The authors acknowledge the Swiss National Science Foundation (SNF) for financial support through project no. 200021_160174.

1. Master Mold Fabrication
<ol>
	<li>Perform the photolithographic fabrication of a 4 inch silicon master mold as described in detail previously19; the master mold used in this study has been fabricated using the same protocol. 
	NOTE: Microfluidic devices are typically fabricated through a multi-step process. The first step is the design of the microfluidic channel using a conventional drawing software. Then, high-resolution film photomasks containing the microfluidic network are produced with a feature precision of approximately 5 &#181;m. Next, master molds are fabricated on a 4-in silicon wafer through standard photolithography techniques. SU-8, a negative photoresist, is employed for the fabrication of the master molds in the current investigations. The height of SU-8 structures is defined to be 50 &#181;m in our devices. Finally, microfluidic devices are fabricated by directly casting a transparent polymer, normally polydimethylsiloxane (PDMS), against the master mold.</li>
</ol>
2. Fabrication of Single-layer Microfluidic Devices
NOTE: The protocol requires an oven operating at 70 &#176;C. The temperature of the oven should be stabilized at 70 &#176;C before initiating the fabrication protocol. Lower temperatures can lead to poorly bonded and non-functional devices.
<ol>
	<li>Place the fabricated master mold in a desiccator, equipped with a vacuum pump. Then, pour 100 &#181;L of chlorotrimethylsilane in a glass vial and place this inside the desiccator. 
	NOTE: CAUTION! Chlorotrimethylsilane is a corrosive, hazardous and toxic substance. Accordingly, all handling steps should be performed under a well-ventilated fume hood, and appropriate protective goggles, gloves and lab coat must be worn.</li>
	<li>Close the desiccator and put under vacuum (in this experiment, 51 mbar). Wait for at least 1 h to ensure the deposition of vaporized chlorotrimethylsilane on the surface of master mold. After 1 h, gently open the air valve of the desiccator to equilibrate it to atmospheric pressure and open it. 
	NOTE: CAUTION! As soon as the desiccator is opened, chlorotrimethylsilane vapor leaks out; do not breath directly above the desiccator and always perform the above in a ventilated fume hood.</li>
	<li>Carefully take out the silanized master mold by hand and close the desiccator. Store the master mold in a closed box (or inside a laminar flow hood) to avoid deposition of particulates on its surface. 
	NOTE: All proceeding steps must be performed under a laminar flow hood operating with a uniform air velocity.</li>
	<li>Prepare a mixture of PDMS pre-polymer and curing agent (10:0.9 in weight) in a disposable cup and mix vigorously with a plastic spatula. As a guide, use 20 g of elastomer and 1.8 g curing agent to fabricate four PDMS microfluidic devices approximately 5 mm thick.</li>
	<li>Place the cup containing the well-mixed PDMS in a desiccator under vacuum to degas and remove air bubbles. Once the PDMS is degassed, open the desiccator and remove the cup. 
	NOTE: In this experiment, it takes approximately 30 min at 51 mbar.</li>
	<li>Gently place four square frames (e.g., polytetrafluoroethylene (PTFE) frames with inner dimensions of 24 mm x 24 mm) on the master mold such that each forms a wall around a single patterned structure on the master mold.</li>
	<li>Pour the degassed PDMS into the frames and on top of the master mold until full. Place the master mold with the filled square frames in an oven at 70 &#176;C for 2 h.</li>
	<li>After 2 h, remove the master mold from the oven and leave the assembly to cool to room temperature.</li>
	<li>Manually peel off the structured PDMS slabs (or PDMS chips) and the square frames by carefully separating them from the master mold and slide the PDMS chips out of the square frames.</li>
	<li>Punch inlet and outlet holes using a 1.5 mm biopsy puncher at desired positions in the design, e.g., at the end of the microfluidic channels. Cut the extra pieces of PDMS and remove any debris from the surface of the structured PDMS chips using adhesive tape.</li>
	<li>Place the PDMS chips (with the open channels facing up) as well as the glass coverslips, into the chamber of a plasma generator and close the chamber.</li>
	<li>Put the plasma generator under vacuum (1.4 mbar here); switch the plasma generator on for 1 min.</li>
	<li>After 1 min, switch the plasma generator off, ventilate the chamber and take out the treated PDMS chips and glass coverslips. Bond the PDMS chips (from the side with structured channels) and glass coverslips together to close the channels; at this point the single-layer microfluidic devices are fabricated.</li>
