Fig. 1.

Flow profile assay of SARS-CoV-2 on a paper-based microfluidic chip. (A) Paper-based microfluidic chip design containing green edge and three red squares for recognizing the chip area in automated flow distance measurement. (B) The chip holder and the chip lock. (C) A paper-based microfluidic chip was placed into a chip holder to flatten the chip. (D) 4 μL of sample was loaded directly onto the square inlet (top) of each channel and dried for 10 min. (E) A smartphone camera was held just above the chip to view the chip area and start recording the video. (F) 4 μL of Ab-particles were loaded, and the liquid flow on the paper microfluidic chip was recorded with the smartphone camera.