Thursday, April 25, 2019

Microbe Made Artificial Mother of Pearl Fit for Building Houses on the Moon

Bacteria have been put to work manufacturing artificial mother of pearl and they are doing a good job. The strongest synthetic materials are often those that intentionally mimic nature and micro made nacre is fit for building on the Moon.

Bacteria have been put to work manufacturing artificial mother of pearl and they are doing a good job, microbe made nacre is fit for building on the Moon. 

One natural substance scientists have looked to in creating synthetic materials is nacre, also known as mother-of-pearl. An exceptionally tough, stiff material produced by some mollusks and serving as their inner shell layer, it also comprises the outer layer of pearls, giving them their lustrous shine.

This abalone shell is a natural form of nacre—also known as mother-of-pearl—an exceptionally tough material found in shells and pearls. Rochester biologists have developed an innovative method for creating nacre in the lab—and maybe on the moon. 
close-up of a shell, showing the lustrous properties of nacre, or mother-of-pearl
Credit: University of Rochester photo / J. Adam Fenster

But while nacre’s unique properties make it an ideal inspiration in 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 for making artificial nacre using an innovative component: bacteria. The artificial nacre created by Anne S. Meyer, an associate professor of biology at Rochester, and her colleagues is made of biologically produced materials and has the toughness of natural nacre, while also being stiff and, surprisingly, bendable.

The method used to create the novel material could lead to new applications in medicine, engineering—and even constructing buildings on the moon.

Impressive mechanical properties

The impressive mechanical properties of natural nacre arise from its hierarchical, layered structure, which allows energy to disperse evenly across the material. In a paper published in the journal Small, Meyer and her colleagues outline their method of using two strains of bacteria to replicate these layers. When they examined the samples under an electron microscope, the structure created by the bacteria was layered similarly to nacre produced naturally by mollusks.

Although nacre-inspired materials have been created synthetically before, the methods used to make them typically involve expensive equipment, extreme temperatures, high-pressure conditions, and toxic chemicals, Meyer says. “Many people creating artificial nacre use polymer layers that are only soluble in nonaqueous solutions, an organic solvent, and then they have this giant bucket of waste at the end of the procedure that has to be disposed of.”

To produce nacre in Meyer’s lab, however, all researchers have to do is grow bacteria and let it sit in a warm place.

From bacteria to nacre

In order to make the artificial nacre, Meyer and her team create alternating thin layers of crystalized calcium carbonate—like cement—and sticky polymer. They first take a glass or plastic slide and place it in a beaker containing the bacteria Sporosarcina pasteurii, a calcium source, and urea (in the human body, urea is the waste product excreted by the kidneys during urination). This combination triggers the crystallization of calcium carbonate. To make the polymer layer, they place the slide into a solution of the bacteria Bacillus licheniformis, then let the beaker sit in an incubator.

The combination of the bacteria Sporosarcina pasteurii, a calcium source, and urea triggers the crystallization of calcium carbonate, pictured above in extreme close up.

Credit: University of Rochester / J. Adam Fenster

Right now it takes about a day to build up a layer, approximately five micrometers thick, of calcium carbonate and polymer. Meyer and her team are currently looking at coating other materials like metal with the nacre, and “we’re trying new techniques to make thicker, nacre-like materials faster and that could be the entire material itself,” Meyer says.

In order to make artificial nacre, Anne S. Meyer and her team use bacteria to create alternating thin layers of crystalized calcium carbonate and sticky polymer. Each layer is approximately five micrometers thick.

 Credit: University of Rochester photo / J. Adam Fenster

Building houses on the moon

One of the most beneficial characteristics of the nacre produced in Meyer’s lab is that it is biocompatible—made of materials the human body produces or that humans can eat naturally anyway. This makes the nacre ideal for medical applications like artificial bones and implants, Meyer says. “If you break your arm, for example, you might put in a metal pin that has to be removed with a second surgery after your bone heals. A pin made out of our material would be stiff and tough, but you wouldn’t have to remove it.”

And, while the material is tougher and stiffer than most plastics, it is very lightweight, a quality that is especially valuable for transportation vehicles like airplanes, boats, or rockets, where every extra pound means extra fuel. Because the production of bacterial nacre doesn’t require any complex instruments, and the nacre coating protects against chemical degradation and weathering, it holds promise for civil engineering applications like crack prevention, protective coatings for erosion control, or for conservation of cultural artifacts, and could be useful in the food industry, as a sustainable packaging material.

The nacre might also be an ideal material to build 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 moon dust, so the calcium’s already there. The astronaut brings the bacteria, and the astronaut makes the urea, which is the only other thing you need to start making calcium carbonate layers.”

Associate professor of biology Anne S. Meyer. Meyer and her colleagues are using bacteria to replicate the hierarchical, layered structure of nacre to produce a synthetic material with the strength and flexibility of natural mother-of-pearl.

