Name: Construction Methods for Hybrid Polycarbonate-Silicon Microfluidic Devices (Video) | JoVE Journal
Uploaded: 2026-07-28T12:35:00.000+00:00
Duration: 8 min 18 s
Description: Learn three low-cost bonding strategies for hybrid polycarbonate–silicon microfluidic devices using solvent bonding, LDPE interlayers, or gasket compression. These methods enable reliable prototyping without specialized equipment.

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5 minutes

Thank you to Dr. Dorian Liepmann from UC Berkeley for his guidance and expertise in microfluidic device fabrication.
Funding: National Institutes of Health Grant U01 EB025136, National Institutes of Health Grant R21 HD113527, Department of Defense Grant PR2104827, Pediatric Scientist Development Program &#38; March of Dimes, National Institutes of Health K12HD047349

1. Device design: polycarbonate housing modifications
NOTE: Each bonding strategy required targeted design modification to the polycarbonate housing. The base microfluidic layout was therefore adapted to facilitate simple and effective implementation of different bonding approaches for our hybrid devices. Device design files are provided in Supplemental File 1.
<ol>
	<li>General housing design
	<ol>
		<li>Design the polycarbonate layer to include a recessed seat for the silicon chip with an interior perimeter trough to contain epoxy adhesive.</li>
	</ol>
	</li>
	<li>Design considerations for LDPE bonding
	<ol>
		<li>Include dowel pin holes in the housing design to allow precise alignment of the polycarbonate layers and the LDPE sheet.</li>
		<li>Account for the additional channel height created by the thickness of the LDPE layer.</li>
		<li>Ensure that the final LDPE design features are as follows: sealed surface area: ~15 cm2, target channel height: 200 &#181;m.</li>
	</ol>
	</li>
	<li>Design considerations for solvent bonding
	<ol>
		<li>Include dowel pin holes to allow alignment between polycarbonate layers.</li>
		<li>Adjust channel height to compensate for potential reduction in height after solvent bonding.</li>
		<li>Create a lip or ledge by recessing the edges of one polycarbonate piece. This facilitates solvent wicking at the bonding interface.</li>
		<li>Ensure that the final solvent design features are as follows: sealed surface area: ~11 cm2, target channel height: 200 &#181;m.</li>
	</ol>
	</li>
	<li>Design considerations for gasket compression bonding
	<ol>
		<li>Design a gasket gland for a gasket cord that follows the fluidic channel path. Dimension the gland to achieve approximately 25% compression of the selected gasket cross-section.</li>
		<li>Include the gasket gland in the bottom polycarbonate piece; design the top polycarbonate surface to be flat.</li>
		<li>Add bolt holes around the perimeter to allow for screws. To create even compression, use washers or strong compression plates. Use bolts for layer alignment during assembly, instead of dowel pins.</li>
		<li>Ensure that the final gasket design features are as follows: sealed surface area: ~3 cm2, target channel height: 200 &#181;m.</li>
	</ol>
	</li>
</ol>
2. Fabrication and preparation of device layers
<ol>
	<li>Fabricate the polycarbonate housing.
	<ol>
		<li>Fabricate the polycarbonate layers according to the design specifications using an appropriate method (e.g., CNC milling). To follow this protocol, perform CNC machining to obtain a flat bonding surface and a surface roughness of 0.8 &#181;m. 
		&#8203;NOTE: 3D printing was also evaluated but resulted in bowing, which reduced the effective bonding area.</li>
	</ol>
	</li>
	<li>Clean the polycarbonate housings and silicon chips.
	<ol>
		<li>Inspect and clean the fabricated housings for debris, burs, or machining residue under optical magnification. Rinse the parts thoroughly with isopropyl alcohol and allow to dry completely at room temperature.</li>
		<li>Inspect and clean the silicon chips for defects or excess residue. Clean as necessary using isopropyl alcohol to remove particulate debris. 
		&#8203;NOTE: No further surface preparation was incorporated for the purpose of this evaluation.</li>
	</ol>
	</li>
	<li>Prepare epoxy adhesive.
	<ol>
		<li>Mix a two-part epoxy according to the manufacturer&#39;s instructions. Allow the epoxy to partially cure at room temperature until it reaches a thicker viscosity suitable for precise application.</li>
