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 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 µm.
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 °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’ 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.
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
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.
3. Clean and bond
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.
5. Perform high-pressure testing
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 illustration of CO2 foam transport and stability in the UV-lithography microfluidic device (4 MPa and 40 ˚C) during the first 20 min of generation/isolation. The multiphase moved across the fracture/microcracks and foam was generated through the microfractures. Figure 13 shows scCO2 foam generation in a SLE microfluidic device (7.72 MPa and 40 °C) starting from ambient condition with no flow to fully developed scCO2 foam at high and low flow rates. Figure 14 presents images of foam distribution and stability under reservoir conditions (7.72 MPa and 40 °C) during the first 20 min of generation/isolation. Figure 15 shows the distribution of the bubble diameters and the raw and intermediate images as part of the quantification of the foam microstructure including, raw image, post-processed image with improved brightness, contrast and sharpness, and its binarized equivalent.
Figure 1: Example photomask designs for fabrication of microfluidic devices (black and white colors are inverted for clarity). (a) Entire field of view for a connected fracture network containing a main fracture and micro cracks. (b) Zoomed-in view of the main feature comprising a connected fracture network containing a main fracture and micro-cracks. (c) A third port is added at the bottom. (d) Zoomed-in view of the main feature comprising a connected fracture network containing a main fracture and micro-cracks along with a distribution network connecting the network to the port at the bottom of the device. Please click here to view a larger version of this figure.
Figure 2: 3D Microfludic design used in SLE fabrication and high-pressure foam flow through microchannels. Please click here to view a larger version of this figure.
Figure 3: Examination of channel depth via confocal microscopy for substrate dipped in BD-etchant for 136 h (no sonication in this case). (a) channel overview (b) channel depth measurement (~43 μm). Please click here to view a larger version of this figure.
Figure 4: Examination of channel depth via confocal microscopy for a substrate with chrome layer removed after NMP rinsing. (a) Channel overview. (b) Channel depth measurement (~42.5 μm). Please click here to view a larger version of this figure.
Figure 5: Schematic of thermal bonding process. (a) Placing two glass wafers between two smooth ceramic plates. (b) Placing the ceramic plates between two metallic plates and tightening the bolts. (c) Placing the metallic and ceramic holder containing the substrates inside a programmable furnace to achieve the desired temperatures for thermal bonding. Please click here to view a larger version of this figure.
Figure 6: The completed UV-etched glass microfluidic device. Please click here to view a larger version of this figure.
Figure 7: SLE design and fabrication process. (a) Schematic of SLE design and fabrication process (this figure has been reprinted with permission from Elsevier27), and (b) the resulting 3D printed microfluidic device. Design and fabrication steps include (a.i) designing the inner volume of channels, (a.ii) slicing the 3D model to create a z-stack of lines to define the laser path, (a.iii) laser irradiation on the polished fused silica substrate, (a.iv) preferential KOH etching of laser etched materials, and (a.v) the finished product. Please click here to view a larger version of this figure.
Figure 8: Microfluidic device placed inside a holder and the imaging system comprising a high-resolution camera and an illumination system. (a) A photograph of laboratory setup, and (b) schematic of a lab-on-a-chip under observation via the high-resolution camera and illumination system. Please click here to view a larger version of this figure.
Figure 9: High-pressure scCO2 foam injection setup into a microfluidic device and a visualization system using a high-resolution camera and image processing unit. (a) photograph of laboratory setup, and (b) schematic of process flow diagram and the image processing unit. Please click here to view a larger version of this figure.
Figure 10: De-bonded device at an injection port (right entrance) as a result of mishandling the pressure profile by BPR and water pump during injection. Please click here to view a larger version of this figure.
Figure 11: Comparative fabrication methods of glass microfluidic device. (a) Fabrication process for fractured media microfluidic device using photo-lithography (a.i) design for a positive photoresist, (a.ii) printed photomask on a polyester-based transparency film, (a.iii) blank and photoresist/chrome coated glass substrates, (a.iv) transferring the pattern to the substrate via UV radiation, (a.v) etched substrate, (a.vi) etched substrate after chrome layer removal and the blank substrate prepared for thermal bonding, (a.vii) thermally bonded device, and (a.viii) scCO2 injection. (b) Fabrication using the SLE technique: (b.i) design for SLE printing, (b.ii) laser irradiation on the polished fused silica substrate, (b.iii) SLE printed glass microfluidic device, and (b.iv) scCO2 injection. Please click here to view a larger version of this figure.
