2D label-free imaging of resonant grating biochips in ultraviolet

International audience2D images of label-free biochips exploiting resonant waveguide grating (RWG) are presented. They indicate sensitivities on the order of 1 pg/mm2 for proteins in air, and hence 10 pg/mm2 in water can be safely expected. A 320×256 pixels Aluminum-Gallium-Nitride-based sensor array is used, with an intrinsic narrow spectral window centered at 280 nm. The additional role of characteristic biological layer absorption at this wavelength is calculated, and regimes revealing its impact are discussed. Experimentally, the resonance of a chip coated with protein is revealed and the sensitivity evaluated through angular spectroscopy and imaging. In addition to a sensitivity similar to surface plasmon resonance (SPR), the RWGs resonance can be flexibly tailored to gain spatial, biochemical, or spectral sensitivity

Etude des propriétés optoélectroniques et de transport dans les hétérostructures AlGaN/GaN pour la réalisation de détecteurs UV

L'objet de cette thèse est l'étude des hétérostructures GaN/(Al,Ga)N afin de réaliser des détecteurs UV. Les difficultés de croissance ainsi que les propriétés fondamentales du matériau sont présentées dans le chapitre 1 de manière à constituer les outils de conception des dispositifs à réaliser. Au chapitre 2, les problèmes de fluctuation d'alliage et de localisation de porteurs dans les alliages ternaires (Ga,In)N et (Al,Ga)N sont abordés. Le rôle du champ éléctrique dans les puits et les limites constituées par les fluctuations statistiques d'alliage sont alors mis en évidence. Un modèle permettant d'expliquer certains comportements non idéaux comme l'absorption sous le gap et sa non-linéarité par rapport au flux incident est également élaboré. Enfin les effets photopersistants dans les structures typiques de transistors à effet de champ sont étudiées. Les deux derniers chapitres concernent l'étude de démonstrateurs...This work investigates GaN/(Al,Ga)N heterostructures for achieving Uv photodetectors. In the first chapter, the difficulties in growing these structures are presented. Their fundamental properties are studied in order to understand their limits and develop tools to predict the behavior of devices. Alloy fluctuations and localisation in (Ga,In)N and (Al,Ga)N materials are investigated in the second chapter. The effect of the piezoelectric field and the spontaneous polarization in quantum wells is shown. In bulk materials, the sharpness of band edge absorption is proved to be close to statistic alloy broadening. A model to explain no-ideal behaviours as subbandgap absorption and nonlinearity of response versus optical power is developed. The effects of deep donors in the barrier of field effect transistors on persistent photoconductibilty are also shown...ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Pedestrian detection in poor visibility conditions would swir help

The 2WIDE_SENSE (WIDE spectral band & WIDE dynamics multifunctional imaging SENSor Enabling safer car transportation) EU funded project is aimed at the development of a low-cost camera sensor for Advanced Driver Assistance Systems (ADAS) applications able to acquire the full visible to Short Wave InfraRed (SWIR) spectrum from 400 to 1700 nm. This paper presents the first results obtained by investigating the SWIR contribution to pedestrian detection in difficult visibility conditions as haze and fog employing the wide-bandwidth camera developed within the project. Document type: Part of book or chapter of boo

Design of specific biochips for contrast enhancement of UV biological absorption

International audienc

Design of specific biochips for contrast enhancement of UV biological absorption

International audienc

Modeling the bioconversion of polysaccharides in a continuous reactor: A case study of the production of oligo-galacturonates by Dickeya dadantii

