A method for analyzing biological samples is disclosed herein. In an embodiment, the method includes receiving a fluid sample into a cartridge device, which comprises: a fluidic chamber; at least one microfluidic channel in fluid communication with the fluidic chamber; and a venting port configured to apply a pneumatic force to the fluidic chamber; and inserting the cartridge device into a reader device to perform measurements, wherein the cartridge device is positioned in a vertical or tilted position such that at least a portion of the fluid sample inside the fluidic chamber is pulled by gravity in a direction away from the venting port or towards the bottom of the fluidic chamber.