PolyJet-Based 3D Printing against Micromolds to Produce Channel Structures for Microchip Electrophoresis

In this work, we demonstrate the ability to use micromolds along with a stacked three-dimensional (3D) printing process on a commercially available PolyJet printer to fabricate microchip electrophoresis devices that have a T-intersection, with channel cross sections as small as 48 × 12 μm² being possible. The fabrication process involves embedding removable materials or molds during the printing process, with various molds being possible (wires, brass molds, PDMS molds, or sacrificial materials). When the molds are delaminated/removed, recessed features complementary to the molds are left in the 3D prints. A thermal lab press is used to bond the microchannel layer that also contains printed reservoirs against another solid 3D-printed part to completely seal the microchannels. The devices exhibited cathodic electroosmotic flow (EOF), and mixtures of fluorescein isothiocyanate isomer I (FITC)-labeled amino acids were successfully separated on these 3D-printed devices using both gated and pinched electrokinetic injections. While this application is focused on microchip electrophoresis, the ability to 3D-print against molds that can subsequently be removed is a general methodology to decrease the channel size for other applications as well as to possibly integrate 3D printing with other production processes.