International audienceIn the quest for a sustainable economy of the earth resources and for renewable sources of energy, a promising avenue is to exploit the vast quantity of polysaccharide molecules contained in green wastes. To that end, the decomposition of pectin appears to be an interesting target because this polymeric carbohydrate is abundant in many fruit pulps and soft vegetables. To quantitatively study this degradation process, here we designed a bioreactor that is continuously fed with de-esterified pectin (PGA). Thanks to the pectate lyases produced by bacteria cultivated in the vessel, the PGA is depolymerized into oligo-galacturonates (UGA) which is continuously extracted from the tank. A mathematical model of our system predicted that the conversion efficiency of PGA into UGA increases in a range of coefficient of dilution until reaching an upper limit where the fraction of UGA that is extracted from the bioreactor is maximized. Results from experiments with a continuous reactor hosting a strain of the plant pathogenic bacterium Dickeya dadantii and in which the dilution coefficients were varied, quantitatively validated the predictions of our model. A further theoretical analysis of the system enabled an a priori comparison of the efficiency of eight other pectate lyases-producing microorganisms with that of D. dadantii. Our findings suggest that D. dadantii is as the most efficient microorganism and therefore the best candidate for a practical implementation of our scheme for the bioproduction of UGA from PGA

Pedestrian Detection in Poor Visibility Conditions: Would SWIR Help?Image Analysis and Processing

The 2WIDE SENSE (WIDE spectral band & WIDE dynamics multifunctional imaging SENSor Enabling safer car transportation) EU funded project is aimed at the development of a low-cost camera sensor for Advanced Driver Assistance Systems (ADAS) applications able to acquire the full visible to Short Wave InfraRed (SWIR) spectrum from 400 to 1700 nm. This paper presents the first results obtained by investigating the SWIR contribution to pedestrian detection in difficult visibility conditions as haze and fog employing the wide-bandwidth camera developed within the project

Biodetection of DNA and proteins using enhanced UV absorption by structuration of the chip surface

International audienceDNA and protein absorption at 260 and 280 nm can be used to reveal theses species on a biochip UV image. A first study including the design and fabrication of UV reflective multilayer biochips designed for UV contrast enhancement (factor of 4.0) together with spectrally selective AlGaN detectors demonstrated the control of chip biological coating, or Antigen/Antibody complexation with fairly good signals for typical probe density of 4x1012 molecules/cm2. Detection of fractional monolayer molecular binding requires a higher contrast enhancement which can be obtained with structured chips. Grating structures enable, at resonance, a confinement of light at the biochip surface, and thus a large interaction between the biological molecule and the lightwave field. The highest sensitivity obtained with grating-based biochip usually concerns a resonance shift, in wavelength or diffraction angle. Diffraction efficiency is also affected by UV absorption, due to enhanced light-matter interaction, and this mechanism is equally able to produce biochip images in parallel. By adjusting grating parameters, we will see how a biochip that is highly sensitive to UV absorption at its surface can be obtained. Based on the Ewald construction and diffraction diagram, instrumental resolution and smarter experimental configurations are considered. Notably, in conjunction with the 2D UV-sensitive detectors recently developed in-house, we discuss the obtainment of large contrast and good signals in a diffraction order emerging around the sample normal

Imagerie de bio-puces multiplexes dans l'ultraviolet pour l'identification de menaces biologiques

WorkshopNational audienc

UV imaging of biochips based on resonant grating

International audienceIn the frame of biological threat, security systems require label free biochips for rapid detection. Biosensors enable to detect biological interactions, between probes localized at the surface of a chip, and targets present in the sample solution. Here, we present an optical transduction, enabling 2D imaging, and consequently parallel detection of several reactions. It is based on the absorption of biological molecules in the UV domain. Thus, it is based on an intrinsic property of biological molecules and does not require any labelling of the biological molecules. DNA and proteins absorb UV light at 260 and 280 nm respectively. Sensitivity is a major requirement of biosensing devices. Configurations leading to enhancement of the interaction between light and biological molecules are of interest. For a better sensitivity, resonant grating structures are then studied. They enable to confine the electric field close to the biological layer. Imaging of resonant grating is not largely studied, even for visible wavelengths, but it results in good sensitivity. The protein used in this study is the methionyl-tRNA synthetase. Its absorption is representative of protein absorption, and it can then serve as a model for immunological detection. The best experimental contrast due to a monolayer of proteins is 40%. With data processing currently employed for biochip imaging: average on several acquisitions and on all the pixels imaging the biological spots, the device is able to detect a surface density of proteins in the 10 pg/mm range. © (2010) COPYRIGHT SPIE--The International Society for Optical Engineerin