Abstract
A set of flexible MEMS sensor arrays for flow measurements in boundary layers is presented. The sensor principle of these anemometers is based on convective heat transfer from a hot-film into the fluid. Each sensor consists of a nickel sensing element between copper supply tracks. The functional layers are attached either on a ready-made polyimide foil or on a spin-on polyimide layer. These variants are designed to meet the requirements of measurements in different environments. Spin-on technology enables the use of very thin polyimide layers, ideally suited for measurements in transient flows. It is a unique characteristic of the presented arrays that their total thickness can be scaled from 7 to 52 μm. This is essential, because the sensor thickness has to be adapted to the varying thickness of the boundary layers in different aerodynamic tests. With these sensors we meet the special requirements of a wide range of fluid mechanic experiments but in particular those of future active flow control on airplane wings. For less critical flow conditions with much thicker boundary layers, thicker sensors might be sufficient and cheaper, so that sensors fabricated on ready-made foils are perfect for these applications. Since the presented sensors are flexible, they can be attached on curved aerodynamic structures without any geometric mismatches. The entire development, starting from theoretical investigations, is described. Further, the micro-fabrication is discussed, including photolithography, sputtering and wet-etching. In particular the wet-etching of the sensing element is found to be critical for the functional characteristics.
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References
Berns A, Buder U, Obermeier E, Wang XH, Domhardt J, Leuckert J, Nitsche W (2008) AeroMEMS pressure sensor with integrated wall hot-wire. IEEE Sens Conf 1560–1563. doi:10.1109/ICSENS.2008.4716746
Buder U, Berns A, von Klitzing J, Obermeier E, Petz R, Nitsche W (2006) Family of micromachined wall hot-wire sensors on polyimide foil. AIAA J (August 2007) 1798–1809. doi:10.2514/1.25033
Burkhardt O (2004) Erprobung und Anwendung von Oberflächensensoren und Sensorarrays zur Erfassung instationärer Wandschubspannungen an Schaufelprofilen. Dissertation, Technische Universtität Berlin, Berlin
Davis M (1970) The dynamic response of constant resistance anemometers. J Phys E Sci Instrum 3:15–20
De Vries JWC (1988) Temperature and thickness dependence of the resistivity of thin polycrystalline aluminum, cobalt, nickel, palladium, silver and gold films. Thin Solid Films, Electron Opt 25–32. doi:10.1016/0040-6090(88)90478-6
DuPont (2011) DuPont Kapton HN Technical Datasheet. http://www2.dupont.com/Kapton/en_US/assets/downloads/pdf/HN_datasheet.pdf. Accessed 29 July 2013
Ebefors T (2000) Polyimide V-groove joints for three-dimensional silicon transducers. Dissertation, Royal Institute of Technology, Stockholm. ISBN: 91-7170-568-6
Eckelmann H (1997) Einführung in die Strömungsmeßtechnik. Teubner Verlag, Stuttgart. ISBN: 3-519023792
Frühauf J (2005a) Shape and functional elements of the bulk silicon microtechnique. Springer, Heidelberg. ISBN: 3-540-22109-3
Frühauf J (2005b) Werkstoffe der Mikrotechnik. Fachbuchverlag Leipzig im Hanser Verlag, Leipzig. ISBN: 3-44622-557-9
Gad-El-Hak M (ed.) (2001) MEMS handbook. CRC Press LLC, Boca Raton, Florida, p 938ff. ISBN: 0-8493-0077-0
Haynes WM (2010) CRC handbook of chemistry and physics, 91st edn. Taylor & Francis group, Boca Raton. ISBN: 978-1-4398-2077-3
HD MicroSystems (2009) Product bulletin: PI 2600 series—low stress applications. http://hdmicrosystems.com/HDMicroSystems/en_US/pdf/PI-2600_ProcessGuide.pdf. Accessed 29 July 2013
Kälvesten E (1996) Pressure and wall shear stress sensors for turbulence measurements. Dissertation, Royal Institute of Technology, Stockholm. ISSN: 0281-2878
Kim IC, Lee SJ (2006) Characterization of a miniature thermal shear-stress sensor with backside connections. Sens Actuators 128:305–311
King LV (1914) On the convection of heat from small cylinders in a stream of fluid: determination of the convection constants of small platinum wires with applications to hot-wire anemometry. Philos Trans R Soc RSTA 214(509–522):373–432. doi:10.1098/rsta1914.0023
Lienhard IV JH, Lienhard V JH (2005) A heat transfer textbook. Phlogiston Press, Cambridge
Mailly F, Giani A, Bonnot R, Templ-Boyer P, Pascal-Delannoy F, Foucaran A, Boyer A (2001) Anemometer with hot platinum thin film. Sens Actuators 94, 1–2: 32–38
Morrison JF, Birch DM, Lavoie P (2006) IUTAM symposium on flow control and MEMS, vol 7. Springer, Heidelberg. ISBN: 978-1-4020-6857-7
Riedl X, Bolzmacher C, Wagner C, Bauer K (2009) A novel PDMS based capacitive pressure sensor. IEEE Sens Conf 2255–2258. doi:10.1109/ICSENS.2010.5690709
Rohlfing H, Schmidt H (1993) “Friedrich” Tabellenbuch Elektrotechnik Elektronik, 552 edn. Dümmler, Bonn. ISBN: 3-427-53024-8
Shackelford J, Alexander W (2001) Materials science and engineering handbook. CRC Press, Boca Raton. ISBN: 0-8493-2696-6
Acknowledgments
The authors would like to thank all the project partners for the cooperative and effective work in the framework of the collaborative research center 880. One of the authors (S. B.) gratefully acknowledges the financial support of the Volkswagen Foundation. T. B. also thanks the colleagues at CMST from Ghent University and IMEC Ghent for the nice integration into their group and their cooperation.
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Schwerter, M., Beutel, T., Leester-Schädel, M. et al. Flexible hot-film anemometer arrays on curved structures for active flow control on airplane wings. Microsyst Technol 20, 821–829 (2014). https://doi.org/10.1007/s00542-013-2054-y
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DOI: https://doi.org/10.1007/s00542-013-2054-y