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Semiconducting metal oxide (SMO) gas sensors were designed, fabricated, and characterized in terms of their sensing capability and the thermo-mechanical behavior of the micro-hotplate. The sensors demonstrate high sensitivity at low concentrations of volatile organic compounds (VOCs) at a low power consumption of 10.5 mW. In addition, the sensors realize fast response and recovery times of 20 s and 2.3 min, respectively. To further improve the baseline stability and sensing response characteristics at low power consumption, a novel sensor is conceived of and proposed. Tantalum aluminum (TaAl) is used as a microheater, whereas Pt-doped SnO2 is used as a thin film sensing layer. Both layers were deposited on top of a porous silicon nitride membrane. In this paper, two designs are characterized by simulations and experimental measurements, and the results are comparatively reported. Simultaneously, the impact of a heat pulsing mode and rubber smartphone cases on the sensing performance of the gas sensor are highlighted.

This paper presents design, fabrication, and characterization of a novel microelectromechanical microreed switch, which consists of two Ni 80 Fe 20 magnetic plates as microreeds. One is embedded in a silicon trench. The other is suspended above the substrate and supported by a pair of crab-leg flexures from the two sides. Both Ni 80 Fe 20 plates are split into two long, narrow strips to improve the sensitivity. The switch is actuated by bringing an external magnet closer to the switch. The magnetic field required to turn on the switch can be as low as 0.5 mT and the initial contact resistance is < 10 Ω with gold contacts. The switch has been tested to pass more than 40 million hot switching cycles at 2 mA current at room temperature when packaged at wafer level with SU-8 sealing. The die size is 1.7 × 1.8 × 1.1 mm 3 . The proposed microreed switch can be used as the proximity sensor to sense the magnetic field. It also has the potential to replace the conventional reed switch in portable electronics, such as cellular phones, hearing aids, and laptops, where conserving battery power and device size is critical.[ 2011-0121]Index Terms-Magnetic switch, MEMS switch, nickel-iron alloy, reed.

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