Figure 12: CO2 foam transport and stability in the UV-lithography microfluidic device (4 MPa and 40 ˚C) during the first 20 min of generation/isolation. Please click here to view a larger version of this figure.
Figure 13: scCO2 foam generation in the SLE microfluidic device (7.72 MPa and 40 °C). (a) Ambient condition with no flow through the micro channels. (b) Co-injection of CO2 and aqueous phase (containing surfactant or nanoparticle) at supercritical condition. (c) Onset of scCO2 foam generation 0.5 min after start of co-injection. (d) Fully developed scCO2 foam at high flow rates (e) lowering the flow rates of co-injection to reveal the borders of multiphase. (f) Profoundly low flow rates reveal dispersed scCO2 bubbles in the aqueous phase. Please click here to view a larger version of this figure.
Figure 14: Visualization of foam stability under reservoir conditions (7.72 MPa and 40 ˚C) during the first 20 min of generation/isolation. Please click here to view a larger version of this figure.
Figure 15: Analysis of foam microstructure. (a) Image of scCO2 foam flow in the fracture network, (b) post-processed image with improved brightness, contrast and sharpness, (c) binarized image using ImageJ, and (d) bubble diameter distribution profile obtained from ImageJ, particle analysis mode. Please click here to view a larger version of this figure.
Figure 16: Illustration of in-house collimated UV light source. (a) Photograph and (b) a schematic of laboratory UV light stand containing LED light sources and a stage. Please click here to view a larger version of this figure.
Figure 17: Color-coded plot of UV intensity in a 10 x 10 cm2 area of the stage where the substrate is placed for UV exposure. UV intensity values range from 4 to 5 mW/cm2 as recorded using a UV meter. Please click here to view a larger version of this figure.
Supplementary File 1. Please click here to download this file.
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 surface roughness30. This work is concerned with microfluidic platforms that enable direct, in situ visualization of transport of complex fluids in complex permeable media that faithfully represent the complex structures of subsurface media of interest. As such, this work uses a buffered etchant that enables the study of mass transfer and transport in surrogate media resembling geologic permeable media.
Design of patterns
The patterns are created using a computer aided design software (Table of Materials) and the features are intended to represent factures and microcracks to study transport and stability of foam (see Figure 1). These patterns may be printed on a high-contrast, polyester-based transparent film, or a borofloat or quartz plate (photomask). The patterns used in photolithography comprise a main channel, 127 μm in width and 2.2 cm in length, that serves as the main fracture. This channel is connected to an array of micro-fractures with various dimensions, or a permeable medium consisting of an array of circular posts, with diameters of 300 μm, that are connected to the middle of the fracture path. Additional auxiliary ports may be included in the design to help with the initial saturation of the main features, e.g., fractures.
Photoresist
This work uses a positive photoresist. As a result, the areas in the design that correspond to features that are intended to be etched on the substrate are optically transparent and the other areas obstruct the transmission of light (collimated UV light). In the case of a negative photoresists, the situation would be the opposite: the areas in the design that correspond to the features that are intended to be etched on the substrate shall be optically nontransparent.
