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Scientists create artificial mother-of-pearl that uses bacteria

This abalone shell is a natural form of nacre ̵ 1; also known as mother-of-pearl – an extremely tough material found in shells and beads. Rochester biologists have developed an innovative method of creating nacre in the lab – and perhaps on the moon. Credit: University of Rochester / J. Adam Fenster The strongest synthetic materials are often the ones that deliberately mimic nature. A natural subject researcher has looked at creating synthetic materials is nacre, also known as mother-of-pearl. An extremely tough, rigid material produced by some milk and serving as the inner shell also includes the outer layer of beads, giving them a glossy shine. But while the unique features of nacre make it an ideal inspiration for the creation of synthetic materials, most methods used to produce artificial nacre are complex and energy-intensive. Now, a biologist at the University of Rochester has invented an inexpensive and environmentally friendly method of making artificial nacre with an innovative component: bacteria. The artificial nacre created by Anne S. Meyer, biologist in Rochester, and her colleagues is made of biologically produced materials and has the toughness of natural nacre, while being stiff and surprisingly flexible. The method used to create the new material can lead to new applications in medicine, technology and even constructing buildings on the moon. [embedded content] Impressive Mechanical Properties The impressive mechanical properties of natural nacre derive from its hierarchical layer structure, which allows energy to spread evenly over the material. In a paper published in the…

This abalone shell is a natural form of nacre ̵

1; also known as mother-of-pearl – an extremely tough material found in shells and beads. Rochester biologists have developed an innovative method of creating nacre in the lab – and perhaps on the moon. Credit: University of Rochester / J. Adam Fenster

The strongest synthetic materials are often the ones that deliberately mimic nature.

A natural subject researcher has looked at creating synthetic materials is nacre, also known as mother-of-pearl. An extremely tough, rigid material produced by some milk and serving as the inner shell also includes the outer layer of beads, giving them a glossy shine.

But while the unique features of nacre make it an ideal inspiration for the creation of synthetic materials, most methods used to produce artificial nacre are complex and energy-intensive.

Now, a biologist at the University of Rochester has invented an inexpensive and environmentally friendly method of making artificial nacre with an innovative component: bacteria. The artificial nacre created by Anne S. Meyer, biologist in Rochester, and her colleagues is made of biologically produced materials and has the toughness of natural nacre, while being stiff and surprisingly flexible.

The method used to create the new material can lead to new applications in medicine, technology and even constructing buildings on the moon.

Impressive Mechanical Properties

The impressive mechanical properties of natural nacre derive from its hierarchical layer structure, which allows energy to spread evenly over the material. In a paper published in the journal Small Meyer and her colleagues outline their method of using two bacterial strains to replicate these layers. When examining the samples under an electron microscope, the structure created by the bacteria is stored in the same way as nacre produced naturally by molluscs.

Although nacre-inspired materials have been created synthetically in the past, the methods used to make them usually include expensive equipment, extreme temperatures, high pressure conditions, and toxic chemicals, Meyer says. “Many people who create artificial nacre use polymer layers that are only soluble in aqueous solutions, an organic solvent, and then they have this giant bucket of waste at the end of the process that must be discarded.”

To produce nacre in the Meyers lab, but all scientists have to do is grow bacteria and let it sit in a warm place.

To make artificial nacre, Anne S. Meyer and her team use bacteria to create alternating thin layers of crystallized calcium carbonate and sticky polymer. Each layer is approximately five microns thick. Credit: University of Rochester photo / J. Adam Fenster

From Bacteria to Nacre

To create the artificial nacre, Meyer and her team create alternate thin layers of crystallized calcium carbonate-like cement and sticky polymer. They first take a glass or plastic glass and place it in a beaker containing the bacteria Sporosarcina pasteurii a calcium source and urea (in the body, urea, the waste products are secreted by the kidneys during urination). This combination triggers the crystallization of calcium carbonate. To make the polymer layer, they place the slide in a solution of the bacteria [Bacilluslicheniformis] then allow the beaker to sit in an incubator.

Right now, it takes about a day to build a layer, about five microns thick, calcium carbonate and polymer. Meyer and her team are currently looking at coating other materials like metal with nacre and “we are trying new technologies to make thicker, nacre-like materials faster and it can be the whole material itself,” Meyer says.

To make artificial nacre, Anne S. Meyer and her team use bacteria to create alternating thin layers of crystallized calcium carbonate and sticky polymer. Each layer is approximately five microns thick. Credit: University of Rochester photo / J. Adam Fenster

Building houses on the moon

One of the most advantageous properties of the nacre produced in Meyer’s laboratory is that it is biocompatible made of materials that the human body produces or that people can eat naturally anyway. This makes nacre perfect for medical applications such as artificial legs and implants, Meyer says. “For example, if you break your arm, you can insert a metal pin that needs to be removed with a new operation after your leg heals. A pin made of our material would be hard and hard, but you wouldn’t have to remove it. . “

And while the material is harder and stiffer than most plastic materials, it is very light, a quality that is particularly valuable for transport vehicles such as aircraft, boats or rockets, where each extra pound involves extra fuel. Since the production of bacterial nacre does not require any complex instruments, and the nacre coating protects against chemical degradation and confusion, it has the laws of civil engineering applications such as crack protection, protective coatings for erosion control or for preservation of cultural articles, and may be useful in the food industry as a sustainable packaging material. .

The combination of the bacteria Sporosarcina pasteurii, a calcium source and urea triggers the crystallization of calcium carbonate, the image above in extreme close-up. Credit: University of Rochester / J. Adam Fenster

Nacre can also be an ideal material for building houses on the moon and other planets: the only necessary “ingredients” would be an astronaut and a small tube of bacteria, Meyer says. “The moon has a large amount of calcium in the moonlight, so calcium is already there. The astronaut gives the bacteria and the astronaut does the urea, which is the only thing you need to start making calcium carbonate layers.” [19659005] In addition to its properties as an ideal structural material, nacre itself – as all pearl jewelry owners know is “very beautiful,” says Meyer because of their stacked layers. Each stacked layer is approximately the same wavelength as visible light. When the light hits the nacre, “the wavelengths of light alternate with these layers of the same height so that it bounces back in the same wavelength as visible light.” While bacterial nacre does not interact with visible light because the layers are thicker than natural nacre, it can interact with infrared wavelengths and bounce infrared by itself, says Meyer, who “offers unique optical properties.”


A new way to make synthetic mother-of-pearl


More information:
Ewa M. Spiesz et al. Bacterially produced, Nacre-inspired composite materials, Small (2019). DOI: 10.1002 / smll.201805312
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Small
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Scientists create artificial mother-of-pearl using bacteria (2019, April 23)
April 23, 2019
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