3,069 research outputs found
A spatial contrast retina with on-chip calibration for neuromorphic spike-based AER vision systems
We present a 32 32 pixels contrast retina microchip that provides its output as an address event representation (AER) stream. Spatial contrast is computed as the ratio between pixel photocurrent and a local average between neighboring pixels obtained with a diffuser network. This current-based computation produces an important amount of mismatch between neighboring pixels, because the currents can be as low as a few pico-amperes. Consequently, a compact calibration circuitry has been included to trimm each pixel. Measurements show a reduction in mismatch standard deviation from 57% to 6.6% (indoor light). The paper describes the design of the pixel with its spatial contrast computation and calibration sections. About one third of pixel area is used for a 5-bit calibration circuit. Area of pixel is 58 m 56 m, while its current consumption is about 20 nA at 1-kHz event rate. Extensive experimental results are provided for a prototype fabricated in a standard 0.35- m CMOS process.Gobierno de España TIC2003-08164-C03-01, TEC2006-11730-C03-01European Union IST-2001-3412
Optical sensor system for monitoring the pH of cellular media: application to an organ-on-a-chip platform
Dissertação de mestrado integrado em Engenharia FísicapH is a physiological parameter that changes its value according to cellular state of a human organ.
When a tumour is being developed, it is known that they have a more acid interstitial pH than
normal tissues. This is mainly due to the high metabolic activity of the abnormal cells with increase
of acidic sub-products and the absence of organised vasculature of tumours, that leads to poor
tissue oxygenation. Indeed, in in vitro animal systems, such as static cell culture experiments or
advanced microfluidic devices, the cell’s metabolic activity during incubation causes the alteration
of the cell culture pH, which drops the pH from close to the physiological (7.4) to acidic ones (lower
than 7.0). Because low environmental pH inhibits cell survival, proliferation and activity, cell culture
media has to be consecutively replaced for fresh one.
For the pH monitoring, cell culture media is, in general, complemented with a pH colorimetric
indicator (e.g. phenol red). However, the colour change of the cell culture media does not quantify
the pH value. For this reason, the monitoring and quantification of cell culture medium pH,
especially in advanced cell culture devices, such as organ-on-a-chip (OoC), which contain healthy
and/or tumour organ models, is still a challenge and a parameter of utmost importance for the
maintenance of homeostasis (auto-regulation).
The pH of tissues can be measured by a variety of techniques, being pH electrodes the most used.
Nevertheless, other methods can be used for pH measurement, such as optical sensors. In general,
this technique eliminates the tissue injury effects, but results in an integrated measurement over
a long period and demanding a relatively large volume of sample.
Particularly, in OoC platforms, the small size of each OoC constituent part, has triggered the
development of micro(bio)sensors to be integrated in the microchambers that feed the perfusion
chambers containing the organ models, which are used for monitoring the pH of the cell culture
media in circulation.
In this study, a literature review of pH sensors that can be miniaturised and integrated in OoC was
investigated. Based on this previews literature research, and the presence of a colorimetric pH
indicator (phenol red) that is commercially added to cell culture media, a miniaturization of an
optical pH sensor, for real-time sensing of the cell culture medium feeding advanced microfluidic
devices was investigated. This strategy can have several advantages, such as low-cost
implementation and improvement of the pH reading based on the beam-splitter phenomenon. For this purpose, a microchamber, processed by micromilling in PMMA, was developed and optimised
to support the pH optical sensing system, creating a prototype device that can be directly
incorporated into an OoC platform.
For the pH sensing experiments, buffered solutions with stablished pH and phenol red were used
to test and optimize the optical sensor, by analysing their transmittance signal. In this study, the
colorimetric pH indicator (phenol red) was added in the same concentration than the one used in
commercial cell culture media. The results shown that the pH reading was successful achieved in
intervals of 0.2 pH units, in a range between 6.0 to 8.0.O pH é um parâmetro fisiológico, cujo valor se altera de acordo com o estado celular de um órgão
humano. Quando um tumor está em poliferação, este tem um pH intersticial mais ácido do que
os tecidos normais. Isto deve-se principalmente à elevada atividade metabólica das células
anormais com o aumento de subprodutos ácidos e a ausência de vasculatura organizada dos
tumores, que leva à pobre oxigenação dos tecidos. De facto, em sistemas animais in vitro, tais
como experiências de cultura celular estática ou dispositivos microfluídicos avançados, a atividade
metabólica da célula durante a incubação provoca a alteração do pH da cultura celular, que baixa
o pH de perto do fisiológico (7.4) para um mais ácido (inferior a 7.0). O baixo pH fisiológico inibe
a sobrevivência, proliferação e atividade celular, e, em consequência, os meios de cultura celular
têm de ser substituídos consecutivamente.
