Micromembrane-enhanced evaporating surfaces were developed to enhance capillary evaporation heat transfer coefficient (HTC) and critical heat flux (CHF). Micromembranes made of sintered single-layer copper mesh screen were diffusion bonded on microchannels to effectively promote capillary pressure and reduce flow resistance. Compared with mono-porous evaporating surfaces such as microchannels and copper woven mesh laminates in the same thickness under the similar working conditions, CHF was substantially increased by 83% and 198%, respectively, because of the separation of the capillary pressure generation and fluid transport process that was enabled by the micromembrane. The major features such as "M"-shaped capillary evaporation heat transfer curves and the associated heat transfer regions were identified. Oscillating flows induced by the bubble growth and collapse as well as the capillary flows induced by the receding menisci were observed and believed to play imperative roles in enhancing the heat transfer by inducing advections and improving evaporation and nucleate boiling. (C) 2013 Elsevier Ltd. All rights reserved.