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dc.contributor.authorAiyar, Avishek R.en_US
dc.date.accessioned2008-09-17T19:30:23Z
dc.date.available2008-09-17T19:30:23Z
dc.date.issued2008-07-11en_US
dc.identifier.urihttp://hdl.handle.net/1853/24696
dc.description.abstractMicroelectromechanical systems (MEMS) based artificial sensory hairs for flow sensing have been widely explored, but the processes involved in their fabrication are lithography intensive, making the process quite expensive and cumbersome. Most of these devices are also based on silicon MEMS, which makes the fabrication of out-of plane 3D flow sensors very challenging. This thesis aims to develop new fabrication technologies based on Polymer MEMS, with minimum dependence on lithography for the fabrication of piezoresistive 3D out-of-plane artificial sensory hairs for sensing of air flow. Moreover, the fabrication of a flexible sensor array is proposed and new materials are also explored for the sensing application. Soft lithography based approaches are first investigated for the fabrication of an all elastomer device that is tested in a bench top wind tunnel. Micromolding technologies allow for the mass fabrication of microstructures using a single, reusable mold master that is fabricated by SU-8 photolithography, reducing the need for repetitive processing. Polydimethylsiloxane (PDMS) is used as the device material and sputter deposited gold is used as both the piezoresistive as well as the electrode material for collection of device response. The fabrication results of PDMS to PDMS metal transfer micromolding (MTM) are shown and the limitations of the process are also discussed. A dissolving mold metal transfer micromolding process is then proposed and developed, which overcomes the limitations of the conventional MTM process pertinent to the present application. Testing results of devices fabricated using the dissolving mold process are discussed with emphasis on the role of micro-cr  acking as one failure mode in elastomeric devices with thin film metal electrodes. Finally, a laser microfabrication based approach using thin film Kapton as the device material and an electrically conductive carbon-black elastomer composite as the piezoresistor is proposed and demonstrated. Laminated sheets of thick and thin Kapton form the flexible substrate on which the conductive elastomer piezoresistors are stencil printed. Excimer laser ablation is used to make the micro-stencil as well as to release the Kapton cantilevers. The fluid-structure interaction is improved by the deposition of a thin film of silicon dioxide, which produces a stress-gradient induced curvature, strongly enhancing the device sensitivity. This new approach also enables the fabrication of backside interconnects, thereby addressing the commonly observed problem of flow intrusion while using conventional interconnection technologies like wire-bonding. Devices with varying dimensions of the sensing element are fabricated and the results presented, with smallest devices having a width of 400 microns and a length of 1.5 mm with flow sensitivities as high as 60 Ohms/m/s. Recommendations are also proposed for further optimization of the device.en_US
dc.publisherGeorgia Institute of Technologyen_US
dc.subjectLaminationen_US
dc.subjectSU-8 photolithographyen_US
dc.subjectFlight controlen_US
dc.subjectExcimer laseren_US
dc.subjectPolyacrylic aciden_US
dc.subjectCO2 laseren_US
dc.subjectPolymethylmethacrylateen_US
dc.subjectConductive elastomer compositesen_US
dc.subjectMicrocrackingen_US
dc.subjectKaptonen_US
dc.subjectPolydimethylsiloxaneen_US
dc.subjectMicrostencilen_US
dc.subject.lcshPiezoelectric devices
dc.subject.lcshMicroelectromechanical systems
dc.subject.lcshMicrofabrication
dc.subject.lcshDetectors
dc.subject.lcshAir flow
dc.subject.lcshPolymers
dc.subject.lcshElastomers
dc.titleMicrofabrication of a MEMS piezoresistive flow sensor - materials and processesen_US
dc.typeThesisen_US
dc.description.degreeM.S.en_US
dc.contributor.departmentChemical Engineeringen_US
dc.description.advisorCommittee Chair: Allen, Mark; Committee Member: Allen, Sue Ann Bidstrup; Committee Member: Wong, C.P.en_US


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