Norland optical adhesive (NOA81) microchannels with adjustable wetting behavior and high chemical resistance against a range of mid-infrared-transparent organic solvents

Different methods to adjust the wetting behavior of surfaces of the UV-curable adhesive NOA81 were investigated and quantitatively characterized by dynamic contact angle measurements with an optical goniometer. A new method to make NOA81 surfaces hydrophobic by mixing an additive in the uncured polymer was presented. The effect was confirmed by surface roughness studies using atomic force microscopy and X-ray photoelectron spectroscopy measurements. The chemical resistance of NOA81 microfluidic channels was evaluated by flowing organic solvents therein. Emphasis was placed on IR-transparent organic solvents. A simple, low-cost method to fabricate chemically resistant, hydrophilic, hydrophobic and hybrid (hydrophilic and hydrophobic), all-polymer microfluidic channels made of NOA81 was reported. Applications like oil-in-water and water-in-oil droplet generation or handling of a multi-phase flow were presented to demonstrate the chemical resistance and the control over the wetting behavior of NOA81 microfluidic chips.