Dielectrophoresis (DEP) force-assisted assembly of a colloidal single photonic-crystal monolayer in a microfluidic chamber was demonstrated. Negative DEP force with a high-frequency AC electric field induced the compression of colloidal microspheres to form a colloidal crystal domain at the center of a hexapolar-shaped electrode. While typical assembly by monotonic DEP force forms multicrystalline domains containing crystal defects, repetitions of the DEP/relaxation cycle significantly facilitated crystal growth of 10 mu m monodispersed polystyrene microspheres, allowing a grain-boundary-free single-crystal monolayer domain of ca. 200 mu m in size. Microsphere size as well as size distribution affected the formation of the single-crystal domain. A simple method was used to immobilize the single-crystal domain on the glass substrate without losing its crystallinity. (C) 2010 Elsevier Inc. All rights reserved.