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.