Morphology control of electrospun nanofibers is one of the major tasks in order to facilitate their wide potential applications. In the present work, various dielectric materials were employed as parallel collectors for obtaining electrospun nanofiber meshes with improved nanofiber alignment. Experimental results presented the relationship between nanofiber alignment and the collectors' relative permittivity. Theoretical simulations revealed that the electric field can be tuned manually by choosing different dielectric materials as collectors. The horizontal electric field strength Ex is a key factor to stretch electrospun jet across gap, and to eventually achieve aligned nanofiber meshes. This work is believed to be able to lead to a deeper understanding to the mechanisms of nanofiber alignment, and should be of help to the design of practical collecting structures for promoting the applications of electrospinning technique. (C) 2009 American Institute of Physics. [doi:10.1063/1.3242378]