Indirect fabrication of versatile 3D microfluidic device by a rotating plate combined 3D printing system.

In the past decade, 3D-printing technology has been applied in the field of microfluidics to fabricate microfluidic devices for wide-ranging areas of study including chemistry, biology, medicine, and others. However, these methods face several limitations such as insufficient resolution and long fabrication time. In this study, versatile microfluidic devices with different functions were indirectly fabricated by a rapid sacrificial template printing process using a photocurable fluoropolymer with chemical durability. The Pluronic® F127 hydrogel as a sacrificial template was rapidly patterned on substrates by a non-lithographic printing process using a computer-controlled 3D-printing system. Viscous fluoropolymer was cast on the non-deformable template that was consequently removed by applying heat and negative pressure after UV curing. The chemical-resistant and transparent microchannels were oblate-hemispherical on the cross section. They were tested by performing a heterogeneous catalytic reaction as well as a photochemical reaction. The microchannels with controlled heights were devised to induce convection for functioning as a micromixer with asymmetric flows. Moreover, upon printing the Pluronic® F127 on both sides of the PFPE (perfluoropolyether-urethane dimethacrylate) membrane substrate, the 3D hybrid microfluidic device was embedded with a permeable membrane between the lower and upper channels, which is useful for gas-liquid chemical processes.

Correction: Indirect fabrication of versatile 3D microfluidic device by a rotating plate combined 3D printing system.

[This corrects the article DOI: 10.1039/C8RA08465C.].

Integrated CO2 capture-fixation chemistry via interfacial ionic liquid catalyst in laminar gas/liquid flow.

Simultaneous capture of carbon dioxide (CO2) and its utilization with subsequent work-up would significantly enhance the competitiveness of CO2-based sustainable chemistry over petroleum-based chemistry. Here we report an interfacial catalytic reaction platform for an integrated autonomous process of simultaneously capturing/fixing CO2 in gas-liquid laminar flow with subsequently providing a work-up step. The continuous-flow microreactor has built-in silicon nanowires (SiNWs) with immobilized ionic liquid catalysts on tips of cone-shaped nanowire bundles. Because of the superamphiphobic SiNWs, a stable gas-liquid interface maintains between liquid flow of organoamines in upper part and gas flow of CO2 in bottom part of channel. The intimate and direct contact of the binary reagents leads to enhanced mass transfer and facilitating reactions. The autonomous integrated platform produces and isolates 2-oxazolidinones and quinazolines-2,4(1H,3H)-diones with 81-97% yields under mild conditions. The platform would enable direct CO2 utilization to produce high-valued specialty chemicals from flue gases without pre-separation and work-up steps.

A simple and reliable analytical method based on HPLC-UV to determine oleanonic acid content in Chios gum mastic for quality control.

A reliable analytical method based on high-performance liquid chromatography-ultraviolet detection was established for the determination of oleanonic acid (OA) content in Chios gum mastic (CGM). A simple method involving methanol extraction of CGM powder followed by basification and ether extraction was developed to isolate the triterpenic fraction including OA. The triterpenic fraction was chromatographed on a Phenomenex Gemini C18 column (150 × 4.6 mm, 5 µm) under a simple gradient elution of a mobile phase containing acetonitrile and water at a flow rate of 1.0 mL min-1. The detection wavelength was set at 210 nm. Good linearity was achieved in the range of 100.0-1000.0 µg mL-1 with r2 > 0.9993, and the limit of quantification was 32.22 µg mL-1. Accuracy measured at three concentration levels was in the range of 93.72-99.56%, while intra-day and inter-day precisions estimated using both OA standard and CGM samples were no more than 2.83 and 4.57% RSD, respectively. Finally, this method was applied to real CGM samples from various batches, revealing that the OA contents were between 88.13 and 100.83 µg mg-1. These results suggest that the current method can be applied as an efficient analytical method for quality control of CGM.

Micro-total envelope system with silicon nanowire separator for safe carcinogenic chemistry.

Exploration and expansion of the chemistries involving toxic or carcinogenic reagents are severely limited by the health hazards their presence poses. Here, we present a micro-total envelope system (µ-TES) and an automated total process for the generation of the carcinogenic reagent, its purification and its utilization for a desired synthesis that is totally enveloped from being exposed to the carcinogen. A unique microseparator is developed on the basis of SiNWs structure to replace the usual exposure-prone distillation in separating the generated reagent. Chloromethyl methyl ether chemistry is explored as a carcinogenic model in demonstrating the efficiency of the µ-TES that is fully automated so that feeding the ingredients for the generation is all it takes to produce the desired product. Syntheses taking days can be accomplished safely in minutes with excellent yields, which bodes well for elevating the carcinogenic chemistry to new unexplored dimensions.

Superamphiphobic Silicon-Nanowire-Embedded Microsystem and In-Contact Flow Performance of Gas and Liquid Streams.

Gas and liquid streams are invariably separated either by a solid wall or by a membrane for heat or mass transfer between the gas and liquid streams. Without the separating wall, the gas phase is present as bubbles in liquid or, in a microsystem, as gas plugs between slugs of liquid. Continuous and direct contact between the two moving streams of gas and liquid is quite an efficient way of achieving heat or mass transfer between the two phases. Here, we report a silicon nanowire built-in microsystem in which a liquid stream flows in contact with an underlying gas stream. The upper liquid stream does not penetrate into the lower gas stream due to the superamphiphobic nature of the silicon nanowires built into the bottom wall, thereby preserving the integrity of continuous gas and liquid streams, although they are flowing in contact. Due to the superamphiphobic nature of silicon nanowires, the microsystem provides the best possible interfacial mass transfer known to date between flowing gas and liquid phases, which can achieve excellent chemical performance in two-phase organic syntheses.

A monolithic and flexible fluoropolymer film microreactor for organic synthesis applications.

A photocurable and viscous fluoropolymer with chemical stability is a highly desirable material for fabrication of microchemical devices. Lack of a reliable fabrication method, however, limits actual applications for organic reactions. Herein, we report fabrication of a monolithic and flexible fluoropolymer film microreactor and its use as a new microfluidic platform. The fabrication involves facile soft lithography techniques that enable partial curing of thin laminates, which can be readily bonded by conformal contact without any external forces. We demonstrate fabrication of various functional channels (~300 µm thick) such as those embedded with either a herringbone micromixer pattern or a droplet generator. Organic reactions under strongly acidic and basic conditions can be carried out in this film microreactor even at elevated temperature with excellent reproducibility. In particular, the transparent film microreactor with good deformability could be wrapped around a light-emitting lamp for close contact with the light source for efficient photochemical reactions with visible light, which demonstrates easy integration with optical components for functional miniaturized systems.