The effect of surface tension on adiabatic two-phase flow across a bank of 100 pm diameter staggered circular micro pillars, 100 pm long with pitch-to-diameter ratio of 1.5, for Reynolds number between 5 and 50, was investigated. Experiments with ethanol were performed and compared to results with water. Flow maps revealed similar flow patterns, but the transition lines were different for the two liquids. Void fraction measurements of the two fluids were also compared, and no significant deviations were observed. The two-phase pressure drop characteristics were significantly affected by the reduction in surface tension. Interfacial friction was attributed to this deviation, and a two-fluid model was developed to account for surface tension force. In addition, a modified form of Chisholm correlation was developed that accounts for surface tension. (C) 2008 Elsevier Ltd. All rights reserved.