Bubble propulsion in micro and nanosized devices has attracted much attention with a focus on micromanipulation applications. Such tiny propulsion devices have a micro scale tube cavity that can contain a bubble inside. Ideally, the bubble can oscillate based on specific frequency to thrust the microdevice. Unfortunately, a fundamental challenge has plagued this system in that due to insufficient propulsion force, the device must not only be extremely lightweight, but also have multiple fabrication processes on a parylene polymer substrate. In addition, the bubble contraction motion can generate a micro-flow at the orifices of the open sides of the microtube. Indeed, such challenges affecting the propulsion force limit the field of applications. Literature has it that the hydrophobic property of the cavity surface is significantly important to maintain stable bubble oscillation. In fact, in a recent publication, an increase in the hydrophobicity of the cavity surface by adding a coating via a complicated chemical process was reported. Nevertheless, there is still need for further research.
To this note, Texas A&M University researchers from the Department of Electrical and Computer Engineering: Onder Dincel (PhD candidate), Dr. Tsuyoshi Ueta and led by Professor Jun Kameoka developed an acoustic frequency driven microbubble motor device. Their goal was to present facile technique for creating a faster and cheaper acoustic frequency driven microbubble bidirectional motor for future biomedical and remote actuation applications. Their work is currently published in the research journal, Sensors and Actuators A.
Basically, they fabricated their device by a 3D printer that had been used for the micro mold production in a previous study. In their approach, rotation was based on bubble surface tension forces and pressures induced by the external sound source. Technically, the device was directly constructed from UV curable resin by a micro-3D printer, which had four microscale cavities that contained micro air bubbles when immersed in water.
Their system worked in such a way that once the external 4 kHz acoustic waves stimulated the four cavities, microbubbles were extracted and positioned at the entrances of the cavities. Overall, they discovered that the smallest acoustic frequency driven microbubble motor device had the highest consistency and rotational velocity, meaning higher 3D printing resolution would provide better results.
In summary, the team demonstrated a strong and consistent ability of spinning at high rotational velocities with bidirectional rotation capability. They investigated the rotational motion of acoustic frequency driven microbubble motor devices by the oscillation of microbubbles trapped at the entrance of microtubes in devices. In a statement to Advances in Engineering, Professor Jun Kameoka, the corresponding author pointed out that their design could provide a better understanding for bubble oscillation devices not only for cheaper and easier fabrication, but also better rotational velocity up to 450 revolutions per minute and 2.3 × 10-9 (N/m) torque with a bidirectional capability.
Onder Dincel, Tsuyoshi Ueta, Jun Kameoka. Acoustic driven microbubble motor device. Sensors and Actuators A, volume 295 (2019) page 343–347.
S Jaligama, J Kameoka, “Three-dimensional coaxial multi-nozzle device for high-rate microsphere generation”, Journal of Material Science, 54, 22, 14233, (2019)