A parts per billion (ppb) sensor for NO2 with microwatt (μW) power requirements based on micro light plates

A film of gas sensitive ZnO nanoparticles has been coupled with a low-power micro light plate (μLP) to achieve a NO2-parts-per-billion conductometric gas sensor operating at room temperature. In this μLP configuration, an InGaN-based LED (emitting at 455 nm) is integrated at a few hundred nanometers distance from the sensor material, leading to sensor photoactivation with well controlled, uniform, and high irradiance conditions, and very low electrical power needs. The response curves to different NO2 concentrations as a function of the irradiance displayed a bell-like shape. Responses of 20% to 25 ppb of NO2 were already observed at irradiances of 5 mWatts·cm-2 (applying an electrical power as low as 30 μW). In the optimum illumination conditions (around 60 mWatts·cm-2, or 200 μW of electric power), responses of 94% to 25 ppb were achieved, corresponding to a lower detection limit of 1 ppb of NO2. Higher irradiance values worsened the sensor response in the parts-per-billion range of NO2 concentrations. The responses to other gases such as NH3, CO, and CH4 were much smaller, showing a certain selectivity toward NO2. The effects of humidity on the sensor response are also discussed

Residual Stress Measurement on a MEMS Structure With High-Spatial Resolution

A new approach to the local measurement of residual stress in microstructures is described in this paper. The presented technique takes advantage of the combined milling-imaging features of a focused ion beam (FIB) equipment to scale down the widely known hole drilling method. This method consists of drilling a small hole in a solid with inherent residual stresses and measuring the strains/displacements caused by the local stress release, that takes place around the hole. In the presented case, the displacements caused by the milling are determined by applying digital image correlation (DIC) techniques to high resolution micrographs taken before and after the milling process. The residual stress value is then obtained by fitting the measured displacements to the analytical solution of the displacement fields. The feasibility of this approach has been demonstrated on a micromachined silicon nitride membrane showing that this method has high potential for applications in the field of mechanical characterization of micro/nanoelectromechanical systems

Site-selectively grown SnO2 NWs networks on micromembranes for efficient ammonia sensing in humid conditions

SnO2 NWs networks on heated micromembranes have been characterized as ammonia sensors. The approach allows achieving reproducible growth and stable and long-lasting ammonia sensors with site-specific grown SnO2 NWs. The devices have been tested both in dry and humid conditions showing response time down to two minutes. Sensors have been tested up to 1 month, only presenting variation of the base resistance with full retention of the response towards the gaseous analytes. Different concurrent sensing mechanisms have been identified relating the determined sensing kinetics with previous theoretical calculations. Specifically, oxygen dissociation seems to play a key role in the overall ammonia sensing sequence. In humid conditions, moisture reduces the response to ammonia but also lowers the activation energy of the reaction process

Locally grown SnO2 NWs as low power ammonia sensor

Localized growth of SnO2 nanowires on top of CMOS compatible micromembranes that incorporate a buried heater and prepatterned interdigitated electrodes has been achieved that presents the advantage that it allows to easily and directly integrate the advantageous properties of quasi-one dimensional structures in an advanced electronic device by a Vapor Liquid Solid (VLS) mechanism. A NWs based sensor of this type is characterized as a low power gas sensor towards NH3 at different temperatures. Stable and reproducible response is obtained, that allows detecting concentrations below the time-weighted average exposure limit for 8 h

Formació en l'ús d'eines i recursos de la biblioteca als alumnes de nou ingrés del Campus de Ciències de la Salut de Bellvitge

Poster presentat a les 11es Jornades Catalanes d'Informació i Documentació. COBDC. Barcelona 22 i 23 de maig de 2008Històricament la biblioteca organitzava, a inici de cada curs, sessions informatives adreçades als alumnes de nou ingrès. Aproximadament el nombre d'assistents era el 75% dels alumnes matriculats en els ensenyaments del Campus. A partir de l'any 1996 el nombre d'usuaris assistents a les sessions va disminuir considerablement amb motiu de l'aparició dels crèdits de lliure elecció. Des del curs 2004-05 es comencen a impartir cursos de formació sobre recursos i serveis de la biblioteca amb reconeixement de crèdits de lliure elecció

Nous reptes dins el marc de l’EEES. Una aportació de les biblioteques del CRAI: sessions d’acollida als alumnes de nou ingrés

