Janus droplet as a catalytic micromotor

Institute of Continuous Media Mechanics, Ural Branch of the Russian Academy of Sciences Perm 614013, Russia

Received: 27 January 2015
Accepted: 1 June 2015

Abstract

Self-propulsion of a Janus droplet in a solution of surfactant, which reacts on a half of a drop surface, is studied theoretically. The droplet acts as a catalytic motor creating a concentration gradient, which generates its surface-tension–driven motion; the self-propulsion speed is rather high, and more. This catalytic motor has several advantages over other micromotors: simple manufacturing, easily attained neutral buoyancy. In contrast to a single-fluid droplet, which demonstrates a self-propulsion as a result of symmetry breaking instability, for the Janus one no stability threshold exists; hence, the droplet radius can be scaled down to micrometers.