title: Dynamic self-assembly of polymer colloids to form linear patterns.
abstract: A dynamic self-assembling process is reported which involves drying a droplet of positively charged colloidal suspension on a flat negatively charged hydrophilic surface. This extremely simple method affords lines of colloidal particles with regular 1.5-4.5 microm line spacing and smaller than 2 microm line width over a broad surface area. The ordered region diffracts light to display an iridescent appearance and generates first-order diffraction spots when illuminated by a He-Ne laser. A periodic stick-slip motion of the drying liquid front is observed during the drying process using optical microscopy. The periodic motion must be related to the periodic particle deposition. We propose that the simultaneous deposition of the particles at a fixed distance (i.e., the line spacing) behind the previous line of particles where the contact line is pinned is in turn responsible for the periodic stick-slip motion. The key distinguishing feature of the present system is the attractive interaction between the particles and the surface, which instigates the periodicity of the particle deposition.
authors.affiliation: Department of Chemistry and Emulsion Polymers Institute, Lehigh University, Bethlehem, Pennsylvania 18015, USA.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Ray
authors.forename: Hyungsoo
authors.initials: H
authors.lastname: Kim
authors.forename: Li
authors.initials: L
authors.lastname: Jia