The natural world is full of inspiration for the materials scientist. Many researchers are working in the field of biomimetics trying to develop synthetic materials that equal or even outperform materials found in nature. Many of these synthetic materials, while attaining similar specifications to the natural material, sadly fall short in performance comparisons. However, scientists are discovering that nature’s high performance is not due just to the basic material properties, but to the structure and form of the materials. Two cases in points are the scales of the Arapaima fish and the exoskeletal cuticle of insects.
Arapaima
This was the question that intrigued researchers at the Jacob’s School of Engineering at UC San Diego. They found that, as much as the Piranha would have enjoyed snacking on the Arapaima, their needle-sharp teeth were unable to penetrate the scales of this massive fish.
Investigation of the fish's scales structure showed that they are composed of an outer layer of a hard, mineralized biomaterial with an inner layer of softer collagen fibers. In other words, the fish is “case hardened”, offering a hard outer surface with a flexible inner core. The researchers carried out hardness testing on the scales using an indenter that held an actual piranha tooth at its tip. The tooth was able to penetrate partway through the scale, but it fractured before it would have damaged the underlying muscle of the fish. Further, the outer layer of the scales is corrugated giving the hard scale the ability to bend with the movement of the swimming fish.
Insect Cuticle
Researchers at the Wyss Institute for Biologically Inspired Engineering at Harvard University have been investigating the properties and the structure of insect cuticle.
Insect cuticle is a composite material comprising layers of chitin (a polysaccharide polymer) and fibroin (a protein). These materials are arranged in layers, similar to plywood. Mechanical and chemical interactions between these layers and the different materials give the cuticle unique mechanical and chemical properties. The researchers have developed a thin, clear film from similar materials and with a similar layered structure as insect cuticle. The material is composed of fibroin protein from silk and from chitin extracted from discarded shrimp shells. It is thin, clear, and flexible, and the researchers claim it is as strong as aluminum at half the weight. They have called the new material Shrilk.
One of the biggest advantages of this new low-cost synthetic material is its biodegradability. Shrilk could one day replace plastic for degradable consumer products, such as trash bags, packaging, and diapers, and be used safely in a variety of medical applications, such as sutures or scaffold for tissue regeneration.
Nature has always been an inspiration for materials scientists. Early man used natural materials, such as wood, bone, sinew, and leather to manufacture tools, clothing, and structures. Synthetic materials have improved on the properties of many of these basic materials, but for some of them the limits of their performance have been reached. Research into how nature constructs natural materials, as well as into their basic chemistry, offers the promise of attaining even higher performing synthetic materials in the future.
Arapaima image courtesy of George Chernilevsky in the public domain.
Grasshopper image courtesy of Gilles San Martin under a creative commons license.
Sources:
Piranha Vs. Arapaima: Engineers Find Inspiration for New Materials in Piranha-Proof Armor. Science Daily, Feb 8, 2012
Arapaima fish scales inspire new materials. robaid.com, Feb 9, 2012
Inspired by Insect Cuticle, Wyss Researchers Develop Low-Cost Material with Exceptional Strength and Toughness. Wyss Institute for Biologically Inspired Engineering at Harvard University, December 12, 2011
As Strong As An Insect’s Shell. Harvard Gazette, Alvin Powell, February 2, 2012
Arapaima
The Brazilian Arapaima is a huge fish weighing up to 300 lb. It lives in lakes alongside the better-known Piranha. So how come it doesn’t become Piranha food?
This was the question that intrigued researchers at the Jacob’s School of Engineering at UC San Diego. They found that, as much as the Piranha would have enjoyed snacking on the Arapaima, their needle-sharp teeth were unable to penetrate the scales of this massive fish.Investigation of the fish's scales structure showed that they are composed of an outer layer of a hard, mineralized biomaterial with an inner layer of softer collagen fibers. In other words, the fish is “case hardened”, offering a hard outer surface with a flexible inner core. The researchers carried out hardness testing on the scales using an indenter that held an actual piranha tooth at its tip. The tooth was able to penetrate partway through the scale, but it fractured before it would have damaged the underlying muscle of the fish. Further, the outer layer of the scales is corrugated giving the hard scale the ability to bend with the movement of the swimming fish.
Insect Cuticle
Researchers at the Wyss Institute for Biologically Inspired Engineering at Harvard University have been investigating the properties and the structure of insect cuticle.
Insect cuticle is a composite material comprising layers of chitin (a polysaccharide polymer) and fibroin (a protein). These materials are arranged in layers, similar to plywood. Mechanical and chemical interactions between these layers and the different materials give the cuticle unique mechanical and chemical properties. The researchers have developed a thin, clear film from similar materials and with a similar layered structure as insect cuticle. The material is composed of fibroin protein from silk and from chitin extracted from discarded shrimp shells. It is thin, clear, and flexible, and the researchers claim it is as strong as aluminum at half the weight. They have called the new material Shrilk.One of the biggest advantages of this new low-cost synthetic material is its biodegradability. Shrilk could one day replace plastic for degradable consumer products, such as trash bags, packaging, and diapers, and be used safely in a variety of medical applications, such as sutures or scaffold for tissue regeneration.
Nature has always been an inspiration for materials scientists. Early man used natural materials, such as wood, bone, sinew, and leather to manufacture tools, clothing, and structures. Synthetic materials have improved on the properties of many of these basic materials, but for some of them the limits of their performance have been reached. Research into how nature constructs natural materials, as well as into their basic chemistry, offers the promise of attaining even higher performing synthetic materials in the future.
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