Nanotechnology Now

Our NanoNews Digest Sponsors
Heifer International



Home > Press > How seashells get their strength: Study shows how calcium carbonate forms composites to make strong materials such as in shells and pearls

When calcium carbonate crystallizes into hard shells, it incorporates soft bits of proteins to add strength. Research done in the lab shows how this might happen, and why it works.
CREDIT: Wikipedia Public Domain
When calcium carbonate crystallizes into hard shells, it incorporates soft bits of proteins to add strength. Research done in the lab shows how this might happen, and why it works.

CREDIT: Wikipedia Public Domain

Abstract:
Seashells and lobster claws are hard to break, but chalk is soft enough to draw on sidewalks. Though all three are made of calcium carbonate crystals, the hard materials include clumps of soft biological matter that make them much stronger. A study today in Nature Communications reveals how soft clumps get into crystals and endow them with remarkable strength.

How seashells get their strength: Study shows how calcium carbonate forms composites to make strong materials such as in shells and pearls

Richland, WA | Posted on January 10th, 2016

The results show that such clumps become incorporated via chemical interactions with atoms in the crystals, an unexpected mechanism based on previous understanding. By providing insight into the formation of natural minerals that are a composite of both soft and hard components, the work will help scientists develop new materials for a sustainable energy future, based on this principle.

"This work helps us to sort out how rather weak crystals can form composite materials with remarkable mechanical properties," said materials scientist Jim De Yoreo of the Department of Energy's Pacific Northwest National Laboratory. "It also provides us with ideas for trapping carbon dioxide in useful materials to deal with the excess greenhouse gases we're putting in the atmosphere, or for incorporating light-responsive nanoparticles into highly ordered crystalline matrices for solar energy applications."

Beautiful and functional

Calcium carbonate is one of the most important materials on earth, crystallizing into chalk, shells, and rocks. Animals from mollusks to people use calcium carbonate to make biominerals such as pearls, seashells, exoskeletons, or the tiny organs in ears that maintain balance. These biominerals include proteins or other organic matter in the crystalline matrix to convert the weak calcium carbonate to hard, durable materials.

Scientists have been exploring how organisms produce these biominerals in the hopes of determining the basic geochemical principles of how they form, and also how to build synthetic materials with unique properties in any desired shape or size.

The strength of a material depends on how easy it is to disrupt its underlying crystal matrix. If a material is compressed, then it becomes harder to break the matrix apart. Proteins trapped in calcium carbonate crystals create a compressive force -- or strain -- within the crystal structure.

Unlike the strain that makes muscles sore, this compressive strain is helpful in materials, because it makes it harder to disrupt the underlying crystal structure, thereby adding strength. Scientists understand how forces, stress and strain combine to make strong materials, but they understand less about how to create the materials in the first place.

Pearls of wisdom

The leading explanation for how growing crystals incorporate proteins and other particles is by simple mechanics. Particles land on the flat surface of calcium carbonate as it is crystallizing, and units of calcium carbonate attach over and around the particles, trapping them.

"The standard view is that the crystal front moves too fast for the inclusions to move out of the way, like a wave washing over a rock," said De Yoreo.

That idea's drawback is that it lacks the details needed to explain where the strain within the material comes from. The new results from De Yoreo and colleagues do, however.

"We've found a completely different mechanism," he said.

To find out how calcium carbonate incorporates proteins or other strength-building components, the team turned to atomic force microscopy, also known as AFM, at the Molecular Foundry, a DOE Office of Science User Facility at Lawrence Berkeley National Laboratory. In AFM, the microscope tip delicately runs over the surface of a sample like a needle running over the grooves in a vinyl record. This creates a three-dimensional image of a specimen under the scope.

The team used a high concentration of calcium carbonate that naturally forms a crystalline mineral known as calcite. The calcite builds up in layers, creating uneven surfaces during growth, like steps and terraces on a mountainside. Or, imagine a staircase. A terrace is the flat landing at the bottom; the stair steps have vertical edges from which calcite grows out, eventually turning into terraces too.

