Filter paper can be hydrophobized by coupling of hydrophobic
silane of OTS to the paper fibers at room temperature within
several minutes, and hydrophobic−hydrophilic patterning of
paper sheets can be achieved by exposing the OTS-paper to
deep UV-lights through a photomask. The UV-exposed region
becomes hydrophilic because the octadecyl hydrocarbon chain
of the OTS is degraded to the oxygen-containing polar moieties
under the coaction of deep UV-lights and the photogenerated
ozone. On the basis of these observations, a facile approach for
fabrication of μPADs has been established. The developed
method features simplicity in operation, low in cost, and no
need for a clean room and expensive equipment and, therefore,
can be employed by analysts or biologists themselves to prepare
μPADs in their own chemical laboratories. Owing to that, the
OTS molecules are covalently bonded to the paper fibers rather
than physically deposited on paper as photoresist or wax does,
and such prepared μPADs are very stable. They can tolerate the
attack of some organic solvents and, consequently, can be used
in both aqueous and organic medium. They can survive from
bending and folding without damage of the patterns as well.
Since various silane agents with different functionalities are
commercially available, the developed approach can be
extended with a few modifications to prepared μPADs withdifferent functionalities for chemical analysis, bioassay, and cellbased
research