Drift Versus Entropic Forces in Overdamped Diffusion Through a Widening Channel.

Area of Science:

• Physics
• Physical Chemistry
• Fluid Dynamics

Background:

• Understanding particle diffusion in confined geometries is crucial for various scientific and engineering applications.
• Deterministic drift and entropic forces are known to significantly influence particle dynamics.

Purpose of the Study:

• To investigate the diffusion of spherical particles in a conical widening channel.
• To analyze the interplay between deterministic drift and entropic forces on particle motion.
• To characterize the transition between different diffusion regimes.

Main Methods:

• Numerical simulations were employed to model particle trajectories.
• Analysis focused on particle motion from a reflecting to an absorbing boundary.
• Key metrics such as mean squared displacement and mean first passage time were calculated.

Main Results:

• Without drift, entropic forces lead to effective superdiffusion.
• Increasing drift strength counterbalances entropic forces, shifting diffusion to standard and then effective subdiffusion.
• Mean squared displacement shows bending points at high drift values, consistent with theoretical predictions.

Conclusions:

• The type of particle diffusion is strongly dependent on drift strength in confined geometries.
• Deterministic drift and entropic forces play critical, interacting roles in particle diffusion.
• The findings highlight the importance of considering these forces for accurate modeling in confined systems.