We propose and analyze a novel two-phase microchannel cooling device that incorporates perforated side walls for potential use as an embedded thermal management solution for high heat flux semiconductor devices. A dense array of perforated side walls separate alternating liquid and vapor microchannels, allowing the vapor generated through evaporation of liquid supplied through micro-perforations to flow only in the dedicated vapor channels. By separating the liquid and vapor flows, these "perspiring" side walls enable us to circumvent flow instabilities and other challenges associated with conventional two-phase microchannel cooling while at the same time effectively take advantage of the large extended surface areas available in high-aspect-ratio microchannels. One implementation of our design is parametrically analyzed using finite element modeling, demonstrating the potential of our proposed device for handling high heat flux electronic and optoelectronic semiconductor devices. (C) 2013 Elsevier Ltd. All rights reserved.