3,895 research outputs found
Widefield multifrequency fluorescence lifetime imaging using a two-tap complementary metal-oxide semiconductor camera with lateral electric field charge modulators.
Widefield frequency-domain fluorescence lifetime imaging microscopy (FD-FLIM) measures the fluorescence lifetime of entire images in a fast and efficient manner. We report a widefield FD-FLIM system based on a complementary metal-oxide semiconductor camera equipped with two-tap true correlated double sampling lock-in pixels and lateral electric field charge modulators. Owing to the fast intrinsic response and modulation of the camera, our system allows parallel multifrequency FLIM in one measurement via fast Fourier transform. We demonstrate that at a fundamental frequency of 20âMHz, 31-harmonics can be measured with 64 phase images per laser repetition period. As a proof of principle, we analyzed cells transfected with Cerulean and with a construct of Cerulean-Venus that shows Förster Resonance Energy Transfer at different modulation frequencies. We also tracked the temperature change of living cells via the fluorescence lifetime of Rhodamine B at different frequencies. These results indicate that our widefield multifrequency FD-FLIM system is a valuable tool in the biomedical field
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A 25 micron-thin microscope for imaging upconverting nanoparticles with NIR-I and NIR-II illumination.
Rationale: Intraoperative visualization in small surgical cavities and hard-to-access areas are essential requirements for modern, minimally invasive surgeries and demand significant miniaturization. However, current optical imagers require multiple hard-to-miniaturize components including lenses, filters and optical fibers. These components restrict both the form-factor and maneuverability of these imagers, and imagers largely remain stand-alone devices with centimeter-scale dimensions. Methods: We have engineered INSITE (Immunotargeted Nanoparticle Single-Chip Imaging Technology), which integrates the unique optical properties of lanthanide-based alloyed upconverting nanoparticles (aUCNPs) with the time-resolved imaging of a 25-micron thin CMOS-based (complementary metal oxide semiconductor) imager. We have synthesized core/shell aUCNPs of different compositions and imaged their visible emission with INSITE under either NIR-I and NIR-II photoexcitation. We characterized aUCNP imaging with INSITE across both varying aUCNP composition and 980 nm and 1550 nm excitation wavelengths. To demonstrate clinical experimental validity, we also conducted an intratumoral injection into LNCaP prostate tumors in a male nude mouse that was subsequently excised and imaged with INSITE. Results: Under the low illumination fluences compatible with live animal imaging, we measure aUCNP radiative lifetimes of 600 ÎŒs - 1.3 ms, which provides strong signal for time-resolved INSITE imaging. Core/shell NaEr0.6Yb0.4F4 aUCNPs show the highest INSITE signal when illuminated at either 980 nm or 1550 nm, with signal from NIR-I excitation about an order of magnitude brighter than from NIR-II excitation. The 55 ÎŒm spatial resolution achievable with this approach is demonstrated through imaging of aUCNPs in PDMS (polydimethylsiloxane) micro-wells, showing resolution of micrometer-scale targets with single-pixel precision. INSITE imaging of intratumoral NaEr0.8Yb0.2F4 aUCNPs shows a signal-to-background ratio of 9, limited only by photodiode dark current and electronic noise. Conclusion: This work demonstrates INSITE imaging of aUCNPs in tumors, achieving an imaging platform that is thinned to just a 25 ÎŒm-thin, planar form-factor, with both NIR-I and NIR-II excitation. Based on a highly paralleled array structure INSITE is scalable, enabling direct coupling with a wide array of surgical and robotic tools for seamless integration with tissue actuation, resection or ablation
Low Noise and High Photodetection Probability SPAD in 180 nm Standard CMOS Technology
A square shaped, low noise and high photo-response single photon avalanche diode suitable for circuit integration, implemented in a standard CMOS 180 nm high voltage technology, is presented. In this work, a p+ to shallow n-well junction was engineered with a very smooth electric field profile guard ring to attain a photo detection probability peak higher than 50% with a median dark count rate lower than 2 Hz/ÎŒm2 when operated at an excess bias of 4 V. The reported timing jitter full width at half maximum is below 300 ps for 640 nm laser pulses
