3D trapping of microbubbles by the Marangoni force

Area of Science:

• Optics and Photonics
• Fluid Dynamics
• Nanotechnology

Background:

• Controlling microscale fluid phenomena is crucial for various applications.
• The Marangoni effect, driven by surface tension gradients, offers a non-contact manipulation method.
• Laser-induced thermal effects are increasingly explored for microfluidic control.

Purpose of the Study:

• To demonstrate 3D steady-state trapping and manipulation of vapor bubbles in liquids.
• To investigate the use of the Marangoni effect for bubble control using a continuous-wave laser.
• To explore nanoparticle-enhanced laser-liquid interactions for generating and manipulating bubbles.

Main Methods:

• Utilized a low-power continuous-wave laser focused on photodeposited silver nanoparticles on an optical fiber tip.
• Generated vapor bubbles of varying diameters through light absorption by nanoparticles.
• Employed numerical simulations to determine temperature profiles and derived analytical expressions for Marangoni forces.

Main Results:

• Achieved 3D steady-state trapping and manipulation of vapor bubbles.
• Demonstrated that thermal effects modulate bubble wall surface tension, creating forces for bubble manipulation.
• Successfully transferred bubbles between fibers using an array of three lasers, showcasing controlled movement.

Conclusions:

• The Marangoni effect, induced by laser-heated nanoparticles, provides a viable method for 3D bubble manipulation.
• This technique creates a 3D potential well for trapping and controlling vapor bubbles in liquids.
• The study highlights the potential for precise microfluidic control using optical fibers and nanoparticles.