Para a monitorização do pH, os meios de cultura celular são, em geral, complementados com um
indicador colorimétrico de pH (por exemplo, vermelho de fenol). No entanto, a mudança de cor
dos meios de cultura celular não quantifica o valor do pH. Por esta razão, a monitorização e
quantificação do pH dos meios de cultura celular, especialmente em dispositivos avançados de
cultura celular, tais como Organ-on-a-chip (OoC), que contêm modelos de órgãos saudáveis e/ou
tumorais, é ainda um desafio e um parâmetro da maior importância para a manutenção da
homeostase (autorregulação).
O pH dos tecidos pode ser medido por uma variedade de técnicas, sendo os elétrodos de pH os
mais utilizados. Contudo, outros métodos podem ser utilizados para a medição do pH, tais como
os sensores óticos. Esta técnica elimina os efeitos da lesão tecidual, mas resulta numa medição
integrada durante um longo período e a partir de um volume relativamente grande de amostra.
Particularmente, nas plataformas de OoC, o pequeno tamanho de cada parte constituinte de OoC,
desencadeou o desenvolvimento de micro(bio)sensores para serem integrados nas microcâmaras
que alimentam as câmaras de perfusão, as quais contêm os modelos de órgãos, e que podem ser
utilizados para monitorizar o pH dos meios de cultura celular em circulação.
Neste estudo, foi investigada uma revisão bibliográfica de sensores de pH que podem ser
miniaturizados e integrados na OoC. Com base nesta pesquisa bibliográfica prévia, e a presença
de um indicador colorimétrico de pH (vermelho fenol) que é comercialmente adicionado aos meios
de cultura celular, foi investigada uma miniaturização de um sensor ótico de pH para a deteção em tempo real do meio de cultura celular que alimenta dispositivos microfluídicos avançados. Esta
estratégia pode ter várias vantagens, tais como a implementação a baixo custo e a melhoria da
leitura do pH com base no fenómeno do separador de feixe. Para este efeito, foi desenvolvida e
otimizada uma microcâmara, processada por micromilling em PMMA, para apoiar o sistema de
deteção ótica de pH, criando um dispositivo protótipo que pode ser diretamente incorporado numa
plataforma OoC.
Para as experiências de deteção de pH, foram utilizadas soluções tampão com pH estabilizado e
vermelho fenol para testar e otimizar o sensor ótico, através da análise do seu sinal de
transmitância. Assim, o indicador colorimétrico de pH vermelho de fenol foi adicionado na mesma
concentração encontrada nos meios de cultura celular comerciais. Os resultados mostram que a
leitura do pH foi bem-sucedida em intervalos de 0.2 unidades de pH, num intervalo entre 6.0 a
8.0.This work results partially of the project NORTE-01-0145-FEDER-029394, RTChip4Theranostics, supported by Programa Operacional Regional do Norte - Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF) and by Fundação para a Ciência e Tecnologia (FCT), IP, project reference PTDC/EMD-EMD/29394/2017
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 großen Zahl von Haushaltsprodukten verwendet wird.Charakteristisch ist seine hohe Flüchtigkeit aufgrund einer niedrigen Siedetemperatur (). Daher ist HCOH fast überall als Luftschadstoff in Innenräumen vorhanden. Die Miniaturisierung analytischer Systeme zu Handheld-Gerät hat das Potenzial, nicht nur effizientere, sondern auch empfindlichere Instrumente für die Echtzeitüberwachung dieses gefährlichen Luftschadstoffs zu ermöglichen.
Die vorliegende Doktorarbeit präsentiert die Entwicklung eines Mikrofluidik-Geräts für die Erfassung von HCHO basierend auf der Hantzsch-Reaktion.Hierbei wurde der Schwerpunkt auf die Komponente für Fluoreszenzdetektion gelegt.
Es wurde eine umfangreiche Literaturrecherche durchgeführt, 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, einschließlich des Integrationsprozesses der Standardkomponenten und der experimentellen Verfahren.
Der CIS-basierte Fluoreszenzdetektor bewies seine Leistungsfähigkeit, eine anfängliche HCHO-Konzentration von 10 µg/L vollständig in 3,5-Diacetyl-1,4-dihydrolutidin (DDL- derivatisiert) sowohl für die Quarz- als auch für die Silizium-Fluidikzellen zu detektieren. Beide Systemewiesenein Abfragevolumen von 3,5 µL auf. Ein offensichtlich höheres Signal-Rausch-Verhältnis (SNR) wurde für die Silizium-Fluidzelle () im Vergleich zur Quarz-Fluidzelle () beobachtet. Die Verstärkung der Signalintensität in der Silizium-Fluidzelle ist wahrscheinlich auf den Silizium-Absorptionskoeffizienten bei der Anregungswellenlänge zurückzuführen,. Dieser Koeffizient ist ungefähr fünfmal höher als der Absorptionskoeffizient bei der Fluoreszenzemissionswellenlänge
.
