Analysis of free chlorine in aqueous solution at very low concentration with lateral flow tests.

Test strips are convenient tools for rapid, semi-quantitative analysis of a variety of parameters by dipping them for a few seconds in a sample solution followed by a simple colorimetric read-out. Their sensitivity is mainly determined by the reactivity of the test dyes on the reaction zone and is not sufficient for some applications. The detection limit of commercially available free chlorine test strips, for example, is at present not low enough to confirm the absence of this analyte as disinfectant in rinsing solutions after disinfection or to control required residual amounts of chlorine in drinking water.

Combining Wax Printing with Hot Embossing for the Design of Geometrically Well-Defined Microfluidic Papers.

A simple, efficient, and repeatable combination of wax printing and hot embossing is reported. This combination yields microfluidic channels in paper, where fluid transport driven by paper-intrinsic capillary forces takes place inside the noncompressed areas, whereas embossed and wax-bonded areas serve as hydrophobic barriers laterally confining the fluid flow. Lab-made paper sheets first coated with a hydrophobic wax were hot-embossed with a tailor-made metal stamp.