In this paper we demonstrate, for the first time, the use of 3D printing (also known as additive manufacturing or rapid prototyping) to create porous media with precisely defined packing morphologies, directly from computer aided design (CAD) models. We used CAD to design perfectly ordered beds with octahedral beads (115 μm apothem) packed in a simple cubic configuration and monoliths with hexagonal channels (150 μm apothem) in parallel and herringbone arrangements. The models were then printed by UV curing of acrylonitrile-butadiene-styrene powder layers. Each porous bed was printed at 1.0, 1.5 and 2.0 mL volumes, within a complete column, including internal flow distributors and threaded 10-32 flow connectors. Close replication of CAD models was achieved. The resultant individual octahedral beads were highly uniform in size, with apothems of 113.6±1.9 μm, while the monolith hexagonal cross-section channels had apothems of 148.2±2.0 μm. Residence time distribution measurements show that the beds largely behaved as expected from their design void volumes. Radial and fractal flow distributor designs were also tested. The former displayed poor flow distribution in parallel and herringbone pore columns, while the fractal distributors provided uniform flow distribution over the entire cross section. The results show that 3D printing is a feasible method for producing precisely controlled porous media. We expect our approach to revolutionize not only fundamental studies of flow in porous media but methods of chromatography column production.

Polypropylene (PP) capillary-channeled polymer (C-CP) fiber stationary phases are investigated for applications in HPLC. Specifically, the roles that fiber size and shape, linear velocity, interstitial fraction, and column inner diameter play in separation efficiency were evaluated using a uracil and butylparaben mixture eluted under isocratic conditions. Four fiber types, having nominal diameters ranging from 30 to 65 μm, were used in 250 mm × 2.1 mm columns. Optimum flow characteristics, as judged by plate height and resolution, were observed for 40 μm diameter PP C-CP fibers packed at an interstitial fraction of ~0.63, over a broad range of linear velocities (~2 to 37 mm/s). The influence of column inner diameter was studied on 1.5, 2.1, and 4.6 mm columns packed at the optimal interstitial fraction. The best performing column in terms of plate height and resolution was the 2.1 mm inner diameter. C-CP columns were also evaluated for the separation of a protein mixture composed of ribonuclease A, cytochrome c, and transferrin. Results obtained with the biomacromolecules mixture validate the optimal structural and operative conditions determined with the small solutes, laying the groundwork towards biomacromolecule applications, focusing more on the chemical aspects of separations.

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