manipulating soft, wet biological tissues during the development process is much harder than people outside the field might think, said Takeuchi. “For instance, if sterility is not maintained, bacteria can enter and the tissue will die. However, now that we can do this, living skin can bring a range of new abilities to robots.

“Self-healing is a big deal. Some chemical-based materials can be made to heal themselves, but they require triggers such as heat, pressure or other signals, and they also do not proliferate like cells. Biological skin repairs minor lacerations as ours does, and nerves and other skin organs can be added for use in sensing and so on.”

Major implications for cosmetic and surgical procedures

“A face-on-a-chip could be useful in research into skin aging, cosmetics, surgical procedures, plastic surgery and more. And if sensors can be embedded, robots may be endowed with better environmental awareness and improved interactive capabilities,” Takeuchi said.

“We believe that creating thicker and more realistic skin can be achieved by incorporating sweat glands, sebaceous glands, pores, blood vessels, fat and nerves. And creating humanlike expressions by integrating sophisticated actuators, or muscles, inside the robot.

“Creating robots that can heal themselves, sense their environment more accurately and perform tasks with humanlike dexterity is incredibly motivating.”

Citation: M. Kawai, M. Nie, H. Oda, S. Takeuchi. “PERFORATION-TYPE ANCHORS INSPIRED BY SKIN LIGAMENT FOR THE ROBOTIC FACE COVERED WITH LIVING SKIN,” Cell Reports Physical Science, https://www.cell.com/cell-reports-physical-science/fulltext/S2666-3864(24)00335-7 (open access) 

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