Shape-directed rotation of homogeneous micromotors via catalytic self-electrophoresis

• Published in: Nature communications Vol. 10; no. 1; p. 495
• Main Authors: Brooks, Allan M., Tasinkevych, Mykola, Sabrina, Syeda, Velegol, Darrell, Sen, Ayusman, Bishop, Kyle J. M.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 30-01-2019; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/923/916; 639/766/189; Anodizing; Asymmetry; bio-inspired; Catalysis; catalysis (homogeneous); charge transport; Colloid chemistry; Electrokinetics; Electrophoresis; Humanities and Social Sciences; Hydrogen peroxide; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; materials and chemistry by design; Mathematical models; mesostructured materials; Micromotors; Microparticles; multidisciplinary; Organic chemistry; Oxidation; Particle motion; Particle shape; Platinum; Science; Science (multidisciplinary); solar (photovoltaic); synthesis (novel materials); synthesis (self-assembly)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-08423-7

The pursuit of chemically-powered colloidal machines requires individual components that perform different motions within a common environment. Such motions can be tailored by controlling the shape and/or composition of catalytic microparticles; however, the ability to design particle motions remains limited by incomplete understanding of the relevant propulsion mechanism(s). Here, we demonstrate that platinum microparticles move spontaneously in solutions of hydrogen peroxide and that their motions can be rationally designed by controlling particle shape. Nanofabricated particles with
n
-fold rotational symmetry rotate steadily with speed and direction specified by the type and extent of shape asymmetry. The observed relationships between particle shape and motion provide evidence for a self-electrophoretic propulsion mechanism, whereby anodic oxidation and cathodic reduction occur at different rates at different locations on the particle surface. We develop a mathematical model that explains how particle shape impacts the relevant electrocatalytic reactions and the resulting electrokinetic flows that drive particle motion.
Self-propelled motors operating at the micro- or nanoscale can be powered by catalytic reactions and show appealing potential in robotic applications. Brooks et al. describe how the motions of platinum spinners in hydrogen peroxide solutions can be rationally designed by controlling particle shape.