A two-phase thermodynamic system includes a porous microstructure sheet to increase an aggregate thin-film evaporation area of a working fluid. The porous microstructure sheet may be disposed at a liquid-vapor boundary of the working fluid. The porous microstructure sheet has “micro” pores through which the working fluid flows from a liquid flow path on one side of the porous microstructure sheet to a vapor flow path on the other side of the porous microstructure sheet. Individual pores induce the working fluid to form thin-film evaporation regions. The porous microstructure sheet may have a pore density so as to increase an aggregate thin-film evaporation area of the working fluid. In this way, the overall thermal resistance across all liquid-vapor interfaces (menisci) of the working fluid is substantially decreased over conventional vapor chamber.