Two-dimensionally steering microswimmer propelled by oscillating bubbles

This paper presents how two-dimensional propulsion with steering capability is developed and realized for micro swimmers that may be used to navigate inside of human body. The propelling and steering forces are produced by oscillating multiple bubble columns, which are arranged in different directions on the micro swimmer. Since the resonant frequency of the bubbles highly depends on their length, only bubbles having the frequency-matching length can be selectively resonated by an acoustic excitation. This allows us to control which bubbles among many can be activated for propulsion, simply by adjusting the frequency. As a result, the controlling of propulsion and steering can be made by changing the frequency. This paper describes experimental results of a variety of controlled 2-D motions including back/forth translations, forward-and-backward rotations, steered propulsion on a 2-D plane, and carrying of objects in a T-junction microchannel.