Poster presentat a la Trobada de Professorat de Ciències de la Salut. Facultat de Medicina de la UB, 30 i 31 de maig i 1 de juny de 2007El nou paradigma d'ensennyament dins de l'entorn de l'EEES comporta uns nous models d'aprenentatge i genera unes noves necessitats a l'alumnat. La Biblioteca del Campus de Ciències de la Salut de Bellvitge organitzà, duranrt el curs 2006-2007, conjuntament amb l'Escola Universitària d'Infermeria i Podologia, l'assignatura Accés als Serveis i Recursos de la Biblioteca, adreçada als alumnes de nou ingrés dels enseynaments d'Infermeria i Podologia. Assignatura de lliure elecció amb reconeixement d'1,5 crèdits

La Biblioteca del Campus i la seva adaptació a l’EEES: noves oportunitats, nous reptes

Poster presentat a la 5a Trobada de Professorat de Ciències de la Salut. Barcelona, Campus de Ciències de la Salut de Bellvitge, 4, 5 i 6 de febrer de 2009.El Centre de Recursos per a l'Aprenentatge i la Investigació (CRAI) de la Universitat de Barcelona es crea a principis de 2004, davant de la necessitat d'adaptar les biblioteques universitaries al nou E.poi Europeu d'Educocíó Superior (EEE5) i a l'E.poi Europeu de Recerco (ERA) en qué es configura un nou marc d'ensenyament universitari basat en I'aprenentatge, la recerca, el desenvolupament i la innovació. En aquesta direcció, la biblioteca del Campus ha iniciat un procés continuat d'adaptació als nous requeriments, que sorgeixen amb la progressiva adequació deis ensenyaments que s'imparteixen al Campus de Bellvitge al nou model de Bolonya

Site-specific growth and in situ integration of different nanowire material networks on a single chip: towards a nanowire-based electronic nose for gas detection

A new method for the site-selective synthesis of nanowires has been developed to enable material growth with defined morphology and at the same time different composition on the same chip surface. The chemical vapour deposition approach for the growth of these nanowire-based resistive devices using micromembranes can be easily modified and represents a simple, adjustable fabrica-tion process for the direct integration of nanowire meshes in multifunctional devices. This proof-of-concept study includes the deposition of SnO2, WO3 and Ge nanowires on the same chip. The individual resistors exhibit adequate gas sensing responses to-wards changing gas concentration of CO, NO2 and humidity diluted in synthetic air. The data have been processed by principal component analysis with cluster responses that can be easily separated and thus the devices described herein are in principle suita-ble for environmental monitoring

Site-specific growth and in situ integration of different nanowire material networks on a single chip: towards a nanowire-based electronic nose for gas detection

A new method for the site-selective synthesis of nanowires has been developed to enable material growth with defined morphology and at the same time different composition on the same chip surface. The chemical vapour deposition approach for the growth of these nanowire-based resistive devices using micromembranes can be easily modified and represents a simple, adjustable fabrica-tion process for the direct integration of nanowire meshes in multifunctional devices. This proof-of-concept study includes the deposition of SnO2, WO3 and Ge nanowires on the same chip. The individual resistors exhibit adequate gas sensing responses to-wards changing gas concentration of CO, NO2 and humidity diluted in synthetic air. The data have been processed by principal component analysis with cluster responses that can be easily separated and thus the devices described herein are in principle suita-ble for environmental monitoring

Residual Stress Measurement on a MEMS Structure With High-Spatial Resolution

A new approach to the local measurement of residual stress in microstructures is described in this paper. The presented technique takes advantage of the combined milling-imaging features of a focused ion beam (FIB) equipment to scale down the widely known hole drilling method. This method consists of drilling a small hole in a solid with inherent residual stresses and measuring the strains/displacements caused by the local stress release, that takes place around the hole. In the presented case, the displacements caused by the milling are determined by applying digital image correlation (DIC) techniques to high resolution micrographs taken before and after the milling process. The residual stress value is then obtained by fitting the measured displacements to the analytical solution of the displacement fields. The feasibility of this approach has been demonstrated on a micromachined silicon nitride membrane showing that this method has high potential for applications in the field of mechanical characterization of micro/nanoelectromechanical systems