Volume 125, Number 2, January 2019
|Number of page(s)||6|
|Section||Interdisciplinary Physics and Related Areas of Science and Technology|
|Published online||08 February 2019|
Controlling stability and transport of magnetic microswimmers by an external field
1 Institute of Physics, Johannes Gutenberg- University - Staudingerweg 7-9, 55128 Mainz, Germany
2 Kavli Institute for Theoretical Physics, University of California - Santa Barbara, CA 93106, USA
Received: 13 November 2018
Accepted: 11 January 2019
The interplay between external field and fluid-mediated interactions in active suspensions leads to patterns of collective motion that are poorly understood. Here, we study the hydrodynamic stability and transport of microswimmers with weak magnetic dipole moments in an external field using a kinetic theory framework. Combining linear stability analysis and non-linear 3D continuum simulations, we show that for sufficiently high activity and moderate magnetic field strengths, a homogeneous polar steady state is unstable and distinct types of splay and bend instabilities for puller and pusher swimmers emerge. The instabilities arise from the amplification of anisotropic hydrodynamic interactions due to the external alignment and lead to a partial depolarisation and a reduction of the average transport speed of the swimmers in the field direction. Interestingly, at higher field strengths the homogeneous polar state becomes stable and a transport efficiency identical to that of active particles without hydrodynamic interactions is restored.
PACS: 87.18.Hf – Spatiotemporal pattern formation in cellular populations / 05.90.+m – Other topics in statistical physics, thermodynamics, and nonlinear dynamical systems (restricted to new topics in section 05) / 47.54.-r – Pattern selection; pattern formation
© EPLA, 2019
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