Second flexural and torsional modes of vibration in suspended microfluidic resonator for liquid density measurements

Abstract

Suspended microfluidic resonators enable detection of fluid density and viscosity with high sensitivity. Here, a two-legged suspended microchannel resonator that probes pico-litres of liquid is presented. The higher resonant modes (flexural and torsional) were explored for increased sensitivity and resolution. Unlike other reported microchannel resonators, this device showed an increase in the quality factor with resonant frequency value. The performance of the resonator was tested by filling the channel with three liquids, one at a time, over a density range of 779−1110 kg m−3 and a viscosity range of 0.89−16.2 mPa s. The highest resolution obtained was 0.011% change in density. Measurements with torsional mode showed an improvement of about six times in sensitivity and about fifteen times in resolution compared to the first flexural mode. When the empty channel was filled with liquids of different viscosity, the quality factor of the first flexural mode remained overall constant with a variation below 3.3% between the fluids, and confirming the inherent property of suspended microchannel resonators. However, it significantly decreased for second flexural and torsional modes. No noticeable difference was observed in the quality factor between different liquid viscosities for all modes.

Characterization of higher-order resonant cantilevers for density determination in different flowing liquids

“…Density sensing plays a fundamental role in (bio)chemical liquids, and numerous studies have pursued the optimal design of the cantilever-based resonator. Belardinelli et al [25] presented a cantilever with an embedded microchannel, which was utilized as a sensitive element of density sensors. The highest resolution reached a change of 0.011% in density.…”

Piezoelectric-AlN resonators at two-dimensional flexural modes for the density and viscosity decoupled determination of liquids

“…The fundamental out-of-plane bending is a typical vibrating mode of cantilevers that can be flexibly excited by electrostatic 8 , piezoelectric 9 , 10 , photothermal 11 , and magnetic 12 , 13 forces. Meanwhile, torsional vibration 14 – 16 is used as an alternative for enhancing the sensing behavior of cantilevers. These conventional vibrations of a cantilever-based resonator have been shown to present two separate dependencies of resonant frequency on density and Q-factor on viscosity.…”

“…When focusing on the output interface of resonators, optical characterization is still a common approach 14 , 27 , 28 ; it detects slight deflections even in the sub-Angstrom regime, but it is bulky and alignment-dependent. Thin-film piezoelectric-on-silicon technology offers full electrical interfaces, including input and output transductions, for resonators to simplify their design by applying piezoelectric self-actuation and self-sensing methods.…”

Diamagnetically levitating resonant weighing scale

“…Mechanical resonators are nowadays being adopted in billions of products, including quartz crystals, Micro-Electro-Mechanical Systems (MEMS), and acoustic wave resonators for timekeeping, frequency referencing and electronic filtering, but also for addressing a wide range of sensor applications in modern technology. These resonant sensors can be used to measure parameters like mass [1][2][3], stiffness [4], density [5], viscosity [6], and pressure [7], for a diverse range of applications, ranging from environmental monitoring to life sciences [8][9][10]. The working principle of these devices is based on tracking a resonance frequency f r of the sensor that depends on the sensing parameter.…”