Microfluidic Device with Porous Membrane and an Unbranched Channel

The invention relates to a microfluidic device for detection of a substance in a sample fluid, and to a cartridge for performing a biological assay, containing such a device. The microfluidic device comprises two housing parts ( 52, 54 ) with a porous membrane ( 50 ) there between. Each housing part has recesses, or channel parts, ( 56 - 1, 56 - 2, 56 -n , 58 - 1, 58 - 2, 58 -n) that are connected via a recess of the opposite housing part, and through the membrane ( 50 ), such that an unbranched channel is defined for the sample fluid. At one or more of the positions where the channel crosses the membrane ( 50 ), a spot ( 48 - 1, 48 - 2, 48 -n) with an immobilized indicator substance is present, to which a target substance in the sample fluid may bind. An advantage of the present device is that in principle all of the sample fluid passes each spot. Hence there is no need to recirculate and/or mix the sample fluid, as is the case in devices with parallel flow-through paths for the fluid. The device will therefore be simpler, and give a more reliable detection result.