Directed drift and fluid pumping of nanoswimmers by periodic rectification-diffusion

Area of Science:

• Physics
• Fluid Dynamics
• Nanotechnology

Background:

• Microfluidic devices enable precise control over small fluid volumes.
• Run-and-tumble motion is a common strategy for biological and synthetic microswimmers.
• Understanding transport phenomena in microfluidics is crucial for applications like drug delivery and diagnostics.

Purpose of the Study:

• To investigate the ratchet transport of run-and-tumble nanoswimmers in a 3D microfluidic channel.
• To identify and characterize different transport regimes within the channel.
• To explore the induced autonomous fluid pumping by nanoswimmers.

Main Methods:

• Dissipative particle dynamics simulations were employed to model nanoswimmer behavior.
• A 3D microfluidic channel with periodic chambers and half-cylinder funnels was designed.
• Analysis focused on concentration gradients, diffusion rates, and fluid flow patterns.

Main Results:

• Two distinct transport regions were identified: rectification and active diffusion.
• The active diffusion region was further classified into normal and Knudsen types, with normal diffusion obeying Fick's law.
• Nanoswimmers near funnels induced autonomous fluid pumping, with flow directionality mirroring the ratchet current.
• Fluid velocity was found to be dependent on nanoswimmer characteristics, such as self-propulsion velocity and run time.

Conclusions:

• The study elucidates the complex transport dynamics of nanoswimmers in engineered microfluidic environments.
• Autonomous fluid pumping by nanoswimmers offers potential for novel micro-mixing and transport strategies.
• The findings contribute to the fundamental understanding of active matter in confined geometries.