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Proceedings Paper

A study on tunable resonators for rheological measurements
Author(s): Martin Heinisch; Erwin K. Reichel; Bernhard Jakoby
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Paper Abstract

In this contribution a feasibility study on resonating sensors for rheologic properties such as e.g., viscosity facilitating measurements at tunable frequencies is presented. For the concepts presented in this work, sample liquids are subjected to time harmonic shear stresses induced by a resonating wire and a suspended resonating platelet, respectively. From the resulting frequency response the liquid's rheological properties can be deduced by fitting the parameters of an appropriate closed-form model representing the physical behavior of the sensors. To allow large penetration depths of the shear waves being imposed by the resonating mechanism into the test liquid, it is desired to have oscillators with resonance frequencies in the low kilohertz range. Large penetration depths become important when examining complex liquids such as multi-phase systems as, e.g., emulsions. For the investigation of liquids showing shear thinning (or thickening) or viscoelastic behavior, it is necessary to record the liquid's characteristics not only at one single frequency but in a range of different frequencies, which in the best case should cover several decades of resonance frequencies. For this purpose, especially in the case of resonating microsensors, it is desired to have devices, which can be operated at tunable frequencies without changing their geometries. For the two concepts presented in this work, the ability of tuning the sensor's resonance frequency is based on varying the normal stresses within tungsten wires. The use of appropriate materials and different micro-fabrication techniques are discussed and the applicability of the devices for rheological measurements are outlined. The models are compared to measurement results and the capability of the particular resonator for accurate and reliable sensing is discussed.

Paper Details

Date Published: 5 May 2011
PDF: 8 pages
Proc. SPIE 8066, Smart Sensors, Actuators, and MEMS V, 806629 (5 May 2011); doi: 10.1117/12.887103
Show Author Affiliations
Martin Heinisch, Johannes Kepler Univ. Linz (Austria)
Erwin K. Reichel, Katholieke Univ. Leuven (Belgium)
Bernhard Jakoby, Johannes Kepler Univ. Linz (Austria)

Published in SPIE Proceedings Vol. 8066:
Smart Sensors, Actuators, and MEMS V
Ulrich Schmid; José Luis Sánchez-Rojas; Monika Leester-Schaedel, Editor(s)

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