Additions and corrections

Out of the cleanroom, self-assembled magnetic artificial cilia

Ye Wang, Yang Gao, Hans Wyss, Patrick Anderson and Jaap den Toonder

Lab Chip, 2013, 13, 3360–3366 (DOI: 10.1039/C3LC50458A). Amendment published 3rd December 2013.

Recently, we published a cost-effective in situ fabrication technique of artificial cilia (Lab Chip, 2013, DOI: 10.1039/C3LC50458A). The cilia were constructed by self-assembly of micron sized magnetic beads and encapsulated with soft polymer coatings. By carrying out direct flow visualization experiments, we found that actuation of the cilia along a tilted cone induces an effective fluid flow (with flow velocities in the range of several µm/s). The cilia lengths and area coverage could be adjusted by varying magnetic bead concentration and fabrication parameters.

As became apparent to us only after publication of this paper, we omitted citation of an earlier work with a similar approach of making artificial cilia. Babataheri et al.1 reported the fabrication of artificial magnetic cilia based on the self-assembly of superparamagnetic colloids in a fluid chamber. The cilia were made permanent and anchored to the bottom of the chamber by a layer of polymer (polyacrylic acid). These cilia were actuated with three sets of coils to perform planar and conical motion. To realize higher densities of cilia (limited to a few per mm2 in reference 1) and extended cilia carpet geometries, an additional fabrication step based on soft lithography was introduced in Coq et al.2 to create arrays of magnetic anchoring points of the cilia formation. The time-dependent shape and dynamic response of the cilia was studied,1,3 as was the influence of the presence of neighboring cilia on the cilia motion.2 On the basis of the measured motion of individual cilia, an estimate was obtained of the generated fluid flux for the planar actuation of the cilia; due to intrinsic limitations in the filament dynamics, the calculated flux was low.

Our approach shows clear differences with this earlier approach: we use a more sophisticated method to form the permanent cilia, using soft polymer latex with a intentionally engineered surface charge to promote the generation of the coating, which is critical for creating a dense, functional ciliated surface without the help of anchoring points (around 3000 cilia per mm2 in our case); we show control of cilia length and surface area coverage by varying magnetic bead concentration and fabrication parameters; and we make direct observations of induced fluid flows. It is evidently clear that these earlier papers have a very similar approach and deserve to be mentioned. In fact the combination of all results, with our paper more directed towards realizing functional (flow generating) devices, and ref. [1-3] more on fundamentals of cilia motion, gives a more complete picture of magnetic artificial cilia actuation and its application.

1. Avin Babataheri, Marcus Roper, Marc Fermigier, and Olivia du Roure, Tethered fleximags as artificial cilia, Journal of Fluid Mechanics, 2011, 678, 5-13.
2. Nais Coq, Antoine Bricard, Francois-Damien Delapierre, Laurent Malaquin, Olivia du Roure, Marc Fermigier and Denis Bartolo, Collective beating of artificial microcilia, Phys. Rev. Lett., 2011, 107, 014501.
3. Nais Coq, Sandrine Ngo, Olivia du Roure, Marc Fermigier and Denis Bartolo, Three-dimensional beating of magnetic microrods, Phys. Rev. E, 2010, 82, 041503.

The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.

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