Conventional spacers most commonly consist of a layered or woven fiber structure that creates fluid vortices or turbulence to mix the fluid in the flow channel. This mixing comes at the expense of increased pressure drop and associated pumping costs. A novel spacer design is evaluated that moves fluid uniquely within the flow channel. The spacer performs like a static mixer for planar flow channels. Fluid adjacent to the top and bottom boundaries of the flow channel is moved to the middle and replaced by fluid from the middle of the flow channel. Experimental measurements of spacer performance for filtration of dextran solutions are reported for the static mixing spacer and compared to a conventional spacer. The static mixing spacer offers comparable or better mass transfer performance at the same power input; at the lowest power inputs the mass transfer coefficient for the static mixing spacer was 20% higher. (C) 2013 Elsevier B.V. All rights reserved.