Nanoparticle Metal-Oxide Films on Microhotplate Platforms: Fabrication and Gas-Sensitive Properties
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0915-R07-12
Nanoparticle Metal-Oxide Films on Microhotplate Platforms: Fabrication and GasSensitive Properties Alexey Tomchenko, and Brent Marquis Sensor Research and Development Corp., Orono, ME, 04473
ABSTRACT In the paper, the authors discuss preparation and properties of nanostructured gas-sensitive thin films on MEMS microhotplate sensor platforms. The films were deposited by microprinting technique and characterized using optical microscopy and electrical measurements. The formulation of the nanoparticulated metal-oxide suspensions for microprinting is described; the control over the thickness of the films through the composition of the suspensions is demonstrated. The procedure for the microprinting is described. The deposited films are evaluated as chemical sensors. The performance of the microsensors – sensitivity, stability, speed of operation, and selectivity – is compared with that of analogous traditional thick-film sensors. INTRODUCTION Chemical sensors are devices generating analytically useful electrical signals in response to variations in chemical composition of the surrounding aquatic or gaseous mediums. Reliable miniature chemical sensors are greatly expected in order to provide the global chemical monitoring for the environment and thereby to make human life safer and more comfortable. Nevertheless, the current state-of-the-art devices are not able to satisfy all numerous demands of real-world applications. The expected sensors have to be very sensitive, selective to a particular agent, stable, robust, miniature, reasonably power consuming, inexpensive, and simple in production. One of the most promising today’s approaches in the development of chemical sensors is a combination of specially designed silicon MEMS structures, called microhotplates or microplatforms (µHPs), with chemically sensitive films based on metal-oxide suspensions. Such hybrid devices could potentially satisfy all of the above requirements. The remarkable reduction in power consumption for the chemical sensors on µHP – below 100 mW – has been demonstrated recently [1-4]. There successfully advanced several methods for depositing suspensions onto microhotplates [5]. The most popular among them is microdrop-coating or microprinting [6-8] – the method is quite simple, doesn’t require complex equipment and special facilities. At the same time, the process for microprinting onto microplatforms has not been optimized yet; many aspects related to the functioning suspension-based metal-oxide sensors on heated microplatforms need further investigations. The authors of this article have recently demonstrated the feasibility of their SMO sensor arrays to discriminate and recognize various constituents of combustion gas [9]. Later on they successfully applied some of their arrays coupled with appropriate pattern recognition tools for detecting toxic gases (toxic industrial chemicals, CW agents) in air in presence of interfering gases [10]. However, the arrays, which consisted of several discrete thick-film sensors, had a serious drawb
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