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We present a microfluidic paper analytical device (μPAD) that relies on flow in hollow channels, rather than through a cellulose network, to transport fluids. The flow rate in hollow channels is 7 times higher than in regular paper channels and can be conveniently controlled from 0 to several mm/s by balancing capillary and pressure forces. More importantly, the pressure of a single drop of liquid (0.2 mbar) is sufficient to induce fast pressure-driven flow, making hollow channels suitable for point of care diagnostics. We demonstrate their utility for simple colorimetric glucose and BSA assays in which the time for liquid transport is reduced by a factor of 4 compared to normal cellulose channels. [ABSTRACT FROM AUTHOR]

We report a plasmonic paper-based analytical platform with functional versatility and subattomolar (<10-18 M) detection limit using surface-enhanced Raman scattering as a transduction method. The microfluidic paper-based analytical device (μPAD) is made with a lithography-free process by a simple cut and drop method. Complex samples are separated by a surface chemical gradient created by differential polyelectrolyte coating of the paper. The μPAD with a starlike shape is designed to enable liquid handling by lateral flow without microchannel patterning. This design generates a rapid capillary-driven flow capable of dragging liquid samples as well as gold nanorods into a single cellulose microfiber, thereby providing an extremely preconcentrated and optically active detection spot. [ABSTRACT FROM AUTHOR]

A low cost, microfluidic paper electrochemical device (μPED) was fabricated using screen printing of electrodes and heat transfer of patterned wax paper onto filter paper. The μPED features films of a light-emitting ruthenium metallopolymer, microsomal metabolic enzymes, and DNA to detect potential genotoxic pollutant activity in environmental samples. Unlike conventional analytical methods that detect specific pollutant compounds, the μPED was designed to rapidly measure the presence of genotoxic equivalents in environmental samples with the signal related to benzo[a]pyrene (B[a]P) as a reference standard. The analytical end point is the detection of DNA damage from metabolites produced in the device using an electrochemiluminescence output measured with a charge-coupled device (CCD) camera. Proof-of-concept of this measurement was established for smoke, water, and food samples. The μPED provides a rapid screening tool for on-site environmental monitoring that specifically monitors the genotoxic reactivity of metabolites of toxic compounds present in the samples. [ABSTRACT FROM AUTHOR]