title: Suppression of the sidewall effect in pillar array columns with radially elongated pillars.
abstract: An important bottleneck of pillar array columns designed for liquid chromatography is that small deviations of the target 'magical distance' at the sidewall region leads to detrimental sidewall effects, due to local differences of linear velocities at the sidewall region versus other locations in the pillar bed. In the present study, we demonstrate that a lateral elongation of the pillar significantly increases the tolerance for offsets of the magical distance. By shifting the sidewall distance 600 nm for 2 pillar aspect ratio (AR) designs (AR=3 and 9), only minor sidewall effects on the measured plate heights could be observed for the AR=9 columns, while the plate height was roughly doubled when using the wrong versus the correct sidewall distance for the AR=3 columns. Technologically, this constitutes a huge advantage because small deviations (order of 100 nm) between the set and the finally achieved value for the inter-pillar distance are very common using mid-UV lithography based etching processes.
authors.affiliation: Department of Chemical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium.
authors.forename: Jeff
authors.initials: J
authors.lastname: Op De Beeck
authors.affiliation: Department of Chemical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium; B-PHOT, Department of Applied Physics, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium.
authors.forename: Manly
authors.initials: M
authors.lastname: Callewaert
authors.affiliation: B-PHOT, Department of Applied Physics, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium.
authors.forename: Heidi
authors.initials: H
authors.lastname: Ottevaere
authors.affiliation: Mesoscale Chemical Systems, Mesa+ Institute for Nanotechnology, P.O. Box 217, 7500AE Enschede, The Netherlands.
authors.forename: Han
authors.initials: H
authors.lastname: Gardeniers
authors.affiliation: Department of Chemical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium.
authors.forename: Gert
authors.initials: G
authors.lastname: Desmet
authors.affiliation: Department of Chemical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium. Electronic address: wdemalsc@vub.ac.be.
authors.forename: Wim
authors.initials: W
authors.lastname: De Malsche
mesh_terms: D002853:Chromatography, Liquid / Q000295:instrumentation* / Q000379:methods; D008855:Microscopy, Electron, Scanning
keywords: Chip chromatography; Etching limitations; Pillar array column; Radially elongated pillars; Sidewall effect