We and others have developed microfluidic paper-based analytical devices (μPADs) by patterning hydrophobic barriers of wax or photoresist (or other hydrophobic polymers) in hydrophilic paper. When the end of a μPAD is dipped into a fluid (e.g., urine), capillary wicking transports the fluid through the paper. The cost and physical characteristics of these systems make them appropriate for a range of bioanalyses. Paper-based systems are, of course, widely used
in bioanalysis. Examples range from pH paper to lateral-flow immunoassays and blood glucose analysis. Extending electro- chemical methodologies increases the scope of this flexible, low-cost technology; electrochemistry is, of course, essential to most commercial “glucometers” for use in testing blood glucose.