The present application discloses two-phase cooling devices that may include at least three substrates: a metal with a wicking structure, an intermediate substrate and a backplane. A fluid may be contained within the wicking structure and vapor cavity for transporting thermal energy from one region of the thermal ground plane to another region of the thermal ground plane, wherein the fluid may bedriven by capillary forces within the wicking structure. The titanium thermal ground plane may be adapted for use in a mobile device, such as a portable device or smartphone, where it may offer compelling performance advantages.