Herein, we established a testing model with self-calibration,
achieved by running colorimetric assays on a tree-shaped
hydrophilic paper. Results can either be observed by naked eyes
or analyzed by software. Cameras and cell phones could help in
semi-quantification and telecommunication. Therefore, a simple inexpensive and rapid method is obtained. Here, we are not only
aiming at analyzing the concentration of a certain chemical but also
developing a practical approach which could satisfy the growing
demands of portable, low-cost and easy operated devices with further
application in the areas of medical health and environmental
monitoring.