Alternative Patterning Methods for Paper-based Analytical Devices Using Nail Polish as a Hydrophobic Reagent

Abstract

A rapid, easy, and cost effective fabrication method for paper-based analytical devices (PADs) is described. This newly developed method is based on the use of nail polish as an alternative hydrophobic reagent, and the nail polish was resistant to basic and organic solvents. Three approaches for fabrication of paper-based analytical devices (PADs) were investigated, namely writing, stamping, and spraying. The writing approach was carried out by drawing the hydrophobic area of a pre-designed pattern on filter paper with a simple lab-made pen filled with nail polish as the hydrophobic agent. The stamping and spraying approaches required the use of a designed mask, which was made by laser cutting of the magnet rubber sheet. With laser cutting, two types of templates were made, i.e., positive and negative counterparts. The positive counterpart was the inside pattern and the negative counterpart was the outside pattern of the magnet sheets. For the stamping approach, the negative counterpart of the magnet rubber mask was attached onto a simple rubber stamper that was then stamped onto filter paper after loading with nail polish solution. With the spraying method, the positive counterpart was used to cover the hydrophilic area on the paper. Then, the nail polish solution was used with an air brush and sprayed on the paper covered with the magnet rubber mask. All approaches were cost effective and required neither extra equipment nor any pretreatment step. Among all three methods, however, the spraying method was found most suitable for mass production and provided the best resolution when compared with the other two approaches. With this approach, the actual channel widths obtained were similar to the designed widths, with the narrowest possible channel width of 650 μm. Furthermore, a nail polish-treated PAD was prepared by soaking the paper in the nail polish solution. The ability of the nail polish-treated PAD was examined for its resistance to a strong basic solution and an organic solvent (up to 30% ethanol and dichloromethane). The nail polish-treated paper also showed the potential to be used as an organic-aqueous separator.

An inexpensive, high-throughput μPAD assay of microbial growth rate and motility on solid surfaces using Saccharomyces cerevisiae and Escherichia coli as model organisms

“…A cost analysis comparison of the traditional growth assays and μPAD assay highlights the benefit of the latter over the former. Specifically, the traditional method proposed and implemented here by Li and colleagues [ 26 ] for E . coli sucrose gradient experiments called for individual Petri dishes for each colony, which summed to 24 plates for triplet data sets.…”

“…The linear rate of colony expansion is proportional to the growth rate in S. cerevisiae [25]. Third, we similarly manipulated motility in E. coli by varying sucrose concentration [26]. Both yeast and bacteria manipulations allow for analysis of our μPAD method's sensitivity.…”

“…Third, we similarly manipulated motility in E . coli by varying sucrose concentration [ 26 ]. Both yeast and bacteria manipulations allow for analysis of our μPAD method’s sensitivity.…”

3D-PAD: Paper-Based Analytical Devices with Integrated Three-Dimensional Features

“…The fluoropolymer was patterned on filter papers to form circular barriers to contain selected solvents (e.g., ethanol, acetone) for colorimetric assays. Other solvent-resistant materials such as siloxanes [47,48], nail polish [49], pullulan [50], and correction pens [51] were explored as the patterning material in paper-based devices. Alternatively, the containment of solvents may be enhanced by the surface topology of the device.…”

Development of a High-Throughput Low-Cost Approach for Fabricating Fully Drawn Paper-Based Analytical Devices Using Commercial Writing Tools

“…The disadvantages of these methods are the limited spatial resolution achieved and the need for post-fabrication treatment (by heating or UV irradiation). On the other hand, home-made pens or empty cartridges of commercial pens filled with various hydrophobic materials prepared in-house have been reported for the creation of hydrophobic patterns, including: trichloro perfluoroalkylsilane [27]; nail polish [28]; waterbased alkyl ketene dimer [29,30]; modified commercial permanent ink [31]; and solubilized poly(methyl methacrylate) [32]. However, all these methods require a lengthy preparation step, careful optimization of the composition of the functional material to be used and heating (after the fabrication of the PADs) to eliminate residual solvents.…”