  Three-dimensional (3D) AC electro-osmotic (ACEO) pumps have recently been
developed that are much faster and more robust than previous planar designs.
The basic idea is to create a ``fluid conveyor belt'' by placing opposing ACEO
slip velocities at different heights. Current designs involve electrodes with
electroplated steps, whose heights have been optimized in simulations and
experiments. Here, we consider changing the boundary conditions--rather than
the geometry--and predict that flow rates can be further doubled by fabricating
3D features with non-polarizable materials. This amplifies the fluid conveyor
belt by removing opposing flows on the vertical surfaces, and it increases the
slip velocities which drive the flow.
