Chances are that if you were heading into battle, you wouldn’t wish that you were covered in sponges. It turns out that the sea sponge, however, has a unique structure that allows it to be flexible while remaining relatively impervious to predators. Scientists have now simulated this structure, in a lab-created material that may someday find use in body armor.

Sponges’ “skeletons” – their internal structural elements – are made up of tiny interlinked needle-like structures known as spicules. These are hard, prickly, flexible and lightweight. As a result, they offer enough strength to provide structural support, while they bend to such an extent that they’re difficult to cut. A team of researchers from Germany’s Johannes Gutenberg University Mainz and the Max Planck Institute for Polymer Research set out to develop a material with those same qualities.

The nanoscale spicules they created incorporate a mixture of the mineral calcite, and a protein found in siliceous sponges known as silicatein-α. Each synthetic spicule is composed of a multitude of calcite “nanobricks” stacked together brick chimney-style, with a matrix of the stretchy protein holding them together.

A diagram of one of the man-made spicules, with close-ups of its calcite nanobricks

When mechanical pressure is applied, the nanobricks remain hard and unyielding, but the connective protein allows the spicule as a whole to bend without breaking. In fact, the man-made spicules are reportedly about ten times as flexible as their natural counterparts. As a side benefit, they’re also able to transmit light waves – even when bent.

Sponges aren’t the first aquatic organisms to inspire new protective materials. Scientists are also looking into making armor based on the scales of the Arapaima fish and the shell of the "scaly-foot" snail.

A paper on the sponge research was recently published in the journal Science. The process by which the spicules were created is outlined in the video below.

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