Advances in Paper-Based Analytical Devices

Abstract

Microfluidic paper-based analytical devices (μPADs) are the newest generation of lab-on-a-chip devices and have made significant strides in both our understanding of fundamental behavior and performance characteristics and expansion of their applications. μPADs have become useful analytical techniques for environmental analysis in addition to their more common application as medical point-of-care devices. Although the most common method for device fabrication is wax printing, numerous other techniques exist and have helped address factors ranging from solvent compatibility to improved device function. This review highlights recent reports of fabrication and design, modes of detection, and broad applications of μPADs. Such advances have enabled μPADs to be used in field and laboratory studies to address critical needs in fast, cheaper measurement technologies.

Paper-Based Screen-Printed Electrodes: A New Generation of Low-Cost Electroanalytical Platforms

“…As mentioned before, besides being a flat substrate, paper can have other utilities such as storage of reagents or sample [ 84 , 85 ], support for (biological) reactions [ 42 , 86 , 87 , 88 , 89 ], or platform for taking [ 67 , 90 ] or treating the sample (e.g., preconcentration [ 81 , 91 ] or separation [ 79 , 92 , 93 ]). Taking this into account, paper-based electroanalytical devices integrating SPEs can be designed in different formats: (i) combining paper with a SPE card fabricated on ceramic or polymeric materials [ 79 , 84 , 85 , 86 , 87 , 88 , 89 , 91 , 92 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 ]; (ii) combining one electrode of the electrochemical cell (e.g., WE) made on paper with other electrodes (e.g., RE and CE) of a SPE card printed on a conventional material [ 42 , 103 , 104 , 105 ]; and (iii) printing the SPE directly on paper [ 5 , 106 , 107 , 108 ]. In the last case, 2D devices are the most basic but, by stacking and/or folding the paper along the vertical axis, devices with 3D formats (multilayer and origami) can be easily constructed.…”

“…In the last case, 2D devices are the most basic but, by stacking and/or folding the paper along the vertical axis, devices with 3D formats (multilayer and origami) can be easily constructed. Obviously, the fabrication of 2D devices is much simpler but 3D platforms can improve analytical characteristics (mainly reproducibility and sensitivity) and reduce the steps of the analytical procedure as well as time analysis [ 108 ]. Here, electrodes could be included in the same or different layers.…”

“…Although there are numerous different designs that combine SPEs (in ceramic/polymer substrates) with paper devices, the most integrated approach is achieved by printing electrodes directly onto the paper creating 2D and 3D devices, with all the three electrodes in the same or different layers [ 78 , 108 ]. In two-dimensional devices, the sample is deposited in the same layer in which the electrochemical cell is printed or flows toward it by capillarity.…”

Flow control in a laminate capillary-driven microfluidic device

“…Pregnancy tests are an example of a capillary-driven analytical device, and their widespread use demonstrates the utility of this platform for at-home diagnostic testing (7)(8)(9). Capillary-driven microfluidics have been used in many applications, including the detection of bacteria, viruses, biomarkers, pesticides, and heavy metals (10)(11)(12)(13)(14). In each application, accurate and precise flow control is critical to realize a reduced assay time, simplified operation, and improved analytical performance (15).…”

Metallic Pins as Electrodes in Low-Cost (Bio)Electroanalytical Devices

“…Important current trends in Analytical Chemistry, such as simplicity, miniaturization, reduction of costs and portability, have led to the exploration of the use of common mass-produced materials for the construction of analytical devices. The use of these materials (e.g., paper [1][2][3][4][5], sewing pins [6][7][8][9], office transparency sheets [7,10], thread [11], etc.) provides cheap, highly versatile, and, above all, easily available devices.…”