A lightweight compact self-contained microchannel heat exchanger includes a multi-sided heat transfer member having an array of parallel microgrooves (or rows of micropins) on each of the side, and positioned in thermal contact with the heat generating object to be cooled. A fluid distribution unit having a developed system of feed channels and exhaust channels is mounted to the micropatterned surface for guiding an incoming cold working fluid to remove heat from the microgrooves (or micropins). The heat exchanging device includes in one embodiment a pair of double-sided heat transfer plates having an array of microgrooves extending on each of its opposed surfaces, the fluid distribution unit being sandwiched between the double-sided heat transfer plates. The heat transfer plates and distribution units may be stacked to form a multi-layered cooling system with improved pressure drop and increased heat transfer efficiency. The device may be used in several modes of operation such as single phase convection, thin film evaporation, and forced-feed boiling, and may operate with or without a pump depending on heat transfer requirements.