By Paulo Szwarc, Federal University of Paraná, Brazil
Following the Oscars 2018 Best Picture award to Guillermo del Toro’s The Shape of Water, a weird thought probably navigates our minds: what if we had scales instead of skin? No? Maybe it’s just a crazy thought I had while observing the movie’s creepy yet astonishing “monster”, an amphibian/fish-looking humanoid looking straight out of a Lovecraft story.
But let’s delve deeper into that idea, just for fun. Fish have scales for protection against other predators, offering a resistant layer that can impede easy biting from bigger fish. But not only that. The hydrodynamics of fish scales permits them to travel lightning fast across the ocean, some species speeding over 100 kilometres per hour. These are amazing features.
Could a synthetic material be constructed that replicates the functional advantages of a fish’s scales? Biomimetics (or bioinspiration) is the science of gaining ideas from nature, understanding the underlying concepts and inner workings, and applying them to engineer novel products or tools. It is the exact branch of science we are looking to for our answer. Mimicking fish scales to build a functional artificial tissue with special characteristics.
First, let’s understand that not all fish are alike. Variations in shapes and patterns of scales are found throughout nature, which give a characteristic look to each type of fish. Differences in colour or reflection patterns are some of the more visible results. Additionally, larger differences occur when comparing the scales of bony fish (salmon, tuna) to those of cartilaginous fish (sharks, rays). Nevertheless, most fish scales have an underlying common theme: little segmented individual scales spread over the surface of the skin in a common pattern.
McGill University researcher Francois Barthelat developed a synthetic tissue inspired by fish scales, made from hexagonal glass plates arranged in a segmented pattern over a rubber ’skin‘ base. The pattern of hexagons very much resembles a fish’s scale pattern, with little individual hexagons covering the whole surface. They also built a continuous glass plate design, with no segmented hexagons, for comparison.
Not to anyone’s surprise, the segmented tissue is clearly superior in terms of flexibility. The hexagons can offer a degree of separation between them, which translates to the tissue being able to stretch and contort without loss of performance. In nature this is essential for a fish’s capacity to quickly navigate the water. The continuous glass plate tissue can be compared to a turtle’s hard shell, scoring high in resistance but virtually zero in flexibility.
But is flexibility a necessary trade-off for resistance? When tested against punctures (by literally stabbing the tissue with a sharp needle), the segmented tissue showed a whopping 70% more resistance than the continuous glass plate tissue. This is due to the hexagons acting independently from each other: damage in one does not hamper the others from working.
This early work by Barthelat eventually paved the way for his team to develop a synthetic scaled material that can act as a protective and flexible cover for everyday items. In a 2016 article, they glued the synthetic cover on the surface of a common glove, giving it extra protection without loss of function.
Besides gloves, numerous possibilities arise for this material. Scales appeared in nature for defensive purposes. Why not translate this to humans? Given that it is flexible and resistant, the synthetic skin could be used as armour to protect military or law enforcement personnel from knife wounds. With further improvements in the material used for the plates, this flexible armour could potentially protect an individual from actual firearms.
Let’s move away from purely defensive purposes. The armour could cover the surface of clothing used in construction and industrial applications, offering greater safety for workers who deal with tools that can potentially cut or puncture them. In the best scenario, accidents would be reduced. Astronauts can suffer damage from space debris, so a flexible and resistant armour would also be interesting. Divers and swimmers could also benefit from the combination of extra protection and improved hydrodynamics.
Some of our normal everyday clothing could receive a streamlined synthetic scale surface, adding a protective layer for daily life. Currently some clothes imitate (often with sparkle and colour) tiny scales. Why not add a functional aspect to them? Maybe our future holds this cool biomimetic technology. Fishy scales.
References and further reading
- For those interested in biomimetics, check out other scientific articles on the journal Bioinspiration & Biomimetics
- A behind-the-scenes look on the creature from The Shape of Water
- Francois Barthelat is an Associate Professor at the Department of Mechanical Engineering, McGill University
- Sudo S, Tsuyuki K, Ito, Yoshiyasu I, Ikohagi T. A study on the surface shape of fish scales. Japan Soc Mech Eng Int J. 2002;45(4):1100-1105. doi:10.1299/jsmec.45.1100.
- Hwang J, Jeong Y, Park JM, Lee KH, Hong JW, Choi J. Biomimetics: Forecasting the future of science, engineering, and medicine. Int J Nanomedicine. 2015;10:5701-5713. doi:10.2147/IJN.S83642.
- Chintapalli RK, Mirkhalaf M, Dastjerdi AK, Barthelat F. Fabrication, testing and modeling of a new flexible armor inspired from natural fish scales and osteoderms. Bioinspiration and Biomimetics. 2014;9(3). doi:10.1088/1748-3182/9/3/036005.
- Martini R, Barthelat F. Stretch-and-release fabrication, testing and optimization of a flexible ceramic armor inspired from fish scales. Bioinspiration and Biomimetics. 2016;11(6):1-10. doi:10.1088/1748-3190/11/6/066001.
I am an undergraduate in Biomedical Sciences from the Federal University of Paraná, stationed in lovely southern Brazil. My main interests are microbiology, molecular biology, translational biology and innovation in the biomedical field. I work at the Carlos Chagas Institute, one of the biggest biomedical research organizations in my country. You can find me on Twitter and LinkedIn.
This post is the second in our biomaterials series. The first post was Plant-based biomaterials: engineering the future by Emily May Armstrong. If you are interested in reading more on this topic, you can also check out the February issue of The Biochemist magazine on the theme of biomaterials.