Magnetic enhancement of phototaxing catalytic motors

We use the "stimulus-quench-fuse" (SQF) technique to fabricate micrometer-size colloidal heterodoublets. The doublets consist of silver and magnetic Dynabead microspheres, and the stimulus is a temporal lowering of the pH. The resulting asymmetric colloidal doublets behave as catalytic motors and show self-propulsion and phototaxis under ultraviolet (UV) light in the presence of hydrogen peroxide (H₂O₂), by the mechanism of diffusiophoresis. The magnetic heterodoublets show autonomous movement, in random directions, in the presence of H₂O₂ and UV light, but if an external magnetic field is also present, they align themselves and show a directed motion forming exclusion regions around them. The assembly process described in this Article can be adapted to a wide variety of materials providing a simple, quick, inexpensive, reliable, and scalable approach for the development of synthetic motors capable of performing directed motion and forming exclusion zones and patterns.