A new optofluidic technique uses laser-generated heat and Marangoni flows to precisely guide micro- and nanoparticles, opening new possibilities for lab-on-a-chip technology and micro-robotics.
Controlling tiny particles inside liquids is important for many areas of modern science and technology. Micro- and nanoparticles are used in biological research, medical diagnostics, chemical analysis, micro-robotics, and lab-on-a-chip devices. However, moving these extremely small objects with high precision remains challenging.
Light offers an attractive way to control microscopic objects because laser beams can be focused and moved without physically touching the particles. Yet conventional light-driven fluid systems often have important limitations. Their flow patterns can become unstable, their direction of movement can be difficult to control, and changing the particle trajectory often requires complicated hardware.
Now, Liu and his research team have demonstrated a new approach that could make light-based particle manipulation far more flexible. Their technique, called multibeam engineering of Marangoni convection technique (MEMCT), provides programmable control over fluid flows around tiny air bubbles. By carefully controlling where laser light creates heat, researchers can change the direction and shape of microscopic flows and use them to steer particles along selected paths.
How Does the New Technique Work?
The basic idea combines laser light, photothermal heating, air bubbles, and Marangoni convection.
At the center of the system is a thin gold film. Gold is useful because it can absorb laser light and convert part of that optical energy into heat. When a focused laser beam is directed onto the gold film near an air bubble inside water, it produces a highly localized increase in temperature.
This heating changes the temperature distribution around the surface of the bubble.
The difference in temperature creates differences in surface tension along the air-water interface. This phenomenon generates a type of fluid motion known as Marangoni convection. In simple terms, liquid moves along the surface of the bubble because warmer and cooler regions have different surface-tension properties.
The researchers use this effect as a microscopic flow-control mechanism.
Instead of relying on a single laser-generated heat source, MEMCT uses multiple laser beams or heat sources. By changing their positions, number, and arrangement, the researchers can reshape the flow around the bubble.
This gives them a programmable way to control how the surrounding liquid moves.
From Straight Movement to Complex Vortices
One of the most important features of MEMCT is its ability to create different types of flow patterns.
For example, researchers can arrange the laser-induced heat sources to produce a directional flow. Such a flow can transport a particle toward a chosen location.
By changing the laser configuration, however, the same system can generate much more complicated patterns, including rotating or vortical flows.
This means that the fluid environment surrounding the particle does not have to remain fixed. It can be dynamically changed simply by modifying the laser beams.
The approach therefore turns light into a kind of remote-control system for microscopic fluid motion.
Precise Particle Steering
The ability to generate controllable flows is particularly useful because micro- and nanoparticles are strongly affected by the surrounding liquid.
When the researchers create a specific Marangoni flow, particles suspended in the liquid can be carried by that flow. By controlling the direction and structure of the fluid motion, the researchers can guide particles along predetermined trajectories.
Importantly, both experiments and computer simulations supported the ability of the technique to generate predictable interfacial stress fields and particle movement.
This deterministic control is significant. Rather than allowing particles to move randomly or relying only on fixed flow patterns, researchers can actively determine where particles should travel.
The system can also manipulate more than one particle, making it potentially useful for applications requiring the simultaneous handling of multiple microscopic objects.
No Traditional Pump Required
Another interesting feature of the research is the integration of the technique with microfluidic cross-junctions.
Microfluidic devices contain extremely small channels through which tiny amounts of liquid can be transported. Conventional microfluidic systems often use external pumps, valves, or pressure sources to control fluid movement.
The researchers demonstrated that their light-controlled Marangoni system can provide an alternative approach.
By combining MEMCT with microfluidic structures, they achieved pump-free, on-demand particle routing. In other words, laser-controlled heating can be used to influence where particles travel without requiring a conventional mechanical pumping system.
The researchers also extended the concept to arrays of air bubbles. This could allow more complex particle-routing operations by creating multiple controllable flow regions within the same platform.
Why Is This Important?
The biggest advantage of MEMCT is its reconfigurability.
Traditional microfluidic systems are often designed for specific tasks. Once channels, pumps, and flow structures are fabricated, changing their function can be difficult.
A programmable optical system offers much greater flexibility. The flow can potentially be changed simply by adjusting the laser positions or activation pattern.
This could allow the same microscopic device to perform different operations without requiring major physical modifications.
The technique also avoids direct mechanical contact with the particles. This can be valuable when handling delicate biological materials, cells, or sensitive nanoparticles.
Potential Applications
The new platform could have applications across several fields.
In lab-on-a-chip technology, it could help researchers move, separate, sort, or route microscopic particles inside compact analytical devices.
In biophotonics, controlled particle manipulation could support experiments involving biological samples and microscopic components.
The technique could also contribute to micro- and nanorobotics, where precise control of tiny objects is essential.
Another possible area is automated laboratory systems. Since laser beams can be digitally controlled, future systems could potentially use software to determine particle pathways and modify them in real time.
Such an approach could make microscopic fluidic systems more programmable and adaptable.
A New Direction for Optofluidics
The work by Liu and his team demonstrates how combining optical heating with interfacial fluid physics can overcome some limitations of conventional optofluidic manipulation.
Instead of treating unwanted fluid motion as a problem, the researchers turn thermally generated flow into a useful control mechanism. By engineering multiple heat sources around an air bubble, they can create customized Marangoni flows capable of moving particles in controlled directions.
The result is a simple yet versatile platform in which light effectively becomes a tool for programming microscopic fluid motion.
Although further research will be needed to understand the full range of particles, operating conditions, scalability, and practical applications, MEMCT represents an important step toward more flexible microfluidic systems.
In the future, programmable light-controlled flows could help create smarter lab-on-a-chip devices, contact-free particle manipulation systems, and advanced micro- and nanorobotic technologies. The ability to dynamically control microscopic movement using nothing more than carefully engineered light and heat could ultimately provide scientists with a powerful new way to manipulate the tiny world.
Reference: Liu, C., Huang, Z., Nan, F. et al. Reconfigurable multibeam engineering of Marangoni convection for programmable optofluidic steering. Nat Commun (2026). https://doi.org/10.1038/s41467-026-76930-5
Comments
Post a Comment