Gradient-temperature hot-embossing for dense micropillar array fabrication on thick cyclo-olefin polymeric plates: An example of a microfluidic chromatography column fabrication

The fabrication of dense and high aspect ratio pillar arrays is important for several applications. In particular polymeric microfluidic chromatography columns are of high importance for various biological, pharmaceutical and chemical separations. Here, a cyclo-olefin polymeric (COP) microcolumn fabrication process is developed using hot embossing with a temperature gradient for replication of a fine and highly dense array of micropillars on the surface of a 2mm thick polymer plate without chip deformation. The design consists of an array of ordered cylindrical pillars with 15 mu m diameter, 4 mu m interpillar, and 2 mu m pillar-wall distance with 20 mu m height. The produced microcolumn is subsequently sealed with thermal bonding in a laminator and tested for liquid pressure operation up to 20 bar. Since COPs are hydrophobic by nature and have been used for reversed-phase liquid chromatographic (RPLC) separations in the past, preliminary separation experiments are also demonstrated in the fabricated column.