In this paper, a high step-up magnetic-less DC/DC nX converter is designed and experimentally evaluated. GaN transistors are applied in a nX converter topology, yielding ultrahigh power density and high conversion efficiency. The absence of magnetic materials results in a constant efficiency throughout the power range; the power capability of the system is only limited by the ratings of the semiconductor devices. To effectively extract the dissipated power, a novel micro-fluidic heat sink is designed, based on microchannels fabricated on Silicon substrate and a laser-cut acrylic manifold. The developed liquid cooling heat sink yields a much smaller volume and higher cooling capability compared to conventional heat sinks. A 10X converter prototype with the integrated micro-fluidic heat sink is experimentally evaluated at various operating conditions and different flow rates for the cooling system. At a transferred power of 1.2 kW the converter exhibits an overall efficiency of 96%, while occupying 260 mL of volume, resulting in 4.62 W/cm 3 , a notable power density for such a high step-up DC/DC converter.