Fabrication of Miniaturized Paper-Based Microfluidic Devices (MicroPADs)

Abstract

Microfluidic paper-based analytical devices (microPADs) are emerging as cost-effective and portable platforms for point-of-care assays. A fundamental limitation of microPAD fabrication is the imprecise nature of most methods for patterning paper. The present work demonstrates that paper patterned via wax printing can be miniaturized by treating it with periodate to produce higher-resolution, high-fidelity microPADs. The optimal miniaturization parameters were determined by immersing microPADs in various concentrations of aqueous sodium periodate (NaIO4) for varying lengths of time. This treatment miniaturized microPADs by up to 80% in surface area, depending on the concentration of periodate and length of the reaction time. By immersing microPADs in 0.5-M NaIO4 for 48 hours, devices were miniaturized by 78% in surface area, and this treatment allowed for the fabrication of functional channels with widths as small as 301 µm and hydrophobic barriers with widths as small as 387 µm. The miniaturized devices were shown to be compatible with redox-based colorimetric assays and enzymatic reactions. This miniaturization technique provides a new option for fabricating sub-millimeter-sized features in paper-based fluidic devices without requiring specialized equipment and could enable new capabilities and applications for microPADs.

Wax-Printed Fluidic Time Delays for Automating Multi-Step Assays in Paper-Based Microfluidic Devices (MicroPADs)

“…However, these techniques have a limited range of fluid control [6,31,34]. While there are many additional methods of passive fluid control in microPADs (e.g., fluidic diodes, delay shunts, altering pore size, ionogel passive pumps, laser direct writing, sucrose delays, chemical modifications, dissolvable/erodible bridges) [6,11,[36][37][38][39][40][41][42][43][44][45][46], all of these have significant limitations, such as the extensive use of additional fabrication materials or equipment beyond what is required for wax printing (e.g., laser cutters, plastic sheets, or adhesives) [39,40,44,45], use of reagents that could impact downstream assays (e.g., sugars, polymers, or surfactants) [11,38,42,43,46], or the use of techniques not compatible with high-volume fabrication [36,37,41].…”

Desktop Fabrication of Lab-On-Chip Devices on Flexible Substrates: A Brief Review

“…The limitation of paper substrates is not every kind of paper can be used because of additives and unknown composition of other materials added during the manufacturing process. Therefore, mostly nitrocellulose and Whatman filter paper (1 and 4) have been widely employed, due to their known and reliable physical and chemical properties [16,17]. A standardized micro paper analytical device (µPAD) is shown in Figure 2 [17].…”

“…Since 2009, solid wax printers have been widely used to print designed patterns onto cellulose-based substrates [17,33]. Recently, so called 'wax-on-plastic' platforms were developed which involved wax patterns on PET substrates.…”

Preparation of a high‐performance thermally shrinkable polystyrene SERS substrate via Au@Ag nanorods self‐assembled to detect pesticide residues

“…This creates a shape‐memory effect in the processed plastic, which gives stretched polystyrene molecules more leeway when they are heated and softened again, and they tend to return to their more twisted, shrunken state before stretching. The film, stretched in both directions, contracts more evenly, so that after some magical distortions, the film eventually returns to a nearly flat state, without any visible distortion of the pattern . In 2008, Chen et al used Shrinky Dinks to create tiny structures for microfluidics applications in fields like stem cell research .…”

“…In 2008, Chen et al used Shrinky Dinks to create tiny structures for microfluidics applications in fields like stem cell research . TSP has since been used in both microfluidic and micro/nanodevice manufacturing . TSP can shrink to different degrees according to different heating temperatures and form 3D folds after shrinkage.…”