Earth is a factory for a plethora of strong materials, most of which humans have yet to comprehend, dissect, and imitate. Similar to spider’s silk and a mollusk’s limpet teeth, nacre, or mother-of-pearl, is a material of extraordinary strength. Nacre is found inside the shells of some mollusks and mussels, characterized by a pearl-like iridescence. The material’s composition of ‘brickwork’ arrangement has been known for a while – tablets made of aragonite cemented together by thin layer made of an organic mixture. A recent study has now potentially brought us closer to understanding from where nacre derives its true strength.
Scientists from the University of Michigan and Australia’s Macquarie University crushed a miniscule, protected Mediterranean clam species (a fan mussel) and used an electron microscope to observe the effects. Under compression, nacre’s binding organic layer dissipates to areas of lower pressure (like squeezing a bag of liquid and the liquid moves to everywhere but where you’re squeezing). Then the separated aragonite tablets rigidify, blocking crack formation and lending the material its tensile strength. This functionality is similar to concrete, a material that is very good at resisting compression. Once decompressed, the structure fully restores its original build and mechanical strength as the organic material fills back in. Nacre’s resilience indicates its superiority to plastic, which springs back to its original form but has generally lost most of its strength in the process.
The observations highlight nature’s design prowess that human technology is yet to achieve. Researchers deem nacre to be “the toughest material” and now look for ways to synthesize lighter and stronger materials inspired by the mollusk’s methods. While inspiring the materials sciences to learn from nature’s own nanoengineering, the study also advocates creating better materials in a sustainable manner.
Managing Correspondent: Rhea Grover
Original Science Article: Nanoscale deformation mechanics reveal resilience in nacre of Pinna nobilis shell. Nature Communications.
Original Press Article: Cracking the mystery of nature’s toughest material. Phys.org.
Image Credits: Wikimedia Commons