Volume Contraction and Substrate Fluidization as a Means to Reduce Drag on Bodies Moving Through a Granular Substrate

Technology #13498

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Illustrates an apparatus for penetrating a particulate substrate according to an example embodiment of the present invention. Illustration of the apparatus according to an example embodiment of the present invention.
Professor Alexander Slocum
Department of Mechanical Engineering, MIT
External Link (pergatory.mit.edu)
Professor Anette Hosoi
Department of Mechanical Engineering, MIT
External Link (hosoigroup.wordpress.com)
Professor Amos Winter
Department of Mechanical Engineering, MIT
External Link (gear.mit.edu)
Managed By
Christopher Noble
MIT Technology Licensing Officer - Clean and Renewable Energy
Patent Protection

Method and Apparatus for Penetrating Particulate Substrates

US Patent 8,496,410
Razor Clam-inspired Burrowing in Dry Soil
Elsevier, 12/19/2015, p.30-39
Localized fluidization burrowing mechanics of Ensis directus
Journal of Experimental Biology, 2012 215: 2072-2080; doi: 10.1242/jeb.058172
Razor clam to RoboClam: burrowing drag reduction mechanisms and their robotic adaptation
IOP Science, 2014 (9): p.1-11


Volume contraction-induced fluidization would allow for the design of compact anchoring technologies applicable to various industries. A razor-clam based system can be used for underwater robot tethering, oil rig mooring, down-hole tool transportation, and underwater mine neutralization.

Problem Addressed

Existing anchoring technologies have limited applications due to their high energy dependence and also to the transportation difficulties that arise from their large size and heavy weight. This invention would allow for an efficient means of burrowing through underwater granular substrates that is both reversible and dynamic. Current technologies pump water into the substrate to facilitate penetration; however, it is expensive and requires a significant amount of energy. This method removes pumping water from the process and therefore decreases the amount of energy expended. By employing a process found in nature, this technology allows for the design of ultra-efficient burrowing machines for a variety of sizes, substrates, and applications. 


Razor clams are able to reduce drag on their body by nearly 4 orders of magnitude compared to penetrating packed, static soil by quickly reducing the volume of their bodies to fluidize the substrate surrounding their shell. Experiments have shown that drag reduction due to fluidization increases with greater depth, greater void fraction, and reduced velocity. As a result, the razor clam is able to quickly burrow through granular substrates and expends very little energy during the process.  This invention uses a similar technique of volume contraction and localized fluidization to efficiently move through granular substrates. A razor clam-based anchor will provide significant performance advantages over existing technologies. 


  • Scalable
  • Reversible
  • Compact
  • Low-power
  • Light-weight
  • Can attach to a variety of seabeds (silt, mud, sand, loose gravel, etc.)