Air bubbles that move horizontally when a container is shaken vertically? This unexpected phenomenon, observed by researchers at the University of North Carolina at Chapel Hill, contradicts classical principles of fluid dynamics. A discovery that opens the way to promising technological applications.
a) Sequence of a self-propelled bubble under a vibrating fluid chamber, oscillating in a galloping form (Supplementary Movie 1).
b) Rectilinear motion limited by the chamber walls.
c) Increase in amplitude A inducing an orbital trajectory.
d) Irregular trajectory at high amplitude, reminiscent of run-and-tumble motion (Supplementary Movie 2).
e) Phase map at f = 40 Hz, showing the effect of acceleration and volume on bubble dynamics.
This study, published in
Nature Communications, reveals that bubbles can adopt a rhythmic and directional motion under the effect of controlled vibrations. Far from being anecdotal, this observation could have impacts in fields such as microprocessor cooling, surface cleaning, or even space technologies.
A counter-intuitive phenomenon
The research team discovered that bubbles subjected to vertical shaking spontaneously move horizontally. This behavior, contrary to physical intuition, results from a fluid instability transforming vibrations into directional motion.
By adjusting the frequency and amplitude of the shaking, the scientists observed that bubbles can adopt different modes of movement: rectilinear, circular, or even chaotic trajectories. These variations recall the food search strategies observed in certain bacteria.
This discovery offers a novel way to control bubble motion, a problem that was previously difficult to solve. The researchers emphasize that this control opens perspectives in fields such as microfluidics and heat transfer.
Concrete and varied applications
Bubbles play an important role in many industrial and natural processes, from water treatment to climate regulation. The ability to direct their movement could thus have a significant impact in several sectors.
In space, where gravity is absent, bubble control is essential to avoid overheating of electronic equipment. This new method allows for the active removal of bubbles without relying on gravity, a major advance for space technologies.
In the laboratory, experiments have shown that these "dancing bubbles" can clean dusty surfaces by moving autonomously. This property could be exploited to develop innovative cleaning systems or targeted drug delivery devices.
To go further: What is microfluidics?
Microfluidics is a science that studies the behavior of fluids at the microscopic scale. It allows for the manipulation of tiny amounts of liquid in channels with dimensions smaller than a millimeter.
This discipline finds applications in various fields, such as biology, chemistry, or medicine. For example, it is used to develop chips capable of analyzing biological samples in a few minutes.
Advances in microfluidics could also impact medical diagnostics, enabling rapid and low-cost analyses directly at the patient's bedside.
Article author: Cédric DEPOND