[Zurück]

G. Pfusterschmied, J. Toledo, M. Kucera, W. Steindl, S. Zemann, V Ruiz-Díez, M. Schneider, A. Bittner, J.L. Sànchez-Rojas, U. Schmid:
"Potential of Piezoelectric MEMS Resonators for Grape Must Fermentation Monitoring";
Micromachines, 8 (2017), 200; S. 1 - 12.

In this study grape must fermentation is monitored using a self-actuating/self-sensing
piezoelectric micro-electromechanical system (MEMS) resonator. The sensor element is excited in
an advanced roof tile-shaped vibration mode, which ensures high Q-factors in liquids (i.e., Q ~100
in isopropanol), precise resonance frequency analysis, and a fast measurement procedure. Two sets
of artificial model solutions are prepared, representing an ordinary and a stuck/sluggish wine
fermentation process. The precision and reusability of the sensor are shown using repetitive
measurements (10 times), resulting in standard deviations of the measured resonance frequencies of
~0.1%, Q-factor of ~11%, and an electrical conductance peak height of ~12%, respectively. With the
applied evaluation procedure, moderate standard deviations of ~1.1% with respect to density values
are achieved. Based on these results, the presented sensor concept is capable to distinguish between
ordinary and stuck wine fermentation, where the evolution of the wine density associated with the
decrease in sugar and the increase in ethanol concentrations during fermentation processes causes
a steady increase in the resonance frequency for an ordinary fermentation. Finally, the first test
measurements in real grape must are presented, showing a similar trend in the resonance frequency
compared to the results of an artificial solutions, thus proving that the presented sensor concept is a
reliable and reusable platform for grape must fermentation monitoring.

In this study grape must fermentation is monitored using a self-actuating/self-sensing
piezoelectric micro-electromechanical system (MEMS) resonator. The sensor element is excited in
an advanced roof tile-shaped vibration mode, which ensures high Q-factors in liquids (i.e., Q ~100
in isopropanol), precise resonance frequency analysis, and a fast measurement procedure. Two sets
of artificial model solutions are prepared, representing an ordinary and a stuck/sluggish wine
fermentation process. The precision and reusability of the sensor are shown using repetitive
measurements (10 times), resulting in standard deviations of the measured resonance frequencies of
~0.1%, Q-factor of ~11%, and an electrical conductance peak height of ~12%, respectively. With the
applied evaluation procedure, moderate standard deviations of ~1.1% with respect to density values
are achieved. Based on these results, the presented sensor concept is capable to distinguish between
ordinary and stuck wine fermentation, where the evolution of the wine density associated with the
decrease in sugar and the increase in ethanol concentrations during fermentation processes causes
a steady increase in the resonance frequency for an ordinary fermentation. Finally, the first test
measurements in real grape must are presented, showing a similar trend in the resonance frequency
compared to the results of an artificial solutions, thus proving that the presented sensor concept is a
reliable and reusable platform for grape must fermentation monitoring.

http://dx.doi.org/10.3390/mi8070200