Design Issues for Low Power Integrated Thermal Flow Sensors with Ultra-Wide Dynamic Range and Low Insertion Loss

Flow sensors are the key elements in most systems for monitoring and controlling fluid flows. With the introduction of MEMS thermal flow sensors, unprecedented performances, such as ultra wide measurement ranges, low power consumptions and extreme miniaturization, have been achieved, although several critical issues have still to be solved. In this work, a systematic approach to the design of integrated thermal flow sensors, with specification of resolution, dynamic range, power consumption and pressure insertion loss is proposed. All the critical components of the sensors, namely thermal microstructure, package and read-out interface are examined, showing their impact on the sensor performance and indicating effective optimization strategies. The proposed design procedures are supported by experiments performed using a recently developed test chip,including several different sensing structures and a flexible electronic interface

Comparison between bulk micromachined and CMOS detectors for X-ray measurements

This paper compares two x-ray detectors fabricated using two different technologies: one is based on a bulk micromachined silicon photodetector and the other is based on a standard CMOS photodetector. The working principle of the two detectors is similar: a scintillating layer of CsI:Tl is placed above the photodetector, so the x-rays are first converted into visible light (560 nm) which is then converted into an electrical signal by the photodetector. The different aspects of the fabrication and the experimental results of both x-ray detectors are presented and discussed.This work was supported by The Foundation of Science and Technology, Portugal, FCT-CTM/POCTI/33751/1999; Grant-BD SFRH/BD/1296/2000

Xray detector based on bulk micromachined photodiode

This paper reports the design, fabrication, assembly and testing of a xray detector based on a bulk micromachined photodiode (BMMPD) with a cavity filled with a scintillating crystal. The xray photons that reach the detector are first converted to visible light by the scintillating crystal. The visible light is then detected by the BMMPD, producing an electric current whose value is proportional to the incident xray intensity. The tests are done using a xray tube powered with a voltage of 35 kV, and a current ranging from 0 mA to 1 mA. With this setup, very promising results were obtained. may be divided into three classes: Dose reduction, image processing and display in real time, and flexibility in image storage and retrieval. The first advantage of digital radiography is the possibility of dose reduction. In conventional radiology, the dose is determined by the sensitivity ofThis work was supported by the Foundation Science and Technology, Portugal: FCT-CTM/POCTI/33751/1999; Grant-BD SFRH/BD/1296/2000

Properties and customization of sensor materials for biomedical applications.

Low-power chemo- and biosensing devices capable of monitoring clinically important parameters in real time represent a great challenge in the analytical field as the issue of sensor calibration pertaining to keeping the response within an accurate calibration domain is particularly significant (1–4). Diagnostics, personal health, and related costs will also benefit from the introduction of sensors technology (5–7). In addition, with the introduction of Registration, Evaluation, Authorization, and Restriction of Chemical Substances (REACH) regulation, unraveling the cause–effect relationships in epidemiology studies will be of outmost importance to help establish reliable environmental policies aimed at protecting the health of individuals and communities (8–10). For instance, the effect of low concentration of toxic elements is seldom investigated as physicians do not have means to access the data (11)

Realisation of very high voltage electrode-nozzle systems for MEMS

A number of applications would benefit from MEMS devices that can produce very strong electrical fields with high potential differences; in particular the production and acceleration of ions or charged droplets for spacecraft or biomedical applications. We have carried out investigations into the use of silicon dioxide as an insulator in MEMS devices designed for such applications. The work focuses on axisymmetric electrode configurations that produce 108 V/m electrical fields close to the axis, in vacuum. To accelerate ions to high velocities (>100 m/s) potentials of over 1 kV are required. MOS devices, consisting of aluminium insulated from the silicon substrate by SiO2, were produced with a number of different geometries. Thermal oxides of 2 µm thickness and thermal oxides augmented by 2 µm of CVD oxide were tested for the maximum voltage held before permanent destruction. The insulator surface between two electrodes placed 50 µm apart, successfully held voltages of over 3 kV without surface flashover. We have shown that breakdown occurred through the oxide with a mean hold-off voltage of 1340 V for 2 µm oxides and 2960 V for 4 µm oxides. In the course of the experiments, we have found the importance of chip cleanliness, voltage polarity and the external measuring circuit

Design and Fabrication of a Self-Aligning Gas/Liquid Micropump.

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X-ray detector based on a bulk micromachined photodiode combined with a scintillating crystal

This paper reports the design, fabrication, assembly and testing of a x-ray detector based on a bulk micromachined photodiode (BMMPD) with a cavity filled with a scintillating crystal. The x-ray photons that reach the detector are first converted to visible light by the scintillating crystal. The visible light is then detected by the BMMPD, producing an electric current with value proportional to the incident x-ray intensity. Tests were performed using two x-ray setups: an experimental one and a professional one. The first was powered with a maximum voltage of 35kV, and a current ranging to 1mA and the second was powered with voltages from 40kV to 60kV and currents ranging from 10mA to 55mA