Publication: Precision density and viscosity measurement using two cantilevers with different widths
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Kılınç, Necmettin
Yaralıoğlu, G. G.
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Abstract
Weintroduceanovelmethodforfastmeasurementofliquidviscosityanddensityusingtwocantilevers withdifferentgeometries.Ourmethodcanbeusedforreal-timemonitoringinlabonchipsystemsand offerhighaccuracyforalargerangeofdensitiesandviscosities.Themeasurementprincipleisbasedon trackingtheoscillationfrequenciesoftwocantileverswithaphase-lockedloop(PLL)andcomparingwith referencemeasurementswithaknownfluid.Asetofequationsandasimplealgorithmisdevelopedto relatethedensityandtheviscositytothefrequencyshiftsofthecantilevers.Wefoundthattheeffectof thedensityandtheviscositycanbewellseparatedifcantilevershavedifferentwidths.Intheexperiments, twoNickelmicrocantilevers(widths25 mand100 m,length:200 m,thickness:1.75 m)werefully immersedintheliquidandthetemperaturewascontrolled.TheactuationwasusinganexternalelectrocoilandtheoscillationsweremonitoredusinglaserDopplervibrometer.Thus,electricalconnectionsto thecantileversarenotrequired,enablingmeasurementsalsoinconductiveliquids.ThePLLisusedto setthephasedifferenceto90◦betweentheactuatorandthesensor.Calibrationmeasurementswere performedusingglycerolandethyleneglycolsolutionswithknowndensitiesandviscosities.Themeasurementerrorwiththenewmethodwaslowerthan3%indensityintherange995–1150kg/m3and 4.6%inviscosityintherange0.935–4mPa.s.Basedonthesignal-to-noiseratio,theminimumdetectable differenceintheviscosityis1 Pa.sandthedensityis0.18kg/m3.Furtherimprovementsintherange andtheaccuracyarepossibleusing3ormorecantileverswithdifferentgeometries.
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Engineering, Electrical electronic engineering, Instruments, Instrumentation
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Sensors and Actuators A-Physical
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DOI
10.1016/j.sna.2015.05.024