The authors from the University of Wyoming gratefully acknowledge support as part of the Center for Mechanistic Control of Water-Hydrocarbon-Rock Interactions in Unconventional and Tight Oil Formations (CMC-UF), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science under DOE (BES) Award DE-SC0019165. The authors from the University of Kansas would like to acknowledge the National Science Foundation EPSCoR Research Infrastructure Improvement Program: Track -2 Focused EPSCoR Collaboration award (OIA- 1632892) for funding of this project. Authors also extend their appreciation to Jindi Sun from the Chemical Engineering Department, University of Wyoming for her generous help in instrument training. SAA thanks Kyle Winkelman from the University of Wyoming for his help with constructing the imaging and UV stands. Last but not the least, the authors gratefully acknowledge John Wasserbauer from microGlass, LLC for useful discussions regarding the SLE technique.

CAUTION: This protocol involves handling a high-pressure setup, a high-temperature furnace, hazardous chemicals, and UV light. Please read all relevant material safety data sheets carefully and follow chemical safety guidelines. Review pressure testing (hydrostatic and pneumatic) safety guidelines including required training, safe operation of all equipment, associated hazards, emergency contacts, etc. before starting the injection process.
1. Design geometrical patterns
<ol>
	<li>Design a photomask comprising geometrical features and flow pathways of interest (Figure 1, Supplementary File 1: Figure S1).</li>
	<li>Define the bounding box (surface area of the device) to identify the area of the substrate and confine the design to the dimensions of the desired medium.</li>
	<li>Design inlet/outlet ports. Choose port dimensions (e.g., 4 mm in diameter in this case) to achieve a relatively uniform distribution of foam prior to entering the medium (Figure 1).</li>
	<li>Prepare a photomask of the designed geometrical pattern by printing the design onto a sheet of transparent film or a glass substrate.
	<ol>
		<li>Extrude the two-dimensional design to the third dimension and incorporate inlet and outlet ports (for use in SLE). 
		NOTE: The SLE technique requires a three-dimensional drawing (Figure 2).</li>
	</ol>
	</li>
</ol>
2. Transfer the geometric patterns to the glass substrate using photolithography
NOTE: Etchants and piranha solutions must be handled with extreme care. Use of personal protective equipment including facepiece reusable respirator, goggles, gloves and use of acid/corrosion resistant tweezers (Table of Materials) is recommended.
<ol>
	<li>Prepare the solutions needed in the wet-etching process by following these steps (also see the electronic supporting information provided as Supplementary File 1).
	<ol>
		<li>Pour an adequate amount of chrome etchant solution in a beaker such that the substrate can be submerged in the etchant. Heat up the fluid to approximately 40 &#176;C.</li>
		<li>Prepare a solution of developer (Table of Materials) in deionized water (DI water) with a volumetric ratio of 1:8 such that the substrate is able to be fully submerge in the mixture.</li>
	</ol>
	</li>
	<li>Imprint the geometrical pattern on a borosilicate substrate coated with a layer of chromium and a layer of photoresist using UV irradiation.
	<ol>
		<li>Using gloved hands, place the mask (glass substrate or the transparent film bearing the geometrical pattern) directly on the side of the borosilicate substrate that is covered with chrome and photoresist.</li>
		<li>Place the photomask and substrate combination under the UV light with the photomask facing the source. 
		NOTE: This work uses UV light with a wavelength of 365 nm (to match the peak sensitivity of the photoresist) and at an average intensity of 4.95 mW/cm2.</li>
		<li>Transfer the geometrical pattern into the layer of photoresist by exposing the stack of the substrate and the mask to UV light. 
		NOTE: Optimum exposure time is a function of the thickness of the photoresist layer and the strength of UV radiation. Photoresist is sensitive to light and the entire process of imprinting the pattern must be performed in a dark room equipped with yellow lighting.</li>
	</ol>
	</li>
	<li>Develop the photoresist.
	<ol>
		<li>Remove the photomask and substrate stack from the UV stage using gloved hands.</li>
		<li>Remove the photomask and submerge the substrate in the developer solution for approximately 40 s, thereby transferring the pattern to the photoresist.</li>
		<li>Cascade-rinse the substrate by flowing DI water from the top of the substrate and over all its surfaces a minimum of three times and allow the substrate to dry.</li>
	</ol>
	</li>
	<li>Etch the pattern in the chrome layer.
	<ol>
		<li>Submerge the substrate in a chrome etchant heated to about 40 &#176;C for approximately 40 s, thereby transferring the pattern from the photoresist to the chrome layer.</li>
		<li>Remove the substrate from the solution, cascade-rinse the substrate using DI water and allow it to dry.</li>
	</ol>
	</li>
	<li>Etch the pattern in the borosilicate substrate. 
	NOTE: A buffered etchant (Table of Materials) is used to transfer the geometrical pattern to the glass substrate. Prior to the use of the buffered etchant, the backside of the substrate is coated with a layer of photoresist to shield it from the etchant. The thickness of this protective layer is immaterial to the overall fabrication process.
	<ol>
		<li>Using a brush, apply several layers of hexamethyldisilazane (HMDS) on the uncovered face of the substrate and allow it to dry. 
		NOTE: HMDS helps promote adhesion of photoresist to the surface of the borosilicate substrate.</li>
		<li>Apply one layer of photoresist on top of the primer. Place the substrate in an oven at 60&#8210;90 &#176;C for 30&#8211;40 min.</li>
		<li>Pour an adequate amount of the etchant into a plastic container and fully submerge the substrate in the etchant. 
		NOTE: The etching rate is influenced by the concentration, temperature and duration of exposure. The buffered etchant used in this work etches an average of 1&#8210;10 nm/min.</li>
		<li>Leave the patterned substrate in the etchant solution for a predetermined amount of time based on the desired channel depths. 
		NOTE: Etching time may be reduced by intermittent bath sonication of the solution.</li>
		<li>Remove the substrate from the etchant using a solvent-resistant pair of tweezers and cascade-rinse the substrate using DI water.</li>
		<li>Characterize the etched features on the substrate to ensure desired depths have been achieved. 
		NOTE: This characterization may be done using a laser scanning confocal microscope (Figure 3). In this work, a 10x magnification is used for data acquisition. Once channel depths are satisfactory, move to the cleaning and bonding stage.</li>
	</ol>
	</li>
</ol>
3. Clean and bond
<ol>
	<li>Remove photoresist and chrome layers.
	<ol>
		<li>Remove the photoresist from the substrate by exposing the substrate to an organic solvent, such as N-Methyl-2-pyrrolidone (NMP) solution heated using a hot plate under a hood to approximately 65 &#176;C for approximately 30 min.</li>
		<li>Cascade-rinse the substrate with acetone (ACS grade), followed by ethanol (ACS grade) and DI water.</li>
		<li>Place the cleaned substrate in chrome etchant heated using a hot plate under a hood to approximately 40 &#176;C for about 1 min, thus removing the chrome layer from the substrate.</li>
		<li>Once the substrate is free from chrome and photoresist, characterize the channel depths using laser scanning confocal microscopy. 
		NOTE: This work uses a 10x magnification for data acquisition (Figure 4).</li>
	</ol>
	</li>
	<li>Prepare the cover plate and the etched substrate for bonding.
	<ol>
		<li>Mark the positions of the inlet/out holes on a blank borosilicate substrate (cover plate) by aligning the cover plate against the etched substrate.</li>
		<li>Blast through-holes in the marked locations using a micro abrasive sandblaster and 50 &#181;m aluminum-oxide micro sandblasting media. 
		NOTE: Alternatively, the ports may be created using a mechanical drill.</li>
		<li>Cascade rinse both the etched substrate and the cover plate with DI water.</li>
		<li>Perform an RCA wafer cleaning procedure to remove contaminants prior to bonding using standard technique. Perform the wafer cleaning steps under a hood due to the volatility of the solutions involved in the process.</li>