For their inclusions, the team created spheres out of organic molecules and added them to the mix. These spheres called micelles are molecules that roll up like roly-poly bugs based on the chemistry along their bodies -- pointing outwards are the parts of their molecules that play well chemically with both the surrounding water and the calcite, while tucked inside are the parts that don't get along with the watery environment.

Better composites through chemistry

The first thing the team noticed under the microscope is that the micelles do not randomly land on the flat terraces. Instead they only stick to the edges of the steps.

"The step edge has chemistry that the terrace doesn't," said De Yoreo. "There are these extra dangling bonds that the micelles can interact with."

The edges hold onto the micelles as the calcium carbonate steps close around them, one after another. The team watched as the growing steps squeezed the micelles. As the step closed around the top of the micelle, first a cavity formed and then it disappeared altogether under the surface of the growing crystal.

To verify that the micelles were in fact buried within the crystals, the team dissolved the crystal and looked again. Like running a movie backwards, the team saw micelles appear as the layers of crystal disappeared.

Finally, the team recreated the process in a mathematical simulation. This showed them that the micelles -- or any spherical inclusions -- are compressed like springs as the steps close around them. These compressed springs then create strain in the crystal lattice between the micelles, leading to enhanced mechanical strength. This strain likely accounts for the added strength seen in seashells, pearls and similar biominerals.

"The steps capture the micelles for a chemical reason, not a mechanical one, and the resulting compression of the micelles by the steps then leads to forces that explain where the strength comes from," said De Yoreo.

###

This work was supported by the Department of Energy Office of Science, National Institutes of Health.

####

About Pacific Northwest National Laboratory
Interdisciplinary teams at Pacific Northwest National Laboratory address many of America's most pressing issues in energy, the environment and national security through advances in basic and applied science. Founded in 1965, PNNL employs 4,400 staff and has an annual budget of nearly $1 billion. It is managed by Battelle for the U.S. Department of Energy's Office of Science. As the single largest supporter of basic research in the physical sciences in the United States, the Office of Science is working to address some of the most pressing challenges of our time. For more information on PNNL, visit the PNNL News Center, or follow PNNL on Facebook, Google+, LinkedIn and Twitter.

For more information, please click here

Contacts:
Mary Beckman

509-375-3688

Copyright © Pacific Northwest National Laboratory

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

Reference: Kang Rae Cho, Yi-Yeoun Kim, Pengcheng Yang, Wei Cai, Haihua Pan, Alexander N. Kulak, Jolene L. Lau, Prashant Kulshreshtha, Steven P. Armes, Fiona C. Meldrum & James J. De Yoreo. Direct observation of mineral-organic composite formation reveals occlusion mechanism, Nature Communications January 6, 2016, doi:10.1038/NCOMMS10187:

Related News Press

News and information

New class of protein misfolding simulated in high definition: Evidence for recently identified and long-lasting type of protein misfolding bolstered by atomic-scale simulations and new experiments August 8th, 2025

Sensors innovations for smart lithium-based batteries: advancements, opportunities, and potential challenges August 8th, 2025

Deciphering local microstrain-induced optimization of asymmetric Fe single atomic sites for efficient oxygen reduction August 8th, 2025

Lab to industry: InSe wafer-scale breakthrough for future electronics August 8th, 2025

Imaging

ICFO researchers overcome long-standing bottleneck in single photon detection with twisted 2D materials August 8th, 2025

Simple algorithm paired with standard imaging tool could predict failure in lithium metal batteries August 8th, 2025

First real-time observation of two-dimensional melting process: Researchers at Mainz University unveil new insights into magnetic vortex structures August 8th, 2025

Laboratories

Giving batteries a longer life with the Advanced Photon Source: New research uncovers a hydrogen-centered mechanism that triggers degradation in the lithium-ion batteries that power electric vehicles September 13th, 2024

A 2D device for quantum cooling:EPFL engineers have created a device that can efficiently convert heat into electrical voltage at temperatures lower than that of outer space. The innovation could help overcome a significant obstacle to the advancement of quantum computing technol July 5th, 2024

A battery’s hopping ions remember where they’ve been: Seen in atomic detail, the seemingly smooth flow of ions through a battery’s electrolyte is surprisingly complicated February 16th, 2024

