A method of conducting an assay on a sample, the method comprising: introducing, a fluid sample into a microfluidic cartridge; the cartridge comprising: a substrate comprising one or more microfluidic channels disposed therein and comprising a binding agent disposed within said channel(s) for binding any analyte within the sample, the binding agent comprising magnetic properties; a sample port for introducing said fluid sample into the cartridge; a fluid outlet sink for removing fluid from said channel(s); one or more stop features designed to prevent the sample or other liquids from passing through the stop feature(s) by capillary action alone and at least one fluid input port for allowing one or more fluids to be introduced to the cartridge and transported through the microfluidic channel(s) and/or air to be vented from the cartridge; permitting the fluid sample to be drawn through the cartridge, such that the fluid sample comes into contact with said binding agent before being stopped by said one or more stop features, whereby at least a portion of any analyte present in the sample is bound by the binding agent comprising magnetic properties; holding the bound analyte in place using the magnet or magnetic field applied by a reader; washing any unbound material away from the bound analyte using the reader; and fluorescently detecting any bound analyte present in the cartridge; characterised in that the washing step is conducted using only air present in the cartridge and the fluorescent detection is carried out in air. introducing, a fluid sample into a microfluidic cartridge; the cartridge comprising: a substrate comprising one or more microfluidic channels disposed therein and comprising a binding agent disposed within said channel(s) for binding any analyte within the sample, the binding agent comprising magnetic properties; a sample port for introducing said fluid sample into the cartridge; a fluid outlet sink for removing fluid from said channel(s); one or more stop features designed to prevent the sample or other liquids from passing through the stop feature(s) by capillary action alone and at least one fluid input port for allowing one or more fluids to be introduced to the cartridge and transported through the microfluidic channel(s) and/or air to be vented from the cartridge; permitting the fluid sample to be drawn through the cartridge, such that the fluid sample comes into contact with said binding agent before being stopped by said one or more stop features, whereby at least a portion of any analyte present in the sample is bound by the binding agent comprising magnetic properties; holding the bound analyte in place using the magnet or magnetic field applied by a reader; washing any unbound material away from the bound analyte using the reader; and fluorescently detecting any bound analyte present in the cartridge; characterised in that the washing step is conducted using only air present in the cartridge and the fluorescent detection is carried out in air. a substrate comprising one or more microfluidic channels disposed therein and comprising a binding agent disposed within said channel(s) for binding any analyte within the sample, the binding agent comprising magnetic properties; a sample port for introducing said fluid sample into the cartridge; a fluid outlet sink for removing fluid from said channel(s); one or more stop features designed to prevent the sample or other liquids from passing through the stop feature(s) by capillary action alone and at least one fluid input port for allowing one or more fluids to be introduced to the cartridge and transported through the microfluidic channel(s) and/or air to be vented from the cartridge; permitting the fluid sample to be drawn through the cartridge, such that the fluid sample comes into contact with said binding agent before being stopped by said one or more stop features, whereby at least a portion of any analyte present in the sample is bound by the binding agent comprising magnetic properties; holding the bound analyte in place using the magnet or magnetic field applied by a reader; washing any unbound material away from the bound analyte using the reader; and fluorescently detecting any bound analyte present in the cartridge; characterised in that the washing step is conducted using only air present in the cartridge and the fluorescent detection is carried out in air.