	</ol>
	</li>
	<li>Apply epoxy and mount the silicon chip.
	<ol>
		<li>Load the viscous epoxy into a syringe fitted with a dispensing needle. Apply a controlled bead of epoxy into the trough surrounding the chip seat.</li>
		<li>Gently place the silicon chip into the recessed seat, ensuring full contact with the epoxy and no trapped air bubbles. Apply additional epoxy as necessary to fill any gaps. 
		&#8203;NOTE: Using partially cured, viscous epoxy minimizes overflow beyond the bonding area. However, trapped bubbles can create failure points, so consider degassing or poking residual bubbles out of the trough.</li>
	</ol>
	</li>
	<li>Cure the primary bond.
	<ol>
		<li>Allow the assembly to cure at room temperature or low heat (&#60;40 &#176;C). 
		&#8203;NOTE: Avoid excessive heating, as polycarbonate has a low glass transition temperature (150 &#176;C), which can result in warping or bowing.</li>
	</ol>
	</li>
	<li>Seal residual gaps.
	<ol>
		<li>Prepare a fresh batch of epoxy and load it into a syringe fitted with a thin needle (27&#8211;30 G needle). Run a thin bead of epoxy along the perimeter seam between the silicon and polycarbonate housing, allowing epoxy to fill cracks. Allow the sealant epoxy layer to cure completely before further handling.</li>
	</ol>
	</li>
</ol>
3. Solvent bonding
<ol>
	<li>Apply adhesive tape to define the channel walls. Laser-cut adhesive tape to match the shape of the channel walls. 
	NOTE: Microfluidic diagnostic tape was used for temporary channel walls (see the Table of Materials).</li>
	<li>Remove one liner layer from the tape. Align and apply the tape to the channel wall surfaces using dowel pins for alignment.</li>
	<li>Coat the fluidic channel with polyvinyl alcohol (PVA). Add enough 1% PVA solution to cover the entire fluidic channel area. Allow the PVA solution to dry completely at room temperature. 
	NOTE: PVA does not readily dissolve in dichloromethane, thus protects epoxy, silicon, as well as coatings, such as PDMS and PEG.</li>
	<li>Remove the adhesive mask. Once the PVA layer has fully cured, carefully peel off the double-sided adhesive, leaving a PVA-coated fluidic channel. Inspect and, if necessary, clean any residual adhesive from the channel walls.</li>
	<li>Assemble the polycarbonate layers. Align the top and bottom polycarbonate housings using dowel pins.</li>
	<li>Apply solvent along the bonding interface.
	<ol>
		<li>Fill a 5 mL syringe with a 30 G needle with the chosen solvent (e.g., dichloromethane, acetone). Position the syringe tip at the lip/ledge created in the device design. Carefully dispense the solvent along the lip/ledge on both sides of the assembly, allowing the solvent to wick into the bonding interface and reach the PVA barrier. 
		&#8203;NOTE: Perform all solvent handling in a chemical fume hood wearing gloves and eye protection. Dispense solvent steadily to minimize bubble formation at the interface. CAUTION: Dispose of excess solvent in a labeled, appropriate chemical waste container in accordance with institutional guidelines.</li>
	</ol>
	</li>
	<li>Apply pressure and cure.
	<ol>
		<li>Place a moderate weight (approximately 2&#8211;3 lbs) evenly over the assembled device. Allow the device to cure fully at room temperature for 10&#8211;15 min.</li>
		<li>Under a microscope, ensure no large bubbles are present to reduce points of failure.</li>
	</ol>
	</li>
	<li>Remove the PVA sacrificial layer. After curing, flow 80 &#176;C deionized water through the fluidic channel at low flows (1&#8211;5 mL/min) for a minimum of 3 h to dissolve and remove the PVA coating. Allow up to 24 h of water flow to ensure complete PVA removal.
	<ol>
		<li>Inspect the device visually for residual PVA in the channel. If PVA is apparent, repeat the flow of water until no PVA is visually apparent.</li>
	</ol>
	</li>
</ol>
4. LDPE bonding
<ol>
	<li>Prepare LDPE bonding sheets. Laser-cut low-density polyethylene (LDPE) sheets to match the shape of the channel wall regions. For a 100&#8211;200 &#181;m LDPE sheet, use 75% power and 100% speed for the referenced desktop laser cutter (see the Table of Materials).</li>
	<li>Clean the LDPE sheets.
	<ol>
		<li>Inspect the laser-cut LDPE sheets for ash, residue, or particulates. Rinse thoroughly with isopropyl alcohol (IPA) and allow to dry completely.</li>
	</ol>
