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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.


Related in: MedlinePlus

Three-dimensional images of fluorescent particles in microfluidic channels taken using confocal and DIRI.The image was taken with a 30× objective lens (NA 1.05, silicone oil immersion). (9a) Confocal fluorescence image. (9b) Image obtained by simultaneous using a confocal fluorescence excitation and DIRI (Darkfield Internal Reflection Illumination). (9c) Image obtained by simultaneous using confocal fluorescence excitation, and brightfield illumination.
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pone.0116925.g009: Three-dimensional images of fluorescent particles in microfluidic channels taken using confocal and DIRI.The image was taken with a 30× objective lens (NA 1.05, silicone oil immersion). (9a) Confocal fluorescence image. (9b) Image obtained by simultaneous using a confocal fluorescence excitation and DIRI (Darkfield Internal Reflection Illumination). (9c) Image obtained by simultaneous using confocal fluorescence excitation, and brightfield illumination.

Mentions: The images shown in Fig. 9 were obtained by simultaneously using DIRI and fluorescent illumination. No flow was induced in this case, and the three-dimensional confocal image was obtained using a 30× silicone oil immersion objective lens (NA 1.05). In the case of fluorescent illumination alone (Fig. 9A), fluorescent beads could be observed clearly, but the edges of the channel were difficult to identify. When fluorescent and brightfield illumination were used simultaneously (Fig. 9C), the shape of the channel became clear, but the contrast of the fluorescent beads was lost because the background image was brighter. The bright background considerably reduced the contrast of the image. When DIRI and fluorescent illumination were used simultaneously (Fig. 9B), the shape of the channel could be observed clearly, and the contrast of the fluorescent beads was maintained. This technique can also be applied to dynamic phenomena, such as fluorescent beads flowing through the microchannel. A movie taken using simultaneous fluorescent and DIRI is available as supplementary data (S1 Video).


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)

Three-dimensional images of fluorescent particles in microfluidic channels taken using confocal and DIRI.The image was taken with a 30× objective lens (NA 1.05, silicone oil immersion). (9a) Confocal fluorescence image. (9b) Image obtained by simultaneous using a confocal fluorescence excitation and DIRI (Darkfield Internal Reflection Illumination). (9c) Image obtained by simultaneous using confocal fluorescence excitation, and brightfield illumination.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0116925.g009: Three-dimensional images of fluorescent particles in microfluidic channels taken using confocal and DIRI.The image was taken with a 30× objective lens (NA 1.05, silicone oil immersion). (9a) Confocal fluorescence image. (9b) Image obtained by simultaneous using a confocal fluorescence excitation and DIRI (Darkfield Internal Reflection Illumination). (9c) Image obtained by simultaneous using confocal fluorescence excitation, and brightfield illumination.
Mentions: The images shown in Fig. 9 were obtained by simultaneously using DIRI and fluorescent illumination. No flow was induced in this case, and the three-dimensional confocal image was obtained using a 30× silicone oil immersion objective lens (NA 1.05). In the case of fluorescent illumination alone (Fig. 9A), fluorescent beads could be observed clearly, but the edges of the channel were difficult to identify. When fluorescent and brightfield illumination were used simultaneously (Fig. 9C), the shape of the channel became clear, but the contrast of the fluorescent beads was lost because the background image was brighter. The bright background considerably reduced the contrast of the image. When DIRI and fluorescent illumination were used simultaneously (Fig. 9B), the shape of the channel could be observed clearly, and the contrast of the fluorescent beads was maintained. This technique can also be applied to dynamic phenomena, such as fluorescent beads flowing through the microchannel. A movie taken using simultaneous fluorescent and DIRI is available as supplementary data (S1 Video).

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.


Related in: MedlinePlus