Abstract: A binding assay device can provide an array of parallel channels with reservoirs for accommodating varying volumes of liquid samples for assay. The device generally can comprise a substantially planar base and a substantially planar top plate with open channels formed in its bottom surface. One embodiment includes a removable cassette, which forms the open channels when placed between the base and top plates. Reservoirs can be formed at the ends of the open channels with closed channels extending from the reservoirs to the top surface of the top plate. Open channels or elongated grooves or sockets can be formed in the top surface of the top plate to accommodate plug-in manifolds that can be in fluid communication with the closed channels. By allowing varying volumes of liquid samples to be placed in the reservoirs, the device can provide improved and/or optimized binding assay reactivities and/or band intensities.