A creature called the Atlantic razor clam had a secret. Digging in wet sand should be slow and take lots of effort. But the razor clam could burrow a centimeter per second and go half a kilometer using only about a AA battery’s worth of energy.
These talents intrigued M.I.T. researchers, who thought that a robotic version of the clam would have practical uses. So they studied how the mollusk moves.
They found that the clam first contracts its shell. That action causes sand to fall inward towards the animal. Further shell contraction draws water into the mix. At that point, the watery sand starts to behave as a fluid—think quicksand. The drag on the burrowing clam is dramatically reduced and it starts to really move. The process requires pinpoint timing of contractions and digging.
Based on their findings, the researchers built a metal mimic. Its two halves contract and expand, and a rod digs through the sand. They believe that an energy-efficient Roboclam could anchor an autonomous underwater vehicle, search for mines or lay underwater cables. The scientists discuss their efforts in the journal Bioinspiration and Biomimetics. [Amos Winter and Annette Hosoi, in press] Rather than clamming up.
—Cynthia Graber
