In situ tertiary amine-catalyzed thiol-acrylate chemistry was employed to produce hydrophilic microfluidic devices via a soft lithography process. The process involved the Michael addition of a secondary amine to a multifunctional acrylate producing a nonvolatile in situ tertiary amine catalyst/comonomer molecule. The Michael addition of a multifunctional thiol to a multifunctional acrylate was facilitated by the catalytic activity of the in situ catalyst/comonomer. These cost-efficient thiol-acrylate devices were prepared at room temperature, rapidly, and with little equipment. The thiol-acrylate thermoset materials were more natively hydrophilic than the normally employed poly(dimethylsiloxane) (PDMS) thermoset material, and the surface energies were stable compared to PDMS. Because the final chip was self-adhered via a simple chemical process utilizing the same chemistry, and it was naturally hydrophilic, there was no need for expensive instrumentation or complicated methods to "activate" the surface. There was also no need for postprocessing removal of the catalyst as it was incorporated into the polymer network. These bottom-up devices were fabricated to completion proving their validity as microfluidic devices, and the materials were manipulated and characterized via various analyses illustrating the potential diversity and tunability of the devices.

No abstract

No abstract

Fabrication of 2.5D rock-based micromodels with high resolution features is presented using SU-8 multi-layer lithography and nickel electroforming for nickel molds. Processes associated with SU-8 were carefully optimized by the use of the vacuum contact, the use of UV filter, and controls of UV exposure doses and baking times. The use of SU-8 MicroSpray enabled the easy fabrication of multi-layers of SU-8, while exhibiting some total thickness variations. The thirteen layered SU-8 samples showed reliable patterning results for features at 10 and 25 μm resolutions, and minor pattern distortions of features at the 5 μm resolution. Flycutting method employed in multi-layer lithography of SU-8 yielded accurate total thickness control within ±1.5 μm and excellent pattern formation for all of 5, 10, and 25 μm features. Electroforming of nickel was optimized with electroplating bath composition and electroplating parameters such as current density to realize the high resolution nickel mold. The fabricated nickel molds from flycutting based SU-8 samples revealed the feasibility of manufacturing the minimum features down to 5 μm for thirteen layers without any pattern distortions. The replication-based micromolding method will allow for fabrication of micromodels in a variety of materials such as polymers and ceramics. The high resolution, 2.5D micromodels will be used for investigation of pore-scale fluid transport, which will aid in understanding the complicated fluidic phenomena occurring in the 3D reservoir rock.