a method and an apparatus for the efficient transfer of heat utilizing micro heat pipes that include a cellular foam or interconnected cellular / truss network having hollow ligaments . a predetermined fraction of the internal volume of the hollow ligaments is filled with a carefully chosen working fluid , and the ends of the hollow ligaments are sealed . in operation , the working fluid evaporates in the region of high heat flux and condenses in regions of lower temperature , resulting in the transfer or redistribution of the fluid &# 39 ; s latent heat of vaporization . for open cell foams and interconnected networks , a second fluid flowing through the open cells , separate from the working fluid but also in thermal contact with the hollow ligaments , assists in the transfer of heat from the foam and networks .