Out of the cleanroom, self-assembled magnetic artificial cilia

Abstract

Micro-sized hair-like structures, such as cilia, are abundant in nature and have various functionalities. Many efforts have been made to mimic the fluid pumping function of cilia, but most of the fabrication processes for these "artificial cilia" are tedious and expensive, hindering their practical application. In this paper a cost-effective in situ fabrication technique for artificial cilia is demonstrated. The cilia are constructed by self-assembly of micron sized magnetic beads and encapsulated with soft polymer coatings. Actuation of the cilia induces an effective fluid flow, and the cilia lengths and distribution can be adjusted by varying the magnetic bead concentration and fabrication parameters.

Artificial cilia fabricated using magnetic fiber drawing generate substantial fluid flow

“…1d), consisting of a chamber containing the artificial cilia and a side channel providing a recirculation pathway for the fluid. This differs from previous studies, where tests were always performed in a closed chamber or channel, resulting in the combination of a ciliadriven forward flow near the ciliated surface and a recirculation backflow along the opposite surface and along the periphery within the chamber or channel itself, which made the quantification of the ''net flow'' hard to achieve Vilfan et al 2010;Wang et al 2013;den Toonder et al 2008;Shields et al 2010). By reducing (not eliminating) backflow within the main cilia chamber and observing the flow profile in the recirculation pathway, our device provides a straightforward manner to characterize the ''pumping efficiency'' of our artificial cilia.…”

“…The existence of a maximum value of the flow speed has also been observed in another artificial cilia system in our previous study, where an ''optimal'' actuation frequency was observed, albeit at a lower frequency (Wang et al 2013). In order to understand the reason for the existence of Change of the aspect ratio of the ellipsoidal cone at different frequencies is shown in the embedded graphs.…”

“…3c, d, movie as online supplement material 1). It has been previously shown that such motions are highly successful in generating net flow in a low Reynolds number environment (Evans et al 2007;Wang et al 2013;Vilfan et al 2010). In order to further increase pumping performance, the stroke length in each cycle of the cilia motion was increased by making the cilia tracing an ellipsoidal cone with the long axis parallel to the pumping direction, which was done by setting a higher amplitude to the oscillating current driving the electromagnet pair in that direction.…”

“…The same process was used by Babataheri et al with the additional use of a polymer coating (polyacrylic acid) to link the chains permanently to the substrate (Babataheri et al 2011). We have recently published a cleanroom-free in situ fabrication method combining a similar self-assembly of magnetic microbeads with electrostatic polymer coating techniques, avoiding tedious and costly microfabrication requirements and making a step toward practical implementation of artificial cilia (Wang et al 2013). The artificial cilia reported above all have slender and cylindrical shape, and they were actuated by an external magnetic field to perform a 3D tilted conical motion, in an effort to mimic the movement of natural cilia.…”

“…In order to address this issue, our research is aimed at fabricating artificial cilia in a cost-efficient, cleanroom-free manner, while realizing an effective pumping function that can be practically used in lab-on-achip devices. Recently, we reported a self-assembling in situ fabrication method of artificial cilia (Wang et al 2013) able to generate a net flow of up to 5 lm/s. Although the fabrication process is more cost-effective than for earlier examples, Vilfan et al 2010;Evans et al 2007;den Toonder et al 2008) expensive magnetic beads were used and the flow generated was rather low for practical lab-on-a-chip applications.…”