		<li>Bring a 1:4 by volume H2O2:H2SO4 piranha solution to a boil and submerge the substrate and the cover plate in the solution for 10 min under a hood.</li>
		<li>Cascade rinse the substrate and the cover plate with DI water.</li>
		<li>Submerge the substrate and the cover plate in the buffered etchant for 30&#8211;40 s.</li>
		<li>Cascade rinse the substrate and the cover plate with DI water.</li>
		<li>Submerge the substrate and the cover plate for 10 min in a 6:1:1 by volume DI water:H2O2:HCl solution that is heated to approximately 75 &#176;C. 
		NOTE: Etching and bonding are preferably performed in a cleanroom. If a cleanroom is not available, performing the following steps in a dust-free environment is recommended. In this work, steps 3.2.9&#8211;3.2.12 are performed in a glovebox to minimize the possibility of contamination of the substrates.</li>
		<li>Press the substrate and the cover plate tightly against each other while submerged.</li>
		<li>Remove the substrate and the cover plate from DI water:H2O2:HCl solution. Cascade rinse with DI water and submerge in DI water.</li>
		<li>Make sure the substrate and the cover plate are firmly attached together and carefully remove the two while pressed against each other from DI water.</li>
	</ol>
	</li>
	<li>Bond the substrates thermally.
	<ol>
		<li>Place the stacked substrates (the etched substrate and the cover plate) between two smooth, 1.52 cm-thick, glass-ceramic plates for bonding.</li>
		<li>Place the glass-ceramic plates between two metallic plates made of Alloy X (Table of Materials), which is able to withstand the required temperatures without significant distortion.</li>
		<li>Center the glass wafers in the ceramic-metallic holder. 
		NOTE: This work uses glass-ceramic plates that are 10 cm x 10 cm x 1.52 cm in thickness. The stacked setup is secured using 1/4&#8221; bolts and nuts (Figure 5).</li>
		<li>Hand-tighten the nuts and place the holder in a vacuum chamber for 60 min at approximately 100 &#176;C.</li>
		<li>Remove the holder from the chamber and carefully tighten the nuts using approximately 10 lb-in of torque.</li>
		<li>Place the holder inside a furnace and execute the following heating program. Raise the temperature at 1 &#176;C/min up to 660 &#176;C; keep the temperature constant at 660 &#176;C for 6 h followed by a cooling step at approximately 1 &#176;C/min back down to room temperature.</li>
		<li>Remove the thermally bonded microfluidic device, rinse it with DI water, place it in HCl (12.1 M) and bath-sonicate (40 kHz at 100 W of power) the solution for one hour (Figure 6).</li>
	</ol>
	</li>
</ol>
4. Fabricate laser-etched glass microfluidic devices
NOTE: Device fabrication was performed by a third-party glass 3D printing service (Table of Materials) via an SLE process and using a fused silica substrate as the precursor.
<ol>
	<li>Write the desired pattern in a fused silica substrate using a linearly polarized laser beam oriented perpendicular to the stage generated via a femtosecond laser source with a pulse duration of 0.5 ns, a repetition rate of 50 kHz, pulse energy of 400 nJ, and a wavelength of 1.06 &#956;m.</li>
	<li>Remove the glass from the written pattern inside the fused silica substrate using a KOH solution (32 wt%) at 85 &#176;C with ultrasound sonication (Figure 7).</li>
</ol>
5. Perform high-pressure testing
<ol>
	<li>Saturate the microfluidic device with the resident fluid (e.g., DI water, surfactant solution, oil, etc. depending on the type of experiment) using a syringe pump.</li>
	<li>Prepare foam-generating fluids and related instruments.
	<ol>
		<li>Prepare the brine solution (resident fluid) with the desired salinity and dissolve the surfactant (such as lauramidopropyl betaine and alpha-olefin-sulfonate) with the desired concentration (according to surfactant&#8217;s critical micelle concentration) in the brine.</li>
		<li>Fill the tanks of the CO2 and water pumps with adequate amounts of fluids per the experiment at room temperature.</li>
		<li>Fill the brine accumulator and flow lines with the surfactant solution using a syringe. This work uses an accumulator with a capacity of 40 mL.</li>
		<li>Rinse the brine line with the brine solution.</li>
		<li>Rinse the line connecting the accumulator to the device and the outlet lines with the resident fluid (the brine solution in this case).</li>
		<li>Place the saturated microfluidic device in a pressure-resistant holder and connect the inlet/outlet ports to the appropriate lines using 0.010&#8221; inner diameter tubing (Figure 8, Supplementary File 1: Figure S5).</li>
		<li>Increase the temperature of the circulating bath, which controls the temperature of the brine and CO2 lines, to the desired temperature (e.g., 40 &#176;C here (Figure 9)).</li>
		<li>Check all the lines to ensure the integrity of the setup prior to injection.</li>
	</ol>
	</li>
	<li>Generate the foam.
	<ol>
		<li>Begin injecting the brine at a rate of 0.5 mL/min and check the flow of surfactant solution into the device and the backpressure line.</li>
		<li>Increase the backpressure and brine-pump pressure simultaneously in gradual steps (~ 0.006 MPa/s) while maintaining continuous flow from the outlet of the backpressure regulator (BPR). Increase the pressure up to ~7.38 MPa (minimum required scCO2 pressure) and stop the pumps.</li>
		<li>Increase the CO2 line pressure up to a pressure above 7.38 MPa (minimum scCO2 pressure).</li>
		<li>Open the CO2 valve and allow the scCO2 mixed with the high-pressure surfactant solution to flow through an inline mixer to generate foam.</li>
		<li>Wait until flow is fully developed inside the device and the channels are saturated. Monitor the outlet for the onset of foam generation. 
		NOTE: Auxiliary ports may be used to help pre-saturate the medium fully with the resident fluid (Figure 1). Inconsistencies in the rate of pressure build-up and sudden increases in BPR may lead to breakage (Figure 10). Fluid pressures and backpressure must be raised gradually to minimize the risk of damage to the device.</li>
	</ol>
	</li>
	<li>Perform real-time imaging and data analysis.
	<ol>
		<li>Turn on the camera to capture detailed images of flow inside the channels. This work uses a camera featuring a 60 megapixel, monochromatic, full-frame sensor.</li>
		<li>Launch the dedicated shutter control software (Table of Materials). Select a shutter speed of 1/60, a focal ratio (f-number) of f/8.0, and select the appropriate lens.</li>
		<li>Launch the dedicated camera software (Table of Materials). Select the camera, the desired format (e.g., IIQL) and an ISO setting of 200 in the pulldown menu under the &#8220;CAMERA&#8221; setting of the software.</li>
		<li>Adjust the working distance of the camera to the medium as needed to focus on the medium. Capture images at prescribed time-intervals by pressing the capture button in the software.</li>
	</ol>
	</li>
	<li>Depressurize the system back to ambient conditions.
	<ol>
		<li>Stop injection (gas and liquid pumps), close the CO2 and brine pump inlets, open the rest of the line valves and turn off the heaters.</li>
		<li>Decrease the backpressure gradually (e.g., at a rate of 0.007 MPa/s) until the system reaches ambient pressure conditions. Decrease the brine and CO2 pump pressures separately. 
		NOTE: Decreasing the scCO2 pressure may result in inconsistent or turbulent BPR outflow, therefore the pressure drawdown must be executed with requisite care.</li>
	</ol>
	</li>
	<li>Clean the microfluidic device thoroughly after each experiment as needed by flowing the following sequence of solutions through the medium: isopropanol/ethanol/water (1:1:1), 2 M HCl solution, DI water, a basic solution (DI water/NH4OH/H2O2 at 5:5:1) and DI water.</li>
	<li>Post-process collected images.
	<ol>
		<li>Isolate the pore scape by excluding the background from the images.</li>
		<li>Correct minor misalignments by performing perspective transformation and implementing a local thresholding strategy as needed to account for non-uniform illumination28.</li>
		<li>Calculate geometrical and statistical parameters relevant to the experiment such as average bubble size, bubble size distribution and bubble shape for each foam microstructural images in the channel.</li>
	</ol>
	</li>
</ol>

