Clustering induces switching between phoretic and osmotic propulsion in active colloidal rafts

• Published in: Nature communications Vol. 15; no. 1; pp. 5666 - 11
• Main Authors: Boniface, Dolachai, Leyva, Sergi G., Pagonabarraga, Ignacio, Tierno, Pietro
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 06.07.2024; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/923/916; 639/301/923/966; 639/766/189; Chemical elements; Chemical reactions; Clustering; Colloids; Experiments; Humanities and Social Sciences; Hydrogen peroxide; Light; Microspheres; multidisciplinary; Physics; Propulsion; Rafts; Reciprocal theorems; Science; Science (multidisciplinary); Shells; Spheres; Substrates
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-49977-5

Active particles driven by chemical reactions are the subject of intense research to date due to their rich physics, being intrinsically far from equilibrium, and their multiple technological applications. Recent attention in this field is now shifting towards exploring the fascinating dynamics of active and passive mixtures. Here we realize active colloidal rafts, composed of a single catalytic particle encircled by several shells of passive microspheres, and assembled via light-activated chemophoresis. We show that the cluster propulsion mechanism transits from diffusiophoretic to diffusioosmotic as the number of colloidal shells increases. Using the Lorentz reciprocal theorem, we demonstrate that in large clusters self-propulsion emerges by considering the hydrodynamic flow via the diffusioosmotic response of the substrate. The dynamics in our active colloidal rafts are governed by the interplay between phoretic and osmotic effects. Thus, our work highlights their importance in understanding the rich physics of active catalytic systems. Diffusiophoresis and diffusioosmosis govern the dynamics of catalytically active colloids. Here, the authors show that the competition between these effects can control the propulsion direction of active colloidal rafts composed of a central apolar particle and several shells of passive ones.