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Pillar‐structured microchannels for on‐chip liquid chromatography: Evaluation of the permeability and separation performance
Author(s) -
De Pra Mauro,
De Malsche Wim,
Desmet Gert,
Schoenmakers Peter J.,
Kok Wim Th.
Publication year - 2007
Publication title -
journal of separation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.72
H-Index - 102
eISSN - 1615-9314
pISSN - 1615-9306
DOI - 10.1002/jssc.200600468
Subject(s) - porosity , wafer , permeability (electromagnetism) , materials science , analytical chemistry (journal) , chromatography , microchannel , diamond , packed bed , microfluidics , void (composites) , silicon , chemistry , composite material , nanotechnology , membrane , optoelectronics , biochemistry
The chromatographic characteristics were determined for a set of microfabricated separation channels structured with cylindrical and diamond‐shaped pillars with a characteristic size of 5 μm. Channels with different structures and porosities were etched in a silicon wafer using lithographic techniques. The permeability for flow of the channels was shown to increase strongly with the overall porosity. Diamond‐shaped pillars appeared to yield a slightly higher permeability than cylindrical pillars at the same channel porosity. Compared to packed columns, permeabilities were higher by a factor of up to 5. Band dispersion in the channels was measured with an unretained fluorescent probe compound using a fluorescence microscope. A relatively large variation in the observed plate heights between channels was found, which was mainly attributed to the inaccurate geometry of the structure close to the side walls. Reduced plate heights between 0.2 and 1.0 were obtained. The lowest plate heights were found for channels with low porosity. The chromatographic impedances were calculated and compared to the values for the traditional chromatographic systems. For one of the structured microchannels the impedance was found to be more than ten times lower than for a column packed with nonporous spherical particles. With the data collected, predictions are given on the possibilities in terms of efficiency and speed offered by structured microchannels for pressure‐driven separations, taking practical constraints into account.