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D., Carey, J. W., Viswanathan, H. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mixing+in+a+three-phase+system:+Enhanced+production+of+oil-wet+reservoirs+by+CO2+injection.">Mixing in a three-phase system: Enhanced production of oil-wet reservoirs by CO2 injection.</a> Geophysical Research Letters. 43, 196-205 (2016).</li><li>Rognmo, A. U., Fredriksen, S. B., Alcorn, Z. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pore-to-Core+EOR+Upscaling+for+CO2+Foam+for+CCUS.">Pore-to-Core EOR Upscaling for CO2 Foam for CCUS.</a> SPE Journal. 24, 1-11 (2019).</li><li>Erickstad, M., Gutierrez, E., Groisman, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+low-cost+low-maintenance+ultraviolet+lithography+light+source+based+on+light-emitting+diodes.">A low-cost low-maintenance ultraviolet lithography light source based on light-emitting diodes.</a> Lab on a Chip. 15, 57-61 (2015).</li><li>Guo, F., Aryana, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+Experimental+Investigation+of+Flow+Regimes+in+Imbibition+and+Drainage+Using+a+Microfluidic+Platform.">An Experimental Investigation of Flow Regimes in Imbibition and Drainage Using a Microfluidic Platform.</a> Energies. 12 (7), 1-13 (2019).</li><li>Burshtein, N., Chan, S. T., Toda-peters, K., Shen, A. Q., Haward, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3D-printed+glass+microfluidics+for+fluid+dynamics+and+rheology.">3D-printed glass microfluidics for fluid dynamics and rheology.</a> Current Opinion in Colloid &amp; Interface Science. 43, 1-14 (2019).</li><li>Wang, Y., Aryana, S. A., Banerjee, S., Barati, R., Patil, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Creation+of+Saturation+Maps+from+Two-Phase+Flow+Experiments+in+Microfluidic+Devices.">Creation of Saturation Maps from Two-Phase Flow Experiments in Microfluidic Devices.</a> Advances in Petroleum Engineering and Petroleum Geochemistry. Advances in Science, Technology &amp; Innovation. , 77-80 (2019).</li><li>Hermans, M., Gottmann, J., Riedel, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective,+Laser-Induced+Etching+of+Fused+Silica+at+High+Scan-Speeds+Using+KOH.">Selective, Laser-Induced Etching of Fused Silica at High Scan-Speeds Using KOH.</a> Journal of Laser Micro/Nanoengineering. 9, 126-131 (2014).</li><li>Iliescu, C., Jing, J., Tay, F. E. H., Miao, J., Sun, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+masking+layers+for+deep+wet+etching+of+glass+in+an+improved+HF/HCl+solution.">Characterization of masking layers for deep wet etching of glass in an improved HF/HCl solution.</a> Surface &amp; Coatings Technology. 198, 314-318 (2005).</li></ol>

The authors declare no conflicts of interest and disclosure.

This work presents a protocol related to a fabrication platform to create robust, high-pressure glass microfluidic devices. The protocol presented in this work alleviates the need for a cleanroom by performing several of the final fabrication steps inside a glovebox. The use of a cleanroom, if available, is recommended to minimize the potential for contamination. Additionally, the choice of the etchant should be based on the desired surface roughness. The use of a mixture of HF and HCl as the etchant tends to reduce surf...

