Issue 29, 2016

Shape-controlled anisotropy of superparamagnetic micro-/nanohelices

Abstract

Micro-/nanopropellers can be actuated remotely by a rotating magnetic field and steered at high precision through various fluidic environments. Recent progress comprises microfabrication of superparamagnetic microhelices not possessing remanent magnetization, but rather magnetized by an applied magnetic field. In this article we present a numerical approach for computing, from first principles, the effective susceptibility of polarizable helical micro-/nanopropellers. We show that nanopropeller geometry, in particular, filament cross-section elongation and orientation, play a central role in determining its magnetic anisotropy and polarizability. The numerical predictions are in qualitative agreement with the previously reported experiments, showing that tight polarizable helices are propulsive. The numerical results are also supported by the approximate slender-body theory. Finally, we propose a semi-quantitative energy criterion to rank polarizable helices with different geometries of the filament by their propulsive capacity and also estimate their maximal propulsion speed.

Graphical abstract: Shape-controlled anisotropy of superparamagnetic micro-/nanohelices

Associated articles

Supplementary files

Article information

Article type
Paper
Submitted
02 Mar 2016
Accepted
19 May 2016
First published
19 May 2016

Nanoscale, 2016,8, 14127-14138

Shape-controlled anisotropy of superparamagnetic micro-/nanohelices

A. M. Leshansky, K. I. Morozov and B. Y. Rubinstein, Nanoscale, 2016, 8, 14127 DOI: 10.1039/C6NR01803C

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