Structure optimization method of microfluidic paper chip based on image grey-level statistics for chromogenic reaction

Paper-based microfluidic chips are widely used in point-of-care testing (POCT). The structures of the paper chips impose significant impact on the detection accuracy. The mainstream of microfluidic paper chip designs can be divided into two categories, planar diffusion type and vertical diffusion type respectively. According to the two methods above, five different structures of paper chips were designed, namely Y-channel microfluidic chip, three-channel microfluidic chip, rotary array microfluidic chip, oblique double-channel microfluidic chip and multilayer solid microfluidic chip. The mean standard deviation and maximum standard deviation of gray level difference of the best multilayer solid structure comparing with the second best structure reduced by 17% and 39% respectively. Consequently, there was no significant relationship between the color reaction uniformity and the number of channels but a positive correlation with the reaction contact area. This paper offered a step toward designing paper microfluidic chip based on colorimetric method.