Nanochromatography driven by the coffee ring effect.

Area of Science:

• Physics of fluid dynamics and soft matter.
• Biophysical characterization and separation science.

Background:

• The coffee ring phenomenon typically concentrates particles at the edge of drying droplets.
• Its potential for particle separation, particularly for biological entities, remains largely unexplored.

Discussion:

• Elucidating the physics of particle separation during coffee ring formation.
• Identifying a particle-size selection mechanism operating near the contact line of evaporating droplets.
• Demonstrating size-based separation of proteins, microorganisms, and mammalian cells.

Key Insights:

• Achieved nanochromatography of diverse biological entities within a single droplet.
• Demonstrated high separation resolution (∼100 nm) and a broad dynamic range (∼10 nm to tens of micrometers).
• Established a novel, low-cost method for separating nanoscale to microscale biological particles.

Outlook:

• Potential for developing affordable, point-of-care diagnostic technologies.
• Applications in resource-limited settings for disease detection and analysis.
• Further exploration of droplet evaporation dynamics for advanced separation techniques.