title: Fluorescence-based assessment of plasma-induced hydrophilicity in microfluidic devices via Nile Red adsorption and depletion.
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.
authors.affiliation: Department of Biomedical Engineering, Wisconsin Institutes for Medical Research, University of Wisconsin-Madison , 1111 Highland Avenue, Madison, Wisconsin 53705, United States.
authors.forename: David J
authors.initials: DJ
authors.lastname: Guckenberger
authors.forename: Erwin
authors.initials: E
authors.lastname: Berthier
authors.forename: Edmond W K
authors.initials: EW
authors.lastname: Young
authors.forename: David J
authors.initials: DJ
authors.lastname: Beebe
mesh_terms: D000327:Adsorption; D005453:Fluorescence; D057927:Hydrophobic and Hydrophilic Interactions; D044085:Microfluidics / Q000295:instrumentation*; D010078:Oxazines / Q000737:chemistry*; D058626:Plasma Gases
chemical_list: D010078:Oxazines; D058626:Plasma Gases; C044808:nile red