Fluorescence-Based Assessment of Plasma-Induced Hydrophilicity
in Microfluidic Devices via Nile Red Adsorption and Depletion
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Abstract
We
present a simple method, called fluorescence-based assessment
of plasma-induced hydrophilicity (FAPH), that enables spatial mapping
of the local hydrophilicity of surfaces normally inaccessible by traditional
contact angle measurement techniques. The method leverages the change
in fluorescence of a dye, Nile Red, which is adsorbed on an oxygen
plasma-treated surface, and its correlation with the contact angle
of water. Using FAPH, we explored the effect of microchannel geometries
on the penetration distance of oxygen plasma into a microchannel and
found that entrance effects prevent uniform treatment. We showed that
these variations have a significant impact on cell culture, and thus
the design of cell-based microfluidic assays must consider this phenomenon
to obtain repeatable and homogeneous results