UV light source
The patterns are transferred to the photoresist by altering its solubility as a result of its exposure to UV light. A full-spectrum, mercury-vapor lamp may serve as the UV source. The use of a collimated, narrow-band UV source, however, improves the quality and precision of the fabrication significantly. This work uses a photoresist with peak sensitivity at 365 nm, a collimated UV source consisting of an array of light emitting diodes (LED), and an exposure time of approximately 150 s. This UV source is a developed in-house and offers a low maintenance, low-divergence, collimated UV light source for lithography. The UV source consists of a square array of nine high-power LEDs with a target peak emission wavelength of 365 nm at 25 °C (3.45 mm x 3.45 mm UV LED with Ceramic substrate—see Table of Materials). A light-collecting UV lens (LED 5 W UV Lens – see Table of Materials) is used on each LED to reduce the divergence from ~70° to ~12°. The divergence is further reduced (~5°) by using a 3 x 3 array of nine converging polyvinylchloride (PVC) Fresnel lenses. The setup produces collimated and uniform UV radiation over a 3.5-inch squared area. The details of the fabrication of this low-cost light source for UV lithography is adapted from the method presented by Erickstad and co-workers25 with minor modifications15,26. Figure 16 illustrates the LED UV light source mounted on the celling of UV stand alongside the stage at the bottom for substrate UV exposure (the procedure is performed in a darkroom). The UV stage is placed 82.55 cm from the nine Fresnel lenses that are mounted on a rack 13.46 cm below the rack that houses the LEDs. As seen in Figure 16a, there are four small fans (40 mm x 40 mm x 10 mm 12 V DC Cooling Fan—see Table of Materials) on the bottom of the plate that houses the LEDs and there is a larger fan (120 mm x 38 mm 24 V DC Cooling Fan—see Table of Materials) on the top. Three variable DC power supplies (Table of Materials) are used to power the LEDs. One power supply feeds the center LED at 0.15 A, 3.3 V; one power supply feeds the four corner LEDs at 0.6 A, 14.2 V; and one power supply feeds the remaining four LEDs at 0.3 A, 13.7 V. The stage, shown schematically in Figure 16b, is divided into 1 cm2 sub-areas and the intensity of the UV light is measured in each using a UV power meter (Table of Materials) that is equipped with a 2 W 365 nm robe assembly. On average, the UV light has an average strength of 4.95 mW/cm2 with a variability characterized by a standard deviation of 0.61 mW/cm2. Figure 17 presents a color-coded plot of UV intensity map for this UV light source. The intensity over the region of 10 cm 10 cm is relatively uniform with values ranging from 4 to 5 mW/cm2 in the center of the stage where the substrate is placed and exposed to the light. For more information on the development of the in-house collimated UV-light source refer to ESI, Supplementary File 1: Figure S3, S4. The use of the UV source may be coupled with UV blocking shields/covers for its safe use. Additional safety measures may include the use of UV safety goggles (Laser Eye Protection Safety Glasses for Red and UV Lasers – (190–400 nm)), face-shields marked with the term Z87 that meets the ANSI standard (ANSI Z87.1-1989 UV certification) to provide basic UV protection (Table of Materials) lab coats and gloves to minimize the exposure.
Fabrication techniques
This work also presents a step by step roadmap for high-pressure foam injection in fabricated glass microfluidic devices using a high-resolution camera and an illumination source. Examples of CO2 and scCO2 foam microstructure and transport in microfluidic devices are also presented with relevance to fractured tight and ultra-tight formations. Direct observation of transport in these subsurface media is a challenging task. As such, the devices described in this work provide an enabling platform to study transport in permeable media under temperature and pressure conditions that are relevant to subsurface applications such as fractured media, EOR processes and aquifer remediation.
Devices used in this work are fabricated using two different techniques, namely photolithography/wet-etching/thermal-bonding and SLE. The photolithography/wet-etching/thermal-bonding technique comprises a relatively low-cost etching process using a low-maintenance, collimated UV light-source. SLE is executed using a femto-second laser source followed by removal of modified glass from the glass bulk via wet-etching. The main steps involved in the photolithography/wet-etching/thermal-bonding technique include: (i) creation of the map of the channel network, (ii) printing the design on polyester based transparency film or a glass substrate, (iii) transferring the pattern on to a chrome/photoresist coated borosilicate substrate, (iv) removal of exposed area by photo developer and chrome etchant solutions, (v) etching the patterned area of the borosilicate substrate to the desired depth, (vi) preparing a cover plate with entry holes positioned in appropriate locations, and (vii) thermal bonding of the etched substrate and the cover plate. In contrast, SLE employs a two-step process: (i) selective laser-induced printing in a transparent fused silica substrate, and (ii) selective removal of the modified materials via wet chemical etching leading to the development of three-dimensional features in the fused silica substrate. In the first step, laser radiation through the fused silica glass internally modifies the glass bulk to increase the chemical/local etch-ability. The focused laser scans inside the glass to modify a three-dimensional connected volume that is connected to one of the surfaces of the substrate.
