FIG. 1.

Schematic diagram of fabricating μPAD by wet etching. Cross section: (a) native filter paper, (b) hydrophobic filter paper obtained by soaking in TMOS solution, (c) paper mask produced by cutting on the filter paper, (d) paper mask penetrated with NaOH solution, (e) Hydrophobic paper and paper mask sandwiched with glass slides, (f) Assembly after etching, and (g) μPAD with hydrophilic-hydrophobic contrast. (h) Photograph obtained by dropping 10 μl of aqueous blue solution on the hydrophobic filter paper patterned with TMOS. (i) Photograph of a flower-shaped μPAD after dropping aqueous blue solution onto the central unit of μPAD.