Transient thermal response of micro-thermal conductivity detector (μTCD) for the identification of gas mixtures:An ultra-fast and low power method
作者机构：School of Mechanical EngineeringGeorgia Institute of TechnologyAtlantaGA 30332USA KWJ Engineering Inc.NewarkCA 94560USA NASA Glenn Research CenterClevelandOH 44135USA
出 版 物：《Microsystems & Nanoengineering》 (微系统与纳米工程（英文）)
年 卷 期：2015年第1卷第1期
页 面：52-58页
核心收录：
基 金：The sensor that was tested in this work is based on the patents:No.7 911 010 No.8 426 932 and No.8 884 382
主 题：gas sensor MEMS micro-bridge micro-heater μTCD thermal conductivity sensor transient heat transfer modeling
摘 要：Micro-thermal conductivity detector(μTCD)gas sensors work by detecting changes in the thermal conductivity of the surrounding medium and are used as detectors in many applications such as gas chromatography *** TCDs use steady-state resistance(i.e.,temperature)measurements of a *** this work,we developed a new measurement method and hardware configuration based on the processing of the transient response of a low thermal mass TCD to an electric current *** method was implemented for a 100-μm-long and 1-μm-thick micro-fabricated bridge that consisted of doped polysilicon conductive film passivated with a 200-nm silicon nitride *** resistance variations of theμTCD in response to a square current pulse were studied in multiple mixtures of dilute gases in *** and experimental results are presented and compared for the time resolved and steady-state regime of the sensor *** analysis and simulation show that the sensor response is exponential in the transient state,that the time constant of this exponential variation was a linear function of the thermal conductivity of the gas ambient,and that the sensor was able to quantify the mixture *** level of detection in nitrogen was estimated to be from 25 ppm for helium to 178 ppm for carbon *** this novel approach,the sensor requires approximately 3.6 nJ for a single measurement and needs only 300μs of sampling *** is less than the energy and time required for steady-state DC measurements.
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