	<li>Finally, place the bonded microfluidic devices in an oven at 70 &#176;C for at least 4 h to enhance the bonding between the PDMS and glass, substantially.</li>
</ol>
3. Preparation of the Microfluidic Set-up and Precursor Solutions
<ol>
	<li>Prepare a 0.040 M solution of BTCA in acetic acid. 
	NOTE: CAUTION! Acetic acid is a hazardous, corrosive and flammable compound and its vapor is extremely irritating to the eyes and respiratory system. Accordingly, handling steps must be performed in a fume hood. Also, the user must wear a protective lab coat, goggles and gloves.</li>
	<li>Prepare a 0.040 M solution of TAPB in acetic acid. 
	NOTE: The microfluidic device used in the current experiments has four inlet channels (Figure 1B and Figure 2).</li>
	<li>Load BTCA and TAPB solutions into two different syringes (5 mL syringes loaded with 3 mL solution here), place and secure the syringes onto a syringe pump and connect them to the two middle inlets of the fabricated microfluidic chip (one reagent per inlet) using PTFE tubing (0.8 mm inner diameter).</li>
	<li>Load two other syringes with pure acetic acid (here 5 mL syringes fully loaded), place and secure the syringes onto the syringe pump and connect them to the two side inlets of the microfluidic chip using the same type of PTFE tubing.</li>
	<li>Connect a sufficiently long PTFE tubing (in the current experiment, ~15 cm) to the outlet of the microfluidic chip. Use a computer-controlled syringe pump to motivate fluid flows as described in the following steps.</li>
</ol>
4. Continuous Synthesis of MF-COF Fibers
<ol>
	<li>Using the syringe pump introduce two sheath flows of acetic acid each at a flow rate of 100 &#181;L/min; the sheath flows are located on the outer side of the reagent flows (Figure 2).</li>
	<li>Wait for 1 min and inject the two reagents (TAPB and BTCA) via the two middle inlets (one reagent per inlet) each at a flow rate of 50 &#181;L/min. Wait for 1 min until stable flows are established.</li>
	<li>Observe the formation of yellow fibrous microstructures previously characterized as MF-COF by Fourier transform infrared (FT-IR) spectroscopy, elemental analysis and solid state 13C CP-MAS-NMR6; under these conditions the formation of MF-COF is not continuous.</li>
	<li>Increase the flow rate of TAPB and BTCA to 200 &#181;L/min and maintain the two sheath flows of acetic acid at 100 &#181;L/min. Now wait for 1 min until the flow stabilizes. Observe the formation of a highly-concentrated suspension of yellow MF-COF fibers, which ultimately leads to blockage of the outlet.</li>
	<li>As the chip and outlet tubing are now non-functional, use a new chip and prepare it for experiment according to steps 3.3-3.6.</li>
	<li>Introduce two sheath flows of acetic acid each at a flow rate of 100 &#181;L/min and wait for 1 min. Set the flows of TAPB and BTCA each to 100 &#181;L/min and observe the formation of a continuous yellow MF-COF fiber.</li>
	<li>Place the outlet of the tubing in a Petri dish containing acetic acid. For example, place 10 mL of acetic acid in a round glass Petri dish (60 mm in diameter). Once the synthesized fiber exits the tube located at the outlet of the microfluidic device, move the tube over a surface to facilitate the exit of the continuous MF-COF fiber.</li>
</ol>
5. Direct Printing of 2D and 3D MF-COF Structures
NOTE: As the synthetized fiber may not be completely homogeneous, the deposition speed must be adjusted to ensure continuous printing.
<ol>
	<li>Prepare the microfluidic set-up as described in section 3 and inject all four solutions each at a flow rate of 100 &#181;L/min.</li>
	<li>Wait for 1 min until the flows are stabilized and the synthesized MF-COF fiber exits the tube located at the outlet of the microfluidic device. Prepare a clean substrate next to the exit of the tube located at the outlet of the microfluidic device for direct printing of MF-COF fibers. 
	NOTE: In our investigations, 24 mm x 76 mm glass coverslips were employed for all printing experiments.</li>
	<li>Hold the tube connected to the outlet of the microfluidic device so that its end is a few millimeters above the glass coverslip. Slowly move the tube over the glass coverslip to facilitate the exit of the MF-COF fiber and avoid aggregation.</li>
	<li>Once the flows are stabilized, slowly lift the tube located at the outlet of the microfluidic device approximately 2-3 cm away from the glass coverslip to observe a freestanding and stable MF-COF fiber.</li>
	<li>To continue printing, bring the outlet of the tube back towards the glass coverslip and manually move the tube on the surface to draw the desired 2D or 3D MF-COF structure.</li>
</ol>

