Perforations on robot face help adhesion of engineered skin

Humanoid robots could be given a more lifelike appearance and other properties following research that binds engineered skin tissue to the varied surfaces of the machines.

Other methods to bind skin tissue to solid structures come with limitations. This new method can work on complex, curved, and even moving surfaces
Other methods to bind skin tissue to solid structures come with limitations. This new method can work on complex, curved, and even moving surfaces - ©2024 Takeuchi et al. CC-BY-ND

Carried out at the University of Tokyo, the research could lead to other potential benefits for robotic platforms such as increased mobility, self-healing abilities, and embedded sensing capabilities. The team’s findings are detailed in Cell Reports Physical Science.

Taking inspiration from human skin ligaments, the team - led by Professor Shoji Takeuchi and his colleagues in the Biohybrid Systems Laboratory - added perforations into a robot face, which helped a layer of skin to adhere to it.

In a statement, Takeuchi said: “By mimicking human skin-ligament structures and by using specially made V-shaped perforations in solid materials, we found a way to bind 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.”

Previous methods to attach skin tissue to solid surfaces involved mini anchors or hooks, but these limited the kinds of surfaces that could receive skin coatings and could cause damage during motion.

Any shape of surface can have skin applied to it by engineering small perforations. To do so, the team used a collagen gel for adhesion, which is naturally viscous but difficult to feed into the perforations. To overcome this, the team used plasma treatment to coax the collagen into the fine structures of the perforations while also holding the skin close to the surface in question.

“Manipulating soft, wet biological tissues during the development process is much harder than people outside the field might think. For instance, if sterility is not maintained, bacteria can enter and the tissue will die,” said Takeuchi. “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.”

Takeuchi and his lab believe their research could be applied in several areas of medical research; a so-called face-on-a-chip could be useful in research into skin aging, cosmetics, surgical procedures, plastic surgery and more. Also, if sensors can be embedded, robots may be endowed with better environmental awareness and improved interactive capabilities.

“In this study, we managed to replicate human appearance to some extent by creating a face with the same surface material and structure as humans,” said Takeuchi. “Additionally, through this research, we identified new challenges, such as the necessity for surface wrinkles and a thicker epidermis to achieve a more humanlike appearance.”

He continued: “We believe that creating a thicker and more realistic skin can be achieved by incorporating sweat glands, sebaceous glands, pores, blood vessels, fat and nerves. Of course, movement is also a crucial factor, not just the material, so another important challenge is 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.”