MANIPULATION OF AND HYDRODYNAMICS AROUND MAGNETICALLY-ACTUATED MICROSWIMMERS

Lamar Mair, Andrew Berglund, J. Alexander Liddle

 

Biological organisms such as bacteria and microalgae are expert swimmers capable of self-propulsion and on-board local environment sensing. Recent reports have elucidated unexpected hydrodynamics in the vicinity of biological swimmers, and their study has significantly increased our understanding of the propulsion mechanisms, as well as opened new questions regarding the potential implications for processes such as local mixing and quorum sensing1-4. The past decade has given rise to the field of microrobotics, and within this field a variety of micrometer and sub-micrometer scale fluidic environment swimmers have been developed. These swimming microrobots are promising tools for manipulating objects, interacting with cells, and locally manipulating fluids in microfluidic environments5. We have recently started working with one class of controllable microfluidic swimmer: a simple ferromagnetic rod rotationally actuated near a surface. We demonstrate controllable manipulation and cargo pickup using this swimming mechanism. Additionally, we demonstrate and quantify local stirring caused by these swimmers, achieved by seeding fluorescent particles into the swimmer’s environment and performing camera-based particle tracking to extract mean squared displacements of particles near and far from the swimmers.

 

References

1.      Drescher, K., Dunkel, J., Cisneros, L. H., Ganguly, S., & Goldstein, R. E. (2011). Fluid dynamics and noise in bacterial cell – cell and cell – surface scattering. PNAS 108(27), 10940-10945.

2.      Kurtuldu, H., Guasto, J. S., Johnson, K. a, & Gollub, J. P. (2011). Enhancement of biomixing by swimming algal cells in two-dimensional films. PNAS, 108(26), 10391-5.

3.      Rushkin, I., Kantsler, V., & Goldstein, R. (2010). Fluid Velocity Fluctuations in a Suspension of Swimming Protists. Physical Review Letters, 105(18), 1-4.

4.      Guasto, J., Johnson, K., & Gollub, J. (2010). Oscillatory Flows Induced by Microorganisms Swimming in Two Dimensions. Physical Review Letters, 105(16), 18-21.

5.      Ebbens, S. J., & Howse, J. R. (2010). In pursuit of propulsion at the nanoscale. Soft Matter, 6(4), 726.