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Expanding imaging capabilities for microfluidics: applicability of darkfield internal reflection illumination (DIRI) to observations in microfluidics.

Kawano Y, Otsuka C, Sanzo J, Higgins C, Nirei T, Schilling T, Ishikawa T - PLoS ONE (2015)

Bottom Line: Visualization of bubbles, tracer particles, and cells in a microfluidic device is important for designing a device and analyzing results.Whole-slide imaging was also conducted successfully using this system.The tiling function significantly expands the observing area of microfluidics.

View Article: PubMed Central - PubMed

Affiliation: The Department of Biomedical Engineering, Graduate School of Biomedical Engineering, Tohoku University, Sendai, Miyagi, Japan; Olympus Corporation, Shinjuku-Ku, Tokyo, Japan.

ABSTRACT
Microfluidics is used increasingly for engineering and biomedical applications due to recent advances in microfabrication technologies. Visualization of bubbles, tracer particles, and cells in a microfluidic device is important for designing a device and analyzing results. However, with conventional methods, it is difficult to observe the channel geometry and such particles simultaneously. To overcome this limitation, we developed a Darkfield Internal Reflection Illumination (DIRI) system that improved the drawbacks of a conventional darkfield illuminator. This study was performed to investigate its utility in the field of microfluidics. The results showed that the developed system could clearly visualize both microbubbles and the channel wall by utilizing brightfield and DIRI illumination simultaneously. The methodology is useful not only for static phenomena, such as clogging, but also for dynamic phenomena, such as the detection of bubbles flowing in a channel. The system was also applied to simultaneous fluorescence and DIRI imaging. Fluorescent tracer beads and channel walls were observed clearly, which may be an advantage for future microparticle image velocimetry (μPIV) analysis, especially near a wall. Two types of cell stained with different colors, and the channel wall, can be recognized using the combined confocal and DIRI system. Whole-slide imaging was also conducted successfully using this system. The tiling function significantly expands the observing area of microfluidics. The developed system will be useful for a wide variety of engineering and biomedical applications for the growing field of microfluidics.

No MeSH data available.


Schematic drawing of a microfluidic observation system.This system is capable of brightfield, DIRI (Darkfield Internal Reflection Illumination), conventional fluorescence, and confocal imaging. The DIRI image was obtained by illumination using the LEDs at the side of the slide. The system can also provide whole-slide images (WSI).
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pone.0116925.g002: Schematic drawing of a microfluidic observation system.This system is capable of brightfield, DIRI (Darkfield Internal Reflection Illumination), conventional fluorescence, and confocal imaging. The DIRI image was obtained by illumination using the LEDs at the side of the slide. The system can also provide whole-slide images (WSI).

Mentions: A photograph of the system is shown in Fig. 1C, and the optical layout is shown schematically in Fig. 2. The DIRI system consists of LEDs attached to the microscope stage [58], which enables visualization of the sample by refractive index mismatch. The DIRI system can be used with widefield fluorescence or confocal imaging. A microfluidic device on an appropriate stage adapter is placed on the stage, and the condenser lens for the transmitted illumination is set up about 10 mm below the Köhler illumination position. The condenser lens is located between the stage and mirror unit below the stage (not shown in Fig. 2). The halogen lamp is used for transmitted illumination. The spinning disk confocal system is set between two dichromatic mirrors (cf. Fig. 2). Mercury vapor short-arc lamps are used for confocal and fluorescence illumination. The observed images are recorded with a CCD camera (Orca R2; Hamamatsu Photonics, Hamamatsu, Japan). We typically use the Orca R2 camera for all modes of image capture, including DIRI, fluorescence, confocal, and brightfield imaging.


Expanding imaging capabilities for microfluidics: applicability of darkfield internal reflection illumination (DIRI) to observations in microfluidics.

Kawano Y, Otsuka C, Sanzo J, Higgins C, Nirei T, Schilling T, Ishikawa T - PLoS ONE (2015)

Schematic drawing of a microfluidic observation system.This system is capable of brightfield, DIRI (Darkfield Internal Reflection Illumination), conventional fluorescence, and confocal imaging. The DIRI image was obtained by illumination using the LEDs at the side of the slide. The system can also provide whole-slide images (WSI).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4352060&req=5

pone.0116925.g002: Schematic drawing of a microfluidic observation system.This system is capable of brightfield, DIRI (Darkfield Internal Reflection Illumination), conventional fluorescence, and confocal imaging. The DIRI image was obtained by illumination using the LEDs at the side of the slide. The system can also provide whole-slide images (WSI).
Mentions: A photograph of the system is shown in Fig. 1C, and the optical layout is shown schematically in Fig. 2. The DIRI system consists of LEDs attached to the microscope stage [58], which enables visualization of the sample by refractive index mismatch. The DIRI system can be used with widefield fluorescence or confocal imaging. A microfluidic device on an appropriate stage adapter is placed on the stage, and the condenser lens for the transmitted illumination is set up about 10 mm below the Köhler illumination position. The condenser lens is located between the stage and mirror unit below the stage (not shown in Fig. 2). The halogen lamp is used for transmitted illumination. The spinning disk confocal system is set between two dichromatic mirrors (cf. Fig. 2). Mercury vapor short-arc lamps are used for confocal and fluorescence illumination. The observed images are recorded with a CCD camera (Orca R2; Hamamatsu Photonics, Hamamatsu, Japan). We typically use the Orca R2 camera for all modes of image capture, including DIRI, fluorescence, confocal, and brightfield imaging.

Bottom Line: Visualization of bubbles, tracer particles, and cells in a microfluidic device is important for designing a device and analyzing results.Whole-slide imaging was also conducted successfully using this system.The tiling function significantly expands the observing area of microfluidics.

View Article: PubMed Central - PubMed

Affiliation: The Department of Biomedical Engineering, Graduate School of Biomedical Engineering, Tohoku University, Sendai, Miyagi, Japan; Olympus Corporation, Shinjuku-Ku, Tokyo, Japan.

ABSTRACT
Microfluidics is used increasingly for engineering and biomedical applications due to recent advances in microfabrication technologies. Visualization of bubbles, tracer particles, and cells in a microfluidic device is important for designing a device and analyzing results. However, with conventional methods, it is difficult to observe the channel geometry and such particles simultaneously. To overcome this limitation, we developed a Darkfield Internal Reflection Illumination (DIRI) system that improved the drawbacks of a conventional darkfield illuminator. This study was performed to investigate its utility in the field of microfluidics. The results showed that the developed system could clearly visualize both microbubbles and the channel wall by utilizing brightfield and DIRI illumination simultaneously. The methodology is useful not only for static phenomena, such as clogging, but also for dynamic phenomena, such as the detection of bubbles flowing in a channel. The system was also applied to simultaneous fluorescence and DIRI imaging. Fluorescent tracer beads and channel walls were observed clearly, which may be an advantage for future microparticle image velocimetry (μPIV) analysis, especially near a wall. Two types of cell stained with different colors, and the channel wall, can be recognized using the combined confocal and DIRI system. Whole-slide imaging was also conducted successfully using this system. The tiling function significantly expands the observing area of microfluidics. The developed system will be useful for a wide variety of engineering and biomedical applications for the growing field of microfluidics.

No MeSH data available.