I thought they used surface-tension / capillary-action to move the fuel. Like with passive geosatellite heat distribution. Think a radiator, lots of tiny fins,

I thought they used surface-tension / capillary-action to move the fuel. Like with passive geosatellite heat distribution. Think a radiator, lots of tiny fins, but all inward pointing in a tube. Coat the fins so they are '-philic' to the liquid. Get creative with the geometries of the fins. Surface tension / capillary-action spread over a lot of the fins in the tube will move the liquid to a sink, like the combustion chamber.