	</li>
	<li>Assemble the housing with LDPE layers.
	<ol>
		<li>Align the LDPE cutouts onto the side walls of the fluid channel using dowel pins for alignment. Place the top polycarbonate piece onto the bottom assembly, sandwiching the LDPE layers at the bonding interface.</li>
	</ol>
	</li>
	<li>Bond the assembly in a heated oven.
	<ol>
		<li>Place the assembled housing into a preheated programmable oven set to 145 &#176;C with a temperature sensor.</li>
		<li>Apply moderate pressure (2&#8211;3 pounds per square inch (PSI)) on top of the assembly using a calibrated weight such as a metal plate.</li>
	</ol>
	</li>
	<li>Complete the assembly.
	<ol>
		<li>After 2 h, remove the assembly from the oven. Ensure an even LDPE transparency across the entire bonded surface area. Allow the device to cool to room temperature under ambient conditions.</li>
	</ol>
	</li>
</ol>
5. Gasket sealing
<ol>
	<li>Cut and place the gasket.
	<ol>
		<li>Cut the gasket cord material to the required length to match the fluidic channel path.</li>
		<li>Place the gasket cord into the gasket gland on the bottom polycarbonate housing, ensuring a snug and continuous fit along the entire path.</li>
	</ol>
	</li>
	<li>Assemble the housing.
	<ol>
		<li>Align the top polycarbonate piece with the bottom piece using bolts for alignment. Insert bolts through the top layer and into the hex nut, including washers or a compression plate as needed to evenly distribute pressure.</li>
	</ol>
	</li>
	<li>Tighten the bolts to seal the assembly.
	<ol>
		<li>Hand-tighten each screw to hold the bolts and device in place.</li>
		<li>Use a torque wrench to tighten each screw, moving in a cross pattern.</li>
		<li>Tighten to 0.5 lb-in to avoid cracking the silicon chip or deforming the polycarbonate housing. Tighten further as necessary. 
		&#8203;NOTE: Even compression is critical to ensure a fluid-tight seal and to avoid cracking of the silicon.</li>
	</ol>
	</li>
</ol>
6. Inlet-outlet (I/O) port
NOTE: The following steps have been optimized for evaluating our hybrid device design, as outlined in the remainder of the protocol. The following steps in this section are not required for use of the bonding techniques. The I/O port design used in this portion has been added to Supplemental File 1.
<ol>
	<li>Design and fabricate the appropriate I/O port for the microfluidic design.
	<ol>
		<li>Design an I/O port that can fit with the microfluidic design and attach to a fluidic circuit (i.e., tube fitting, luer lock).</li>
		<li>3D print the design with a high-precision 3D printer. 
		&#8203;NOTE: Other I/O ports can be used for the design, such as purchased I/O ports or luer-locked connectors.</li>
	</ol>
	</li>
	<li>Attach the I/O ports to the assembled microfluidic device.
	<ol>
		<li>Prepare epoxy according to the manufacturer&#39;s instructions and place it in a 1 mL syringe with a 27 G needle.</li>
		<li>Dispense 100&#8211;200 &#181;L onto the I/O ports face, taking care not to get epoxy in the flow path, and attach the I/O ports to the microfluidic device ports. Allow to cure for 24 h.</li>
	</ol>
	</li>
</ol>
7. Testing the device
<ol>
	<li>Connect the hybrid microfluidic device to a fluidic circuit.
	<ol>
		<li>Using peristaltic pump tubing (see the Table of Materials), connect a water reservoir, roller pump, pressure sensor, and the hybrid microfluidic device in series.</li>
		<li>Position the pressure sensor as close to the device inlet as possible to ensure accurate pressure measurements.</li>
	</ol>
	</li>
	<li>Pressure and leak testing
	<ol>
		<li>Pump water through the circuit at an initial flow rate of 10 mL/min.</li>
		<li>Increase the flow rate in increments of 10 mL/min every minute.</li>
		<li>Measure and record the pressure at each flow rate. If additional pressure is required, add a needle restriction downstream of the device to increase circuit resistance.</li>
		<li>Define the rated pressure as the pressure at which the first visible leak occurs.</li>
	</ol>
	</li>
	<li>Pressure drop testing
	<ol>
		<li>Using the same circuit, insert a second pressure sensor immediately downstream of the device.</li>
		<li>Flow water at a selected flow rate (10 mL/min in this study).</li>
		<li>Calculate the pressure drop across the device as the difference between pre- and post-device pressure measurements.</li>
	</ol>
	</li>
</ol>