Hydraulic fracturing has been used for quite some time as a means to stimulate flow especially in tight formations1. Large amounts of water needed in hydraulic fracturing are compounded with environmental factors, water-availability issues2, formation damage3, cost4 and seismic effects5. As a result, interest in alternate fracturing methods such as waterless fracturing and the use of foams is on the rise. Alternative methods may provide important benefits such as reduction in water use6, compatibility with water sensitive formations7, minimal to no plugging of the formation8, high apparent viscosity of the fracturing fluids9, recyclability10, ease of clean-up and proppant carrying capability6. CO2 foam is a potential waterless fracturing fluid that contributes to more efficient production of petroleum fluids and improved CO2 storage capacities in the subsurface with a potentially smaller environmental footprint compared to conventional fracturing techniques6,7,11.
Under optimal conditions, supercritical CO2 foam (scCO2 foam) at pressures beyond the minimum miscibility pressure (MMP) of a given reservoir provides a multi-contact miscible system that is able to direct flow into less permeable parts of the formation, thereby improving sweep efficiency and recovery of the resources12,13. scCO2 delivers gas like diffusivity and liquid like density14 and is well suited for subsurface applications, such as oil recovery and carbon capture, utilization and storage (CCUS)13. The presence of the constituents of foam in the subsurface helps reduce the risk of leakage in long-term storage of CO215. Moreover, coupled-compressibility-thermal shock effects of scCO2 foam systems may serve as effective fracturing systems11. Properties of CO2 foam systems for subsurface applications have been studied extensively at various scales, such as characterization of its stability and viscosity in sand-pack systems and its effectiveness in displacement processes3,6,12,15,16,17. Fracture level foam dynamics and its interactions with porous media are less studied aspects that are directly relevant to the use of foam in tight and fractured formations.
Microfluidic platforms enable direct visualization and quantification of the relevant microscale processes. These platforms provide real-time control of the hydrodynamics and chemical reactions to study pore-scale phenomena alongside recovery considerations1. Foam generation, propagation, transport and dynamics may be visualized in microfluidic devices emulating fractured systems and fracture-microcrack-matrix conductive pathways relevant to oil recovery from tight formations. Fluid exchange between fracture and matrix is directly expressed in accordance with the geometry18, thereby highlighting the importance of simplistic and realistic representations. A number of relevant microfluidic platforms have been developed over the years to study various processes. For example, Tigglaar and coworkers discuss fabrication and high-pressure testing of glass microreactor devices through in-plane connection of fibers to test flow through glass capillaries connected to the microreactors19. They present their findings related to bond inspection, pressure tests and in-situ reaction monitoring by 1H NMR spectroscopy. As such, their platform may not be optimal for relatively large injection rates, pre-generation of multiphase fluid systems for in situ visualization of complex fluids in permeable media. Marre and coworkers discuss the use of a glass microreactor to investigate high-pressure chemistry and supercritical fluid processes20. They include results as a finite-element simulation of stress distribution to explore the mechanical behavior of modular devices under the load. They use nonpermanent modular connections for interchangeable microreactor fabrication, and the silicon/Pyrex microfluidic devices are not transparent; these devices are suited for kinematic study, synthesis and production in chemical reaction engineering where visualization is not a primary concern. The lack of transparency makes this platform unsuitable for direct, in situ visualization of complex fluids in surrogate media. Paydar and coworkers present a novel way to prototype modular microfluidics using 3D printing21. This approach does not seem well-suited for high-pressure applications since it uses a photocurable polymer and the devices are able to withstand only up to 0.4 MPa. Most microfluidic experimental studies related to transport in fractured systems reported in literature focus on ambient temperature and relatively low-pressure conditions1. There have been several studies with a focus on direct observation of microfluidic systems that mimic subsurface conditions. For example, Jimenez-Martinez and co-workers introduce two studies on critical pore-scale flow and transport mechanisms in a complex network of fractures and matrix22,23. The authors study three-phase systems using microfluidics under reservoir conditions (8.3 MPa and 45 &#176;C) for production efficiency; they assess scCO2 usage for re-stimulation where the leftover brine from a prior fracturing is immiscible with CO2 and the residual hydrocarbon23. Oil-wet silicon microfluidic devices have relevance to mixing of oil-brine-scCO2 in Enhanced Oil Recovery (EOR) applications; however, this work does not directly address pore-scale dynamics in fractures. Another example is work by Rognmo et al. who study an upscaling approach for high-pressure, in situ CO2 foam generation24. Most of the reports in literature that leverage microfabrication are concerned with CO2-EOR and they often do not include important fabrication details. To the best of the authors&#8217; knowledge, a systematic protocol for fabrication of high-pressure capable devices for fractured formations is currently missing from the literature.
This work presents a microfluidic platform that enables the study of scCO2 foam structures, bubble shapes, sizes and distribution, lamella stability in the presence of oil for EOR and hydraulic fracturing and aquifer remediation applications. The design and fabrication of microfluidic devices using optical lithography and Selective Laser-induced Etching29 (SLE) are discussed. Additionally, this work describes fracture patterns that are intended to simulate the transport of fluids in fractured tight formations. Simulated pathways may range from simplified patterns to complex microcracks based on tomography data or other methods that provide information regarding realistic fracture geometries. The protocol describes step-by-step fabrication instructions for glass microfluidic devices using photolithography, wet-etching and thermal bonding. An in-house developed collimated Ultra-Violet (UV) light source is used to transfer the desired geometric patterns onto a thin layer of photoresist, which is ultimately transferred to the glass substrate using a wet-etching process. As part of quality assurance, the etched patterns are characterized using confocal microscopy. As an alternative to photolithography/wet-etching, an SLE technique is employed to create a microfluidic device and a comparative analysis of the platforms is presented. The setup for flow experiments comprise gas cylinders and pumps, pressure controllers and transducers, fluid mixers and accumulators, microfluidic devices, high-pressure capable stainless-steel holders along with a high-resolution camera and an illumination system. Finally, representative samples of observations from flow experiments are presented.

