Advances in nanofiber fabrication techniques (e.g., electrospinning) have come to allow control over fiber distribution and orientation such that an ordered coating with fibers arranged in layers orthogonal to one another can potentially be produced. Such coatings can serve as a nano-sieve that can be designed and placed on the downstream side of a conventional nonwoven fibrous filter to enhance its performance (collection efficiency for a given, pressure drop). This paper presents a thorough analysis of the performance characteristics of these thin coatings to guide the fabrication process in terms of the coatings' microstructural properties. In particular, we have found a correlation such that, for coatings composed of a given fiber size, there exists a corresponding particle size for which a coating's performance becomes independent of variations in fiber-to-fiber spacing (i.e., coating's non-homogeneity). We have also found that a coating's performance improves when its mass is distributed across more than one pair of orthogonal layers. (C) 2013 Elsevier B.V. All rights reserved.