Chemical/Electrochemical Corrosion-Created Dynamic Metal Ion Gradients Enable the Assembly of Colloidal Particles

Controlling and directing colloidal micro/nanoparticle assembly using external forces is essential to developing modern electro-optical devices. Here we show that the concentration gradients of metal ions produced by chemical/electrochemical corrosion could drive the motion of colloidal microspheres under the assistance of a well-known osmotic force. This force is programmable in both direction and strength which enables us to guide the moving directions of microspheres at controlled rates. To demonstrate the utility of this force in producing ordered assemblies, dynamic colloidal “crystals” built with one and/or two types of microspheres that replicate the electrode templating patterns are created. In addition, the motion of particles and their dynamic assembly are reproduced by a simulation combining Poisson–Nernst–Planck and Navier–Stokes equations. We believe this method opens the door to the development of complex patterns (e.g., differing in pattern shapes, homo- and/or heterojunctions with two or multiple components) self-assembled by colloidal particles and functional materials with electro-optical properties.