Low Light CMOS Contact Imager with an Integrated Poly-Acrylic Emission Filter for Fluorescence Detection
This study presents the fabrication of a low cost poly-acrylic acid (PAA) based emission filter integrated with a low light CMOS contact imager for fluorescence detection. The process involves the use of PAA as an adhesive for the emission filter. The poly-acrylic solution was chosen due its optical transparent properties, adhesive properties, miscibility with polar protic solvents and most importantly its bio-compatibility with a biological environment. The emission filter, also known as an absorption filter, involves dissolving an absorbing specimen in a polar protic solvent and mixing it with the PAA to uniformly bond the absorbing specimen and harden the filter. The PAA is optically transparent in solid form and therefore does not contribute to the absorbance of light in the visible spectrum. Many combinations of absorbing specimen and polar protic solvents can be derived, yielding different filter characteristics in different parts of the spectrum. We report a specific combination as a first example of implementation of our technology. The filter reported has excitation in the green spectrum and emission in the red spectrum, utilizing the increased quantum efficiency of the photo sensitive sensor array. The thickness of the filter (20 ÎŒm) was chosen by calculating the desired SNR using Beer-Lambertâs law for liquids, Quantum Yield of the fluorophore and the Quantum Efficiency of the sensor array. The filters promising characteristics make it suitable for low light fluorescence detection. The filter was integrated with a fully functional low noise, low light CMOS contact imager and experimental results using fluorescence polystyrene micro-spheres are presented
Optofluidic Formaldehyde Sensing: Towards On-Chip Integration
International audienceFormaldehyde (HCHO), a chemical compound used in the fabrication process of a broad range of household products, is present indoors as an airborne pollutant due to its high volatility caused by its low boiling point ( T=â19 °C). Miniaturization of analytical systems towards palm-held devices has the potential to provide more efficient and more sensitive tools for real-time monitoring of this hazardous air pollutant. This work presents the initial steps and results of the prototyping process towards on-chip integration of HCHO sensing, based on the Hantzsch reaction coupled to the fluorescence optical sensing methodology. This challenge was divided into two individually addressed problems: (1) efficient airborne HCHO trapping into a microfluidic context and (2) 3,5âdiacetyl-1,4-dihydrolutidine (DDL) molecular sensing in low interrogation volumes. Part (2) was addressed in this paper by proposing, fabricating, and testing a fluorescence detection system based on an ultra-low light Complementary metal-oxide-semiconductor (CMOS) image sensor. Two three-layer fluidic cell configurations (quartzâSU-8âquartz and siliconâSU-8âquartz) were tested, with both possessing a 3.5 ”L interrogation volume. Finally, the CMOS-based fluorescence system proved the capability to detect an initial 10 ”g/L formaldehyde concentration fully derivatized into DDL for both the quartz and silicon fluidic cells, but with a higher signal-to-noise ratio (SNR) for the silicon fluidic cell ( SNRsilicon=6.1 ) when compared to the quartz fluidic cell ( SNRquartz=4.9 ). The signal intensity enhancement in the silicon fluidic cell was mainly due to the silicon absorption coefficient at the excitation wavelength, a(λabs=420 nm)=5Ă104 cmâ1 , which is approximately five times higher than the absorption coefficient at the fluorescence emission wavelength, a(λem=515 nm)=9.25Ă103 cmâ
Development of a microfluidic device for gaseous formaldehyde sensing = Développement d\u27un dispositif microfluidique pour la détection de formaldéhyde à l\u27état gazeux
Formaldehyd (HCHO) ist eine chemische Verbindung, die bei der Herstellung einer groĂen Zahl von Haushaltsprodukten verwendet wird.Charakteristisch ist seine hohe FlĂŒchtigkeit aufgrund einer niedrigen Siedetemperatur (). Daher ist HCOH fast ĂŒberall als Luftschadstoff in InnenrĂ€umen vorhanden. Die Miniaturisierung analytischer Systeme zu Handheld-GerĂ€t hat das Potenzial, nicht nur effizientere, sondern auch empfindlichere Instrumente fĂŒr die EchtzeitĂŒberwachung dieses gefĂ€hrlichen Luftschadstoffs zu ermöglichen.