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 create high-precision etched micro-channels and capable lab-on-a-chip devices. The photolithography/wet-etching/thermal-bonding technique is robust in terms of the geometry of the channels and may be used to etch complex channel networks, whereas SLE is limited to relatively simple networks due to practical reasons. On the other hand, devices made with photolithography/wet-etching/thermal-bonding may be more vulnerable to breakage due to bonding imperfections, residual thermal stresses from fast heating/cooling rates during thermal bonding and structural flaws from the wet-etching process. In contrast to photolithography, SLE devices appear more resilient under high pressures (tested up to 9.65 MPa). Regardless of the fabrication technique, rapid pressure buildup rates may increase the chance of mechanical failures in microfluidic devices.
The authors have nothing to disclose.
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.
1/4” bolts and nuts | For fabrication of the metallic plates to sandwich the glass chip between them for thermal bonding | ||
3.45 x 3.45 mm UV LED | Kingbright | To emitt LED light | |
3D measuring Laser microscope | OLYMPUS | LEXT OLS4000 | To measure channel depths |
40 mm x 40 mm x 10 mm 12V DC Cooling Fan | Uxcell | To cool the UV LED lights | |
120 mm x 38 mm 24V DC Cooling Fan | Uxcell | To cool the UV LED lights | |
5 ml (6 ml) NORM-JECT Syringe | HENKE SASS WOLF | Lot #16M14CB | To rinse the chip before each experiment |
Acetone (Certified ACS) | Fisher Chemical | Lot #177121 | For cleaning |
Acid/ corossion resistive tweezer | TED PELLA | To handle the glass piece in corosive solutions | |
Acid/solvent resistance tweezers | TED PELLA, INC | #53009 and #53010 | To handle the glass in corrosive solutions |
Alloy X | AMERICAN SPECIAL METALS | Heat Number: ZZ7571XG11 | |
Ammonium hydroxide (ACS reagent) | Sigma Aldrich | Lot #SHBG9007V | To clean the chip at the end of process |
AutoCAD | Autodesk, San Rafael, CA | To design 2D patterns and 3D chips | |
BD Etchant for PSG-SiO2 systems | TRANSENE | Lot #028934 | An improved buffered etch formulation for delineation of phosphosilica glass – SiO2 (PSG), and borosilica glass – SiO2 (BSG) systems |
Blank Borofloat substrate | TELIC | CG-HF | Upper substrate for UV etching |
Borofloat substrate with metalizations | TELIC | PG-HF-LRC-Az1500 | Lower substrate for UV etching |
Capture One photo editing software | Phase One | To Capture/Edit/Convert the pictures taken by Phase One Camera | |
Capture station | DT Scientific | DT Versa | To place of the chip in the field of view of the camera |
Carbon dioxide gas (Grade E) | PRAXAIR | UN 1013, CAS Number 124-38-9 | non-aqeous portion of foam |
Chromium etchant 1020 | TRANSENE | Lot #025433 | High-purity ceric ammonium nitrate systems for precise, clean etching of chromium and chromium oxide films. |
Circulating baths with digital temperature controller | PolyScience | To control the brine and CO2 temperatures | |
CO2 | Airgas | 100% pure – 001013 – CAS: 124-38-9 | For CO2/scCO2 injection |
Computer | NVIDIA Tesla K20 Graphic Card – 706 MHz Core – 5 GB GDDR5 SDRAM – PCI Express 2.0 x16 | To process and visualize the images obtained via the Phase One camera | |
Custom made high pressure glass chip holder | To tightly hold the chip and its connections for high pressure testing | ||
Cutrain (Custom) | To protect against UV/IR Radiations | ||
Deionized water (DI) | For cleaning | ||
Digital camera with monochromatic 60 MP sensor | Phase One | IQ260 | Visualization system |
Ethanol, Anhydrous, USP Specs | DECON LABORATORIES, INC. | Lot #A12291505J, CAS# 64-17-5 | For cleaning |
Facepiece reusable respirator | 3M | 6502QL, Gases, Vapors, Dust, Medium | To protect against volatile solution inhalation |
