Polymer solution above a critical concentration is generally required for making a uniform diameter nano fiber by electrospinning. Below this critical concentration, nanofibers; are accompanied with bead formation and, therefore, this concentration region has not received much attention. A systematic investigation reveals that unique particle shapes can be obtained by electroprocessing within this lower concentration range. Several micrometer diameter poly(methyl methacrylate) PMMA cups with wall thickness in the 200-800 nm range and 50-300 nm size pores have been obtained by electroprocessing in high dielectric constant solvents. (c) 2005 Elsevier Ltd. All rights reserved.