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The authors have nothing to disclose.

The microfluidic-based synthetic method reported here provides a novel and simple approach for direct printing of COF materials on surfaces. Synthesis is performed using a single-layer microfluidic device, comprised of a microfluidic PDMS chip bonded to a glass coverslip. The fabrication of the microfluidic device can be achieved through conventional casting of PDMS against a silicon master mold and subsequently bonding the PDMS with the imprinted microchannels against a glass coverslip.
For t...

Covalent organic frameworks (COFs) are a well-established class of porous and crystalline material in which the organic building blocks are firmly held together by covalent bonds1,2,3,4,5. COFs are typically assembled following supramolecular chemistry principles, where the constituent molecular building blocks are selectively reacted to define a final and predetermined porous assembly. Such an approach allows the synthesis of materials with controlled and ordered structure (e.g.,with defined pore dimensions) and composition3,6,7,8. Compared to other porous materials, COFs are unique since they are comprised of light elements (C, H, B, N and O) and have tunable porosities1,5. Inspired by these unique and intrinsic characteristics, COFs have been assessed for potential application in chemical separations9, gas storage10and catalysis11, sensors12, optoelectronics13, clean energy technologies14 and electrochemical energy devices15.
To date, the vast majority of methods used for the preparation of COF materials are based on solvothermal self-condensation and co-condensation reactions, where high temperatures and pressures are the standard. Although COFs are thermally robust, they commonly suffer from limited processability, i.e., COFs are usually insoluble and unprocessable crystalline powders, and this significantly limits their use in a range of potential and practical applications2,6,8,16,17. Despite the remarkable progress made in COF synthesis, a major challenge in the field is to develop a method enabling the preparation of COFs in appropriate reaction conditions (e.g., temperature and pressure), which can then facilitate their processability on surfaces.
Recently, studies have shown that Shiff-base chemistry can be used to synthesize an imine-based COF at room temperature. The COF produced, named RT-COF-1, forms due to the fast and efficient reaction between 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 1,3,5-benzenetricarbaldehyde (BTCA)17 (Figure 1A). The efficacy of this synthetic method was demonstrated by the direct printing of micron and submicron patterns of RT-COF-1 on both rigid and flexible surfaces using lithography or inkjet printing techniques. More recently, and making use of microfluidics, we have demonstrated an effective approach for the continuous synthesis of fibers of the same imine-based COF hereafter called MF-COF6. Unlike other reported synthetic approaches for the generation of COFs18, this microfluidic-based synthetic method enabled the rapid synthesis of MF-COF fibers at ambient temperatures and pressures within a few seconds. Furthermore, and owing to the mechanical stability of the synthesized MF-COF fibers, we have demonstrated how such microfluidic-based method can enable the direct printing of 2D and 3D structures on surfaces. Herein, we demonstrate that this method can be used to draw COF structures on various surfaces having different chemical and physical properties. We believe that this novel method opens new avenues for the well-controlled patterning and direct printing of COFs in different orientations and on various surfaces.

