A smartphone-based image analysis system is advantageous for point-of-care testing applications. However, the processes of observation and image recording rely heavily on an external attachment that includes additional light sources. Moreover, microfluidic point-of-care devices are highly miniaturized, and can be clearly observed only under magnification. To address these issues, the present work proposes a novel imaging box for converting the built-in light source of a smartphone into uniform backlight illumination to avoid interference arising from reflections. A multi-piece orthoscopic lens is embedded in the imaging box to enable the imaging of micro-sized samples. As such, the colorimetric signal of a microchannel with a width as small as 25 µm can be faithfully recorded. Protein concentration quantification based on the bicinchoninic acid assay method was demonstrated with the proposed smartphone/imaging box system from an analysis of colorimetric signals. In addition, a microfluidic chip for conducting ABO blood typing was fabricated, and the microscopic imaging of induced blood coagulation can be clearly observed in a 3 µL sample using the proposed system. These results highlight the potential for adopting smartphone-based analysis systems in point-of-care testing applications.
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