A method for vibrational viscometers capable of high-viscosity measurements using self-excited oscillations is proposed and assessed both theoretically and experimentally. Such viscometers are well-known for their rapid response and miniaturization. Unlike conventional methods based on Q-value estimations obtained experimentally from the frequency response or resonance curve, we describe the use of self-excited oscillations in viscosity measurements using positive velocity feedback control without relying on the frequency response curve. Such measurements become possible even for high viscosities where the peak of the frequency response curve is ambiguous or does not exist, i.e., the Q-value cannot be estimated from such curves. Furthermore, the validity of the proposed method is experimentally tested using a prototype self-excited viscometer. Downsized oscillators such as micro- or nanoscale cantilevers can be self-excited following a straightforward application of the method. They are expected to enable not only localized monitoring of changes in high viscosity with time but also spatial high-viscosity measurements by the distributed arrangement of the devices.
The design and operation of new viscometers are often presented with a focus on the miniaturization of the device and online monitoring of small amounts of liquid samples. The vibrational viscometers commonly used for viscosity measurements exploit the peak value of the frequency-response curve obtained from excitations of the oscillator submerged in the liquid. However, for high-viscosity liquids, the peak of the frequency-response curve is ambiguous or nonexistent, and hence hard to measure. To overcome this drawback and with a view to miniaturizing the device, we use the self-excited oscillations produced by a velocity feedback control. Our design uses a viscometer employing a cantilever driven by a piezo-actuator with analytics that do not rely on the frequency-response curve. A prototype piezo-driven macrocantilever with an oscillating plate attached at its tip was experimentally performed according to specifications. The proposed mechanism can be integrated into microelectromechanical systems (MEMS).
This paper reports ultrasensitive mass detection based on the relative change in the amplitude ratio of the first mode oscillation using self-excited coupled microcantilevers. The method proposed and demonstrated using the macrocantilevers in the previous study can measure eigenstate shifts caused by objects with high accuracy without being affected by the viscous damping effect of measurement environments. In this study, moving towards the use of this method for small mass measurements, we established the self-excited coupled microcantilevers and we have achieved in measurements of very small mass (about 1 ng) with 1% order of error.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.