Fused Silica (UV Grade) wafer | SIEGERT WAFER | UV grade | Glass precursor for SLE printing |
GIMP | Open-source image processing software | To characterize image texture and properties | |
Glovebox (vinyl anaerobic chamber) | Coy | To provide a clean, dust-free environment | |
Heated ultrasonic cleaning bath | Fisher Scientific | To accelerate the etching process | |
Hexamethyldisilazane (HMDS) Cleanroom® MB | KMG | 62115 | Primer for photoresist coating |
Hose (PEEK tubing) | IDEX HEALTH & SCIENCE | Natural 1/16" OD x .010" ID x 5ft, Part # 1531 | Flow connections |
Hydrochloric acid, certified ACS plus | Fisher Chemical | Lot # 187244 | Solvent in RCA semiconductor cleaning protocol |
Hydrogen Peroxide | Fisher Chemical | H325-500 | Solvent in RCA semiconductor cleaning protocol |
ImageJ | NIH | To characterize image texture and properties | |
ISCO syringe pump | TELEDYNE ISCO | D-SERIES (100DM, 500D) | To pump the fluids |
Kaiser LED light box | Kaiser | To illuminate the chip | |
Laser printing machine | LightFab GmbH, Germany. | FILL | Glass-SLE chip fabrication |
Laser safety glasses | FreeMascot | B07PPZHNX4 | To protect against UV/IR Radiations |
LED Engin 5W UV Lens | LEDiL | To emitt LED light | |
Light Fab 3D Printer (femtosecond laser) | Light Fab | To selectively laser Etch of fused silica | |
LightFab 3D printer | LightFab GmbH, Germany | To SLE print the fused silica chips | |
MATLAB | MathWorks, Inc., Natick, MA | To characterize image texture and properties | |
Metallic plates | |||
Micro abrasive sand blasters (Problast 2) | VANIMAN | Problast 2 – 80007 | To craete holes in cover plates |
MICROPOSIT 351 developer | Dow | 10016652 | Photoresist developer solution |
Muffle furnace | Thermo Scientific | Thermolyne Type 1500 | Thermal bonding |
N2 pure research grade | Airgas | Research Plus – NI RP300 | For drying the chips in each step |
NMP semiconductor grade – 0.1μm Filtered | Ultra Pure Solutions, Inc | Lot #02191502T | Organic solvent |
Oven | Gravity Convection Oven | 18EG | |
Phase One IQ260 with an achromatic sensor | Phase One | IQ260 | To visulize transport in microfluidic devices using an ISO 200 setting and an aperture at f/8. |
Photomask | Fine Line Imaging | 20,320 DPI FILM | Pattern of channels |
Photoresist (SU-8) | MICRO CHEM | Product item: Y0201004000L1PE, Lot Number: 18110975 | Photoresist |
Polarized light microscope | OLYMPUS | BX51 | Visual examination of micro channels |
Ports (NanoPort Assembly) | IDEX HEALTH & SCIENCE | NanoPort Assembly Headless, 10-32 Coned, for 1/16" OD, Part # N-333 | Connections to the chip |
Python | Python Software Foundation | To characterize image texture and properties | |
Safety face shield | Sellstrom | S32251 | To protect against UV/IR Radiations |
Sealing film (Parafilm) | Bemis Company, Inc | Isolation of containers | |
Shutter Control Software | Schneider-Kreuznach | To adjust shutter settings | |
Smooth ceramic plates | |||
Stirring hot plate | Corning® | PC-620D | To heat the solutions |
Sulfuric acid, ACS reagent 95.0-98.0% | Sigma Aldrich | Lot # SHBK0108 | Solvent in RCA semiconductor cleaning protocol |
Syringe pump (Standard Infuse/Withdraw PHD ULTRA) | Harvard Apparatus | 70-3006 | To saturate the chip before each experiment |
Torque wrench | Snap-on | TE25A-34190 | To tighten the screws |
UV power meter | Optical Associates, Incorporated | Model 308 | To measure the intesity of UV light |
UV power meter | Optical Associates, Incorporated | Model 308 | To quantify the strength of UV light |
UV radiation stand (LED lights) | To transfer the pattern to glass (photoresist layer) | ||
Vaccum pump | WELCH VACCUM TECHNOLOGY, INC | 1380 | To dry the chip |
Variable DC power supplies | Eventek | KPS305D | To power the UV LED lights |