The
dynamics of dielectrophoretic-force-directed assembly of polarizable
colloidal upconverting β-NaYF<sub>4</sub> nanocrystals into
tunable multilayers on charge micropatterns written by atomic force
microscopy is investigated. Multilayered nanocrystal assembly by this
nanoxerography process occurs in two phases. During the first phase
typically lasting a few minutes, the nanocrystal assemblies grow up
to a maximum thickness under the influence of strong dielectrophoretic
forces exerted by the charge patterns. Subsequently, the nanocrystals
start to diffuse back into the solvent, leaving a single layer attached
to the charge patterns. A theoretical model based on the Fokker–Planck
equation is formulated to describe this dynamics involving an interplay
of diffusive and dielectrophoretic forces. Being in good agreement
with the experimental results, this approach may be reliably extended
to simulate the directed assembly of other types of polarizable colloids
from liquid phase by nanoxerography
