Abstract: A specimen processing cartridge includes a reservoir having a fluid inlet, an elastic diaphragm, and a fluid outlet. The reservoir is operable to receive a volume of liquid from the fluid inlet, and the fluid outlet is positioned along a fluid flow path between the reservoir and a downstream reservoir. The cartridge includes a dissolvable membrane that occludes flow through the fluid outlet when the dissolvable membrane is in a first, undissolved state, and that permits flow from the reservoir to the downstream reservoir when in a second, dissolved state. The elastic diaphragm is operable to pressurize the reservoir upon receiving the volume of liquid when the dissolvable membrane is in the first, undissolved state, and is operable to contract and propel at least a portion of the volume of liquid from the reservoir to the downstream reservoir when the dissolvable membrane is in the second, dissolved state.