Pair-Interactions of Self-Propelled SiO2-Pt Janus Colloids: Chemically Mediated Interactions

TL;DR

This experimental study explores how chemically active SiO2-Pt Janus colloids interact through hydrodynamic and chemophoretic forces, revealing collision behaviors influenced by surface reactivity and implications for material assembly.

Contribution

It provides the first detailed categorization and analysis of pair-wise collision mechanisms of Janus colloids considering chemical interactions and orientation effects.

Findings

Collision types depend on chemical and orientation factors.

Particle speed decreases during contact due to interactions.

Collision configurations influence assembly processes.

Abstract

Driven by the necessity to achieve a thorough comprehension of the bottom-up fabrication process of functional materials, this experimental study investigates the pair-wise interactions or collisions between chemically active SiO2-Pt Janus Colloids. These collisions are categorized based on the Janus colloids orientations before and after they make physical contact. In addition to the hydrodynamic interactions, the Janus colloids are also known to affect each others chemical field, resulting in chemophoretic interactions, which depend on the degree of surface anisotropy in reactivity and solute-surface interaction. These interactions lead to a noticeable decrease in particle speed and changes in orientation that correlate with the contact duration and yield different collision types. Our findings reveal distinct configurations of contact during collisions, whose mechanisms and likelihood is found to be dependent primarily on the chemical interactions. Such estimates of collision and their characterization in dilute suspensions shall have key impact in determining the arrangement and time scales of dynamical structures and assemblies of denser suspensions, and potentially the functional materials of the future.