<table>
	<tbody>
		<tr>
			<td>1/4&#8221; bolts and nuts</td>
			<td></td>
			<td></td>
			<td>For fabrication of the metallic plates to sandwich the glass chip between them for thermal bonding</td>
		</tr>
		<tr>
			<td>3.45 x 3.45 mm UV LED</td>
			<td>Kingbright</td>
			<td></td>
			<td>To emitt LED light</td>
		</tr>
		<tr>
			<td>3D measuring Laser microscope</td>
			<td>OLYMPUS</td>
			<td>LEXT OLS4000</td>
			<td>To measure channel depths</td>
		</tr>
		<tr>
			<td>40 mm x 40 mm x 10 mm 12V DC Cooling Fan</td>
			<td>Uxcell</td>
			<td></td>
			<td>To cool the UV LED lights</td>
		</tr>
		<tr>
			<td>120 mm x 38 mm 24V DC Cooling Fan</td>
			<td>Uxcell</td>
			<td></td>
			<td>To cool the UV LED lights</td>
		</tr>
		<tr>
			<td>5 ml (6 ml) NORM-JECT Syringe</td>
			<td>HENKE SASS WOLF</td>
			<td>Lot #16M14CB</td>
			<td>To rinse the chip before each experiment</td>
		</tr>
		<tr>
			<td>Acetone (Certified ACS)</td>
			<td>Fisher Chemical</td>
			<td>Lot #177121</td>
			<td>For cleaning</td>
		</tr>
		<tr>
			<td>Acid/ corossion resistive tweezer</td>
			<td>TED PELLA</td>
			<td></td>
			<td>To handle the glass piece in corosive solutions</td>
		</tr>
		<tr>
			<td>Acid/solvent resistance tweezers</td>
			<td>TED PELLA, INC</td>
			<td>#53009 and #53010</td>
			<td>To handle the glass in corrosive solutions</td>
		</tr>
		<tr>
			<td>Alloy X</td>
			<td>AMERICAN SPECIAL METALS</td>
			<td>Heat Number: ZZ7571XG11</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium hydroxide (ACS reagent)</td>
			<td>Sigma Aldrich</td>
			<td>Lot #SHBG9007V</td>
			<td>To clean the chip at the end of process</td>
		</tr>
		<tr>
			<td>AutoCAD</td>
			<td>Autodesk, San Rafael, CA</td>
			<td></td>
			<td>To design 2D patterns and 3D chips</td>
		</tr>
		<tr>
			<td>BD Etchant for PSG-SiO2 systems</td>
			<td>TRANSENE</td>
			<td>Lot #028934</td>
			<td>An improved buffered etch formulation for delineation of phosphosilica glass &#8211; SiO2 (PSG), and borosilica glass &#8211; SiO2 (BSG) systems</td>
		</tr>
		<tr>
			<td>Blank Borofloat substrate</td>
			<td>TELIC</td>
			<td>CG-HF</td>
			<td>Upper substrate for UV etching</td>
		</tr>
		<tr>
			<td>Borofloat substrate with metalizations</td>
			<td>TELIC</td>
			<td>PG-HF-LRC-Az1500</td>
			<td>Lower substrate for UV etching</td>
		</tr>
		<tr>
			<td>Capture One photo editing software</td>
			<td>Phase One</td>
			<td></td>
			<td>To Capture/Edit/Convert the pictures taken by Phase One Camera</td>
		</tr>
		<tr>
			<td>Capture station</td>
			<td>DT Scientific</td>
			<td>DT Versa</td>
			<td>To place of the chip in the field of view of the camera</td>
		</tr>
		<tr>
			<td>Carbon dioxide gas (Grade E)</td>
			<td>PRAXAIR</td>
			<td>UN 1013, CAS Number 124-38-9</td>
			<td>non-aqeous portion of foam</td>
		</tr>
		<tr>
			<td>Chromium etchant 1020</td>
			<td>TRANSENE</td>
			<td>Lot #025433</td>
			<td>High-purity ceric ammonium nitrate systems for precise, clean etching of chromium and chromium oxide films.</td>
		</tr>
		<tr>
			<td>Circulating baths with digital temperature controller</td>
			<td>PolyScience</td>
			<td></td>
			<td>To control the brine and CO2 temperatures</td>
		</tr>
		<tr>
			<td>CO2</td>
			<td>Airgas</td>
			<td>100% pure - 001013 - CAS: 124-38-9</td>
			<td>For CO2/scCO2 injection</td>
		</tr>
		<tr>
			<td>Computer</td>
			<td></td>
			<td>NVIDIA Tesla K20 Graphic Card - 706 MHz Core - 5 GB GDDR5 SDRAM - PCI Express 2.0 x16</td>
			<td>To process and visualize the images obtained via the Phase One camera</td>
		</tr>
		<tr>
			<td>Custom made high pressure glass chip holder</td>
			<td></td>
			<td></td>
			<td>To tightly hold the chip and its connections for high pressure testing</td>
		</tr>
		<tr>
			<td>Cutrain (Custom)</td>
			<td></td>
			<td></td>
			<td>To protect against UV/IR Radiations</td>
		</tr>
		<tr>
			<td>Deionized water (DI)</td>
			<td></td>
			<td></td>
			<td>For cleaning</td>
		</tr>
		<tr>
			<td>Digital camera with monochromatic 60 MP sensor</td>
			<td>Phase One</td>
			<td>IQ260</td>
			<td>Visualization system</td>
		</tr>
		<tr>
			<td>Ethanol, Anhydrous, USP Specs</td>
			<td>DECON LABORATORIES, INC.</td>
			<td>Lot #A12291505J, CAS# 64-17-5</td>
			<td>For cleaning</td>
		</tr>
		<tr>
			<td>Facepiece reusable respirator</td>
			<td>3M</td>
			<td>6502QL, Gases, Vapors, Dust, Medium</td>
			<td>To protect against volatile solution inhalation</td>
		</tr>
		<tr>
			<td>Fused Silica (UV Grade) wafer</td>
			<td>SIEGERT WAFER</td>
			<td>UV grade</td>
			<td>Glass precursor for SLE printing</td>
		</tr>
		<tr>
			<td>GIMP</td>
			<td>Open-source image processing software</td>
			<td></td>
			<td>To characterize image texture and properties</td>
		</tr>
		<tr>
			<td>Glovebox (vinyl anaerobic chamber)</td>
			<td>Coy</td>
			<td></td>
			<td>To provide a clean, dust-free environment</td>
		</tr>
		<tr>
			<td>Heated ultrasonic cleaning bath</td>
			<td>Fisher Scientific</td>
			<td></td>
			<td>To accelerate the etching process</td>
		</tr>
		<tr>
			<td>Hexamethyldisilazane (HMDS) Cleanroom&#174; MB</td>
			<td>KMG</td>
			<td>62115</td>
			<td>Primer for photoresist coating</td>
		</tr>
		<tr>
			<td>Hose (PEEK tubing)</td>
			<td>IDEX HEALTH &#38; SCIENCE</td>
			<td>Natural 1/16&#34; OD x .010&#34; ID x 5ft, Part # 1531</td>
