Tuning the rheology and microstructure of particle-laden fluid interfaces with Janus particles

TL;DR

This study demonstrates how Janus particles can significantly enhance the stability and rheological properties of particle-laden fluid interfaces by inducing local clustering, offering a new method to control interfacial mechanics.

Contribution

The paper introduces the use of Janus particles to tune the microstructure and rheology of particle-laden interfaces, showing substantial improvements in stability and elasticity.

Findings

Janus particles increase surface moduli by over tenfold.

Local particle clustering correlates with enhanced elasticity.

Microstructure control affects macroscopic interfacial properties.

Abstract

Hypothesis: Particle-laden fluid interfaces are the central component of many natural and engineering systems. Understanding the mechanical properties and improving the stability of such interfaces are of great practical importance. Janus particles, a special class of heterogeneous colloids, might be utilized as an effective surface-active agent to control the assembly and interfacial rheology of particle-laden fluid interfaces. Experiments: Using a custom-built interfacial stress rheometer, we explore the effect of Janus particle additives on the interfacial rheology and microscopic structure of particle-laden fluid interfaces. Findings: We find that the addition of a small amount of platinum-polystyrene (Pt-PS) Janus particles within a monolayer of PS colloids (1:40 number ratio) can lead to more than an order-of-magnitude increase in surface moduli with enhanced elasticity, which greatly improves the stability of the interface. This drastic change in interfacial rheology is associated with the formation of local particle clusters surrounding each Janus particle. We further explain the origin of local particle clusters by considering the interparticle interactions at the interface. Our experiments reveal the effect of local particle structures on the macroscopic rheological behaviors of particle monolayers and demonstrate a new way to tune the microstructure and mechanical properties of particle-laden fluid interfaces.