A cooling device for a heat source, such as an electronic component, has a single or set of nano- and/or micro-sized channel(s) connected to a single or multiple reservoir(s). The heat source causes nucleation within a channel, and a vapor bubble forms removing heat from the heat source via evaporation of liquid to vapor in the bubble and condensation of the generated vapor at the cooler ends of the bubble. Thus, the channel operates as a passive heat pipe and removes heat from the source by passively circulating the cooling fluid between the vapor bubble and the reservoir(s).