Bubbles don’t just rise - they can 'gallop' sideways

Scientists have uncovered a type of sideways motion in bubbles that hints at surprising ways to control fluids.

In a recent study, researchers have demonstrated that a simple vertical shake can push these pockets of air horizontally. The study was led by Pedro Sáenz, principal investigator and professor of applied mathematics at UNC-Chapel Hill.

The unexpected behavior of bubbles may open fresh possibilities for practical uses in electronics and other fields.

Unexpected movement of bubbles

“Here we introduce bubbles that spontaneously start to ‘gallop’ along horizontal surfaces inside a vertically-vibrated fluid chamber, self-propelled by a resonant interaction between their shape oscillation modes,” wrote the researchers.

Vertical vibrations somehow trigger steady sideways motion in bubbles, even though it defies common physics instincts that expect up-and-down movement only.

“Our research not only answers a fundamental scientific question but also inspires curiosity and exploration of the fascinating, unseen world of fluid motion. After all, the smallest things can sometimes lead to the biggest changes,” said Professor Sáenz.

New approach to controlling bubbles

The shapes of these energetic bubbles can change by shifting the frequency and intensity of the vertical shaking. Adjusting those conditions can make them move in a straight line, spin in a circle, or scramble around in a zigzag pattern similar to the random search used by microbes.

Study co-author Connor Magoon is a graduate student in mathematics at UNC-Chapel Hill.

“This discovery transforms our understanding of bubble dynamics, which is usually unpredictable, into a controlled and versatile phenomenon with far-reaching applications in heat transfer, microfluidics, and other technologies,” explained Magoon.

Potential use in microgravity

Space-based electronics can overheat if air pockets linger on heated surfaces without buoyancy to lift them away. According to NASA, microgravity means the force of gravity is nearly undetectable, which can hinder heat removal.

The new galloping behavior offers an alternative that doesn’t rely on gravity. By simply shaking the liquid in satellites or space experiments, these agile bubbles can be coaxed to move off critical spots.

Cleaner surfaces and fresh possibilities

When bubbles were tested on dusty surfaces, their bouncing and sidestepping cleared grime in proof-of-concept demonstrations. This approach may pave the way for new strategies in industrial cleaning or even targeted drug delivery, where controlling bubble paths is key.

Saiful Tamim is a joint author of the study and a postdoctoral research assistant at UNC-Chapel Hill. 

“The newly discovered self-propulsion mechanism allows bubbles to travel distances and gives them an unprecedented capacity to navigate intricate fluid networks. This could offer solutions to long-standing challenges in heat transfer, surface cleaning, and even inspire new soft robotic systems,” said Tamim.

Complex behavior of bubbles

The American Physical Society acknowledged this fascinating bubble motion by featuring the work in its Gallery of Fluid Motion, a showcase of captivating and insightful fluid flow videos.

This recognition from top experts highlights the increasing interest in leveraging the bubble phenomenon for practical applications.

Study co-author Jian Hui Guan is a postdoctoral research assistant at UNC-Chapel Hill.

“It’s fascinating to see something as simple as a bubble reveal such complex and surprising behavior,” said Hui Guan. “By harnessing a new method to move bubbles, we’ve unlocked possibilities for innovation in fields ranging from microfluidics to heat transfer.”

Vibrating bubbles may change future tech

Leonardo da Vinci made early notes about odd twists in how air pockets glide through water. Now, modern researchers have taken an additional stride by showing that shaking alone can be an effective steering tool.

“Bubbles often appear to have a life of their own. Da Vinci was a pioneer in documenting their capricious behavior, observing how rising bubbles spontaneously abandon straight paths for mesmerizing helices – a paradox that has persisted for centuries,” noted the study authors.

As technology advances, tapping into galloping bubbles may shape new approaches to cooling systems, flexible robotic designs, and even space exploration.

“Given the multifaceted physics of bubbles, harnessing their dynamics may be challenging but holds significant potential rewards,” said the researchers.

The study is published in the journal Nature Communications.

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