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G. Pfusterschmied, M. Kucera, E Wistrela, T. Manzaneque, V Ruiz-Díez, J.L. Sànchez-Rojas, A. Bittner, U. Schmid:
"Temperature dependent performance of piezoelectric MEMS resonators for viscosity and density determination of liquids";
Journal of Micromechanics and Microengineering, 25 (2015).

It is the objective of this paper to report on the performance of piezoelectric MEMS resonators
for viscosity and density measurements at elevated temperatures. A custom-built temperature
controlled measurement setup is designed for fluid temperatures up to 100 °C. Piezoelectric
single-side clamped resonators are fabricated, excited in 2nd order of the roof tile-shaped
mode (13-mode) and exposed to several liquids (i.e. D5, N10, N35, PAO8, olive oil, ester oil
and N100). At the next step, these results are analysed applying a straightforward evaluation
model, thus demonstrating that with piezoelectric MEMS resonators the density (i.e. from
min = 785 kg m−3 to max = 916 kg m−3) and viscosity (i.e. from μmin = 1.20 mPa s
to μmax = 286.36 mPa s) values of liquids can be precisely determined in a wide range.
Compared to standard measurement techniques, the results show for the first parameter a mean
deviation of about 1.04% at 100 °C for all the liquids investigated. For the second parameter,
the standard evaluation model implies a systematic deviation in viscosity with respect to the
calibration being N35 in this study. This inherent lack of strength has a significant influence on
the accuracy, especially at 100 °C due to fluids having a viscosity reduced by a factor of 30 for
N100 compared to room temperature. This leads to relative deviations of about 23% at 100 °C
and indicates the limits of the evaluation model.

It is the objective of this paper to report on the performance of piezoelectric MEMS resonators
for viscosity and density measurements at elevated temperatures. A custom-built temperature
controlled measurement setup is designed for fluid temperatures up to 100 °C. Piezoelectric
single-side clamped resonators are fabricated, excited in 2nd order of the roof tile-shaped
mode (13-mode) and exposed to several liquids (i.e. D5, N10, N35, PAO8, olive oil, ester oil
and N100). At the next step, these results are analysed applying a straightforward evaluation
model, thus demonstrating that with piezoelectric MEMS resonators the density (i.e. from
min = 785 kg m−3 to max = 916 kg m−3) and viscosity (i.e. from μmin = 1.20 mPa s
to μmax = 286.36 mPa s) values of liquids can be precisely determined in a wide range.
Compared to standard measurement techniques, the results show for the first parameter a mean
deviation of about 1.04% at 100 °C for all the liquids investigated. For the second parameter,
the standard evaluation model implies a systematic deviation in viscosity with respect to the
calibration being N35 in this study. This inherent lack of strength has a significant influence on
the accuracy, especially at 100 °C due to fluids having a viscosity reduced by a factor of 30 for
N100 compared to room temperature. This leads to relative deviations of about 23% at 100 °C
and indicates the limits of the evaluation model.

piezoelectric, liquid sensing, MEMS resonators, elevated temperature

http://dx.doi.org/10.1088/0960-1317/25/10/105014