Dispersion Studies of Pressure-Driven Flow in Deep-Reactive-Ion-Etched Microfluidic Channels

Multi-layer microfluidic glass chips for microanalytical applications

“…Figure 7 presents two curves showing the influence of flow rate on the dispersion induced in the microfluidic chip. As expected from theory [11,24,25], dispersion increases with increasing flow rates. The two types of chip have different dispersion properties, with the wider chip inducing more dispersion than the narrow one under the same flow conditions.…”

“…After the addition of reagent 3 there is a long reaction coil, to enable full development of the reaction product before reaching the optical cuvette. The channel meander was therefore designed as a compromise between low dispersion, low flow resistance, and short mixing times [11,22]. For a given chip volume, the wider the channels, the shorter the reaction coil.…”

“…A summary of the typical channel dimensions of chip 30a and chip 30b is given in Table 1. Following the same experimental protocol as described elsewhere [11], these two different geometries were studied with respect to the dispersion that they induce. During the experiments the total flow rate in the chip was kept constant.…”

“…Concentrations are expressed in terms of ppm N present in the form of NH 4 + . Absorbance was measured in the optical cuvette drilled in the Pyrex wafer (525 µm thick) by SAE [8,11] (total path-length including depths of inlet and outlet channels (30 µm each): 585 µm), and compared with the absorbance measured in a silicon optical cuvette formed by deep reactive-ion-etching (optical pathlength: 400 µm) [7] Fig. 6 Initial part of the absorbance profile of indophenol blue solution plugs for two different geometries.…”

“…The fabrication of a low-volume detector with a long path-length is, therefore, one of the challenges to be met in the successful fabrication of the microfluidic device. Deep reactive-ion-etching (DRIE) can be used to fabricate narrow holes through silicon chips [11], but DRIE is not yet sufficiently developed for producing similar structures in quartz or glass. Use of wet-etching to produce holes through glass is also not applicable, because this is an isotropic process, producing structures which are twice as wide as they are deep.…”