Protocol for assembling micro- and nanoparticles in a viscous liquid above a vibrating plate

In this protocol, we demonstrate the use of a vibrating plate to drive the assembly of micro- and nanoparticles as an approach to high-throughput, large-scale directed assembly in a viscous liquid. Vibration drives the assembly of glass bead microparticles and iron oxide nanoparticles in contact with water over an area of 6400 mm2. We use a scaling analysis to show that there is a competition between acoustic radiation force and vibration-generated fluid flow in a viscous medium, which determines particle transport characteristics. For assembly in a viscous liquid, we find close agreement between the observed experimental results when compared to a numerical solution of the 2D wave equation that describes plate displacement. This model indicates that microparticles migrate along displacement gradients towards displacement anti-nodes where the magnitude of displacement is maximum. We also observe that nanoparticles migrate toward displacement nodes where the magnitude of displacement is zero. • Cost-effective directed assembly technique without the need for microfabrication facilities • Large-scale assembly produces heterogeneously ordered structures on a vibrating substrate Method name: Protocol for assembling micro- and nanoparticles in a viscous liquid above a vibrating plate, Keywords: Directed assembly, Acoustophoresis, Colloids