<table><tbody><tr><td>High resolution film masks</td><td>Microlitho, UK</td><td>-</td><td>Features down to 5um</td></tr><tr><td>Silicon wafers</td><td>Silicon Materials Inc., Germany</td><td>4&quot; Silicon Wafers</td><td>Front surface: polished, back surface: etched</td></tr><tr><td>Silicone Elastomer KIT (PDMS)</td><td>Dow Corning, USA</td><td>Sylgard 184</td><td>-</td></tr><tr><td>Chlorotrimethylsilane</td><td>Sigma-Aldrich, Switzerland</td><td>386529</td><td>&amp;ge;97%, CAUTION: Handle it only under fume hood.</td></tr><tr><td>Biopsy puncher</td><td>Miltex GmBH, Germany</td><td>33-31A-P/25</td><td>1.5 mm</td></tr><tr><td>Glass coverslip</td><td>Menzel-Glaser, Germany</td><td>BB024040SC</td><td>24 mm &amp;times; 40 mm, #5</td></tr><tr><td>Plasma generator instrument</td><td>Diener</td><td>Zepto B</td><td>Frequency: 40 kHz and plasma generator power: 0-30 W</td></tr><tr><td>PTFE tubing</td><td>PKM SA, Switzerland</td><td>AWG-TFS-XXX</td><td>AWG 20TFS, roll of 100 m</td></tr><tr><td>neMESYS Syringe Pumps</td><td>Cetoni GmbH, Germany</td><td>Low Pressure (290N)</td><td>-</td></tr><tr><td>Disposable Cup</td><td>Semadeni, Switzerland</td><td>8323</td><td>PS, 200 ml</td></tr><tr><td>Plastic Spatula</td><td>Semadeni, Switzerland</td><td>3340</td><td>L &amp;times; W : 135 mm x 14 mm</td></tr><tr><td>Disposable Scalpels</td><td>B. Braun, Switzerland</td><td>233-5320</td><td>Nr. 20</td></tr><tr><td>Disposable Syringes</td><td>VWR, Switzerland</td><td>613-3951</td><td>5 ml, Discardit II</td></tr><tr><td>Acetic Acid</td><td>Sigma-Aldrich, Switzerland</td><td>695092-500</td><td>&gt;=99.7%, CAUTION: Handle it only under fume hood.</td></tr><tr><td>1,3,5-benzenetricarbaldehyde</td><td>Aldrich-Fine Chemicals</td><td>753491</td><td>97%</td></tr><tr><td>1,3,5-Tris(4-aminophenyl)benzene</td><td>Tokyo Chemical Industry</td><td>T2728-5G</td><td>&gt;93.0%</td></tr></tbody></table>

microfluidic-based synthesis of covalent organic frameworks (cofs): a tool for continuous production of cof fibers and direct printing on a surface

Covalent Organic Frameworks (COFs) are a class of porous covalent materials which are frequently synthesized as unprocessable crystalline powders. The first COF was reported in 2005 with much effort centered on the establishment of new synthetic routes for its preparation. To date, most available synthetic methods for COF synthesis are based on bulk mixing under solvothermal conditions. Therefore, there is increasing interest in developing systematic protocols for COF synthesis that provide for fine control over reaction conditions and improve COF processability on surfaces, which is essential for their use in practical applications. Herein, we present a novel microfluidic-based method for COF synthesis where the reaction between two constituent building blocks, 1,3,5-benzenetricarbaldehyde (BTCA) and 1,3,5-tris(4-aminophenyl)benzene (TAPB), takes place under controlled diffusion conditions and at room temperature. Using such an approach yields sponge-like, crystalline fibers of a COF material, hereafter called MF-COF. The mechanical properties of MF-COF and the dynamic nature of the approach allow the continuous production of MF-COF fibers and their direct printing onto surfaces. The general method opens new potential applications requiring advanced printing of 2D or 3D COF structures on flexible or rigid surfaces.

