Lab on paper: iodometric titration on a printed card.

A paper test card has been engineered to perform an iodometric titration, an application that requires storage and mixing on demand of several mutually incompatible reagents. The titration is activated when a user applies a test solution to the test card: the dried reagents are reconstituted and combined through a surface-tension-enabled mixing (STEM) mechanism. The device quantifies 0.