Variable valve apparatus and methods

A valved process chamber on a sample processing device, the valved process chamber comprising:

• a process chamber comprising a process chamber volume located between opposing first and second major sides of the sample processing device, wherein the process chamber occupies a process chamber area on the sample processing device, and wherein the process chamber includes an axis;
• and
• a valve chamber located at least partially within the process chamber area, the valve chamber located between the process chamber volume and the second major side of the sample processing device, wherein the valve chamber is isolated from the process chamber by a valve septum separating the valve chamber and the process chamber, wherein a portion of the process chamber volume lies between the valve septum and the first major side of the sample processing device, and wherein the valve septum includes a length that extends along or substantially parallel to the axis of the process chamber, such that the valve septum is configured to provide fluid communication between the process chamber and the valve chamber at a variety of selected locations along the length.