The microfluidic device used in our investigations is fabricated using conventional PDMS replica molding20 and incorporates four microfluidic inlet channels that merge into a main microchannel. The final microfluidic device consists of a structured PDMS layer and a glass coverslip used to close the imprinted microchannels, as shown in Figure 1B.
<img alt="Figure 1" class="xfi...

Watch this Scientific Journal Video about Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface at JoVE.com

Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

We present a novel microfluidic-based method for synthesis of covalent organic frameworks (COFs). We demonstrate how this approach can be used to produce continuous COF fibers, and also 2D or 3D COF structures on surfaces.

Microfluidic-based Synthesis of Covalent Organic Frameworks (COFs): A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

Covalent Organic Frameworks (COFs) are a class of porous covalent materials which are frequently synthesized as unprocessable crystalline powders. The ...

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13.3K Views.  ETH Zurich.  Wij presenteren een nieuwe microfluïdische methode voor synthese van covalente organische kaders (COF's). We tonen aan hoe deze aanpak kan worden gebruikt om continue COF-vezels te produceren, en ook op 2D- of 3D-COF-structuren op oppervlakken. 

Video: Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

Manufacturing of Three-dimensionally Microstructured Nanocomposites through Microfluidic Infiltration

Microstructured composite beams reinforced with complex three-dimensionally (3D) patterned nanocomposite microfilaments are fabricated via nanocomposite in&#64257;ltration of 3D interconnected microfluidic networks. The manufacturing of the reinforced beams begins with the fabrication of microfluidic networks, which involves layer-by-layer deposition of fugitive ink filaments using a dispensing robot, filling the empty space between filaments using a low viscosity resin, curing the resin and finally removing the ink.&#160;Self-supported 3D structures with other geometries and many layers (e.g.&#160;a few hundreds layers) could be built using this method. The resulting tubular micro&#64258;uidic networks are then infiltrated with thermosetting nanocomposite suspensions containing nanofillers (e.g.&#160;single-walled carbon nanotubes), and subsequently cured. The infiltration is done by applying a pressure gradient between two ends of the empty network (either by applying a vacuum or vacuum-assisted microinjection). Prior to the infiltration, the nanocomposite suspensions are prepared by dispersing nanofillers into polymer matrices using ultrasonication and three-roll mixing methods. The nanocomposites (i.e.&#160;materials infiltrated) are then solidified under UV exposure/heat cure, resulting in a 3D-reinforced composite structure. The technique presented here enables the design of functional nanocomposite macroscopic products for microengineering applications such as actuators and sensors.

Three-dimensional (3D) microstructured composite beams are fabricated through the directed and localized infiltration of nanocomposites into 3D porous microfluidic networks. The flexibility of this manufacturing method enables the utilization of different thermosetting materials and nanofillers in order to achieve a variety of functional 3D reinforced nanocomposite macroscopic products.

Microstructured composite beams reinforced with complex three-dimensionally (3D) patterned nanocomposite microfilaments are fabricated via nanocomposite ...

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

Microfluidic Pneumatic Cages: A Novel Approach for In-chip Crystal Trapping, Manipulation and Controlled Chemical Treatment

The precise localization and controlled chemical treatment of structures on a surface are significant challenges for common laboratory technologies. Herein, we introduce a microfluidic-based technology, employing a double-layer microfluidic device, which can trap and localize in situ and ex situ synthesized structures on microfluidic channel surfaces. Crucially, we show how such a device can be used to conduct controlled chemical reactions onto on-chip trapped structures and we demonstrate how the synthetic pathway of a crystalline molecular material and its positioning inside a microfluidic channel can be precisely modified with this technology. This approach provides new opportunities for the controlled assembly of structures on surface and for their subsequent treatment.

