The proposed work addresses energy transfer from a specific device, an x-ray tube, whose performance is limited by the magnitude of cooling. A composite microfabricated device is proposed to achieve the necessary heat transfer. This research has promise for the proposed device and will have general application in numerous other areas. The work seeks to establish the feasibility of microfabricated heatpipes to improve the heat transfer from x-ray tube anodes. The objective of this proposal is to define the range of wall materials, dimensions, and working fluids that provide optimum performance in various anode operating regimes. The proposed effort will develop a comprehensive device model, validate the model experimentally, and then optimize the design of the device.