Even Tiny Droplets in Oil Keep the Beat

Discovery of Synchronized Droplet Formation on Lab-on-a-Chip
Elucidation of Vibrational Interactions at Fluid Interfaces (Water-Oil)

[Asia Economy Reporter Junho Hwang] Fireflies flash simultaneously in sync without a conductor. Two vibrating pendulums also gradually synchronize their rhythms. This phenomenon is called synchronization. A domestic research team has discovered that synchronization occurs even in flowing liquids. They also proposed a theory to explain this phenomenon. It is expected that this technology could be used in the future to control the flow of liquid samples inside lab-on-a-chip devices for diagnosing cancer or pathogens.

The research team led by Professor Junwoo Jeong of the Department of Physics at Ulsan National Institute of Science and Technology (UNIST) was the first to discover the phenomenon of droplets naturally synchronizing their rhythms when formed in tiny oil channels (microfluidic channels). They also presented a theoretical model explaining the cause of this synchronization phenomenon, which was recently published in the international journal Nature Communications, the team announced on the 19th.

Controlling the flow of droplets in oil-flowing channels

When water is injected from both sides into a microfluidic channel through which oil flows, the water, which does not mix with the oil, breaks up spontaneously into droplets. Originally, it was natural for these droplets to be formed out of sync from both sides. However, under certain conditions, the research team captured the scene where droplets that were initially formed independently gradually synchronized their rhythms over time.

The team explained this by the physical principle of 'interaction between interfaces.' They regarded the tiny vibrations occurring at the water-oil interface as a single oscillator, like a pendulum. When multiple droplets form, multiple oscillators appear corresponding to the number of droplets, and interactions among these oscillators synchronize the droplet formation cycles. Similarly, if the cilia of cells floating in water are considered as oscillators, this can explain how the cilia move in synchronized rhythms.

The researchers also adjusted the degree of synchronization between two droplets by controlling factors such as the distance between the two droplets (interfaces), the flow speed of the liquid, and its viscosity.

Future-oriented lab-on-a-chip technology

First author and co-corresponding author Yujin Eom, a research professor in the Department of Physics at UNIST, said, "This is the first observation of 'simultaneous generation' synchronization, which previous studies on droplet generation using lab-on-a-chip devices had overlooked," adding, "Using this model system, we can deepen our understanding of synchronization phenomena occurring within microfluidics."

Professor Jeong stated, "This is a textbook model system that can intuitively explain synchronization phenomena and will be useful as a future-oriented lab-on-a-chip technology that can control fluids without the need for complex structural fabrication."

This content was produced with the assistance of AI translation services.