Credit: University of Rochester photo / J. Adam Fenster

Even beyond its qualities as an ideal structural material, nacre itself—as any pearl jewelry owner knows—is “very beautiful,” Meyer says, owing to its stacked layers. Each stacked layer is approximately the same wavelength as visible light. When light hits the nacre, “the wavelengths of light interact with these layers of the same height so it bounces back off in the same wavelength as visible light.” While the bacterial nacre does not interact with visible light because the layers are thicker than natural nacre, it could interact with infrared wavelengths and bounce infrared off itself, Meyer says, which “may offer unique optical properties.”

Contacts and sources:
Lindsey Valich
University of Rochester

Citation: Bacterially Produced, Nacre‐Inspired Composite Materials.
Ewa M. Spiesz, Dominik T. Schmieden, Antonio M. Grande, Kuang Liang, Jakob Schwiedrzik, Filipe Natalio, Johann Michler, Santiago J. Garcia, Marie‐Eve Aubin‐Tam, Anne S. Meyer. Small, 2019; 1805312 DOI: 10.1002/smll.201805312

Supersolidity's Paradoxical State 50 Years in the Making: Matter Is Both Crystallized and Superfluid

An exotic phase of matter was just made,  supersolids were created from quantum gases, a state in which matter is a crystal and a superfluid. It took 50 years from idea to the making.    

Researchers led by Francesca Ferlaino at the University of Innsbruck and Austrian Academy of Sciences report in Physical Review X on the observation of supersolid behavior in dipolar quantum gases of erbium and dysprosium. In the dysprosium gas these properties are unprecedentedly long-lived. This sets the stage for future investigations into the nature of this exotic phase of matter.

Image: Several tens of thousands of particles spontaneously organize in a self-determined crystalline structure while sharing the same macroscopic wavefunction - hallmarks of supersolidity. 

Credit: Uni Innsbruck

Supersolidity is a paradoxical state where the matter is both crystallized and superfluid. Predicted 50 years ago, such a counter-intuitive phase, featuring rather antithetic properties, has been long searched in superfluid helium. However, after decades of theoretical and experimental efforts, an unambiguous proof of supersolidity in these systems is still missing. Two research teams led by Francesca Ferlaino, one at the Institute for Experimental Physics at the University of Innsbruck and one at the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences now report on the observation of hallmarks of this exotic state in ultracold atomic gases.

While so far, most work has focused on helium, researchers have recently turned to atomic gases—in particular, those with strong dipolar interactions. The team of Francesca Ferlaino has been investigating quantum gases made of atoms with a strong dipolar character for a long time. “Recent experiments have revealed that such gases exhibit fundamental similarities with superfluid helium”, says Lauriane Chomaz referring to experimental achievements in Innsbruck and in Stuttgart over the last few years. “These features lay the groundwork for reaching a state where the several tens of thousands of particles of the gas spontaneously organize in a self-determined crystalline structure while sharing the same macroscopic wavefunction - hallmarks of supersolidity.”

The researchers in Innsbruck experimentally created states showing these characteristics of supersolidity by tuning the interaction strength between the particles, in both erbium and dysprosium quantum gases. “While in erbium the supersolid behavior is only transient, in line with recent beautiful experiments in Pisa and in Stuttgart, our dysprosium realization shows an unprecedented stability”, says Francesca Ferlaino. “Here, the supersolid behavior not only lives long but can also be directly achieved via evaporative cooling, starting from a thermal sample.” Like blowing over a cup of tea, the principle here is to remove the particles that carry the most of energies so that the gas becomes cooler and cooler and finally reaches a quantum-degenerate stationary state with supersolid properties at thermal equilibrium.

This offers exciting prospects for near-future experiments and theories as the supersolid state in this setting is little affected by dissipative dynamics or excitations, thus paving the way for probing its excitation spectrum and its superfluid behavior. The work was financially supported by the Austrian Science Fund FWF, the Austrian Academy of Sciences and the European Union.

Long-lived and transient supersolid behaviors in dipolar quantum gases. L. Chomaz, D. Petter, P. Ilzhöfer, G. Natale, A. Trautmann, C. Politi, G. Durastante, R. M. W. van Bijnen, A. Patscheider, M. Sohmen, M. J. Mark, and F. Ferlaino. Phys. Rev. X 9, 021012
Dipolar Quantum Gases

Contacts and sources:
University of Innsbruck

Citation: Long-Lived and Transient Supersolid Behaviors in Dipolar Quantum Gases.
L. Chomaz, D. Petter, P. Ilzhöfer, G. Natale, A. Trautmann, C. Politi, G. Durastante, R. M. W. van Bijnen, A. Patscheider, M. Sohmen, M. J. Mark, F. Ferlaino. Physical Review X, 2019; 9 (2) DOI: 10.1103/PhysRevX.9.021012