Abstract
In this communication, we report a physical method for the fabrication of organic solvent and surfactant-resistant barriers on paper-based fluidic devices. When nonwoven polypropylene sheet is embossed with a steel mold, the embossed region acts as a physical barrier that can prevent the flow of liquids. Embossed polypropylene barriers not only block water, but also block organic solvents and surfactants, which are known to be difficult to handle on previous paper-based devices. Various amounts of embossing pressures were tested to determine the minimum embossing pressure required for leakproof barrier formation. The compatibility of the barrier was also investigated with several surfactants and organic solvents. As a demonstration, a lysis buffer, which was known to leak through wax-printed barriers, was used to detect Escherichia coli (E. coli) O157:H7. To the best of our knowledge, this paper is the first to report a one-step fabrication method of paper-fluidic devices capable of handling surfactants and organic solvents, including alcohols.
Highlights
Since their emergence, microfluidic paper-based analytical devices have gained a significant amount of attention and are growing rapidly
The term μL/κWH can be regarded as a resistance by comparing the equation with the Ohm’s Law, where Q is equivalent to the current, ∆P is equivalent to the voltage, which means that the resistance can be increased by decreasing the channel height and permeability
Various amounts of embossing pressure were applied to the sheet in order to determine the minimum embossing pressure required to prevent flow
Summary
Microfluidic paper-based analytical devices (μPADs) have gained a significant amount of attention and are growing rapidly. Various methods have been developed to create barriers on many types of paper materials, and new methods are continuously being developed to improve the fabrication process of μPADs. A majority of publications involved the formation of hydrophobic barriers by embedding hydrophobic materials such as photoresist [1,2,3], wax [4,5,6] or parafilm [7,8] into various paper substrates, including nitrocellulose (NC) membrane, fabric, and chromatography paper. Other creative methods were developed using a knife plotter to cut the papers into specific shapes [12]; a laser to hydrophillize a hydrophobic substrate [13], to polymerize pre-impregnated photopolymers in the NC membrane to create hydrophobic barriers [14], or to pattern hollow microstructures to form barriers [15]. It has been reported that wax-printed devices are not capable of handling surfactants and organic solvents [4]
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