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<li>Islam, M. M., Loewen, A., Allen, P. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Simple%2C+low-cost+fabrication+of+acrylic+based+droplet+microfluidics+and+its+use+to+generate+DNA-coated+particles%5BTitle%5D)+AND+%22Sci+Rep%22%5BJournal%5D)">Simple, low-cost fabrication of acrylic based droplet microfluidics and its use to generate DNA-coated particles.</a> Sci Rep. 8 (1), 8763(2018).</li>
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<li>Wan, A. M. D., Moore, T. A., Young, E. W. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Solvent+bonding+for+fabrication+of+PMMA+and+COP+microfluidic+devices%5BTitle%5D)+AND+%22J+Vis+Exp%22%5BJournal%5D)">Solvent bonding for fabrication of PMMA and COP microfluidic devices.</a> J Vis Exp. (119), e55175(2017).</li>
<li>Ogończyk, D., Węgrzyn, J., Jankowski, P., Dąbrowski, B., Garstecki, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Bonding+of+microfluidic+devices+fabricated+in+polycarbonate%5BTitle%5D)+AND+%22Lab+Chip%22%5BJournal%5D)">Bonding of microfluidic devices fabricated in polycarbonate.</a> Lab Chip. 10 (10), 1324-1327 (2010).</li>
<li>Ahmed, M. A. M., Jurczak, K. M., Lynn, N. S., Mulder, J. -P. S. H., Verpoorte, E. M. J., Nagelkerke, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Rapid+prototyping+of+PMMA-based+microfluidic+spheroid-on-a-chip+models+using+micromilling+and+vapour-assisted+thermal+bonding%5BTitle%5D)+AND+%22Sci+Rep%22%5BJournal%5D)">Rapid prototyping of PMMA-based microfluidic spheroid-on-a-chip models using micromilling and vapour-assisted thermal bonding.</a> Sci Rep. 14 (1), 2831(2024).</li>
<li>Hassanpour-Tamrin, S., Sanati-Nezhad, A., Sen, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+simple+and+low-cost+approach+for+irreversible+bonding+of+polymethylmethacrylate+and+polydimethylsiloxane+at+room+temperature+for+high-pressure+hybrid+microfluidics%5BTitle%5D)+AND+%22Sci+Rep%22%5BJournal%5D)">A simple and low-cost approach for irreversible bonding of polymethylmethacrylate and polydimethylsiloxane at room temperature for high-pressure hybrid microfluidics.</a> Sci Rep. 11 (1), 4821(2021).</li>
<li>Zhao, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Plastic+polymers+for+efficient+DNA+microarray+hybridization%3A+application+to+microbiological+diagnostics%5BTitle%5D)+AND+%22J+Clin+Microbiol%22%5BJournal%5D)">Plastic polymers for efficient DNA microarray hybridization: application to microbiological diagnostics.</a> J Clin Microbiol. 46 (11), 3752-3758 (2008).</li>
<li>Nielsen, J. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Microfluidics%3A+innovations+in+materials+and+their+fabrication+and+functionalization%5BTitle%5D)+AND+%22Anal+Chem%22%5BJournal%5D)">Microfluidics: innovations in materials and their fabrication and functionalization.</a> Anal Chem. 92 (1), 150-168 (2020).</li>
<li>Washburn, A. L., Gunn, L. C., Bailey, R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Label-free+quantitation+of+a+cancer+biomarker+in+complex+media+using+silicon+photonic+microring+resonators%5BTitle%5D)+AND+%22Anal+Chem%22%5BJournal%5D)">Label-free quantitation of a cancer biomarker in complex media using silicon photonic microring resonators.</a> Anal Chem. 81 (22), 9499-9506 (2009).</li>
<li>Kojic, S. P., Stojanovic, G. M., Radonic, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Novel+cost-effective+microfluidic+chip+based+on+hybrid+fabrication+and+its+comprehensive+characterization%5BTitle%5D)+AND+%22Sensors+%28Basel%29%22%5BJournal%5D)">Novel cost-effective microfluidic chip based on hybrid fabrication and its comprehensive characterization.</a> Sensors (Basel). 19 (7), 1719(2019).</li>
<li>Boursier, M., Bayon, Y., Negrell, C., Pinaud, J., Caillol, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Biocompatible+glues%3A+recent+progress+and+emerging+frontiers+in+surgical+adhesion%5BTitle%5D)+AND+%22Polymers%22%5BJournal%5D)">Biocompatible glues: recent progress and emerging frontiers in surgical adhesion.</a> Polymers. 17 (13), 1749(2025).</li>
<li>Higgins, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Engineering+a+silicon+membrane+oxygenator+for+an+artificial+placenta%5BTitle%5D)+AND+%22eScholarship%22%5BJournal%5D)">Engineering a silicon membrane oxygenator for an artificial placenta.</a> eScholarship. , (2025).</li>
<li>Wei, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Rapid+prototyping+of+multi-functional+and+biocompatible+Parafilm%C2%AE-based+microfluidic+devices+by+laser+ablation+and+thermal+bonding%5BTitle%5D)+AND+%22Micromachines%22%5BJournal%5D)">Rapid prototyping of multi-functional and biocompatible Parafilm®-based microfluidic devices by laser ablation and thermal bonding.</a> Micromachines. 14 (3), 656(2023).</li>
<li>Madadi, M., Madadi, A., Zareifar, R., Nikfarjam, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+simple+solvent-assisted+method+for+thermal+bonding+of+large-surface%2C+multilayer+PMMA+microfluidic+devices%5BTitle%5D)+AND+%22Sens+Actuators+A+Phys%22%5BJournal%5D)">A simple solvent-assisted method for thermal bonding of large-surface, multilayer PMMA microfluidic devices.</a> Sens Actuators A Phys. 349, 114077(2023).</li>
<li>Riegger, L., Strohmeier, O., Faltin, B., Zengerle, R., Koltay, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Adhesive+bonding+of+microfluidic+chips%3A+influence+of+process+parameters%5BTitle%5D)+AND+%22J+Micromech+Microeng%22%5BJournal%5D)">Adhesive bonding of microfluidic chips: influence of process parameters.</a> J Micromech Microeng. 20 (8), 087003(2010).</li>
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</ol>

