Patent ID: 8137984

Claim:
A device for detecting the presence of caffeine in a liquid sample comprising a caffeinated beverage, comprising a testing substrate comprising: a contact region; a particle region comprising particles diffusely bound to the testing substrate, wherein each particle further comprises: an anti-caffeine antibody that is attached to each particle surface as a first member of an inverse ligand-receptor pair and a second antibody that is attached to the particle surface as a first member of a direct ligand-receptor pair; and a signal means; a signal region of the testing substrate spatially distinct from the contact region, the signal region comprising: a first signal area comprising a second member of the inverse ligand-receptor pair bound to the testing substrate that acts as a competitive inhibitor of caffeine binding to the first member of the inverse ligand-receptor pair; and a second signal area comprising a third antibody as a second member of the direct ligand-receptor pair bound to the testing substrate; a nitrocellulose binding membrane in the testing substrate with a flow rate of 90 sec./4 cm; wherein the testing substrate has a water absorption capacity of at least 1000 g/m 2 ; wherein the contact region, particle region, and signal region are arranged in sequential fluid communication such that the liquid sample flows sequentially through the regions; wherein a visible indication of exceeding a predetermined concentration threshold for caffeine corresponding to a caffeinated beverage can be discerned in the signal region from a ratio of signals in the first and second signal areas; and wherein the materials of the testing substrate are selected such that the visible indication is ready for detecting within three minutes of applying the liquid sample.