Researchers at ETH Zurich, Switzerland, have developed a means of 3D printing a self repairing skin using hydrogels loaded with fungal mycelia.
The skin repairs itself when damaged, provided that it the fungal network is allowed to metabolize, and it does so by receiving nutrients. The fact that it is capable of metabolism means that it is a living organism.
When draped over a robotic body, it is the very definition of a cybernetic organism, as described in The Terminator franchise.
Feast your eyes on the living skinned robotic gripper below.
“Living tissue over a metal endoskeleton”
Materials have a tendency to wear and break over time. To repair them requires energy and effort, usually in the form of maintenance, which is performed by a human being. Conversely, living materials have the ability to regenerate and self repair when damaged.
Think of a growing tree trunk, or your own skin. Of course, living materials also require energy to repair, and that is provided by nutrients.
This concept has been applied to an artificial skin which has been 3D printed in the form of a hydrogen grid, and infused with the Ganoderma Lucidum fungus. This type of fungus grows on hardwood in Asia and parts of Europe.
You can see the fruiting body of the fungus in this image.
The Process
The first step in making the living skin involved inoculating the hydrogel with the fungal mycelia. This resulted in the production of a mycelium ink, which was then harvested and loaded into a direct ink writing (DIW) 3D printer.
The hyphae distributed in the ink form an interconnected network of fungal cells within the printed objects, which in this case, were grid like structures in various shapes.
The grid structure allows airways and gaps for the potential dosing of nutrition. The structure can be printed into any geometry, allowing full customisation and directing the growth of the skin.
As mycelium has evolved to grow between gaps, it follows the geometry of the printed grid structure. This property also allows it to self-repair by bridging damaged areas within its own skin.
The mycelium grows according to two different strategies named as phalanx, or guerrilla.
The phalanx strategy involves the coordinated growth of multiple hyphae in a dense, interconnected network, forming a structure known as a mycelial mass or mycelial mat (the skin).
This short-reaching strategy allows the fungus to efficiently explore and colonize new areas in search of food, and it also allows the fungus to defend itself against competitors and predators.
Conversely, the guerrilla strategy is more opportunistic and far-reaching, allowing the mycelium to explore patchy resource landscapes.
The printed mycelia showed both types of growth in the printed network, leading to the growth of a fractal hyphae network giving strength to the printed grid. The hyphae proved to be capable of healing cracks measuring up to 2 mm in width.
The researchers state that there needs to be further development into how the nutrients are provided into the printed skin, as well as how the waste is removed.
In addition to the printed mycelial gripper pictured at the beginning of the article, the researchers printed a skin for an untethered robot.
The combination of living skin over an artificial endoskeleton is the very definition of a cybernetic organism, at least according to James Cameron. Exciting times ahead.
You can read the full paper, titled “Self-regenerating living material made of printed fungi”, published in Nature Materials”, at this link.