SR is the founder of Silicon Kidney. NCH, DGB, and SR are co-inventors on a provisional patent related to the technology described in this manuscript. The authors have no other competing interests to declare.

Reliable enclosure and sealing continue to present significant challenges in hybrid microfluidic systems, particularly where structural integrity must be maintained during pressurized operation. Standard microfluidic device fabrication has leveraged a wide range of bonding strategies, including laser welding, thermal bonding, adhesive layers, and chemical surface modification, depending on the material and application42,43,44<su...

Microfluidic systems enable controlled manipulation of small fluid volumes and have become essential tools in biomedical applications, including point-of-care diagnostics1,2, organ-on-chip platforms3,4, and sensor technologies5,6. Despite the diversity of their applications, these devices share core engineering demands: appropriate material selection, reproducible fabrication strategies, and sustained biocompatibility7,8. These requirements become more stringent in blood-contacting systems, where materials and device architectures must ensure hemocompatibility, form&#160;robust fluid sealing, and maintain physiologic flow parameters such as shear stress and pressure gradients9,10,11.
Hybrid microfluidic systems integrate thermoplastics with rigid substrates such as silicon and glass, expanding the functionality of biomedical devices (Supplemental Figure S1)12,13,14,15,16,17. This approach is particularly intriguing for blood-contacting applications, where mechanically fragile yet highly precise silicon or glass components are coupled to low-cost polymer housings to enable scalable, biocompatible designs18,19,20,21,22,23,24. While PDMS and thermoplastic microdevices remain prevalent due to their fabrication simplicity, these materials limit chemical resistance, mechanical durability, and incorporation of rigid functional materials, motivating the development of hybrid architectures25,26,27,28. Despite the advantages of hybrid devices, assembling dissimilar materials presents inherent challenges. Differences in thermal expansion and mechanical properties can undermine seal integrity, and fabrication conditions must be tightly controlled to preserve hemocompatibility, maintain channel geometry, and prevent damage to brittle silicon or glass structures. Successful implementation of hybrid systems, therefore, depends on deliberate choices of material properties with appropriate fabrication strategies.
Thermoplastic materials, including polycarbonate and poly(methyl methacrylate) (PMMA), are widely used in microfluidic systems because they provide mechanical strength, biocompatibility, cost efficiency, and are compatible with scalable fabrication strategies such as solvent bonding, thermocompression, and adhesives12,29,30,31,32,33,34,35. In contrast, silicon and glass substrates offer enhanced chemical resistance and high-precision geometries, yet their integration with thermoplastics remains technically challenging due to disparities in surface chemistry and mechanical properties36,37,38,39. Conventional thermocompression bonding can subject brittle silicon or glass components to elevated pressures, increasing the risk of cracking. Alternatively, adhesive-based approaches may reduce mechanical stress but can introduce variability in bond uniformity or raise concerns regarding long-term biocompatibility40.
Our lab is developing blood-contacting devices intended for organ replacement functions, including oxygenators and hemofilters17,21. These systems integrate silicon nanopore membranes as active functional elements with polycarbonate housings that establish the blood flow pathway and provide mechanical support18,19,21. Achieving robust and scalable fabrication of these platforms depends on reliable bonding between these dissimilar materials.
This work evaluates three bonding approaches developed to address the constraints of conventional high-temperature and high-pressure assembly methods used for hybrid polycarbonate&#8211;silicon microfluidic systems. The platform design is derived from ongoing efforts to develop modular components for a microfluidic extracorporeal membrane oxygenator17. The device incorporates a rigid polycarbonate housing that provides mechanical stability and defines a machined blood flow channel, integrated with a semi-permeable silicon membrane intended to facilitate gas exchange. To isolate bonding performance during testing, a non-porous silicon substrate was used in place of the functional membrane.
The three bonding approaches evaluated were: 1) a solvent-based method that avoids high-temperature and significant mechanical load with a protective masking strategy to preserve channel geometry, 2) a low-temperature thermal bonding technique incorporating a 100 &#181;m low-density polyethylene (LDPE) interlayer between polycarbonate plates, and 3) a mechanically sealed configuration using an O-ring gasket cord positioned around the fluidic channel. These strategies were systematically compared to determine their feasibility and reliability for rapid prototyping of hybrid microfluidic devices in a laboratory research setting. All methods were designed to enable low-temperature assembly while supporting moderate operating pressures (10&#8211;700 mmHg) and flow conditions relevant to blood-contacting microfluidic systems. The following article builds upon a chapter from the dissertation of the first author41.