Herein, we describe the fabrication and operation of a double-layer microfluidic system made of polydimethylsiloxane (PDMS). We demonstrate the potential of this device for trapping, directing the coordination pathway of a crystalline molecular material and controlling chemical reactions onto on-chip trapped structures.

The precise localization and controlled chemical treatment of structures on a surface are significant challenges for common laboratory technologies. ...

Millifluidics for Chemical Synthesis and Time-resolved Mechanistic Studies

Procedures utilizing millifluidic devices for chemical synthesis and time-resolved mechanistic studies are described by taking three examples. In the first, synthesis of ultra-small copper nanoclusters is described. The second example provides their utility for investigating time resolved kinetics of chemical reactions by analyzing gold nanoparticle formation using in situ X-ray absorption spectroscopy. The final example demonstrates continuous flow catalysis of reactions inside millifluidic channel coated with nanostructured catalyst.

Millifluidic devices are utilized for controlled synthesis of nanomaterials, time-resolved analysis of reaction mechanisms and continuous flow catalysis.

Procedures utilizing millifluidic devices for chemical synthesis and time-resolved mechanistic studies are described by taking three examples. In the ...

Bioengineering

Microfluidic Fabrication of Polymeric and Biohybrid Fibers with Predesigned Size and Shape

A &#8220;sheath&#8221; fluid passing through a microfluidic channel at low Reynolds number can be directed around another &#8220;core&#8221; stream and used to dictate the shape as well as the diameter of a core stream.&#160;Grooves in the top and bottom of a microfluidic channel were designed to direct the sheath fluid and shape the core fluid.&#160;By matching the viscosity and hydrophilicity of the sheath and core fluids, the interfacial effects are minimized and complex fluid shapes can be formed.&#160;Controlling the relative flow rates of the sheath and core fluids determines the cross-sectional area of the core fluid.&#160;Fibers have been produced with sizes ranging from 300 nm to ~1 mm, and fiber cross-sections can be round, flat, square, or complex as in the case with double anchor fibers. Polymerization of the core fluid downstream from the shaping region solidifies the fibers.&#160;Photoinitiated click chemistries are well suited for rapid polymerization of the core fluid by irradiation with ultraviolet light.&#160;Fibers with a wide variety of shapes have been produced from a list of polymers including liquid crystals, poly(methylmethacrylate), thiol-ene and thiol-yne resins, polyethylene glycol, and hydrogel derivatives. Minimal shear during the shaping process and mild polymerization conditions also makes the fabrication process well suited for encapsulation of cells and other biological components.

Two adjacent fluids passing through a grooved microfluidic channel can be directed to form a sheath around a prepolymer core; thereby&#160;determining both shape and cross-section. Photoinitiated polymerization, such as thiol click chemistry, is well suited for rapidly solidifying the core fluid into a microfiber with predetermined size and shape.

A &#8220;sheath&#8221; fluid passing through a microfluidic channel at low Reynolds number can be directed around another &#8220;core&#8221; stream and ...

Continuous Flow Chemistry: Reaction of Diphenyldiazomethane with p-Nitrobenzoic Acid

Continuous flow technology has been identified as instrumental for its environmental and economic advantages leveraging superior mixing, heat transfer and cost savings through the &#34;scaling out&#34; strategy as opposed to the traditional &#34;scaling up&#34;. Herein, we report the reaction of diphenyldiazomethane with p-nitrobenzoic acid in both batch and flow modes. To effectively transfer the reaction from batch to flow mode, it is essential to first conduct the reaction in batch. As a consequence, the reaction of diphenyldiazomethane was first studied in batch as a function of temperature, reaction time, and concentration to obtain kinetic information and process parameters. The glass flow reactor set-up is described and combines two types of reaction modules with &#34;mixing&#34; and &#34;linear&#34; microstructures. Finally, the reaction of diphenyldiazomethane with p-nitrobenzoic acid was successfully conducted in the flow reactor, with up to 95% conversion of the diphenyldiazomethane in 11 min. This proof of concept reaction aims to provide insight for scientists to consider flow technology&#39;s competitiveness, sustainability, and versatility in their research.

