World’s First Ciliary Stroke Motion Microrobots
A research team led by Professor
Hongsoo Choi developed microrobots with high propulsion efficiency in highly-viscous
fluid environments, applying propulsion techniques that mimic the ciliary stroke
motion of paramecia.
The research team at DGIST developed ciliary
microrobots with high propulsion efficiency in highly-viscous fluid
environments in the human body such as blood by mimicking the movement of
paramecia’s cilia. The ciliary microrobots are for chemical and cell delivery that
can be precisely controlled and that move via paramecium-like ciliary motion.
Choi’s research team succeeded in fabricating the
world’s first ciliary microrobots utilizing ultra-fine three-dimensional
processing technology and asymmetric magnetic drive technology by applying
microorganism’s ciliary movement, which thus far had only been theorized but
never put into practice.
image of microorganism, Paramecium, using ciliary stroke motion.
layouts for artificial ciliary microrobots.
fabrication process for the ciliary microrobot using 3D laser lithography and
image of ciliary stroke motion microrobots developed by Prof. Choi’s research
team (3D view, scale bar = 100 μm)
e) SEM image of ciliary stroke motion microrobots
developed by Prof. Choi’s research team (top view, scale bar = 100 μm)
environments in which microorganisms move include highly viscous environments like
the human body’s internal fluids; thus, in a macro environment, it is difficult
to create propulsion with swimming-based mechanisms such as inertia-based
symmetrical rowing like that used by large animals such as humans. As such,
microorganisms moving in highly-viscous environments utilize various other
propulsion techniques such as spiral drive motion, progressive wave motion,
ciliary asymmetric reciprocating motion, and the like.
that use propulsion mechanisms such as spiral drive motion and progressive wave
motion were first realized and implemented at the Zurich Federal Institute of Technology,
Switzerland; University of Twente, Netherlands; and Harvard University, USA. However,
the development of microrobots that move utilizing ciliary motion has thus far
been absent due to the difficulty of producing a microstructure with a large
number of cilia as well as with asymmetrical drive.
Choi’s research team has produced a ciliary microrobot with nickel and titanium
coating on top of photo-curable polymer material, using three-dimensional laser
process technology and precise metal coating techniques.
addition, the team verified that the speed and propulsion efficiency of their newly-developed
microrobots were much higher than those of existing conventional microrobots moving
under magnetic attraction drive after measuring the ciliary microrobots’
movement utilizing asymmetrical magnetic actuation technology.
capture of linear motion of ciliary microrobots according to reciprocating
magnetic drive under magnetic field control
capture of rotary motion of ciliary microrobots according to reciprocating
magnetic axis rotation under magnetic field control
movement of ciliary microrobots tracing the letters D. G. I. S. T.
maximum speed of ciliary microrobots with a length of 220 micrometers and a
height of 60 micrometers is 340 micrometers per second, thus they can move at least
8.6 times faster and as much as 25.8 times faster than conventional microrobots
moving under magnetic attraction drive.
comparison to previously developed microrobots, Professor Choi’s ciliary
microrobots are expected to deliver higher amounts of chemicals and cells to
target areas in the highly viscous body environment thanks to their ability to
freely change direction and to move in an 80 micrometer-diameter sphere to the
target point shown in the experiment using the magnetic field.
Choi from DGIST’s Department of Robotics Engineering said, “With precise three-dimensional
fabrication techniques and magnetic control technology, my team has developed
microrobots mimicking cilia’s asymmetric reciprocation movement, which has been
never realized so far. We’ll continually strive to study and experiment on
microrobots that can efficiently move and operate in the human body, so that
they can be utilized in chemical and cell delivery as well as in non-invasive
research outcome was published in the online edition of Scientific Reports, a sister publication of Nature, on July 29, 2016. Professor Choi Hong-soo from DGIST’s Department of Robotics Engineering
was a corresponding author and PhD student Kim Sang-won from DGIST’s Department of Robotics Engineering participated
as the first author.
Sangwon Kim, Hongsoo Choi, et. al., “Fabrication and
Manipulation of Ciliary Microrobots with Non-reciprocal Magnetic Actuation”,
Scientific Reports 2016.
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