nn9b02100_si_011.pdf (600.73 kB)
Confined 1D Propulsion of Metallodielectric Janus Micromotors on Microelectrodes under Alternating Current Electric Fields
journal contribution
posted on 2019-07-25, 16:34 authored by Liangliang Zhang, Zuyao Xiao, Xi Chen, Jingyuan Chen, Wei WangThere is mounting
interest in synthetic microswimmers (“micromotors”)
as microrobots as well as a model system for the study of active matters,
and spatial navigation is critical for their success. Current navigational
technologies mostly rely on magnetic steering or guiding with physical
boundaries, yet limitations with these strategies are plenty. Inspired
by an earlier work with magnetic domains on a garnet film as predefined
tracks, we present an interdigitated microelectrodes (IDE) system
where, upon the application of AC electric fields, metallodielectric
(e.g., SiO2–Ti) Janus particles are hydrodynamically
confined and electrokinetically propelled in one dimension along the
electrode center lines with tunable speeds. In addition, comoving
micromotors moved in single files, while those moving in opposite
directions primarily reoriented and moved past each other. At high
particle densities, turbulence-like aggregates formed as many-body
interactions became complicated. Furthermore, a micromotor made U-turns
when approaching an electrode closure, while it gradually slowed down
at the electrode opening and was collected in large piles. Labyrinth
patterns made of serpentine chains of Janus particles emerged by modifying
the electrode configuration. Most of these observations can be qualitatively
understood by a combination of electroosmotic flows pointing inward
to the electrodes, and asymmetric electrical polarization of the Janus
particles under an AC electric field. Emerging from these observations
is a strategy that not only powers and confines micromotors on prefabricated
tracks in a contactless, on-demand manner, but is also capable of
concentrating active particles at predefined locations. These features
could prove useful for designing tunable tracks that steer synthetic
microrobots, as well as to enable the study of single file diffusion,
active turbulence, and other collective behaviors of active matters.