<table><tbody><tr><td>.040&quot; (1.00 mm) Buna-N 70 O-Ring Cord Stock</td><td>The O-Ring Store</td><td>N70.040</td><td>1 mm gasket used in assembly; diameter adjustable per design</td></tr><tr><td>18-8 Stainless Steel Dowel Pin</td><td>McMaster</td><td>90145A876</td><td>Used for alignment in LDPE and solvent bonding</td></tr><tr><td>18-8 Stainless Steel Washer</td><td>McMaster</td><td>92141A006</td><td>Used in gasket compression assembly</td></tr><tr><td>316 Stainless Steel Ultra-Low-Profile Socket Head Screw</td><td>McMaster</td><td>91223A315</td><td>Screws used in gasket assembly</td></tr><tr><td>CAD Software</td><td>OnShape or SolidWorks (or equivalent)</td><td>Used for device design</td><td></td></tr><tr><td>Desktop CO2 Laser Cutter</td><td>Universal Laser Systems (or equivalent)</td><td>Used for cutting LDPE sheets and adhesive tape</td><td></td></tr><tr><td>Dichloromethane, anhydrous, 99.7+%</td><td>ThermoFisher</td><td>047352.M1</td><td>Solvent used for solvent bonding</td></tr><tr><td>Digital Torque Screwdriver</td><td>Checkline</td><td>TSD-400</td><td>Used to apply controlled compression in gasket assembly</td></tr><tr><td>Epoxy Resin, two-part</td><td>Epoxy Technology (or equivalent)</td><td>MED-302</td><td>Used for bonding silicon to polycarbonate</td></tr><tr><td>Hex Nut, Low-Strength Steel</td><td>McMaster</td><td>90480A007</td><td>Used with screws for gasket compression</td></tr><tr><td>Low-Density Polyethylene (LDPE) Film</td><td>McMaster</td><td>8593K71</td><td>100&amp;ndash;200 &amp;micro;m LDPE sheet for thermal bonding</td></tr><tr><td>Microfluidic Diagnostic Adhesive Tape</td><td>3M</td><td>9965; 9972A</td><td>Used as temporary masking layer during solvent bonding</td></tr><tr><td>Peristaltic Pump Tubing (Size 16 equivalent)</td><td>Masterflex (or equivalent)</td><td>Compatible with roller pump used in testing</td><td></td></tr><tr><td>Polycarbonate Housing (machined)</td><td>Xometry (or equivalent)</td><td>CNC-machined polycarbonate device layers</td><td></td></tr><tr><td>Pressure Sensor</td><td></td><td></td><td>Used to measure inlet and outlet pressures</td></tr><tr><td>Programmable Laboratory Oven</td><td></td><td></td><td>Capable of maintaining 145 &amp;deg;C for LDPE bonding</td></tr><tr><td>Roller Pump</td><td></td><td></td><td>Used for pressure and flow testing</td></tr><tr><td>Silicon Substrate (solid chip)</td><td>MicroDicing (or equivalent)</td><td>Used as model silicon component</td><td></td></tr><tr><td>Stainless Steel Dispensing Needles with Luer Lock</td><td>McMaster</td><td>75165A688</td><td>Used for dispensing epoxy and solvent</td></tr></tbody></table>

construction methods for hybrid polycarbonate-silicon microfluidic devices

Construction Methods for Hybrid Polycarbonate-Silicon Microfluidic Devices

Hybrid microfluidic devices combining thermoplastics with rigid substrates, such as silicon and glass, enable advanced biological applications but are difficult to bond due to differences in thermal and mechanical properties. These challenges render conventional high-temperature and high-pressure methods unsuitable, motivating the need for alternative sealing strategies. Here, we present three relatively low-cost sealing strategies for polycarbonate&#8211;silicon microfluidic devices: solvent bonding with protective masking to preserve channel geometry; low-temperature thermal bonding layer using a 100 &#181;m low-density polyethylene (LDPE) interlayer; and mechanical compression with an O-ring cord that serves as a gasket. Each approach requires tailored design and assembly steps to ensure leak-tight seals. These strategies require no specialized equipment or expensive infrastructure, making them well-suited for prototyping hybrid microfluidic devices in academic research laboratories and resource-limited environments. Solvent bonding produced the highest leak resistance (up to 692 mmHg) with a robust polycarbonate&#8211;polycarbonate interface, while gasket compression yielded the most reproducible, visually clean seals with minimal pressure drop (2 mmHg at 10 mL/min). In contrast, LDPE bonding showed channel intrusion, elevated pressure drop (196 mmHg), and instances of delamination.

Figure 1 summarizes the overall assembly sequence for the three bonding approaches evaluated in this study. The device architecture consisted of two machined polycarbonate layers, each incorporating a fluidic channel. A silicon element was bonded to each layer to complete half of the intended flow path. The selected sealing strategies were then used to join the two polycarbonate assemblies, thereby enclosing the microchannel. Performance metrics for each configuration are presented in <stron...

