Assay cartridges and methods of using the same

An assay cartridge comprising:

• a cartridge body having a top longitudinal plane and an opposite bottom,
• a sample introduction port located on the top longitudinal plane of the cartridge body;
• a sample indicator window located on the top longitudinal plane of the cartridge body;
• a sample chamber including a sample well configured to receive a liquid sample through the sample introduction port, and further configured such that a liquid surface at a liquid level of the liquid sample represents an air-liquid boundary when the sample well cannot contain any additional liquid and the liquid surface of the liquid sample is substantially parallel to the opposite bottom of the cartridge body,
• wherein the cartridge body is configured to permit passage of light therethrough and includes an angled surface providing a reflecting surface located and disposed so as to reflect light from the liquid surface at the air-liquid boundary when the sample well cannot contain any additional liquid approximately ninety degrees to the sample indicator window,
• wherein the reflecting surface is positioned at a non-zero angle relative to the liquid surface of the liquid sample when the sample well cannot contain any additional fluid, between the sample indicator window and the opposite bottom and on a side of the sample chamber.