Tethered fleximags as artificial cilia

Flexible superparamagnetic filaments (‘fleximags’) are very slender elastic filaments, which can be driven by distributed magnetic torques to mimic closely the behaviour of biological flagella. Previously, fleximags have been used as a basis for artificial micro-swimmers capable of transporting small cargos Dreyfus et al. (Nature, vol. 437, 2005, p. 862). Here, we demonstrate how these filaments can be anchored to a wall to make carpets of artificial micro-magnetic cilia with tunable densities. We analyse the dynamics of an artificial cilium under both planar and three-dimensional beating patterns. We show that the dynamics are controlled by a single characteristic length scale varying with the inverse square root of the driving frequency, providing a mechanism to break the fore and aft symmetry and to generate net fluxes and forces. However, we show that an effective geometrical reciprocity in the filament dynamics creates intrinsic limitations upon the ability of the artificial flagellum to pump fluid when driven in two dimensions.

[1]  Dynamics of a chain of magnetic particles connected with elastic linkers , 2003 .

[2]  J. Baudry,et al.  Flexible magnetic filaments as micromechanical sensors. , 2003, Physical review letters.

[3]  O. Piro,et al.  Fluid-dynamical basis of the embryonic development of left-right asymmetry in vertebrates. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[4]  R. Superfine,et al.  Biomimetic cilia arrays generate simultaneous pumping and mixing regimes , 2010, Proceedings of the National Academy of Sciences.

[5]  N. Hirokawa,et al.  Randomization of Left–Right Asymmetry due to Loss of Nodal Cilia Generating Leftward Flow of Extraembryonic Fluid in Mice Lacking KIF3B Motor Protein , 1999, Cell.

[6]  M. Maxey,et al.  Spiral swimming of an artificial micro-swimmer , 2008, Journal of Fluid Mechanics.

[7]  M. Vilfan,et al.  Self-assembled artificial cilia , 2010, Proceedings of the National Academy of Sciences.

[8]  S. Melle,et al.  Microstructure evolution in magnetorheological suspensions governed by Mason number. , 2003, Physical review. E, Statistical, nonlinear, and soft matter physics.

[9]  Marcus L. Roper,et al.  On the dynamics of magnetically driven elastic filaments , 2006, Journal of Fluid Mechanics.

[10]  A. Alexander-Katz,et al.  Controlled surface-induced flows from the motion of self-assembled colloidal walkers , 2009, Proceedings of the National Academy of Sciences.

[11]  Christopher E. Brennen,et al.  Fluid Mechanics of Propulsion by Cilia and Flagella , 1977 .

[12]  H. Stark,et al.  Beating kinematics of magnetically actuated cilia , 2009 .

[13]  Frank Jülicher,et al.  Self-Organized Beating and Swimming of Internally Driven Filaments , 1999 .

[14]  Marcus L. Roper,et al.  Microscopic artificial swimmers , 2005, Nature.

[15]  R. Netz,et al.  Pumping fluids with periodically beating grafted elastic filaments. , 2006, Physical review letters.

[16]  R Lloyd Carroll,et al.  Magnetically actuated nanorod arrays as biomimetic cilia. , 2007, Nano letters.

[17]  N. Hirokawa,et al.  Nodal cilia dynamics and the specification of the left/right axis in early vertebrate embryo development. , 2005, Biophysical journal.

[18]  Three-dimensional beating of magnetic microrods. , 2010, Physical review. E, Statistical, nonlinear, and soft matter physics.

[19]  E. Gauger,et al.  Fluid transport at low Reynolds number with magnetically actuated artificial cilia , 2008, The European physical journal. E, Soft matter.

[20]  J. Bibette,et al.  Self-assembled magnetic nanowires made irreversible by polymer bridging. , 2005, Langmuir : the ACS journal of surfaces and colloids.