Low Power Perforated Dielectric Membrane Microheater For Gas Sensors

Some of the advantages of Microelectromechanical Systems(MEMS)that gave it an edge in portable electronics applications are low-voltage and low-power design which has become a key component of system designs.The demand for microelectromechanical Systems(MEMS)gas sensors is inevitable for support in safety applications,where combustible or toxic gases are present.Low power has attracted a great deal of attention with the increasing demand for gas sensors especially in the field of civil consumer electronics.However,the low power properties of any gas sensor(thermo-calorimetric device)is always a function of its micro heater design,thus this has brought importance to the design of low power microheater.The design of low-power microheaters has continually been under research in the past decades until now and has birthed a whole lot of successful development.Researchers have achieved great feats in the design of low power microheaters so much that the power consumptions of microheaters can go as low as 10mW at 400? by the miniaturization of the active head of the microheater.However most thermo-calorimetric device,gas sensors included requires a large active area to achieve better sensitivity,therefore the miniaturization of the active area of the device invariably leads to lower sensitivity.The trading-off of one or some of the properties of the microheater in order to achieve low power consumption property has been a dilemma faced by researchers in the design of microheater designs.The geometry of the dielectric membrane of the microheater has hereby been optimized by designing a perforated membrane low-power microheater that maintains the large active area of the microheater without a consequential trade-off in performance.The microheater was designed by exploiting the joule heating and heat loss properties of microheaters.Conduction mode of heat transfer been the largest mode of heat loss in heat transfer was exploited in the theoretical analysis of the microheater by incorporating holes in the dielectric membrane of the microheater.The effect of the perforated design in the 127?m X 46?m rectangular-shaped microheater device was simulated to ensure it has no consequential effect on the thermal and mechanical performance of the microheater.The FEA(Finite Elements Analysis)of the device was done using COMSOL Multiphysics.The perforated membrane of the proposed microheater distinguishes it from the general MEMS microheater fabrication processes.The perforated membrane of the dielectric membrane of the microheater was achieved using the same RIE(Reactive Ion Etching)process used in etching out the etch window for the microheater.All fabrication process was achieved using MEMS fabrication process.The microheater design in this thesis presents an answer to one of the questions in the MEMS sensing academic world and also presents a low-power consuming microheater.It's shown that the power consumption can be decreased by decreasing heat loss in the supporting membrane on which the heating resistor sits on.A modified structured two beams suspended membrane microheater with a perforated dielectric layer is designed.The test result shows an 18.6%reduction in power consumption with 15.18mW and a response time of 0.42ms at 400?.The result was observed to be thermally stable and should provide a good platform for exploitation in the design of commercial MEMS sensors that have microheaters as one of its components.