Building and Construction

Sea Sponge Spikes Could Lead to Stronger Columns

06 January 2017

The shape of rib-like structures in sea sponges could inform structural design for structures like building columns and bicycle spokes. Two engineers from Brown University discovered the tapering, pointed structure of strongloxea spicules in the orange puffball sponge (Tethya aurantia).

Sea sponges are subject to multiple pressure sources, including underwater waves and tidal forces. The Brown researchers were curious to understand how these soft-bodied creatures withstand these pressures. Too much compression deprives a sponge of its ability to feed.

Sponge spicule compared to Clausen column. Credit: Kesari Lab/Brown UniversitySponge spicule compared to Clausen column. Credit: Kesari Lab/Brown UniversityThe answer lies in the spicules, which are about 2 mm long and thinner than a human hair. These are bundled together to form rib-like structures that prevent overcompression.

The spicules have a toothpick-like shape—wider in the center, tapering to points on each end. The research team searched for information on slender, tapered structures, and discovered work by Thomas Clausen, a German scientist who in 1851 proposed that columns tapered towards the end would be stronger than plain cylinders. In the 1960s, mathematician Joseph Keller published a proof that the Clausen column has optimum resistance to buckling.

The orange puffball’s spicules are almost identical to Clausen’s optimum shape, which is 33% stronger than a plain cylindrical column.

Haneesh Kesari, assistant professor of engineering, pointed to two two outcomes of the research he and Michael Monn conducted. First, among other applications, the Clausen profile would be easy to 3D-print into nanoscale truss structures.

Second, nature might already have designed many ideal structures that have withstood the test of evolution. These structures could be technologically interesting, if investigators continue to look.

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Discussion – 4 comments

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Re: Sea Sponge Spikes Could Lead to Stronger Columns
2017-Jan-07 1:28 PM

The idea that this shape might inform better bicycle spokes is kind of silly.

Bicycle spokes are in tension and the failure mode is not buckling. Some bicycle spokes are offered butted with the ends slightly greater in diameter to provide additional strength at the bend or at the threads.

The tension will be pretty much the same down the length of the spoke. Any additional material not being used to offset some potential weakness (like threads or bend) will not increase the tensile strength above the thinnest section.

Re: Sea Sponge Spikes Could Lead to Stronger Columns
2017-Jan-07 3:15 PM

I have two such shaped composite (8 vertical, 16 horizontal sawn lumber and plywood components per column) 6-meter tall columns supporting the outboard perimeter of a 70 square meter front porch roof on my 35 year old home.

Re: Sea Sponge Spikes Could Lead to Stronger Columns
2017-Jan-08 2:03 AM

If I understand this correctly, these thin, double- tapered columns inserted perpendicular to a structural membrane sub later will perform better than non- tapered cylindrical rods.

Re: Sea Sponge Spikes Could Lead to Stronger Columns
2017-Jan-18 2:59 PM

My thinking is that the tapered spikes allow interlock when in compression.

Spikes with blunt ends will not

Cannot see practical application in structural colomns

Definitely not in tension

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