Experimental investigation of the phase interactions in two-phase mini-channel serpentine systems is performed with a focus on determining the effect of radius of curvature of the serpentine on two-phase flow pattern transitions. The initial formation of two-phase flow patterns in T-junction contactors and the resulting effect on the flow through serpentine geometries are studied to predict the initiation of bubble breakup and/or coalescence in planar serpentine arrangements. Bubble breakup maps are developed for each of the serpentine geometries, identifying curvature-induced shifts in the transitions between flow patterns. Single-phase dimensionless analysis for curved geometries is extended to two-phase flow to identify the geometric dependence of critical bubble breakup. Further analysis performed shows that the characteristic length for curved geometries encountered in the Dean number for single-phase flow is suitable for capturing the effects of curvature on the initiation of bubble breakup. The dependence of Weber number on the characteristic length is reported and a critical We(CD)L(C) = 10 is identified for predicting bubble breakup inception in the serpentine system. (C) 2011 Published by Elsevier Ltd.