title: Electric field-induced self-assembly of micro- and nanoparticles of various shapes at two-fluid interfaces.
abstract: Particle lithography which explores the capability of particles to self-assemble offers an attractive means to manufacture nanostructured materials. Although traditional techniques typically lead to the formation of dense crystals, adjustable non-close-packed crystals are crucial in a number of applications. We have recently proposed a novel method to assemble spherical micro- and nanoparticles into monolayers. The technique consists of trapping particles at a liquid-fluid interface and applying an electric field normal to the interface. Particles rearrange themselves under the influence of interfacial and electrostatic forces to form 2-D hexagonal arrays of long-range order and whose lattice constant depends on the electric field strength and frequency. Furthermore, the existence of an electric field-induced capillary force makes the technique applicable to submicron and nanosized particles. Although spherical particles are often used, non-spherical particles can be beneficial in practice. Here, we review the method, discuss its applicability to particles of various shapes, and present results for particles self-assembly on air-liquid and liquid-liquid interfaces. In the case of non-spherical particles, the self-assembly process, while still taking place, is more complex as particles experience a torque which causes them to rotate relative to one another. This leads to a final arrangement displaying either a dominant orientation or no well-defined orientation. We also discuss the possibility of dislodging the particles from the interface by applying a strong electric field such that the Weber number is of order 1 or larger, a phenomenon which can be utilized to clean particles from liquid-fluid surfaces.
authors.affiliation: Department of Mechanical Engineering, Lake Superior State University, Sault St. Marie, MI, USA.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Janjua
authors.forename: Sai
authors.initials: S
authors.lastname: Nudurupati
authors.forename: Pushpendra
authors.initials: P
authors.lastname: Singh
authors.forename: Nadine
authors.initials: N
authors.lastname: Aubry
mesh_terms: D004574:Electromagnetic Fields; D004586:Electrophoresis / Q000379:methods*; D008956:Models, Chemical; D053758:Nanoparticles / Q000737:chemistry*; D013500:Surface Tension; D019415:Torque