Continuous Flow Chemistry: Reaction of Diphenyldiazomethane with p-Nitrobenzoic Acid

Flow chemistry carries environmental and economic advantages by leveraging superior mixing, heat transfer and cost benefits. Herein, we provide a blueprint to transfer chemical processes from batch to flow mode. The reaction of diphenyldiazomethane (DDM) with p-nitrobenzoic acid, conducted in batch and flow, was chosen for proof of concept.

Continuous flow technology has been identified as instrumental for its environmental and economic advantages leveraging superior mixing, heat transfer and ...

Electrophoretic Crystallization of Ultrathin High-performance Metal-organic Framework Membranes

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and non-porous supports (polymer, ceramic, metal, carbon, and graphene). We developed a novel crystallization technique, which is termed the ENACT approach: the electrophoretic nuclei assembly for the crystallization of highly intergrown thin films (ENACT). This approach allows for a high density of heterogeneous nucleation of MOFs on a chosen substrate via the electrophoretic deposition (EPD) directly from the precursor sol. The growth of well-packed MOF nuclei leads to a highly intergrown polycrystalline MOF film. We show that this simple approach can be used for the synthesis of thin, intergrown zeolite imidazole framework (ZIF)-7 and ZIF-8 films. The resulting 500 nm-thick ZIF-8 membranes show a considerably high H2 permeance (8.3 x 10-6 mol m-2 s-1 Pa-1) and ideal gas selectivities (7.3 for H2/CO2, 15.5 for H2/N2, 16.2 for H2/CH4, and 2655 for H2/C3H8). An attractive performance for C3H6/C3H8 separation is also achieved (a C3H6 permeance of 9.9 x 10-8 mol m-2 s-1 Pa-1 and a C3H6/C3H8 ideal selectivity of 31.6 at 25 &#176;C). Overall, the ENACT process, owing to its simplicity, can be extended to synthesize intergrown thin films of a wide range of nanoporous crystalline materials.

A simple, reproducible, and versatile approach for the synthesis of intergrown, polycrystalline metal-organic framework membranes on a wide range of unmodified porous and non-porous supports is presented.

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and ...

Microfluidic Fabrication Techniques for High-Pressure Testing of Microscale Supercritical CO2 Foam Transport in Fractured Unconventional Reservoirs

Pressure limitations of many microfluidic platforms have been a significant challenge in microfluidic experimental studies of fractured media. As a result, these platforms have not been fully exploited for direct observation of high-pressure transport in fractures. This work introduces microfluidic platforms that enable direct observation of multiphase flow in devices featuring surrogate permeable media and fractured systems. Such platforms provide a pathway to address important and timely questions such as those related to CO2 capture, utilization and storage. This work provides a detailed description of the fabrication techniques and an experimental setup that may serve to analyze the behavior of supercritical CO2 (scCO2) foam, its structure and stability. Such studies provide important insights regarding enhanced oil recovery processes and the role of hydraulic fractures in resource recovery from unconventional reservoirs. This work presents a comparative study of microfluidic devices developed using two different techniques: photolithography/wet-etching/thermal-bonding versus Selective Laser-induced Etching. Both techniques result in devices that are chemically and physically resistant and tolerant of high pressure and temperature conditions that correspond to subsurface systems of interest. Both techniques provide pathways to high-precision etched microchannels and capable lab-on-chip devices. Photolithography/wet-etching, however, enables fabrication of complex channel networks with complex geometries, which would be a challenging task for laser etching techniques. This work summarizes a step-by-step photolithography, wet-etching and glass thermal-bonding protocol and, presents representative observations of foam transport with relevance to oil recovery from unconventional tight and shale formations. Finally, this work describes the use of a high-resolution monochromatic sensor to observe scCO2 foam behavior where the entirety of the permeable medium is observed simultaneously while preserving the resolution needed to resolve features as small as 10 &#181;m.

