Cascaded assembly of complex multiparticle patterns.

A method for the cascaded capillary assembly of different particle populations in a single assembly cycle is presented. The method addresses the increasing need for fast and simple fabrication of multicomponent arrays from colloidal micro- and nanoscale building blocks for constructing nanoelectronic, optical, and sensing devices. It is based on the use of a microfluidic device from which two independent capillary bridges extend. The menisci of the capillary bridges are pulled over a template with trapping sites that receive the colloidal particles. We describe the parameters for simultaneous, high-yield assembly from both menisci and demonstrate the applicability of the process by means of the size-selective assembly of particles of different diameters and also by the fabrication of two-component particle clusters with defined shape and composition. This approach allows the fabrication of multifunctional particle clusters having different functionalities at predetermined positions.