Freeze-thaw valves as a flow control mechanism in spatially complex 3D-printed fluidic devices

Optimizing design and employing permeability differences to achieve flow confinement in devices for spatial multidimensional liquid chromatography

“…Moreover, during the 3 D injection the majority of the dye was transferred from the 2 D to the 3 D, but a small percentage entered the 1 D channel before transferring to the 3 D, which caused tailing on the one side of the 3 D cube. For this reason, it would be advisable to use physical barrier flow-confinement methods between the 1 D channel and the 2 D space [17,21]. The operation of the device can still be successful even without physical barriers between the 1 D and the 2 D, but it is suspected that the total separation efficiency would be undermined.…”

“…A suggestion to prevent the flow from entering the 1 D channel and causing this tailing would be to use a barrier between the first and the second dimension, like a rotating valving mechanism, viz. the TWIST [17] or a freezing and thawing valve system used in the COSMIC [21]. In the first case, the device would be modular in the first dimension, while in the second case it would be a single-piece device with additional external jackets surrounding the 1 D channel to allow the flow of heating and cooling liquid for the operation of the valving mechanism.…”

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

“…An alternative approach to confine flows in capillaries or microfluidic channels is by utilizing freeze-thaw valves [49]. This approach is generally limited to solvent systems containing high water content, as water expands during freezing.…”

“…This approach is generally limited to solvent systems containing high water content, as water expands during freezing. This concept was adopted by Nawada et al who developed a titanium device containing a channel for the 1 D stage, which was connected to parallel 2 D channels oriented perpendicular to the 1 D channel and portions of channels were enveloped by cooling and heating jackets [49]. The frozen plug was reported to withstand at least 200 bar of pressure.…”

“…Switching times between a frozen state and a state with the section thawed for a single valve was found to be in the range of 1 -2.5 min using a passive switching approach, which could be reduced by a factor of 3 using an active switching (introducing hot liquid). A 58% increase in switching time was observed when using a T-junction network of 33 of such valves instead of 1 [49]. In pursue of spatial 2D-LC separations, based on thin-layer chromatography, the Svec group used the dewetting properties of super hydrophobic polymer-monolithic materials to confine an aqueous flow within a patterned hydrophilic channel functionalized with ion-exchange moieties during a 1 D separation [50].…”