Abstract
This work demonstrates the fabrication of microfluidic paper-based analytical devices (µPADs) suitable for the analysis of sub-microliter sample volumes. The wax-printing approach widely used for the patterning of paper substrates has been adapted to obtain high-resolution microfluidic structures patterned in filter paper. This has been achieved by replacing the hot plate heating method conventionally used to melt printed wax features into paper by simple hot lamination. This patterning technique, in combination with the consideration of device geometry and the influence of cellulose fiber direction in filter paper, led to a model µPAD design with four microfluidic channels that can be filled with as low as 0.5 µL of liquid. Finally, the application to a colorimetric model assay targeting total protein concentrations is shown. Calibration curves for human serum albumin (HSA) were recorded from sub-microliter samples (0.8 µL), with tolerance against ±0.1 µL variations in the applied liquid volume.
Highlights
In recent years, microfluidic paper-based analytical devices, commonly referred to as μPADs, have gained a lot of attention as potential alternative tools for various analytical tasks
The attractive features of μPADs are to a large extent related to the use of paper as the substrate material and include low cost, easy disposability, as well as external power-free sample transport driven by capillary forces
One disadvantage of μPADs in general, is that they mostly require larger sample volumes compared to conventional microfluidic devices based on glass or polymeric substrates [7,8,9]
Summary
Microfluidic paper-based analytical devices, commonly referred to as μPADs, have gained a lot of attention as potential alternative tools for various analytical tasks. The attractive features of μPADs are to a large extent related to the use of paper as the substrate material and include low cost, easy disposability, as well as external power-free sample transport driven by capillary forces. One disadvantage of μPADs in general, is that they mostly require larger sample volumes compared to conventional microfluidic devices based on glass or polymeric substrates [7,8,9]. This is due to the mostly larger dimensions of microfluidic structures patterned on paper substrates and the fact that μPADs are generally open systems prone to evaporation of sample fluids during the slow wicking process in paper microfluidic channels. Sample volumes in the sub-microliter order are not sufficient to wet out the microfluidic structure of μPADs and to reach the zone where signal creation takes place
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