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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.


The darkfield illuminator and DIRI illumination areas.(1a) The photograph shows the microfluidic device used with the DIRI illuminator. The illuminated area is almost the entire microfluidic device. (1b) The photograph shows the microfluidic device used with a regular darkfield illuminator. The condenser lens is a DCD condenser, NA 0.8–0.92 (Olympus). The illuminated area is shown by the blue arrow. Note the small area properly covered by the illuminator. (1c) The experimental setup for the system. The left side camera is an Orca R2. The microfluidic device consists of a special microfluidics module placed upon a plastic adapter plate. The size of the microfluidics module in the photograph is 25 × 75 mm.
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pone.0116925.g001: The darkfield illuminator and DIRI illumination areas.(1a) The photograph shows the microfluidic device used with the DIRI illuminator. The illuminated area is almost the entire microfluidic device. (1b) The photograph shows the microfluidic device used with a regular darkfield illuminator. The condenser lens is a DCD condenser, NA 0.8–0.92 (Olympus). The illuminated area is shown by the blue arrow. Note the small area properly covered by the illuminator. (1c) The experimental setup for the system. The left side camera is an Orca R2. The microfluidic device consists of a special microfluidics module placed upon a plastic adapter plate. The size of the microfluidics module in the photograph is 25 × 75 mm.

Mentions: Fig. 1A shows the newly developed DIRI (Darkfield Internal Reflection Illumination) unit. A multiple LED light assembly is installed on the stage plate and used for side illumination of a microfluidics cell or a glass slide. The DIRI system can be used alone, or may be used with a fluorescence microscope. Acquired fluorescent images are used to show fluorescent markers of target objects. The DIRI system creates a broad scattering of illumination from the edges of the PMDS channel walls. The refractive index mismatch between PMDS and buffer (liquid) produces good image contrast, resulting in high-quality images of the microchannel walls. Superimposition of the two images (fluorescence and DIRI) allows observation of both fluorescent markers and the edges of the channel walls. There are two ways to produce such superimposed images: (a) fluorescence and DIRI images can be acquired simultaneously, or (b) fluorescence and DIRI images can be acquired sequentially as two or more channels (depending on the number of fluorescent channels to be captured separately), and the channels can be superimposed later. Method (a) can be applied to dynamic phenomena as well as static phenomena, whereas method (b) can be applied only to static phenomena.


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)

The darkfield illuminator and DIRI illumination areas.(1a) The photograph shows the microfluidic device used with the DIRI illuminator. The illuminated area is almost the entire microfluidic device. (1b) The photograph shows the microfluidic device used with a regular darkfield illuminator. The condenser lens is a DCD condenser, NA 0.8–0.92 (Olympus). The illuminated area is shown by the blue arrow. Note the small area properly covered by the illuminator. (1c) The experimental setup for the system. The left side camera is an Orca R2. The microfluidic device consists of a special microfluidics module placed upon a plastic adapter plate. The size of the microfluidics module in the photograph is 25 × 75 mm.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0116925.g001: The darkfield illuminator and DIRI illumination areas.(1a) The photograph shows the microfluidic device used with the DIRI illuminator. The illuminated area is almost the entire microfluidic device. (1b) The photograph shows the microfluidic device used with a regular darkfield illuminator. The condenser lens is a DCD condenser, NA 0.8–0.92 (Olympus). The illuminated area is shown by the blue arrow. Note the small area properly covered by the illuminator. (1c) The experimental setup for the system. The left side camera is an Orca R2. The microfluidic device consists of a special microfluidics module placed upon a plastic adapter plate. The size of the microfluidics module in the photograph is 25 × 75 mm.
Mentions: Fig. 1A shows the newly developed DIRI (Darkfield Internal Reflection Illumination) unit. A multiple LED light assembly is installed on the stage plate and used for side illumination of a microfluidics cell or a glass slide. The DIRI system can be used alone, or may be used with a fluorescence microscope. Acquired fluorescent images are used to show fluorescent markers of target objects. The DIRI system creates a broad scattering of illumination from the edges of the PMDS channel walls. The refractive index mismatch between PMDS and buffer (liquid) produces good image contrast, resulting in high-quality images of the microchannel walls. Superimposition of the two images (fluorescence and DIRI) allows observation of both fluorescent markers and the edges of the channel walls. There are two ways to produce such superimposed images: (a) fluorescence and DIRI images can be acquired simultaneously, or (b) fluorescence and DIRI images can be acquired sequentially as two or more channels (depending on the number of fluorescent channels to be captured separately), and the channels can be superimposed later. Method (a) can be applied to dynamic phenomena as well as static phenomena, whereas method (b) can be applied only to static phenomena.

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.