			<td>Flow connections</td>
		</tr>
		<tr>
			<td>Hydrochloric acid, certified ACS plus</td>
			<td>Fisher Chemical</td>
			<td>Lot # 187244</td>
			<td>Solvent in RCA semiconductor cleaning protocol</td>
		</tr>
		<tr>
			<td>Hydrogen Peroxide</td>
			<td>Fisher Chemical</td>
			<td>H325-500</td>
			<td>Solvent in RCA semiconductor cleaning protocol</td>
		</tr>
		<tr>
			<td>ImageJ</td>
			<td>NIH</td>
			<td></td>
			<td>To characterize image texture and properties</td>
		</tr>
		<tr>
			<td>ISCO syringe pump</td>
			<td>TELEDYNE ISCO</td>
			<td>D-SERIES (100DM, 500D)</td>
			<td>To pump the fluids</td>
		</tr>
		<tr>
			<td>Kaiser LED light box</td>
			<td>Kaiser</td>
			<td></td>
			<td>To illuminate the chip</td>
		</tr>
		<tr>
			<td>Laser printing machine</td>
			<td>LightFab GmbH, Germany.</td>
			<td>FILL</td>
			<td>Glass-SLE chip fabrication</td>
		</tr>
		<tr>
			<td>Laser safety glasses</td>
			<td>FreeMascot</td>
			<td>B07PPZHNX4</td>
			<td>To protect against UV/IR Radiations</td>
		</tr>
		<tr>
			<td>LED Engin 5W UV Lens</td>
			<td>LEDiL</td>
			<td></td>
			<td>To emitt LED light</td>
		</tr>
		<tr>
			<td>Light Fab 3D Printer (femtosecond laser)</td>
			<td>Light Fab</td>
			<td></td>
			<td>To selectively laser Etch of fused silica</td>
		</tr>
		<tr>
			<td>LightFab 3D printer</td>
			<td>LightFab GmbH, Germany</td>
			<td></td>
			<td>To SLE print the fused silica chips</td>
		</tr>
		<tr>
			<td>MATLAB</td>
			<td>MathWorks, Inc., Natick, MA</td>
			<td></td>
			<td>To characterize image texture and properties</td>
		</tr>
		<tr>
			<td>Metallic plates</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Micro abrasive sand blasters (Problast 2)</td>
			<td>VANIMAN</td>
			<td>Problast 2 &#8211; 80007</td>
			<td>To craete holes in cover plates</td>
		</tr>
		<tr>
			<td>MICROPOSIT 351 developer</td>
			<td>Dow</td>
			<td>10016652</td>
			<td>Photoresist developer solution</td>
		</tr>
		<tr>
			<td>Muffle furnace</td>
			<td>Thermo Scientific</td>
			<td>Thermolyne Type 1500</td>
			<td>Thermal bonding</td>
		</tr>
		<tr>
			<td>N2 pure research grade</td>
			<td>Airgas</td>
			<td>Research Plus - NI RP300</td>
			<td>For drying the chips in each step</td>
		</tr>
		<tr>
			<td>NMP semiconductor grade - 0.1&#956;m Filtered</td>
			<td>Ultra Pure Solutions, Inc</td>
			<td>Lot #02191502T</td>
			<td>Organic solvent</td>
		</tr>
		<tr>
			<td>Oven</td>
			<td>Gravity Convection Oven</td>
			<td>18EG</td>
			<td></td>
		</tr>
		<tr>
			<td>Phase One IQ260 with an achromatic sensor</td>
			<td>Phase One</td>
			<td>IQ260</td>
			<td>To visulize transport in microfluidic devices using an ISO 200 setting and an aperture at f/8.</td>
		</tr>
		<tr>
			<td>Photomask</td>
			<td>Fine Line Imaging</td>
			<td>20,320 DPI FILM</td>
			<td>Pattern of channels</td>
		</tr>
		<tr>
			<td>Photoresist (SU-8)</td>
			<td>MICRO CHEM</td>
			<td>Product item: Y0201004000L1PE, Lot Number: 18110975</td>
			<td>Photoresist</td>
		</tr>
		<tr>
			<td>Polarized light microscope</td>
			<td>OLYMPUS</td>
			<td>BX51</td>
			<td>Visual examination of micro channels</td>
		</tr>
		<tr>
			<td>Ports (NanoPort Assembly)</td>
			<td>IDEX HEALTH &#38; SCIENCE</td>
			<td>NanoPort Assembly Headless, 10-32 Coned, for 1/16&#34; OD, Part # N-333</td>
			<td>Connections to the chip</td>
		</tr>
		<tr>
			<td>Python</td>
			<td>Python Software Foundation</td>
			<td></td>
			<td>To characterize image texture and properties</td>
		</tr>
		<tr>
			<td>Safety face shield</td>
			<td>Sellstrom</td>
			<td>S32251</td>
			<td>To protect against UV/IR Radiations</td>
		</tr>
		<tr>
			<td>Sealing film (Parafilm)</td>
			<td>Bemis Company, Inc</td>
			<td></td>
			<td>Isolation of containers</td>
		</tr>
		<tr>
			<td>Shutter Control Software</td>
			<td>Schneider-Kreuznach</td>
			<td></td>
			<td>To adjust shutter settings</td>
		</tr>
		<tr>
			<td>Smooth ceramic plates</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Stirring hot plate</td>
			<td>Corning&#174;</td>
			<td>PC-620D</td>
			<td>To heat the solutions</td>
		</tr>
		<tr>
			<td>Sulfuric acid, ACS reagent 95.0-98.0%</td>
			<td>Sigma Aldrich</td>
			<td>Lot # SHBK0108</td>
			<td>Solvent in RCA semiconductor cleaning protocol</td>
		</tr>
		<tr>
			<td>Syringe pump (Standard Infuse/Withdraw PHD ULTRA)</td>
			<td>Harvard Apparatus</td>
			<td>70-3006</td>
			<td>To saturate the chip before each experiment</td>
		</tr>
		<tr>
			<td>Torque wrench</td>
			<td>Snap-on</td>
			<td>TE25A-34190</td>
			<td>To tighten the screws</td>
		</tr>
		<tr>
			<td>UV power meter</td>
			<td>Optical Associates, Incorporated</td>
			<td>Model 308</td>
			<td>To measure the intesity of UV light</td>
		</tr>
		<tr>
			<td>UV power meter</td>
			<td>Optical Associates, Incorporated</td>
			<td>Model 308</td>
			<td>To quantify the strength of UV light</td>
		</tr>
		<tr>
			<td>UV radiation stand (LED lights)</td>
			<td></td>
			<td></td>
			<td>To transfer the pattern to glass (photoresist layer)</td>
		</tr>
		<tr>
			<td>Vaccum pump</td>
			<td>WELCH VACCUM TECHNOLOGY, INC</td>
			<td>1380</td>
			<td>To dry the chip</td>
		</tr>
		<tr>
			<td>Variable DC power supplies</td>
			<td>Eventek</td>
			<td>KPS305D</td>
			<td>To power the UV LED lights</td>
		</tr>
	</tbody>
</table>

