This paper presents an ultra-low power CMOS voltage reference circuit which is robust under biomedical extreme conditions, such as high temperature and high total ionized dose (TID) radiation. To achieve such performances, the voltage reference is designed in a suitable 130 nm Silicon-on-Insulator (SOI) industrial technology and is optimized to work in the subthreshold regime of the transistors. The design simulations have been performed over the temperature range of -40-200 °C and for different process corners. Robustness to radiation was simulated using custom model parameters including TID effects, such as mobilities and threshold voltages degradation. The proposed circuit has been tested up to high total radiation dose, i.e., 1 Mrad (Si) performed at three different temperatures (room temperature, 100 °C and 200 °C). The maximum drift of the reference voltage V(REF) depends on the considered temperature and on radiation dose; however, it remains lower than 10% of the mean value of 1.5 V. The typical power dissipation at 2.5 V supply voltage is about 20 μW at room temperature and only 75 μW at a high temperature of 200 °C. To understand the effects caused by the combination of high total ionizing dose and temperature on such voltage reference, the threshold voltages of the used SOI MOSFETs were extracted under different conditions. The evolution of V(REF) and power consumption with temperature and radiation dose can then be explained in terms of the different balance between fixed oxide charge and interface states build-up. The total occupied area including pad-ring is less than 0.09 mm2.
Autrefois releguees a des marches cibles et de faible volume, les diodes electroluminescentes (DELs) revolutionnent toutefois deja le monde de l’eclairage grâce a la spectaculaire croissance de leur efficacite energetique et leur duree de vie record. Les projections annoncent des avancees technologiques majeures concernant les DELs d’ici a 2025 [1]. Cependant, plusieurs problemes technologiques limitent l’efficacite d’extraction de photons des DELs emettant sous les 400 nm en raison de l’emplacement de la zone radiative : se trouvant a l’interieur du semiconducteur, une fraction considerable de photons (95%) reste piegee au sein de la diode a cause de la reflexion totale interne [2]. Le CRN2 possede toutes les infrastructures necessaires pour la fabrication de DELs bleues et UV. De la photolithographie a la gravure de type ICP du nitrure de gallium (GaN), plusieurs techniques de fabrications ont ete mises au point pour l’elaboration de DELs. Un solide procede est disponible a l’Universite de Sherbrooke permettant ainsi l’etude de l’extraction de la lumiere de DELs optimisees au sein d’une collaboration internationale.
We present and model a miniaturized field ionization sensor associated with a MEMS actuation system. The sensor consists in parallel plates spaced by a few micrometers and metal nanowires added to one of the electrodes in order to enhance the electric field. A split bottom electrode is used to differentiate between the ionization field monitoring and the electrostatically-actuated gap spacing. Such device is aimed at gas sensing, whereas the tunable electrode spacing replaces the sensor array including several gaps required for gas mixture analysis. Finite element numerical simulations performed with COMSOL Multiphysics® indicate the existence of an optimal distance for both maximizing electrical field enhancement and minimizing interference between the two electric fields. Electrical measurements are focused on the I-V characteristics of ambient air. The influence of gap variation on the breakdown voltage is consistent with the theoretical analysis of the modified Paschen's law, considering direct electron field emission at microscale interelectrode gaps.
Gas sensing can be achieved by fingerprinting the ionization characteristics of distinct species. In this study, the fabrication of a miniaturized gas ionization sensor using polyimide as sacrificial layer is reported. The sensor consists of two planar metallic electrodes with a gap spacing obtained by the polyimide under-etching. This known sacrificial layer has the advantage besides a high planarization factor, to be CMOS compatible. Furthermore, its chemical resistance up to high temperatures, high resistance to radiation from both electrons and neutrons, and low outgassing are of primary importance to avoid interferences with the ionization gas sensing. A suspended micro-bridge with dimensions 20 μm width and 220 μm length has been developed and released by using etching holes in the membrane. The ionization characteristics of air at controlled temperature, humidity and pressure (21°C, 40% humidity and 1 atm) have been obtained during non-destructive electrical characterizations, with a breakdown voltage of 350 V for a 6 μm gap. The growth of metallic nanowires templated in ion track-etched polyimide on the electrode is envisioned in order to enhance the ionization field and to reduce the required measurement power of the sensor.
Capacitive biosensors are promising tools toward detection of bacterial cells. However, their sensitivity remains insufficient compared with more conventional techniques. To understand how to optimize it, we propose a complete and quantitative analysis of the sensitivity of capacitive biosensors using a previously developed 2-D numerical simulator based on Poisson-Nernst-Planck equations. All key parameters of the electrolyte, bacterial cell, and electrode design are investigated, studied, and optimized. For each, an analytical expression relating the sensitivity to the parameter of interest is given. The guidelines and design tools, provided throughout this paper for the designer of capacitive biosensors, are eventually demonstrated by improving the sensitivity of our device under test by a factor of 4. Discussions based on experimental values and analytical models are provided throughout this paper.
A Love Wave (LW) immunosensor was developed for the detection of carbaryl pesticide. The experimental setup consisted on: a compact electronic characterization circuit based on phase and amplitude detection at constant frequency; an automated flow injection system; a thermal control unit; a custom-made flow-through cell; and Quartz /SiO2 LW sensors with a 40 μm wavelength and 120 MHz center frequency. The carbaryl detection was based on a competitive immunoassay format using LIB-CNH45 monoclonal antibody (MAb). Bovine Serum Albumin-CNH (BSA-CNH) carbaryl hapten-conjugate was covalently immobilized, via mercaptohexadecanoic acid self-assembled monolayer (SAM), onto the gold sensing area of the LW sensors. This immobilization allowed the reusability of the sensor for at least 70 assays without significant signal losses. The LW immunosensor showed a limit of detection (LOD) of 0.09 μg/L, a sensitivity of 0.31 μg/L and a linear working range of 0.14–1.63 μg/L. In comparison to other carbaryl immunosensors, the LW immunosensor achieved a high sensitivity and a low LOD. These features turn the LW immunosensor into a promising tool for applications that demand a high resolution, such as for the detection of pesticides in drinking water at European regulatory levels.
This paper introduces MEMS filters based on the use of traveling flexural waves. The underlying concept of these devices draws on an analogy with SAW devices, while replacing the surface elastic wave with a flexural wave on a suspended beam. This is in contrast with traditional flexural MEMS devices whereby all signal processing is done via a resonating element corresponding to a standing flexural wave. As far as the authors are aware this is the first study regarding traveling flexural wave devices and their frequency domain behavior.
