nn0c03311_si_003.avi (4.64 MB)
Wafer-Scale Fabrication of Micro- to Nanoscale Bubble Swimmers and Their Fast Autonomous Propulsion by Ultrasound
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posted on 2020-05-27, 21:32 authored by Jeffrey
M. McNeill, Nitesh Nama, Jesse M. Braxton, Thomas E. MalloukFuel-free, biocompatible
swimmers with dimensions smaller than
one micrometer have the potential to revolutionize the way we study
and manipulate microscopic systems. Sub-micrometer, metallic Janus
particles can be propelled rapidly and autonomously by acoustically
induced fluid streaming, but their operation at acoustic pressure
nodes limits their utility. In contrast, bubble-based microswimmers
have an “on board” resonant cavity that enables them
to operate far from the source of acoustic power. So far, they have
been fabricated by direct writing techniques that limit both their
minimum dimensions and the number that can be produced. Consequently,
the size scaling of the properties of bubble swimmers has not been
explored experimentally. Additionally, 3D autonomous motion has not
yet been demonstrated for this type of swimmer. We describe here a
method for fabricating bubble swimmers in large numbers (>109) with sizes ranging from 5 μm to 500 nm without direct
writing
or photolithographic tools. These swimmers follow a previously proposed
scaling theory and reveal useful phenomena that enable their propulsion
in different modes in the same experiment: with magnetic steering,
autonomously in 3D, and in frequency-specific autonomous modes. These
interesting behaviors are relevant to possible applications of autonomously
moving micro- and nanorobots.