3.2. Principle of the tree-shaped design
To validate the idea of self-calibration, a tree-shaped paper
device is designed, which could assure the uniformity of micro
flows in different branches for multiplex concentration of analytes
on the paper. This tree-shaped paper device offers 7 assays,
which means a set of 7 data could be collected at the same time,
including the color intensity in both the standard solution and the
unknown concentration (Fig. 2).