Swimming Rheometer
CATEGORY
Instrumentation
ABSTRACT
What if rheology of fluids in our environment or in our body could be measured by an untethered robot? – as it swims along an unknown fluid.
In a joint effort, the Shaqfeh and Prakash groups recently demonstrated that swirl, defined as angular velocity pointing along the direction of propulsion, can generate propulsion in viscoelastic fluids even in the absence of propulsion in Newtonian fluids. This was first demonstrated in silico and later through experimentation.
To prove this in the real world, the two groups developed a tetherless self-propelled robotic two-sphere swimmer with a small rotating spherical tail and a large spherical head demonstrated propulsion in several viscoelastic fluids but not in any Newtonian fluid, validating theoretical predictions.
This discovery has three important implications: first, swirling propulsion may be fundamental to microbial propulsion in complex fluids. Many microorganisms across several kingdoms, including bacteria, archaea, and protists, as well as animal spermatozoa, are propelled by swirling filaments attached to the cell body. Thus, swirling propulsion may account for experimentally observed bacterial motility enhancement in polymeric fluids. Secondly, this could become a test-bed for unthethered environmental rheology – where a small robotic probe in an environmental sample could report it’s rheology in industrial and medical applications. Thirdly, this propulsion mechanism can be scaled down for very small robotic swimmers with capacity to communicate, swarm and explore challenging environments at the microscale.
BIG QUESTION
“What if rheology of fluids in our environment or in our body could be measured by an untethered robot?”
Project status
Active
Project collaborators
Joint project with Shaqfeh Lab, Stanford University.
Project is funded by National Science Foundation.