Microfluidic Fabrication Techniques for High-Pressure Testing of Microscale Supercritical CO2 Foam Transport in Fractured Unconventional Reservoirs

This paper describes a protocol along with a comparative study of two microfluidic fabrication techniques, namely photolithography/wet-etching/thermal-bonding and Selective Laser-induced Etching (SLE), that are suitable for high-pressure conditions. These techniques constitute enabling platforms for direct observation of fluid flow in surrogate permeable media and fractured systems under reservoir conditions.

Pressure limitations of many microfluidic platforms have been a significant challenge in microfluidic experimental studies of fractured media. As a ...

Engineering

Multi-step Variable Height Photolithography for Valved Multilayer Microfluidic Devices

Microfluidic systems have enabled powerful new approaches to high-throughput biochemical and biological analysis. However, there remains a barrier to entry for non-specialists who would benefit greatly from the ability to develop their own microfluidic devices to address research questions. Particularly lacking has been the open dissemination of protocols related to photolithography, a key step in the development of a replica mold for the manufacture of polydimethylsiloxane (PDMS) devices. While the fabrication of single height silicon masters has been explored extensively in literature, fabrication steps for more complicated photolithography features necessary for many interesting device functionalities (such as feature rounding to make valve structures, multi-height single-mold patterning, or high aspect ratio definition) are often not explicitly outlined. 
Here, we provide a complete protocol for making multilayer microfluidic devices with valves and complex multi-height geometries, tunable for any application. These fabrication procedures are presented in the context of a microfluidic hydrogel bead synthesizer and demonstrate the production of droplets containing polyethylene glycol (PEG diacrylate) and a photoinitiator that can be polymerized into solid beads. This protocol and accompanying discussion provide a foundation of design principles and fabrication methods that enables development of a wide variety of microfluidic devices. The details included here should allow non-specialists to design and fabricate novel devices, thereby bringing a host of recently developed technologies to their most exciting applications in biological laboratories.

Multilayer microfluidic devices often involve the fabrication of master molds with complex geometries for functionality. This article presents a complete protocol for multi-step photolithography with valves and variable height features tunable to any application. As a demonstration, we fabricate a microfluidic droplet generator capable of producing hydrogel beads.

Microfluidic systems have enabled powerful new approaches to high-throughput biochemical and biological analysis. However, there remains a barrier to ...

Synthesis of Single-Crystalline Core-Shell Metal-Organic Frameworks

Because of their designability and unprecedented synergistic effects, core-shell metal-organic frameworks (MOFs) have been actively examined recently. However, the synthesis of single-crystalline core-shell MOFs is very challenging, and thus a limited number of examples have been reported. Here, we suggest a method of synthesizing single-crystalline HKUST-1@MOF-5 core-shells, which is HKUST-1 at the center of MOF-5. Through the computational algorithm, this pair of MOFs was predicted to have the matched lattice parameters and chemical connection points at the interface. To construct the core-shell structure, we prepared the octahedral- and cubic-shaped HKUST-1 crystals as a core MOF, in which the (111) and (001) facets were mainly exposed, respectively. Via the sequential reaction, the MOF-5 shell was well-grown on the exposed surface, showing a seamless connect interface, which resulted in the successful synthesis of single-crystalline HKUST-1@MOF-5. Their pure phase formation was proved by optical microscopic images and powder X-ray diffraction (PXRD) patterns. This method presents the potential of and insights into the single-crystalline core-shell synthesis with different kinds of MOFs.

Here, we demonstrate a protocol for the two-step synthesis of single-crystalline core-shells using a non-isostructural metal-organic framework (MOF) pair, HKUST-1 and MOF-5, which have well-matched crystal lattices.

Because of their designability and unprecedented synergistic effects, core-shell metal-organic frameworks (MOFs) have been actively examined recently. ...

Microfluidic-based Synthesis of Covalent Organic Frameworks (COFs): A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

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