A thermal ground plane, flat heat pipe (30 cm x 7.6 cm x 4.5 mm thick) was developed as a passive heat spreading component for electronics cooling. The combination of multiscale titanium wick fabrication with laser welding results in an all-titanium device which is light (500 g) yet strong, hermetically sealed, and compatible with water. Numerical simulations were used to optimize the grooved wick design by minimizing viscous drag present in any large scale heat pipe, while maintaining sufficient capillary force. Nanoporous titania coats the grooved wick to further enhance wettability. The resulting heat pipe was tested on two different test configurations, and is capable of a maximum heat flow rate in vertical (reflux) orientation of 500W for chip temperatures of 100 degrees C, and 1000W for chip temperatures of 150 degrees C. This translates into a maximum effective thermal conductivity of similar to 8000 W/m K. Such a high thermal conductivity indicates that the Titanium Thermal Ground Plane is an effective heat pipe, and when combined with a heat sink, useful for cooling an array of electronic components. (C) 2013 Published by Elsevier Ltd.