About the author: Kun Wang is currently a PhD candidate under the direction of Dr. Carlos Silvera Batista. Kun’s research focuses on understanding the long-range kinetics and assembly of colloidal particles under the coupling of electric field and concentration gradient. In the featured publication, Kun and co-authors show how faradaic processes and its induced concentration gradient under ac fields can be used advantageously to control long-range transport, and assembly of charged colloids. At low frequencies, a highly non-linear pH profile is produced near the electrode surface. As a result, negatively charged particles migrate towards the point of highest pH showing a significant focusing tens of microns away from both electrodes. Furthermore, the focused particles show a disorder–order transition forming hexagonal crystals. The insights presented in this article have implications for the directed assembly and fundamental aspects of colloidal electrokinetics.