This contribution discusses the influence of material wettability on gas/liquid flow and reaction in capillaries. It is shown that the performance of microfluidic devices as chemical reactors can be enhanced by choosing wall materials promoting wettability. Previous investigations have revealed differences in gas/liquid flow patterns depending on material wettability. In this work, high speed video observations of flow have been combined with experiments using the absorption of CO2 into aqueous solutions of sodium hydroxide. A pseudo-1st-order reaction assumption has been used to determine values of interfacial area in 250 mu m capillaries of fused silica (contact angle 0 approximate to 50 degrees), PEEK (0 approximate to 65 degrees), and PEP (0 approximate to 95 degrees). Increases in chemical conversion occurring with more wettable materials are attributed to increases in the interfacial area. The interfacial areas correlate with the flow patterns observed. Characterization of important parameters such as interfacial area and mass transport are lacking for microchannel and capillary flows. Chemical reaction can be used to examine these parameters to better understand gas/liquid flow. (c) 2013 Elsevier B.V. All rights reserved.