Rapid fabrication of solvent-compatible NOA 81 microfluidic devices for double-emulsion microfluidics

While PDMS-based microfluidic devices set the rapid prototyping standard, their application is limited by incompatibility with many non-polar solvents. This inability to tolerate organic solvents significantly restricts the types of materials that can be handled and/or synthesized. UV-curable photopolymers, such as NOA 81, present a promising solution to these challenges. NOA 81 enables simple, cost-effective device fabrication, but current limitations on proper fabrication protocols limit its full potential. Here, we present a well-defined, simple, single-step fabrication method for producing NOA 81 microfluidic devices that are compatible with organic solvents. This method allows for the rapid prototyping of devices using similar steps associated with PDMS. We report a rapid heat treatment step that enhances the chemical resistance to a wider range of organic solvents while also increasing the material's elastic modulus by nearly two orders of magnitude. We demonstrate how to control the channel wall wettability for producing water-in-oil-in-water double emulsions which serve as templates for microcapsules and amphiphilic polymer vesicles. This novel method, which we call "hard lithography", reduces the time needed to produce working prototypes to less than one day while expanding the range of solvents that can be used. It simplifies fabrication and enables the production of chemically resistant devices suitable for a wide array of applications.