Rotational and translational drags of a Janus particle close to a wall and a lipid membrane

TL;DR

This study measures how the proximity to walls or membranes affects the rotational and translational drag of spherical particles, revealing insights into hydrodynamic interactions and membrane effects.

Contribution

It introduces experimental measurements of drag coefficients for Janus particles near walls and lipid membranes, highlighting the influence of membrane deformation and particle size.

Findings

Drag coefficients depend on particle size and distance to wall or membrane.

Particles near membranes exhibit larger drag than non-wrapped particles.

Membrane deformation significantly contributes to increased drag coefficients.

Abstract

Hypothesis: Measuring rotational and translational Brownian motion of single spherical particles reveals dissipations due to the interaction between the particle and the environment. Experiments: In this article, we show experiments where the in-plane translational and two rotational drag coefficients of a single spherical Brownian particle can be measured. These particle drags are functions of the particle size and the particle-wall distance, and of the viscous dissipations at play. We measure drag coefficients for Janus particles close to a solid wall and close to a lipid bilayer membrane. Findings: For a particle close to wall, we show that according to hydrodynamic models, particlewall distance and particle size can be determined. For a particle partially wrapped by lipid membranes, in absence of strong binding interactions, translational and rotational drags are significantly larger than the ones of non-wrapped particles. Beside the effect of the membrane viscosity, we show that dissipations in the deformed membrane cap region strongly contribute to the drag coefficients.