This protocol describes three straightforward sealing methods for fabricating a hybrid microfluidic device that integrates polycarbonate and silicon components. By implementing solvent bonding, thermal compression, and mechanical compression strategies, we enable reliable, low-temperature sealing techniques that avoid specialized equipment for hybrid microfluidic devices.

Hybrid microfluidic devices combining thermoplastics with rigid substrates, such as silicon and glass, enable advanced biological applications but are ...

Our research focuses on bonding hybrid microfluidic devices for prototyping in an academic lab setting. We aim to answer the question of, what are low-cost, yet optimal bonding strategies for a hybrid microfluidic channel? Bonding thermoplastics to rigid substrates in hybrid microfluidics is challenging, and conventional high temperature, high pressure methods are unsuitable.This protocol provides a practical research-friendly bonding approach. To begin, obtain the polycarbonate housing with a flat bonding surface. Dispense epoxy into the recessed chip seat of the polycarbonate housing, and place the cleaned silicon chip into position.Let the assembly cure, then seal any gaps with fresh epoxy. Laser cut the adhesive tape to match the shape of the channel walls. To apply adhesive tape, remove one liner layer from the tape.Then align and apply the tape to the channel wall surfaces using dowel pins for alignment. Add enough 1%polyvinyl alcohol solution to cover the fluidic channel area. Then set the coated channel aside to dry completely at room temperature.To remove the adhesive mask, once the polyvinyl alcohol layer has fully cured, carefully peel off the double-sided adhesive, leaving a polyvinyl alcohol-coated fluidic channel. Inspect and clean any residual adhesive from the channel walls if necessary. Align the top and bottom polycarbonate silicon hybrid housing half plates using the dowel pins.Position the 30 gauge needle tip of a five milliliter syringe containing dichloromethane or acetone at the device lip or ledge. Then dispense the solvent along both sides, so it wicks into the bonding interface and reaches the polyvinyl alcohol barrier. Then place a moderate weight of approximately two to three pounds evenly over the assembled device, and allow the device to cure fully at room temperature for 10 to 15 minutes.Ensure no large bubbles are present to reduce points of failure. After curing, flow 80 degrees Celsius deionized water through the fluidic channel at low flows of one to five milliliters per minute for a minimum of three hours. Inspect the device visually for residual polyvinyl alcohol in the channel, and repeat the water flow until no polyvinyl alcohol is visually apparent.Using a desktop laser cutter, laser cut low-density polyethylene sheets to match the shape of the channel wall regions. Inspect the laser cut low-density polyethylene sheets for ash, residue, or particulates. Rinse the sheets thoroughly with isopropyl alcohol and allow them to dry completely.Align the LDPE cutouts onto the side walls of the fluid channel using dowel pins. Place the top polycarbonate piece onto the bottom assembly to create the fluidic channel with the LDPE layers at the bonding interface. To bond the assembly, place the assembled housing into a programmable oven set to 145 degrees Celsius with a temperature sensor.Then position a calibrated weight, such as a metal plate, on top of the assembly to apply moderate pressure of two to three pounds per square inch. After two hours, remove the assembly from the oven. Confirm that the LDPE is evenly transparent across the bonded surface area, then allow the device to cool to room temperature.Cut the gasket cord material to the required length to match the fluidic channel path. Place the gasket cord into the gasket gland on the bottom polycarbonate housing, ensuring a snug and continuous fit along the entire path. Align the top polycarbonate piece with the bottom piece.Then insert bolts through the top layer and into the hex nut, adding washers or a compression plate as needed to evenly distribute pressure. Hand tighten each screw to hold the device in place. Then use a torque wrench to tighten the screws in a cross pattern.Tighten to 0.5 pound inch initially to avoid cracking the silicon chip or deforming the polycarbonate housing, and increase the torque only if additional sealing is required. Prepare to connect the hybrid microfluidic device to a fluidic circuit using peristaltic pump tubing. Connect a water reservoir, roller pump, pressure sensor, and the hybrid microfluidic device in series.Position the pressure sensor as close to the device inlet as possible to ensure accurate pressure measurements. Pump water through the circuit at an initial flow rate of 10 milliliters per minute. Increase the flow rate by 10 milliliters per minute at 60-second intervals, and record the pressure at each flow rate.If additional pressure is required, add a needle restriction downstream of the device to increase circuit resistance. Define the rated pressure as the pressure at which the first visible leak occurs. Finally, insert a second pressure sensor immediately downstream of the device using the same circuit.Flow water at a selected flow rate of 10 milliliters per minute, and calculate the pressure drop across the device as the difference between the pre-device and post-device pressure measurements. The three bonding methods showed different performance outcomes. Solvent bonded devices sustained the highest rated pressure, reaching 692 millimeters of mercury before leakage, but some devices showed trapped air or slight optical haze.LDPE-bonded devices showed a high pressure drop of 196 millimeters of mercury at 10 milliliters per minute, making it less effective. Among the tested techniques, the gasket sealing method demonstrated the highest reproducibility and the cleanest visual interfaces. The gasket-based configuration sustained pressures up to 239 millimeters of mercury before leakage, and showed a low pressure drop of three millimeters of mercury.This protocol allows researchers to study different low-cost bonding modalities suitable for bonding hybrid microfluidic devices in a laboratory setting. The most important consideration when performing this protocol is ensuring precision in both the design fabrication and alignment of the layers for a leak-tight interface and adequate bond surface area. Future studies can compare ceiling surface areas across bonding methods and evaluate this protocol's applicability to hybrid microfluidic systems incorporating brittle or diverse substrate materials.

