Geometrical Alignment of Multiple Fabrication Steps for Rapid Prototyping of Microfluidic Paper-Based Analytical Devices

Abstract

Three main fabrication steps for microfluidic paper-based analytical devices (μPADs) were fully integrated with accurate geometrical alignment between the individual steps in a simple and rapid manner. A wax printer for creating hydrophobic barriers was integrated with an inexpensive (ca. $300) electronic craft plotter/cutter for paper cutting, followed by colorimetric reagent deposition using technical pens. The principal shortcoming in the lack of accurate and precise alignment of the features created by these three individual fabrication steps was addressed in this work by developing appropriate alignment procedures during the multistep fabrication process. The wax printing step was geometrically aligned with the following cutting and plotting (deposition) steps in a highly accurate and precise manner using optical scanning function of the plotter/cutter based on registration marks printed on the paper using the wax printer and scanned by the plotter/cutter. The accuracy and precision of alignment in a two-dimensional plane were quantified by cutting and plotting cross-shaped features and measuring their center coordinates relative to wax printed reference lines. The average accuracy along the X- and Y-axis was 0.12 and 0.16 mm for cutting and 0.19 and 0.17 mm for plotting, respectively. The potential of this approach was demonstrated by fabricating μPADs for instrument-free determination of cobalt in waters using distance-based readout, with excellent precision (%RSD = 5.7) and detection limit (LOD) of 2.5 ng and 0.5 mg/L (mass and concentration LODs, respectively).

A Customized Microfluidic Paper-Based Platform for Colorimetric Immunosensing: Demonstrated via hCG Assay for Pregnancy Test

“…A scanning electron microscopy (SEM, JEOL InTouchScope, JSM-IT 500 HR, Frenchs Forest, NSW, Australia) coupled to an energy-dispersive X-ray spectroscopy (EDS, JEOL, Ex-74600U4L2Q, Frenchs Forest, NSW, Australia) were used for investigation of morphology and elemental analysis of paper device. The microfluidic patterns were designed using the Silhouette Studio ® and wax printed on the paper as reported previously [24,25]. The pattern was composed of a sample zone, test zone (T), control zone (C), and a waste zone.…”

Janus electrochemistry: Simultaneous electrochemical detection at multiple working conditions in a paper-based analytical device

“…[14] Flow is generated via capillary action, precluding the need for mechanical or electrical pumps associated with traditional microfluidic devices. [15] The porous paper matrix allows for storage of dried reagents, [16] facilitating multi-step assays. [17] Through patterning with hydrophobic barriers, multiple fluidic channels can be generated on a single paper device for multiplexing.…”

Distance versus Capillary Flow Dynamics‐Based Detection Methods on a Microfluidic Paper‐Based Analytical Device (μPAD)

“…The most promising method appropriate for POC diagnostics and field‐based assays is the distance‐based measurement on LFA or μPAD. In this method, the length of color development or final flow distance on a paper strip is measured to correlate it to the target concentration . In distance‐based methods, it is possible to implement different sensing modalities over multiple channels because only the distance is measured.…”