Smart chemical sensor application of ZnO nanowires grown on CMOS compatible SOI microheater platform

Smart chemical sensor based on CMOS(complementary metal-oxide- semiconductor) compatible SOI(silicon on insulator) microheater platform was realized by facilitating ZnO nanowires growth on the small membrane at the relatively low temperature. Our SOI microheater platform can be operated at the very low power consumption with novel metal oxide sensing materials, like ZnO or SnO2 nanostructured materials which demand relatively high sensing temperature. In addition, our sol-gel growth method of ZnO nanowires on the SOI membrane was found to be very effective compared with ink-jetting or CVD growth techniques. These combined techniques give us the possibility of smart chemical sensor technology easily merged into the conventional semiconductor IC application. The physical properties of ZnO nanowire network grown by the solution-based method and its chemical sensing property also were reported in this paper.

SOI diode temperature sensor operated at ultra high temperatures-a critical analysis

This paper investigates the performance of diode temperature sensors when operated at ultra high temperatures (above 250°C). A low leakage Silicon On Insulator (SOI) diode was designed and fabricated in a 1 μm CMOS process and suspended within a dielectric membrane for efficient thermal insulation. The diode can be used for accurate temperature monitoring in a variety of sensors such as microcalorimeters, IR detectors, or thermal flow sensors. A CMOS compatible micro-heater was integrated with the diode for local heating. It was found that the diode forward voltage exhibited a linear dependence on temperature as long as the reverse saturation current remained below the forward driving current. We have proven experimentally that the maximum temperature can be as high as 550°C. Long term continuous operation at high temperatures (400°C) showed good stability of the voltage drop. Furthermore, we carried out a detailed theoretical analysis to determine the maximum operating temperature and exlain the presence of nonlinearity factors at ultra high temperatures. © 2008 IEEE.

An experimental model of relay deployment planning tool for a wireless sensor network system to monitor civil engineering structures

It is essential to monitor deteriorated civil engineering structures cautiously to detect symptoms of their serious disruptions. A wireless sensor network can be an effective system for monitoring civil engineering structures. It is fast to deploy sensors especially in difficult-to-access areas, and it is extendable without any cable extensions. Since our target is to monitor deteriorations of civil engineering structures such as cracks at tunnel linings, most of the locations of sensors are known, and sensors are not required to move dynamically. Therefore, we focus on developing a deployment plan of a static network in order to reduce the value of a cost function such as initial installation cost and summation of communication distances of the network. The key issue of the deployment is the location of relays that forward sensing data from sensors to a data collection device called a gateway. In this paper, we propose a relay deployment-planning tool that can be used to design a wireless sensor network for monitoring civil engineering structures. For the planning tool, we formalize the model and implement a local search based algorithm to find a quasi-optimal solution. Our solution guarantees two routings from a sensor to a gateway, which can provide higher reliability of the network. We also show the application of our experimental tool to the actual environment in the London Underground.