NRL discovers two-dimensional waveguides February 16th, 2024

Govt.-Legislation/Regulation/Funding/Policy

New imaging approach transforms study of bacterial biofilms August 8th, 2025

INRS and ELI deepen strategic partnership to train the next generation in laser science:PhD students will benefit from international mobility and privileged access to cutting-edge infrastructure June 6th, 2025

Electrifying results shed light on graphene foam as a potential material for lab grown cartilage June 6th, 2025

Institute for Nanoscience hosts annual proposal planning meeting May 16th, 2025

Nanomedicine

New molecular technology targets tumors and simultaneously silences two ‘undruggable’ cancer genes August 8th, 2025

New imaging approach transforms study of bacterial biofilms August 8th, 2025

Cambridge chemists discover simple way to build bigger molecules – one carbon at a time June 6th, 2025

Electrifying results shed light on graphene foam as a potential material for lab grown cartilage June 6th, 2025

Discoveries

Deciphering local microstrain-induced optimization of asymmetric Fe single atomic sites for efficient oxygen reduction August 8th, 2025

ICFO researchers overcome long-standing bottleneck in single photon detection with twisted 2D materials August 8th, 2025

New molecular technology targets tumors and simultaneously silences two ‘undruggable’ cancer genes August 8th, 2025

Simple algorithm paired with standard imaging tool could predict failure in lithium metal batteries August 8th, 2025

Materials/Metamaterials/Magnetoresistance

First real-time observation of two-dimensional melting process: Researchers at Mainz University unveil new insights into magnetic vortex structures August 8th, 2025

Researchers unveil a groundbreaking clay-based solution to capture carbon dioxide and combat climate change June 6th, 2025

A 1960s idea inspires NBI researchers to study hitherto inaccessible quantum states June 6th, 2025

Institute for Nanoscience hosts annual proposal planning meeting May 16th, 2025

Announcements

Sensors innovations for smart lithium-based batteries: advancements, opportunities, and potential challenges August 8th, 2025

Deciphering local microstrain-induced optimization of asymmetric Fe single atomic sites for efficient oxygen reduction August 8th, 2025

Japan launches fully domestically produced quantum computer: Expo visitors to experience quantum computing firsthand August 8th, 2025

ICFO researchers overcome long-standing bottleneck in single photon detection with twisted 2D materials August 8th, 2025

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers/Posters

New molecular technology targets tumors and simultaneously silences two ‘undruggable’ cancer genes August 8th, 2025

Simple algorithm paired with standard imaging tool could predict failure in lithium metal batteries August 8th, 2025

First real-time observation of two-dimensional melting process: Researchers at Mainz University unveil new insights into magnetic vortex structures August 8th, 2025

Lab to industry: InSe wafer-scale breakthrough for future electronics August 8th, 2025

Environment

Researchers unveil a groundbreaking clay-based solution to capture carbon dioxide and combat climate change June 6th, 2025

New gel could boost coral reef restoration: The substance, applied to surfaces as a coating, improved coral larvae settlement by up to 20 times in experiments compared to untreated surfaces May 16th, 2025

Onion-like nanoparticles found in aircraft exhaust May 14th, 2025

SMART researchers pioneer first-of-its-kind nanosensor for real-time iron detection in plants February 28th, 2025

Energy

Sensors innovations for smart lithium-based batteries: advancements, opportunities, and potential challenges August 8th, 2025

Simple algorithm paired with standard imaging tool could predict failure in lithium metal batteries August 8th, 2025

Portable Raman analyzer detects hydrogen leaks from a distance: Device senses tiny concentration changes of hydrogen in ambient air, offering a dependable way to detect and locate leaks in pipelines and industrial systems April 25th, 2025

KAIST researchers introduce new and improved, next-generation perovskite solar cell​ November 8th, 2024

Solar/Photovoltaic

KAIST researchers introduce new and improved, next-generation perovskite solar cell​ November 8th, 2024

Groundbreaking precision in single-molecule optoelectronics August 16th, 2024

Development of zinc oxide nanopagoda array photoelectrode: photoelectrochemical water-splitting hydrogen production January 12th, 2024

Shedding light on unique conduction mechanisms in a new type of perovskite oxide November 17th, 2023

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project