MEMS technology could be an option for the development of a pressure sensor which allows the monitoring of several electronic signals in humans. In this work, a comparison is made between the typical elasticity curves of several arteries in the human body and the elasticity obtained for MEMS silicon microstructures such as membranes and cantilevers employing Finite Element analysis tools. The purpose is to identify which types of microstructures are mechanically compatible with human arteries. The goal is to integrate a blood pressure sensor which can be implanted in proximity with an artery. The expected benefits for this type of sensor are mainly to reduce the problems associated with the use of bulk devices through the day and during several days. Such a sensor could give precise blood pressure readings in a continuous or periodic form, i.e. information that is especially important for some critical cases of hypertension patients.
In this work a thin film gas microsensor based on both a double polysilicon micro-hotplate (MHP) and a polysilicon floating gate MIS transistor (FG-MIS) is described. Sensing section is a squared polysilicon plate which contains a doped Zinc Oxide (ZnO) thin film. The sensing section is heated by an U-shaped polysilicon stripe which is electrically isolated from the top and the bottom using oxide films. The micro-hotplate is both mechanically supported and thermally isolated using a deep cavity micromachined in the silicon substrate. The sensing film is electrically connected to the floating-gate transistor where the conductivity channel is modulated by the charged generated at the sensing film. The sensor structure was characterized for detecting carbon monoxide (CO) at 300 ºC. The hot area is thermally isolated using an arrangement of cavities micromachined in the silicon substrate. Finally a complete layout of the sensor system is presented in this paper.
Four carbon monoxide microsensor based on semiconducting oxide Zn0:Ga has been developed. The results and analysis of the characterization in an atmosphere containing carbon monoxide (CO), are presented in this work. dilution CO is 50ppm. Zn0:Ga thin films were deposited at 450°C by the spray pyrolysis technique from a 0 . 2 M starting solution with a IGal/[ZnI= 3 at. YO. Microsensors with four different dimensions were designed: 20x20pm2, 20x40pm2, 20x60pm2 and 100x100pm2. Ohmic contacts were manufactured by thermal evaporation of aluminum on the top of the films. Both of gas microsensors and AI terminals were patterned by lift off. A surface resistance variation of several orders of magnitude was found in doped-gallium ZnO thin films when these were introduced into a camera with Oppm, lppm, 5ppm, 50ppm and lOOppm of CO. Thin films gas microsensors were tested at several temperatures and different CO concentrations.The measurement temperatures employed were 2OO0C, 250°C and 300°C. The surface of ZnO thin films doped with Ga was also characterized by AFM, showing a regular and uniform morpholgy.
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