A heat pipe includes a sealed thermally conductive casing having a length that has a first end for coupling to a heat source to be cooled and a second end for coupling to a heat sink opposite the first end. The casing has an inside surface that defines a thermal control volume above. The thermal control volume includes (i) a plurality of hydrophilic particles or clusters of hydrophilic particles in a size range from nano size to micron size attached as a hydrophilic film to the inside surface or to a wick on the inside surface, wherein the plurality of hydrophilic particles occupy only a portion of an area of the inside surface or an internal pore space of the wick or a surface area of the wick, (ii) a vapor cavity above the hydrophilic film or the wick, and (iii) a heat transfer working fluid contained as a liquid on the hydrophilic film or the wick, and as a vapor in the vapor cavity. The plurality of hydrophilic particles or clusters of hydrophilic particles provide a solid-liquid contact angle for the working fluid when in a liquid state of