Microrobots Swim with Cilia

a) This is a SEM image of microorganism, Paramecium, using ciliary stroke motion. b) Design layouts for artificial ciliary microrobots. c) Overall fabrication process for the ciliary microrobot using 3D laser lithography and metal sputtering. d) SEM 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). (Image courtesy of DGIST.)

A team of engineering researchers has developed ciliary microrobots capable of 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 can be used for chemical and cell delivery that can be precisely controlled and that move via paramecium-like ciliary motion.

The research team succeeded in fabricating the world's first ciliary microrobots utilizing ultra-fine three-dimensional processing technology and asymmetric magnetic drive technology.

Microfluidic environments can be highly viscous, like the human body's internal fluids. Microorganisms moving in highly-viscous environments utilize various propulsion techniques such as spiral drive motion and progressive wave motion, ciliary asymmetric reciprocating motion.

There are already microrobots that use propulsion mechanisms, such as spiral drive motion and progressive wave motion. 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 and an asymmetrical drive.

The research team from Daegu Gyeongbuk Institute of Science and Technology (DGIST) 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.

a) This is a screen capture of linear motion of ciliary microrobots according to reciprocating magnetic drive under magnetic field control b) Screen capture of rotary motion of ciliary microrobots according to reciprocating magnetic axis rotation under magnetic field control c) The movement of ciliary microrobots tracing the letters D. G. I. S. T. (Image courtesy of DGIST.)

In addition, the team verified that the speed and propulsion efficiency of their newly-developed microrobots was much higher than those of existing conventional microrobots moving under magnetic attraction drive. This was done by measuring the ciliary microrobots' movement utilizing asymmetrical magnetic actuation technology.

The maximum speed of ciliary microrobots with a length of 220 micrometers and a height of 60 micrometers is 340 micrometers per second, at least 8.6 times faster and as much as 25.8 times faster than conventional microrobots moving under magnetic attraction drive.

In comparison to previously developed microrobots, the 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.

Professor 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 surgery."

For more nanotechnology news, read about controlling microbots with mini force fields .

Microrobots Swim with Cilia

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