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Fabrication of Refractive-index-matched Devices for Biomedical Microfluidics

Published: September 10th, 2018



1Department of Chemical Engineering, University of Utah, 2Huntsman Cancer Institute, University of Utah

This protocol describes the fabrication of microfluidic devices from MY133-V2000 to eliminate artifacts that often arise in microchannels due to the mismatching refractive indices between microchannel structures and an aqueous solution. This protocol uses an acrylic holder to compress the encapsulated device, improving adhesion both chemically and mechanically.

The use of microfluidic devices has emerged as a defining tool for biomedical applications. When combined with modern microscopy techniques, these devices can be implemented as part of a robust platform capable of making simultaneous complementary measurements. The primary challenge created by the combination of these two techniques is the mismatch in refractive index between the materials traditionally used to make microfluidic devices and the aqueous solutions typically used in biomedicine. This mismatch can create optical artifacts near the channel or device edges. One solution is to reduce the refractive index of the material used to fabricate the device by using a fluorinated polymer such as MY133-V2000 whose refractive index is similar to that of water (n = 1.33). Here, the construction of a microfluidic device made out of MY133-V2000 using soft lithography techniques is demonstrated, using O2 plasma in conjunction with an acrylic holder to increase the adhesion between the MY133-V2000 fabricated device and the polydimethylsiloxane (PDMS) substrate. The device is then tested by incubating it filled with cell culture media for 24 h to demonstrate the ability of the device to maintain cell culture conditions during the course of a typical imaging experiment. Finally, quantitative phase microscopy (QPM) is used to measure the distribution of mass within the live adherent cells in the microchannel. This way, the increased precision, enabled by fabricating the device from a low index of refraction polymer such as MY133-V2000 in lieu of traditional soft lithography materials such as PDMS, is demonstrated. Overall, this approach for fabricating microfluidic devices can be readily integrated into existing soft lithography workflows in order to reduce optical artifacts and increase measurement precision.

The development of microfluidic technology has enabled a wide range of new biomedical techniques that leverage the unique physics of microscopic-scale flows1,2. This includes the diagnostic techniques built on microfluidic platforms that quantify clinically relevant biomarkers, including cell stiffness3, surface markers4, and growth5. By manipulating single cells, microfluidic devices can also be used to measure biomarker heterogeneity, for example as an indicator of malignancy6. The ability to combine microfluidic ....

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1. Fabrication of the Polydimethylsiloxane Negative

  1. Preparation of polydimethylsiloxane
    1. Measure 18 g of PDMS silicone elastomer and 1.8 g of the curing reagent. Pour the curing reagent into a measuring boat containing the elastomer.
    2. Mix the elastomer and the curing reagent vigorously for 1 min and put the mixture into a vacuum chamber for 30 min.
    3. Remove the PDMS from the vacuum, pour 15 g onto the negative using a cookie cutter (radius = 3.8 cm) to keep the P.......

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This protocol describes the fabrication of MY133-V2000, a fluorinated polymer with a low refractive index matching that of water. A key feature of this protocol is how to overcome the lack of adhesion that is characteristic of fluorinated polymers by using oxygen plasma and by fabricating the device within an acrylic holder to provide the extra mechanical force required to seal the channel against the PDMS substrate (Figure 1). The low refractive index of the.......

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MY133-V2000 can be used as an alternative to traditional soft lithography fabrication materials such as PDMS. Previous work has shown that materials with a high index of refraction, such as PDMS, introduce significant artifacts near the channel walls due to the mismatching indices of refraction between the fabrication material and the aqueous solution inside the channel13. MY133-V2000 enables matching the refractive index of the microfluidic device to the aqueous solutions commonly used in biomedi.......

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This work was supported by the University of Utah office of the Vice President for Research, as well as by funds in conjunction with grant P30 CA042014 awarded to the Huntsman Cancer Institute and to the CRR Program at the Huntsman Cancer Institute.


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Name Company Catalog Number Comments
MY133-V2000 MY Polymers MY133-V2000
Sylgard 184 Ellsworth Adhesives 184 SIL ELAST KIT 0.5KG
Fisher Premium microscope slides Fisher Scientific 12-544-4
.118"(3.0mm) x 12" x 12" Acrylic Sheet United States Plastic Corp 44290
.060"(1.5mm) x 12" x 12" Acrylic Sheet United States Plastic Corp 44200
SCIGRIP 3 Very Fast Set Acrylic Cement United States Plastic Corp 45735
Standard Aluminum Foil (.6 mm thick) VWR 89107-726
Kim Wipes Fisher Scientific 06-666
Insta-Cure+ Super Glue Bob Smith Industries BSI-109
1/8" PVC tubing McMaster Carr 5231K55
McCormick Food Coloring Target 13353207
X-Acto #1 Precision Knife X-Acto X3201
X-Acto #18 Heavyweight wood chiseling blade X-Acto X218
VWR Razor Blades VWR 55411-055
Surface Treated Cell Culture Dishes Fisher Scientific FBO12922
Fibronectin Human Plasma Sigma-Aldritch F0895-1MG
Trypsin-EDTA 10x Fisher Scientific 15-400-054
Corning Dulbecco's Phosphate Buffered Saline Fisher Scientific MT21030CM
Gibco Penicillin-Streptomycin Fisher Scientific 15-140-148
HyClone Nonessential Amino Acids 100x Fisher Scientific SH3023801
Fetal Bovine Serum Omega Scientific FB-12
Corning DMEM with L-glutamine and glucose Fisher Scientific MT10013CV
Trichloro(1H,1H,2H,2H-perfluorooctyl)silane Sigma-Aldritch 448931 Reacts violently with water
Ethanol, 200 proof Decon Labs Fisher Scientific 04-355-223
Acetone Fisher Scientific A18P-4
Bel-Art 42025 Plastic Dessicator Cole-Parmer EW-06514-30
Epilog Fusion Laser Cutter, 120 W Epilog Laser Epilog Fusion M2 32 Laser
Isotemp Stirring Hotplate Fisher Scientific SP88850200
Ateco 14111 1.5 inch stainless steel cutter Ateco 14111
Pyrex Glass Cell Culture Dish Fisher Scientific 08-747B
Radio Frequency Plasma Cleaner Harrick Plasma PDC-32G Used with Oxygen gas
Black Hole Laboratories Digivac Black Hole Laboratories Model 215
Intelli-Ray Ultraviolet Oven Uvitron UVO338
Compact Spin Coater MTI Corporation VTC-100A
Fisher Brand Isotemp Oven Fisher Scientific 15-103-0510 Forced Air Convection
Gilson Positive Displacement Pipette P1000 Fisher Scientific FD10006G
HeraCell VIOS 160i Fisher Scientific 13 998 212PM

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