Brownian Motion near Soft Interfaces

Introduction

Soft and wet contacts are ubiquitous across scales from geology to physiology and are crucial for engineering. Furthermore, many processes of physics and biology at small scales are governed by the mobility of microscopic entities in soft and confined environments, with the aim of reaching specific targets.

Emergent EHD Lift Force

Interestingly, an emergent elastohydrodynamic (EHD) lift force was theoretically predicted recently for an immersed object moving near an elastic wall. An active community, including the PI, has started to explore this striking effect with various deterministic models and experiments, showing its relevance for nanoscale and biomimetic systems.

Central Claim

In this context, and moving beyond the deterministic, the PI’s central claim is that such EHD effects can be spontaneously triggered by thermal fluctuations. The result would be an original migration scenario in complex and confined environments – with enormous implications. However, studies are scarce on the topic.

Project Ambition

The ambition of EMetBrown is thus to address this challenge at the interface between two mature fields, by solving a fundamental problem involving both continuum and statistical mechanics: Brownian motion near soft interfaces.

Objectives

The three objectives are to:

1. Reveal the signatures of such motion.
2. Explore the implications of these signatures.
3. Harvest the findings to pave the way towards the future design of methods for:
   • Particle transport
   • Surface patterning
   • Confined reactions
   • Nanorheology

Methodology

These objectives will be reached using a combination of experiments, theory, and numerics, domains in which the PI has extensive experience.

Experimental Setups

EMetBrown involves:

• Three core experimental setups:

  • Free colloids
  • Optical trapping
  • Atomic-force microscopy

• Three core theoretical models:

  • Soft lubrication
  • Stochastic theory
  • Langevin simulations

• Three exploratory tools:

  • Microfluidics
  • Suspension rheometry
  • Molecular dynamics

Work Packages

These complementary methods will be employed through four work packages covering various viscous, hard, soft materials, as well as applied flow.