Three-Dimensional Sag Tracking in Falling Liquid Films.

Coating defects often arise during application in the flash stage, which constitutes the ∼10 min interval immediately following film application when the solvent evaporates. Understanding the transient rheology and kinematics of a coating system is necessary to avoid defects such as sag, which results in undesirable appearance. A new technique named variable angle inspection microscopy (VAIM) aimed at measuring these phenomena was developed and is summarized herein.

Ensemble average TIRM for imaging amperometry.

Colloidal particles can function as probes of local electrochemical current density if a functional relationship between the response of the particles and the electric field in the vicinity of the particles can be established. The nanometer scale movement of a single colloidal particle during cyclic voltammetry can be observed with the aid of total internal reflection microscopy. The intensity of scattered light can be related back to the current density local to that particle, and hence the method is called imaging amperometry.

The effect of electrode kinetics on electrophoretic forces.

Electric fields are commonly used to deposit colloidal particles on electrode surfaces and can even be used in directed assembly. The electric field beneath each particle changes as the particle approaches the wall; the proximity of the wall breaks the fore/aft symmetry and drives complicated flows that exert forces on the particle. While two limiting cases have been partially analyzed, constant electrode potential and uniform current density, the full problem has not been explored.

Single and pairwise motion of particles near an ideally polarizable electrode.

Single-particle longitudinal motion and pairwise lateral motion was investigated while the particles were excited by an oscillating electric field directed normally to an electrode proximate to the particles. The electrode was polarized over a range of potential insufficient to drive electrochemical reactions, a range called the "ideally polarizable region". The particles' motion was qualitatively dependent on the choice of electrolyte despite the absence of electrochemical reactions.