Microfluidic Devices for Monolith Polymerization

The microfluidic devices (Figure 1A) were adapted from Bickham et al.^{19 (link)} and designed to have five separated channels, each with a 50 μm × 45 μm cross section. Each channel had a reservoir on one side of the device and a port on the other side for PTFE tubing (0.22 in ID × 0.042 in OD; Cole Parmer, Vernon Hills, IL) to connect to vacuum to flow analyte through the channel. A 600 μm wide monolith polymerization window (MPW), a region with fewer absorber-containing layers in the 3D print, was designed in each device to allow monolith polymerization.^{12 (link)} 97% PEGDA, 2% NPS UV absorber, and 1% Irgacure 819 photoinitiator composed the resin used to fabricate the devices in a custom 3D printer.^{24 (link)}