Particle accumulation and depletion in a microfluidic Marangoni flow

Area of Science:

• Fluid dynamics
• Microfluidics
• Particle manipulation

Background:

• Marangoni convection, driven by temperature and concentration gradients at liquid-gas interfaces, is crucial in microfluidic systems.
• Understanding particle behavior in microchannels is key for applications in diagnostics and materials science.

Purpose of the Study:

• To investigate particle trapping and fractionation mechanisms induced by thermosolutal and thermocapillary Marangoni convection in microchannels.
• To analyze the role of a localized vortex and critical streamlines in particle redistribution and size-dependent confinement.

Main Methods:

• Utilized a microchannel structure (approx. 100 × 90 μm²) to generate Marangoni convection.
• Observed and analyzed the behavior of micrometer and sub-micrometer sized tracer particles within the induced vortex and surrounding fluid flow.

Main Results:

• A localized vortex was formed, acting as an effective trap for tracer particles.
• Particle redistribution occurred due to meniscus collisions, creating particle-depleted regions.
• Particle fractionation based on size was observed, with larger particles exhibiting enhanced localization due to a ratchet effect.

Conclusions:

• Thermosolutal and thermocapillary Marangoni convection can induce size-dependent particle fractionation in microfluidic devices.
• The localized vortex and critical streamline dynamics play a significant role in particle trapping and separation.
• The observed ratchet effect enhances particle localization, offering potential for precise particle manipulation and separation.