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.

This section presents examples of physical observations from scCO2 foam flow through a main fracture connected to array of micro-cracks. A glass microfluidic device made via photolithography or SLE is placed inside a holder and in the field of view of a camera featuring a 60 megapixel, monochromatic, full-frame sensor. Figure 11 illustrates the process of fabrication microfluidic devices and their placement in the experimental setup. Figure 12 is illu...

Watch this Scientific Journal Video about Microfluidic Fabrication Techniques for High-Pressure Testing of Microscale Supercritical CO2 Foam Transport in Fractured Unconventional Reservoirs at JoVE.co

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.

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 ...

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JoVE Journal

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6.6K Views.  University of Kansas. 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.

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

Fabrication of VB2/Air Cells for Electrochemical Testing

A technique to investigate the properties and performance of new multi-electron metal/air battery systems is proposed and presented. A method for synthesizing nanoscopic VB2 is presented as well as step-by-step procedure for applying a zirconium oxide coating to the VB2 particles for stabilization upon discharge. The process for disassembling existing zinc/air cells is shown, in addition construction of the new working electrode to replace the conventional zinc/air cell anode with a the nanoscopic VB2 anode. Finally, discharge of the completed VB2/air battery is reported. We show that using the zinc/air cell as a test bed is useful to provide a consistent configuration to study the performance of the high-energy high capacity nanoscopic VB2 anode.

Fabrication of VB2/Air Cells for Electrochemical Testing

A protocol is presented to study multi-electron metal/air battery systems by using previous technology developed for the zinc/air cell. Electrochemical testing is then performed on fabricated batteries to evaluate performance.

A technique to investigate the properties and performance of new multi-electron metal/air battery systems is proposed and presented. A method for ...

Synthesis and Microdiffraction at Extreme Pressures and Temperatures

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary interiors, design materials with novel properties, understand the mechanical behavior of materials exposed to very high stresses as in explosions or impacts. Synthesis and structural analysis of materials at extreme conditions of pressure and temperature entails remarkable technical challenges. In the laser heated diamond anvil cell (LH-DAC), very high pressure is generated between the tips of two opposing diamond anvils forced against each other; focused infrared laser beams, shined through the diamonds, allow to reach very high temperatures on samples absorbing the laser radiation. When the LH-DAC is installed in a synchrotron beamline that provides extremely brilliant x-ray radiation, the structure of materials under extreme conditions can be probed in situ. LH-DAC samples, although very small, can show highly variable grain size, phase and chemical composition. In order to obtain the high resolution structural analysis and the most comprehensive characterization of a sample, we collect diffraction data in 2D grids and combine powder, single crystal and multigrain diffraction techniques. Representative results obtained in the synthesis of a new iron oxide, Fe4O5 1 will be shown.

The laser heated diamond anvil cell combined with synchrotron micro-diffraction techniques allows researchers to explore the nature and properties of new phases of matter at extreme pressure and temperature (PT) conditions. Heterogeneous samples can be characterized in situ under high pressure by 2D mapping and combined powder, single-crystal and multigrain diffraction approaches.

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary ...

Fabrication and Testing of Microfluidic Optomechanical Oscillators

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including microresonators. However, because of the increased acoustic radiative losses during direct liquid immersion of optomechanical devices, almost all published optomechanical experiments have been performed in solid phase. This paper discusses a recently introduced hollow microfluidic optomechanical resonator. Detailed methodology is provided to fabricate these ultra-high-Q microfluidic resonators, perform optomechanical testing, and measure radiation pressure-driven breathing mode and SBS-driven whispering gallery mode parametric vibrations. By confining liquids inside the capillary resonator, high mechanical- and optical- quality factors are simultaneously maintained.

Parametric optomechanical excitations have recently been experimentally demonstrated in microfluidic optomechanical resonators by means of optical radiation pressure and stimulated Brillouin scattering. This paper describes the fabrication of these microfluidic resonators along with methodologies for generating and verifying optomechanical oscillations.

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including ...

Thermal Measurement Techniques in Analytical Microfluidic Devices

Thermal measurement techniques have been used for many applications such as thermal characterization of materials and chemical reaction detection. Micromachining techniques allow reduction of the thermal mass of fabricated structures and introduce the possibility to perform high sensitivity thermal measurements in the micro-scale and nano-scale devices. Combining thermal measurement techniques with microfluidic devices allows performing different analytical measurements with low sample consumption and reduced measurement time by integrating the miniaturized system on a single chip. The procedures of thermal measurement techniques for particle detection, material characterization, and chemical detection are introduced in this paper.

Here, we present three protocols for thermal measurements in microfluidic devices.

Thermal measurement techniques have been used for many applications such as thermal characterization of materials and chemical reaction detection. ...

Adsorption Device Based on a Langatate Crystal Microbalance for High Temperature High Pressure Gas Adsorption in Zeolite H-ZSM-5

We present a high-temperature and high-pressure gas adsorption measurement device based on a high-frequency oscillating microbalance (5 MHz langatate crystal microbalance, LCM) and its use for gas adsorption measurements in zeolite H-ZSM-5. Prior to the adsorption measurements, zeolite H-ZSM-5 crystals were synthesized on the gold electrode in the center of the LCM, without covering the connection points of the gold electrodes to the oscillator, by the steam-assisted crystallization (SAC) method, so that the zeolite crystals remain attached to the oscillating microbalance while keeping good electroconductivity of the LCM during the adsorption measurements. Compared to a conventional quartz crystal microbalance (QCM) which is limited to temperatures below 80 &#176;C, the LCM can realize the adsorption measurements in principle at temperatures as high as 200-300 &#176;C (i.e., at or close to the reaction temperature of the target application of one-stage DME synthesis from the synthesis gas), owing to the absence of crystalline-phase transitions up to its melting point (1,470 &#176;C). The system was applied to investigate the adsorption of CO2, H2O, methanol and dimethyl ether (DME), each in the gas phase, on zeolite H-ZSM-5 in the temperature and pressure range of 50-150 &#176;C and 0-18 bar, respectively. The results showed that the adsorption isotherms of these gases in H-ZSM-5 can be well fitted by Langmuir-type adsorption isotherms. Furthermore, the determined adsorption parameters, i.e., adsorption capacities, adsorption enthalpies, and adsorption entropies, compare well to literature data. In this work, the results for CO2 are shown as an example.

A protocol for high-temperature and high-pressure gas adsorption measurements on zeolite H-ZSM-5 using an adsorption measurement device based on a langatate crystal microbalance is presented. Prior to the adsorption measurements, the synthesis of zeolite H-ZSM-5 on the langatate crystal microbalance sensor by the steam-assisted crystallization (SAC) method is demonstrated.

We present a high-temperature and high-pressure gas adsorption measurement device based on a high-frequency oscillating microbalance (5 MHz langatate ...

Solvent Bonding for Fabrication of PMMA and COP Microfluidic Devices

Thermoplastic microfluidic devices offer many advantages over those made from silicone elastomers, but bonding procedures must be developed for each thermoplastic of interest. Solvent bonding is a simple and versatile method that can be used to fabricate devices from a variety of plastics. An appropriate solvent is added between two device layers to be bonded, and heat and pressure are applied to the device to facilitate the bonding. By using an appropriate combination of solvent, plastic, heat, and pressure, the device can be sealed with a high quality bond, characterized as having high bond coverage, bond strength, optical clarity, durability over time, and low deformation or damage to microfeature geometry. We describe the procedure for bonding devices made from two popular thermoplastics, poly(methyl-methacrylate) (PMMA), and cyclo-olefin polymer (COP), as well as a variety of methods to characterize the quality of the resulting bonds, and strategies to troubleshoot low quality bonds. These methods can be used to develop new solvent bonding protocols for other plastic-solvent systems.

