Comparison and experimental validation of two potential resonant viscosity sensors in the kilohertz range

Abstract

Oscillating microstructures are well-established and find application in many fields. These include, force sensors, e.g. AFM micro-cantilevers or accelerometers based on resonant suspended plates. This contribution presents two vibrating mechanical structures acting as force sensors in liquid media in order to measure hydrodynamic interactions. Rectangular cross section microcantilevers as well as circular cross section wires are investigated. Each structure features specific benefits, which are discussed in detail. Furthermore, their mechanical parameters and their deflection in liquids are characterized. Finally, an inverse analytical model is applied to calculate the complex viscosity near the resonant frequency for both types of structures. With this approach it is possible to determine rheological parameters in the kilo Hertz range in situ within a few seconds. The monitoring of the complex viscosity of yogurt during the fermentation process is used as a proof of concept to qualify at least one of the two sensors into opaque mixtures.

High-frequency viscoelastic measurements of fluids based on microcantilever sensing: New modeling and experimental issues

“…In lieu of attempting to determine G' and G" over a broad frequency range, the objective could be focused only on the properties at the eigenfrequency, in which case use can be made of a similar model [13]. Recently we achieved consistent measurement of G' and G" for opaque viscoelastic fluids using microstructures [26]. Nevertheless the strategy we employed eliminates completely the advantage of the frequency-dependent analytical method developed in this work.…”

Microcantilever: Dynamical Response for Mass Sensing and Fluid Characterization

“…This system of equations can finally be solved to get the elastic and the viscous components of the dynamic modulus, and , respectively, as functions of the added mass, , and damping coefficient, [ 133 , 134 ]: The two components of the dynamic modulus, calculated with Equations (73) and (74), are shown in Figure 10 as functions of the shear load frequency, and for some representative values of added mass and damping coefficient. In agreement with Figure 9 , the elastic part of the dynamic modulus ( ) mostly depends on the added mass (solid blue and yellow lines), while the viscous term of the dynamic modulus ( ) depends on the damping coefficient (purple and green dashed lines).…”

“…This system of equations can finally be solved to get the elastic and the viscous components of the dynamic modulus, G and G , respectively, as functions of the added mass, m A , and damping coefficient, c V [133,134]:…”

Fast-fabrication process for low environmental impact microsystems

“…To be more specific, from the measurements presented in Figure 11 and knowing the structure's dimensions and properties, the calculation of the mass density and viscosity can be performed. A specific method compatible with a "U-shaped" structure has been developed for this purpose (Belmiloud et al, 2008;Lemaire et al, 2013). After accounting for the internal losses, which are not negligible in this case (the "U-shaped" structure is partially made of plastic), the mass density and viscosity are calculated without calibration.…”