HCHO wird aufgrund seiner relativ hohen Konstanten für das Henry-Gesetz sehr schnell in ein flüssiges Reagenz aufgenommen. Somit hängt die Auswahl des molekularen Einfangverfahrens (Schwallströmung, Ringströmung oder membranbasierte Strömungswechselwirkung) von derLeistungsfähigkeit des Fluoreszenzdetektors ab. Ein vorläufiges Konzept, das auf der Verwendung einer Gas-Flüssigkeitsmembran-basierten Wechselwirkung zum ständigen Abfangen des gasförmigen HCHO basiert, wurde eingeführt. Hierzu wurden kompatible Materialien und Herstellungsmethoden identifiziert. Darüber hinaus wurden CFD-Simulationen durchgeführt, um die Mikrokanallänge unter verschiedenen hydrodynamischen Bedingungen abzuschätzen, die für eine vollständige HCHO-Derivatisierung erforderlich sind.
Eine Verbesserung und Vereinfachung auf der Grundlage von sehrnempfindlichen Fluoreszenzdetektoren mit niedrigen Detektionsgrenzen könnte zukünftig basierend z. B. auf Schwallströmung oder Ringströmung möglich sein
DESIGN OF A BURST MODE ULTRA HIGH-SPEED LOW-NOISE CMOS IMAGE SENSOR
Ultra-high-speed (UHS) image sensors are of interest for studying fast scientific phenomena and may also be useful in medicine. Several published studies have recently achieved frame rates of up to millions of frames per second (Mfps) using advanced processes and/or customized processes.
This thesis presents a burst-mode (108 frames) UHS low-noise CMOS image sensor (CIS) based on charge-sweep transfer gates in an unmodified, standard 180 nm front-side-illuminated CIS process. By optimizing the photodiode geometry, the 52.8 μm pitch pixels with 20x20 μm^2 of active area, achieve a charge-transfer time of less than 10 ns. A proof-of-concept CIS was designed and fabricated. Through characterization, it is shown that the designed CIS has the potential to achieve 20 Mfps with an input-referred noise of 5.1 e− rms
Cryogenic Operation of sCMOS Image Sensors
Scientific CMOS image sensors have lower read noise and dark current than charge coupled devices. They are also uniquely qualified for operation at cryogenic temperatures due to their MOSFET pixel architecture. This paper follows the design of a cryogenic imaging system to be used as a star tracking rocket attitude regulation system. The detector was proven to retain almost all its sensitivity at cryogenic temperatures with acceptably low read noise. Once the star tracker successfully maintains rocket attitude during the flight of the CIBER-2 experiment, the technology readiness level of scientific CMOS detectors will advance enough that they could see potential applications in deep space imaging experiments
A Survey of Positioning Systems Using Visible LED Lights
© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.As Global Positioning System (GPS) cannot provide satisfying performance in indoor environments, indoor positioning technology, which utilizes indoor wireless signals instead of GPS signals, has grown rapidly in recent years. Meanwhile, visible light communication (VLC) using light devices such as light emitting diodes (LEDs) has been deemed to be a promising candidate in the heterogeneous wireless networks that may collaborate with radio frequencies (RF) wireless networks. In particular, light-fidelity has a great potential for deployment in future indoor environments because of its high throughput and security advantages. This paper provides a comprehensive study of a novel positioning technology based on visible white LED lights, which has attracted much attention from both academia and industry. The essential characteristics and principles of this system are deeply discussed, and relevant positioning algorithms and designs are classified and elaborated. This paper undertakes a thorough investigation into current LED-based indoor positioning systems and compares their performance through many aspects, such as test environment, accuracy, and cost. It presents indoor hybrid positioning systems among VLC and other systems (e.g., inertial sensors and RF systems). We also review and classify outdoor VLC positioning applications for the first time. Finally, this paper surveys major advances as well as open issues, challenges, and future research directions in VLC positioning systems.Peer reviewe
Photodetectors
In this book some recent advances in development of photodetectors and photodetection systems for specific applications are included. In the first section of the book nine different types of photodetectors and their characteristics are presented. Next, some theoretical aspects and simulations are discussed. The last eight chapters are devoted to the development of photodetection systems for imaging, particle size analysis, transfers of time, measurement of vibrations, magnetic field, polarization of light, and particle energy. The book is addressed to students, engineers, and researchers working in the field of photonics and advanced technologies
LiNbO3 integrated system for opto-microfluidic sensing
International audience; In this work, we realized and tested an integrated opto-microfluidics platform entirely made on lithium niobate (LiNbO3) crystals, able to detect the single droplet passage and estimate its size without the need of any imaging processing. It is based on the coupling of a self-aligned integrated optical stage, made of an array of optical waveguides, to a microfluidic circuit such as a T-junction or Cross-junction engraved in the same substrate. The platform presented high quality performances in terms of optical triggering, reproducibility and stability in time, allowing in real-time data analysis. The comparison with standard approaches using microscopes and fast camera imagining acquisition and relative post-processing, showed an increased capability better than 50%. The demonstrated feasibility of integration of these two stages will allow the realization of a Lab-On-a-Chip on a monolithic substrate of lithium niobate, exploiting its multiple applications for manipulation of droplets
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