Solvent bonding is a simple and versatile method for fabricating thermoplastic microfluidic devices with high quality bonds. We describe a protocol to achieve strong, optically clear bonds in PMMA and COP microfluidic devices that preserve microfeature details, by a judicious combination of pressure, temperature, an appropriate solvent, and device geometry.

Thermoplastic microfluidic devices offer many advantages over those made from silicone elastomers, but bonding procedures must be developed for each ...

Subsurface Defect Localization by Structured Heating Using Laser Projected Photothermal Thermography

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering thermal wave fields that are disturbed by the defect. This effect is measured and used to locate the defect. We form the destructively interfering wave fields by using a modified projector. The original light engine of the projector is replaced with a fiber-coupled high-power diode laser. Its beam is shaped and aligned to the projector&#39;s spatial light modulator and optimized for optimal optical throughput and homogeneous projection by first characterizing the beam profile, and, second, correcting it mechanically and numerically. A high-performance infrared (IR) camera is set up according to the tight geometrical situation (including corrections of the geometrical image distortions) and the requirement to detect weak temperature oscillations at the sample surface. Data acquisition can be performed once a synchronization between the individual thermal wave field sources, the scanning stage, and the IR camera is established by using a dedicated experimental setup which needs to be tuned to the specific material being investigated. During data post-processing, the relevant information on the presence of a defect below the surface of the sample is extracted. It is retrieved from the oscillating part of the acquired thermal radiation coming from the so-called depletion line of the sample surface. The exact location of the defect is deduced from the analysis of the spatial-temporal shape of these oscillations in a final step. The method is reference-free and very sensitive to changes within the thermal wave field. So far, the method has been tested with steel samples but is applicable to different materials as well, in particular to temperature sensitive materials.

This method aims at locating vertical subsurface defects. Here, we couple a laser with a spatial light modulator and trigger its video input to heat a sample surface deterministically with two anti-phased modulated lines while acquiring highly resolved thermal images. The defect position is retrieved from evaluating thermal wave interference minima.

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering ...

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, interface precipitation, and mini-emulsion. In all methods, well-defined, micrometer-sized spheres are obtained from a self-assembling process in solution. The vapor diffusion method can result in spheres with the highest sphericity and surface smoothness, yet the types of the polymers able to form these spheres are limited. On the other hand, in the mini-emulsion method, microspheres can be made from various types of polymers, even from highly crystalline polymers with coplanar, &#960;-conjugated backbones. The photoluminescent (PL) properties from single isolated microspheres are unusual: the PL is confined inside the spheres, propagates at the circumference of the spheres via the total internal reflection at the polymer/air interface, and self-interferes to show sharp and periodic resonant PL lines. These resonating modes are so-called "whispering gallery modes" (WGMs). This work demonstrates how to measure WGM PL from single isolated spheres using the micro-photoluminescence (&#181;-PL) technique. In this technique, a focused laser beam irradiates a single microsphere, and the luminescence is detected by a spectrometer. A micromanipulation technique is then used to connect the microspheres one by one and to demonstrate the intersphere PL propagation and color conversion from coupled microspheres upon excitation at the perimeter of one sphere and detection of PL from the other microsphere. These techniques, &#181;-PL and micromanipulation, are useful for experiments on micro-optic application using polymer materials.

Protocols for the synthesis of microspheres from polymers, the manipulation of microspheres, and micro-photoluminescence measurements are presented.

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, ...

Focused Ion Beam Fabrication of LiPON-based Solid-state Lithium-ion Nanobatteries for In Situ Testing

Solid-state electrolytes are a promising replacement for current organic liquid electrolytes, enabling higher energy densities and improved safety of lithium-ion (Li-ion) batteries. However, a number of setbacks prevent their integration into commercial devices. The main limiting factor is due to nanoscale phenomena occurring at the electrode/electrolyte interfaces, ultimately leading to degradation of battery operation. These key problems are highly challenging to observe and characterize as these batteries contain multiple buried interfaces. One approach for direct observation of interfacial phenomena in thin film batteries is through the fabrication of electrochemically active nanobatteries by a focused ion beam (FIB). As such, a reliable technique to fabricate nanobatteries was developed and demonstrated in recent work. Herein, a detailed protocol with a step-by-step process is presented to enable the reproduction of this nanobattery fabrication process. In particular, this technique was applied to a thin film battery consisting of LiCoO2/LiPON/a-Si, and has further been previously demonstrated by in situ cycling within a transmission electron microscope.

Focused Ion Beam Fabrication of LiPON-based Solid-state Lithium-ion Nanobatteries for In Situ Testing

A protocol for the fabrication of electrochemically active LiPON-based solid-state lithium-ion nanobatteries using a focused ion beam is presented.

Solid-state electrolytes are a promising replacement for current organic liquid electrolytes, enabling higher energy densities and improved safety of ...

In Situ High Pressure Hydrogen Tribological Testing of Common Polymer Materials Used in the Hydrogen Delivery Infrastructure

High pressure hydrogen gas is known to adversely affect metallic components of compressors, valves, hoses, and actuators. However, relatively little is known about the effects of high pressure hydrogen on the polymer sealing and barrier materials also found within these components. More study is required in order to determine the compatibility of common polymer materials found in the components of the hydrogen fuel delivery infrastructure with high pressure hydrogen. As a result, it is important to consider the changes in physical properties such as friction and wear in situ while the polymer is exposed to high pressure hydrogen. In this protocol, we present a method for testing the friction and wear properties of ethylene propylene diene monomer (EPDM) elastomer samples in a 28 MPa high pressure hydrogen environment using a custom-built in situ pin-on-flat linear reciprocating tribometer. Representative results from this testing are presented which indicate that the coefficient of friction between the EPDM sample coupon and steel counter surface is increased in high pressure hydrogen as compared to the coefficient of friction similarly measured in ambient air.

In Situ High Pressure Hydrogen Tribological Testing of Common Polymer Materials Used in the Hydrogen Delivery Infrastructure

A test methodology for quantifying tribological properties of polymers used in hydrogen infrastructure service is demonstrated and characteristic results for a common elastomer are discussed.

High pressure hydrogen gas is known to adversely affect metallic components of compressors, valves, hoses, and actuators. However, relatively little is ...