title: Contact-Free Templating of 3-D Colloidal Structures Using Spatially Nonuniform AC Electric Fields.
abstract: The formation of ordered and regularly shaped structures of colloidal particles with the aid of spatially nonuniform electric fields is a modern research area of great interest. This work illustrates how alternating current (AC) electrokinetic effects (dielectrophoresis, electroosmosis) can serve as contact-free templates, inside which colloidal microspheres can assemble into a variety of shapes and sizes. We show how three-dimensional colloidal structures of square, circular, and diamond shape of many tens of micrometers in size can be reproducibly formed with a single set of quadrupolar microelectrodes. Numerical simulations performed help to explain the role of AC electroosmosis and AC dielectrophoresis on the shaping of these structures as a function of applied voltage and frequency. We also demonstrate how the templating repertoire is further enhanced with the simultaneous application of a second, individually controlled AC electric field, which enables a variety of asymmetric colloidal structures to be produced using the same set of quadrupolar microelectrodes. As the preservation of shape and size of such electric-field templated structures after medium evaporation still remains a big challenge, here we also report on a novel method that permits the stabilization and isolation of these particle assemblies through medium gelation and subsequent hydrogel removal with a UV/ozone treatment.
authors.affiliation: Department of Chemical Engineering, Queen's University , Kingston, ON, Canada K7L 3N6.
authors.forename: Joshua
authors.initials: J
authors.lastname: Raveendran
authors.forename: Jeffery A
authors.initials: JA
authors.lastname: Wood
authors.affiliation: Department of Chemical Engineering, Queen's University , Kingston, ON, Canada K7L 3N6.
authors.forename: Aristides
authors.initials: A
authors.lastname: Docoslis