There are many material properties, hardest, most malleable, strongest tensile strength, best strength to weight ratio, etc. But what about the first non-cuttable material?
Yes, such material exists and it is next-level. The material is named Proteus after the Greek god of shape-shifting.
This amazing material that seems straight out of a sci-fi movie has been inspired by grapefruits and shells. Created by British and German engineers it blunts any angle grinder or drill that tries to cut into it.
What is non-cuttable material?
This non-cuttable material can’t be cut with angle grinders, drills, or high-pressure water jets in test experiments. The Proteus material is modeled after the structure of shells and grapefruits.
“Proteus is composed of ceramic spheres encased in a cellular aluminum structure and takes inspiration from the tough cellular skin of the grapefruit and the fracture-resistant shells of mollusks”, says the team of researchers from Durham University, UK, and Fraunhofer Institute for Machine Tools and Forming Technology IWU in Chemnitz in Germany.
What inspired this new material?
The lead author Dr. Stefan Szyniszewski, Assistant Professor of Applied Mechanics, in the Department of Engineering, Durham University, said: “We were intrigued by how the cellular structure of the grapefruit and the tiled structure of mollusk shells can prevent damage to the fruit or the creatures inside, despite being made of relatively weak organic building blocks. These natural structures informed the working principle of our metallic-ceramic material, which is based on dynamic interaction with the applied load, in contrast to passive resistance.”
Dr. Stefan worked with a team of researchers to develop the un-cuttable material. Made from ceramic spheres embedded in a cellular structure made of metallic foam. The researchers started by looking at the structure of abalone shells. These shells are made from a relatively weak material but arranged in a way that means sharks can’t easily bite through the shell. “The shell is 2,000 times harder to crack than the bricks that it’s made of,” says Szyniszewski.
The humble grapefruit
The cellular structure is also partly inspired by the peel of a grapefruit, which is strong but lightweight. “We wanted the material to be light because most protective structures are quite heavy,” Szyniszewski says. “When you think of security doors or armored steel, it’s very heavy. And if you look at protective structures in nature, like the peel of grapefruit, they’re usually very light.”
Nature uses hierarchical structures for protection from extreme loads. The freefall of grapefruit from 30 feet does not damage the pulp because pomelo peel consists of vascular bundles. And an open-pored cellular structure with the struts made of parenchymatic cells.
Of course, a power tool such as an angle grinder works nothing like the jaws of a shark. So when it came to Proteus the researchers kept working on the design of the material. “I realized that there is this vulnerability of the cutting tools to vibrations,” he says. “When things move very fast, they have a lot of energy. And if we can somehow amplify this variable it should disrupt the cutting.”
A closer look at Proteus
Hierarchical structure of the proposed metallic-ceramic meta-material. (a) Sandwich panel sample (245 mm × 172 mm × 40 mm), (b) ceramic spheres are organized in lines, (c) cylindrical specimens (60 mm diameter × 150 mm) had a vertical organization of ceramic spheres, (d) cross-section of the cylinder with colors corresponding to the wall thickness of cellular aluminum, (e) ceramic spheres are not in contact with one another but are separated by aluminum cells, (f) foam cells are an order of magnitude smaller than ceramic spheres, (g) thickness of aluminum cell walls varied mostly from 0.2 to 0.4 mm.
Arapaimas fish living in the Amazon resist the attack of piranhas’ triangular teeth arrays through the hierarchical design of their scales2. The highly mineralized external layer of each scale has sinusoidal grooves, with a periodicity that is out-of-phase with that of piranha teeth spacing. The external interface is strengthened by an underlying hierarchical structure consisting of a cross-lamellar arrangement of collagen fibers.
Szyniszewski, S., Vogel, R., Bittner, F. et al. Non-cuttable material created through local resonance and strain rate effects. Sci Rep 10, 11539 (2020). https://doi.org/10.1038/s41598-020-65976-0
The material fights back
The ceramic spheres inside the material vibrate to such an extent that it blunts the cutting tool. As some of the spheres also break apart into smaller, hard fragments, those pieces act like rough sandpaper. Thus further wearing down the tool. This interaction between Proteus and the cutting tool creates an interlocking, vibrational connection. This resists the cutting resource and turns the destructive drive back again on by itself. The team tried every combination of grinder, drill, and even a water jet to try and cut through the material, to zero success.
The truly interesting thing about this amazing non-cuttable material is that as the particles are broken down they provide an abrasive interface with increasing resistance at higher loading rates. In other words, it actually gets stronger the more you try to cut into it.
What are the possible applications for a non-cuttable material?
“This material could have lots of useful and exciting applications in the security and safety industries. In fact, we are not aware of any other manufactured non-cuttable material in existence as of now.” Dr. Szyniszewski.
The resulting material could be used for a variety of applications. From protective equipment for people working with dangerous machinery to the doors of a vault in a bank. No doubt the military will show more than a passing interest in this amazing material.
But it’s possible that bike locks could be one of the first products to come to market; Dr. Szyniszewski says that he’s already been contacted by a bike lock manufacturer interested in using the material.
The researchers are in the process of patenting Proteus and plan to collaborate with various industries.
