Most commercial paper devices use colorimetric detection and have been applied for qualitative and/or semi- quantitative analyte detection [1,7–11]. For colorimetric sensing, analyte flow is directed along the paper matrix by capillary action, and analyte then reacts with a label or organic dye in the test zone. The assay results are quantified by comparing the color hues and/or intensities generated by unknown analytes to known analyte concentrations. Nontechnical personnel can interpret the result by the naked eye in many cases. Paper devices therefore do not require external instrumentation for interpretation or mechanical forces to drive flow.