Preparation and design of PCD. The PCD design and features are displayed in Fig. 5, a previous report
describing the printing technique used for device fabrication19. A circular-shaped paper chip of 7 mm diameter
was designed using a drawing software package that was connected to a cutting plotter (Silhouette GAMEO,
made in Vietnam). Subsequently, we designed a rectangular plastic module with a round-hole (6 mm diameter)
as a detection zone which could support the paper-chips. As the paper was stacked into the printer, multiple
7 mm-diameter paper chips were fabricated at the same time to align with the hole in the plastic support module.
Thus, the fabricated PCD, which combined the plastic support module with the paper-chip, was able to be used
for Hg2+ assay.