Die vorliegende Doktorarbeit prĂ€sentiert die Entwicklung eines Mikrofluidik-GerĂ€ts fĂŒr die Erfassung von HCHO basierend auf der Hantzsch-Reaktion.Hierbei wurde der Schwerpunkt auf die Komponente fĂŒr Fluoreszenzdetektion gelegt.
Es wurde eine umfangreiche Literaturrecherche durchgefĂŒhrt, die es erlaubt, den Stand der Technik auf dem Gebiet der Miniaturisierung des Fluoreszenzsensors zusammenzufassen. Auf Grund dieser Studie wurde ein modulares Fluoreszenzdetektionskonzept vorgeschlagen, das um einen CMOS-Bildsensor (CIS) herum entwickelt wurde. Zwei dreischichtige Fluidikzellenkonfigurationen (Konfiguration 1: Quarz - SU-8 3050 - Quarz und Konfiguration 2: Silizium - SU-8 3050 - Quarz) wurden in Betracht gezogen und parallel unter den gleichen experimentellen Bedingungen getestet. Die Verfahren der Mikrofabrikation der fluidischen Zellen wurden detailliert beschrieben, einschlieĂlich des Integrationsprozesses der Standardkomponenten und der experimentellen Verfahren.
Der CIS-basierte Fluoreszenzdetektor bewies seine LeistungsfĂ€higkeit, eine anfĂ€ngliche HCHO-Konzentration von 10 ”g/L vollstĂ€ndig in 3,5-Diacetyl-1,4-dihydrolutidin (DDL- derivatisiert) sowohl fĂŒr die Quarz- als auch fĂŒr die Silizium-Fluidikzellen zu detektieren. Beide Systemewiesenein Abfragevolumen von 3,5 ”L auf. Ein offensichtlich höheres Signal-Rausch-VerhĂ€ltnis (SNR) wurde fĂŒr die Silizium-Fluidzelle () im Vergleich zur Quarz-Fluidzelle () beobachtet. Die VerstĂ€rkung der SignalintensitĂ€t in der Silizium-Fluidzelle ist wahrscheinlich auf den Silizium-Absorptionskoeffizienten bei der AnregungswellenlĂ€nge zurĂŒckzufĂŒhren,. Dieser Koeffizient ist ungefĂ€hr fĂŒnfmal höher als der Absorptionskoeffizient bei der FluoreszenzemissionswellenlĂ€nge
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HCHO wird aufgrund seiner relativ hohen Konstanten fĂŒr das Henry-Gesetz sehr schnell in ein flĂŒssiges Reagenz aufgenommen. Somit hĂ€ngt die Auswahl des molekularen Einfangverfahrens (Schwallströmung, Ringströmung oder membranbasierte Strömungswechselwirkung) von derLeistungsfĂ€higkeit des Fluoreszenzdetektors ab. Ein vorlĂ€ufiges Konzept, das auf der Verwendung einer Gas-FlĂŒssigkeitsmembran-basierten Wechselwirkung zum stĂ€ndigen Abfangen des gasförmigen HCHO basiert, wurde eingefĂŒhrt. Hierzu wurden kompatible Materialien und Herstellungsmethoden identifiziert. DarĂŒber hinaus wurden CFD-Simulationen durchgefĂŒhrt, um die MikrokanallĂ€nge unter verschiedenen hydrodynamischen Bedingungen abzuschĂ€tzen, die fĂŒr eine vollstĂ€ndige HCHO-Derivatisierung erforderlich sind.
Eine Verbesserung und Vereinfachung auf der Grundlage von sehrnempfindlichen Fluoreszenzdetektoren mit niedrigen Detektionsgrenzen könnte zukĂŒnftig basierend z. B. auf Schwallströmung oder Ringströmung möglich sein
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