Comparison of capillary zone electrophoresis performance of powder‐blasted and hydrogen fluoride‐etched microchannels in glass

Abstract

The applicability of glass chips with powder-blasted microchannels for electrophoretic separations was examined, and the performance was compared to microchannels etched with hydrogen fluoride (HF), using bicarbonate buffer and rhodamine B and fluorescein as model compounds. The measured electroosmotic mobilities in all chips were comparable, with values of ca. 7 x 10(-4) cm(2) V(-1)s(-1). The effect of electrical field strength and detection length on the separation efficiency was monitored. It was found that the main source of dispersion is of the Taylor-Aris type, which was discussed in relation to channel roughness differences. Although in powder-blasted channels with a separation length of 8.20 cm, 7-9 times lower plate numbers were obtained than in a HF-etched channel with similar dimensions, successful separation of five fluorescein isothiocyanate (FITC)-labeled amino acids was obtained on a powder-blasted chip within 80 s. Efficiencies of up to 360 000 plates/m were demonstrated on this chip, when a higher buffer concentration was used at a field strength of 664 V/cm. It can be concluded that powder-blasted microchannel chips, although they have a lower separation efficiency compared to HF-etched chips, perform well enough for many applications. Powder blasting can therefore be considered a low-cost and efficient alternative to HF etching, in particular because of the possibility to fabricate access holes through the glass with the same process.

Coating of powder‐blasted channels for high‐performance microchip electrophoresis

“…The roughness of the surfaces is in the low mm-range as previously described [8]. Comparing channels blasted with different air pressure it can be observed that structures generated at lower pressure exhibit smoother surfaces as expected.…”

“…It could be shown that such devices can in principal be applied in chip electrophoresis. It was, however, found that the resolution in electrophoretic separation obtained in powder-blasted (pb) devices is generally lower compared to wet chemical etched (wc) chips, which was attributed to the much higher surface roughness inducing band broadening [8]. The lower resolution obtainable in pb-chips currently hampers the application of the fast and economic powder-blasting process for manufacturing fluidic devices for chip electrophoresis.…”

“…This makes the technique especially attractive for fast prototyping. The harsh mechanical erosion process, however, results in a much higher surface roughness of structured channels, about a few mm for powder blasting compared to less than 100 nm for HF-etching [8].…”

Single potential electrophoresis microchip with reduced bias using pressure pulse injection

“…Hereafter, the two clean slides were rinsed with distilled water, dried, and assembled under a microscope. While powder blasting intrinsically results in a surface roughness of the eroded surfaces of a few micrometers and electrophoretic separation efficiency is lower than for HF-etched chips [44], Wensink et al [45] have demonstrated the possibility to smoothen powder blasted glass surfaces by heating the glass slides up to their fusion temperature. We have chosen 7007C as the fusion bonding temperature for our microchips, reducing the average channel wall roughness R a from 1.7 to 1.1 mm, while keeping the channel design intact.…”

Evaluation of micromilled metal mold masters for the replication of microchip electrophoresis devices

“…The intrinsic qualities of micromilling may impose some operational limitations on the use of these masters for replicating parts in certain application areas. For example, in the case of microelectrophoresis, wall roughness has been shown to be detrimental to plate numbers produced with electrokinetically driven separations (Slater and Mayer 1995;Blom et al 2001;Pu et al 2003). In addition, the rounded corners of intersecting channels may be troublesome in microfluidic designs, which are dependent on well-defined volumes at channel intersections.…”