ABSTRACT: This work presents a novel and facile method
for fabricating paper-based microfluidic devices by means of
coupling of hydrophobic silane to paper fibers followed by
deep UV-lithography. After filter paper being simply immersed
in an octadecyltrichlorosilane (OTS) solution in n-hexane for
5 min, the hydrophilic paper became highly hydrophobic
(water contact angle of about 125°) due to the hydrophobic
OTS molecules were coupled to paper’s cellulose fibers. The
hydrophobized paper was then exposed to deep UV-lights
through a quartz mask that had the pattern of the to-beprepared
channel network. Thus, the UV-exposed regions turned highly hydrophilic whereas the masked regions remained highly
hydrophobic, generating hydrophilic channels, reservoirs and reaction zones that were well-defined by the hydrophobic regions.
The resolution for hydrophilic channels was 233 ± 30 μm and that for between-channel hydrophobic barrier was 137 ± 21 μm.
Contact angle measurement, X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform-infrared
(ATR-FT-IR) spectroscopy were employed to characterize the surface chemistry of the OTS-coated and UV/O3-treated paper,
and the related mechanism was discussed. Colorimetric assays of nitrite are demonstrated with the developed paper-based
microfluidic devices.