title: Characterization of 2D colloid aggregations created by optically induced electrohydrodynamics.
abstract: Rapid electrokinetic patterning (REP) is a technique for creating self-assembled monolayers (SAMs) of spherical particles in a liquid medium, and dynamically controlling them though the simultaneous application of an electric field and optically induced temperature gradients. Previous work has investigated and characterized REP axisymmetric aggregations generated from a focus laser within a uniform electric field; work herein characterizes line-shaped particle assemblies derived from the application of a linearly scanned laser. The resulting aggregations of spherical polystyrene particles (1 μm) suspended in low-conductivity aqueous potassium chloride solution (KCl, 2.5 mS/m) resembled elliptical-shaped crystalline geometries. The mean particle-to-particle spacing within the aggregation remained greater than 1.5 diameters for experiments herein (6.5 Vrms , 30 kHz) due to dipole-dipole repulsive forces. Interparticle spacing demonstrated a linear relationship (1.6-2.1 μm) with increasing scanning lengths (up to 83 μm), decreased from 1.9 to 1.7 μm with increasing scanning frequency (0.38-16 Hz) for a 53 μm scan length, and decreased from 2.0 to 1.6 μm with increasing laser power (11.9-18.8 mW) for a 59 μm, 16 Hz laser scan.
authors.affiliation: Department of Mechanical Engineering, University of Louisville, Louisville, KY, USA.
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Work
authors.affiliation: Department of Mechanical Engineering, University of Louisville, Louisville, KY, USA.
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Williams
mesh_terms: D003102:Colloids / Q000737:chemistry*; D007091:Image Processing, Computer-Assisted; D044085:Microfluidics / Q000379:methods*; D008863:Microspheres; D011137:Polystyrenes / Q000737:chemistry
chemical_list: D003102:Colloids; D011137:Polystyrenes
keywords: Colloids; Electrokinetics; Microfluidics; Self-assembly