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Research

JoVE Journal

Bioengineering

Microfluidic devices can be used to visualize complex natural processes in real time and at the appropriate physical scales.  We have developed a simple microfluidic device that mimics key features of natural porous media for studying growth and transport of bacteria in the subsurface.

Window on a Microworld: Simple Microfluidic Systems for Studying Microbial Transport in Porous Media

Source: Kurz, D. L., et al. Microfluidic Platform to Study Bioclogging in Porous Media. J. Vis. Exp. (2022)The video demonstrates the use of a microfluidic device to study biofilm formation. A bacterial suspension is introduced into the microchannel, followed by incubation to allow biofilm development. Flow is then resumed, and pressure monitoring along with imaging is used to detect biofilm formation and pore blockage over time.

A Microfluidic Device for Real-Time Imaging and Pressure Tracking During Biofilm Formation

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

Multi-step Variable Height Photolithography for Valved Multilayer Microfluidic Devices

The control of chemical and oxygen gradients is essential for cell cultures. This paper reports a polydimethylsiloxane-polycarbonate (PDMS-PC) microfluidic device capable of reliably generating combinations of chemical and oxygen gradients for cell migration studies, which can be practically utilized in biological labs without sophisticated instrumentation.

Polydimethylsiloxane-polycarbonate Microfluidic Devices for Cell Migration Studies Under Perpendicular Chemical and Oxygen Gradients

We demonstrate a microfluidic platform with an integrated surface electrode network that combines resistive pulse sensing (RPS) with code division multiple access (CDMA), to multiplex detection and sizing of particles in multiple microfluidic channels.

Microfluidic Platform with Multiplexed Electronic Detection for Spatial Tracking of Particles

A protocol for the fabrication of plastic microfluidic devices with transparent view-ports for visible and infrared light imaging is described.

Soft Lithographic Procedure for Producing Plastic Microfluidic Devices with View-ports Transparent to Visible and Infrared Light

Several methods are available for the fabrication of channels of non-rectangular sections embedded in polydimethylsiloxane microfluidic devices. Most of them involve multistep manufacturing and extensive alignment. In this paper, a one-step approach is reported for fabricating microfluidic channels of different geometric cross sections by polydimethylsiloxane sequential wet etching.

One-Step Approach to Fabricating Polydimethylsiloxane Microfluidic Channels of Different Geometric Sections by Sequential Wet Etching Processes

Here we present a protocol to design and fabricate custom microfluidic devices with minimal financial and time investment. The aim is to facilitate the adoption of microfluidic technologies in biomedical research laboratories and educational settings.

Rapid Fabrication of Custom Microfluidic Devices for Research and Educational Applications

The present protocol describes a microfluidic platform to study biofilm development in quasi-2D porous media by combining high-resolution microscopy imaging with simultaneous pressure difference measurements. The platform quantifies the influence of pore size and fluid flow rates in porous media on bioclogging.

A Microfluidic Platform to Study Bioclogging in Porous Media

This article describes protocols for high-throughput gelatin methacryloyl microgel fabrication using microfluidic devices, converting microgels to resuspendable powder (micro-aerogels), the chemical assembly of microgels to form granular hydrogel scaffolds, and developing granular hydrogel bioinks with preserved microporosity for 3D bioprinting.

Gelatin Methacryloyl Granular Hydrogel Scaffolds: High-throughput Microgel Fabrication, Lyophilization, Chemical Assembly, and 3D Bioprinting

The fabrication of a polydimethylsiloxane (PDMS)-based bilayer device for the production of combinatorial libraries in water-in-oil emulsions (plugs) is presented here. The necessary hardware and software required to automate plug production are detailed in the protocol, and the production of a quantitative library of fluorescent plugs is also demonstrated.

Bilayer Microfluidic Device for Combinatorial Plug Production

Learn three low-cost bonding strategies for hybrid polycarbonate–silicon microfluidic devices using solvent bonding, LDPE interlayers, or gasket compression. These methods enable reliable prototyping without specialized equipment.

Construction Methods for Hybrid Polycarbonate-Silicon Microfluidic Devices

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