Improved analytical performance of smartphone-based colorimetric analysis by using a power-free imaging box

Smartphones-based colorimetric analysis systems are favoured for point-of-care testing applications. However, the image quality typically suffers from nonuniform and non-reproducible lighting, which negatively affects the accuracy of analyses. The present work proposed a power-free imaging box to utilize the light source of smartphone. The imaging box effectively eliminated interference arising from ambient light, while a V-shaped optical pipe coupled to the light source of smartphone was adopted to redirect the light to the sides of the box to eliminate the direct reflection of light from the surface of the target. This configuration was verified by numerical simulations. The specular reflection of the microfluidic chip was eliminated by establishing ideal diffuse light conditions. Moreover, the color images of a glucose testing on a paper strip and an enzyme-linked immunosorbent assay (ELISA) on transparent microchannels were captured with the proposed configuration, resulting a reduced assay variation and improving the lowest detection limit. The proposed imaging box improves the detection limit of colorimetric analysis, which highlights the potential of smartphone-based colorimetric analysis systems in point-of-care testing applications.