Engineering solutions for flow control in microfluidic devices for spatial multi-dimensional liquid chromatography

Towards spatial comprehensive three-dimensional liquid chromatography: A tutorial review

“…With respect to peak variance, the bifurcating flow distributors having a minimal volume gave the best dispersion characteristics. Recent on-chip flowimaging experiments demonstrated that bifurcating distributors with an angle of 180 yield the most homogeneous flow profile [37]. When chip prototyping is the limiting factor and local imperfections (constrictions blocking a small segment of a microchannel) exist, a 'hybrid' flow distributor design can be utilized.…”

“…A chip prototype was developed using solventassisted drilling, in which a PEEK tube containing through-holes was drilled at low speeds into an existing small i.d. channel, present in a polymethylmethacrylate chip substrate while adding dichloromethane [37]. Adamopoulou et al reported on a 3D printed device in which a dye was introduced in a transparent cylindrical channel and was directed towards the 2 D channels after 90 rotation [48].…”

“…Themelis et al reported on the development of a leak free microfluidic device for spatial 2D-LC, allowing to successfully confine the flow during the 1 D stage via active-valving and establishing effective transfer of sample to the parallel 2 D channels after rotation of the axis, by flow entering from the 2 D flow distributor, feeding the parallel 2 D channels [37]. By using PEEK tube inserted in an elastic PFA sleeve and constructing a customized chip holder allowing to apply high vertical forces, no leak flow was observed when applying pressure as high as 50 bar.…”

“…In the chip displayed in 6A, the polymer monolith was synthesized in all the microchannels, i.e., in the 1 to confine the flow during the 1 D stage (Fig. 5D) [37]. After sample transfer, sample focusing was achieved at the inlet of the parallel 2 D channels filled with monolith (see Fig.…”

“…Davydova et al discussed size constrictions of 90% of the total area in the last row segments of a bifurcating flow distributor as means of creating preferential flow paths during a 1 D development without recirculation of sample in the 2 D flow distributor [44]. Restricting the cross-section areas further by integrating monolithic stationary phases locally in the flow distributors and 2 D channels while maintaining an open 1 D channel enhances flow confinement, as demonstrated by Liu et al[45] and Themelis et al[37]. From a CFD simulation, Adamopoulou et al…”