Recent advances in high performance microelectronics technologies have resulted in tremendous improvements in functionality, power consumption and energy efficiency. However many of the new electronic instruments operate at higher power densities and require high heat flux thermal management. In this paper, we describe an electrowettingcontrolled cooling system with site-specific treatments on the heat source (evaporator or hot spot) surfaces. For this purpose, an array of electrodes between the reservoir and the cooling targets are patterned on the substrate of the system. Via electrowetting-on-dielectric (EWOD) operations, liquid droplets are generated with precisely-controlled volumes from the reservoir and transported to the heat sources by sequentially actuating the electrode units underneath. EWOD-driven droplet transport has great potential in thermal management due to EWOD's unique characteristics of prompt response, low power consumption and programmable paths. Most importantly, given a two-dimensional array of control electrodes, liquid droplets can be transported over a low-friction hydrophobic surface to the hot spots without the need for any mechanical moving parts. Heat dissipation can be further improved by implementing site-specific treatments on the system surface. Accordingly we coat a fine copper screen (single-layer or multi-layer) on the hot spots to hydrophilize the surfaces. The capillarity associated with the copper screen facilitates the delivered droplets automatically spreading and clinging to the target surfaces. As a result, heat transfer is in the more efficient form of filmwise evaporation at the evaporator sites. To maintain continued thin film evaporation, the EWOD-aided droplet splitting and merging are important to precisely confine the droplet volumes and hence the film thickness. The closed loop of this novel thermal management system can potentially function as a wickless vapor chamber or heat pipe with enhanced heat dissipation capabilities.