We describe continuous flow liquid-liquid phase separation in microfluidic devices based on capillary forces and selective wetting surfaces. Effective liquid-liquid phase separation is achieved by using a thin porous fluoropolymer membrane that selectively wets non-aqueous solvents, has average pore sizes in the 0.1-1 microm range, and has a high pore density for high separation throughput. Pressure drops throughout the microfluidic network are modelled and operating regimes for the membrane phase separator are determined based on hydrodynamic pressure drops and capillary forces. A microfluidic extraction device integrating mixing and phase separation is realized by using silicon micromachining. Modeling of the phase separator establishes the operating limits. The device is capable of completely separating several organic-aqueous and fluorous-aqueous liquid-liquid systems, even with high fractions of partially miscible compounds. In each case, extraction is equivalent to one equilibrium extraction stage.

All for one and one for all: A continuous‐flow, multistep microchemical synthesis of carbamates starting from aqueous azide and organic azoyl chloride by using the Curtius rearrangement reaction is described. The procedure involves three reaction steps and two separation steps (one gas–liquid and one liquid–liquid). Formation of a microreactor network for parallel synthesis of analogous compounds is also demonstrated.

Distillation is a ubiquitous method of separating liquid mixtures based on differences in volatility. Performing such separations in microfluidic systems is difficult because interfacial forces dominate over gravitational forces. We describe distillation in microchemical systems and present an integrated silicon device capable of separating liquid mixtures based on boiling point differences. Microfluidic distillation is realized by establishing vapor-liquid equilibrium during segmented flow. Enriched vapor in equilibrium with liquid is then separated using capillary forces, and thus enabling a single-stage distillation operation. Design criteria for operation of on-chip distillation is set forth, and the working principle demonstrated by separation of binary mixtures of 50 : 50 mol% MeOH-toluene and 50 : 50 mol% DCM-toluene at 70.0 degrees C. Analysis of vapor condensate and liquid exiting a single-stage device gave MeOH mole fractions of 0.22 +/- 0.03 (liquid) and 0.79 +/- 0.06 (vapor). Similarly, DCM mole fractions were estimated to be 0.16 +/- 0.07 (liquid) and 0.63 +/- 0.05 (vapor). These experimental results were consistent with phase equilibrium predictions.

Einer für alle, alle für einen: Eine mehrstufige mikrochemische Durchflusssynthese von Carbamaten aus wässrigem Azid und einem organischen Azoylchlorid mithilfe der Curtius‐Umlagerung wird beschrieben. Der Prozess umfasst drei Reaktionsstufen und zwei Trennschritte (eine Gas‐flüssig‐ und eine Flüssig‐flüssig‐Trennung). Ein Mikroreaktornetzwerk für die Parallelsynthese analoger Verbindungen wird ebenfalls vorgestellt.

Constructing a microsystem compatible with a large variety of chemistries requires a system design that will be robust in the presence of different compounds and at a wide range of conditions. Although microreactors themselves can accommodate a great span of conditions, few packaging schemes are compatible with cryogenic temperatures, high pressures, and aggressive organic solvents. Solder-based connections are designed and implemented on silicon-based microreactors and are demonstrated to withstand elevated pressures (up to 200 atm), a wide range of temperatures (-78 to 160 degrees C) and a variety of solvent systems. Through the deposition of metal bonding pads directly onto silicon and glass surfaces, solder-based chip-to-tube connections can be reliably formed using handheld soldering tools. Packaging techniques are also described for fluidic chip-to-chip bonds, facilitating direct connection of microfluidic modules. This method greatly expands the utility of microfluidic reactors while enabling easy and reproducible fluidic packaging.