Analytical studies on amplitude change enhancement in coupled aluminium nitride coated single crystal silicon oscillator pair applicable to ultra‐sensitive resonating microfluidic flowmeters

Abstract

The use of vibration mode localisation in arrays of micromechanically coupled, nearly identical beam-shaped resonators has been analytically studied for ultra-sensitive resonating-based flowmeters. Eigenstate shifts (amplitude change in this Letter) that are about two times (compared with the single resonator), and orders (compared with the resonator array) of magnitude greater than corresponding shifts in resonant frequency for an induced fluid flow (corresponding to an induced small mass perturbation) are preliminarily obtained by theoretical analysis. When an external force of 100 Pa, corresponding to an estimated fluid flow velocity of about 3.15 m/s, is applied to any one (because of the symmetrical design) of the two coupled aluminium nitride coated single crystal silicon resonators, two orders of the amplitude enhancement can be observed for both the resonators at the higher (second) resonance frequency because of vibration mode localisation, which implies the application possibility to highly sensitive resonating-based flow sensors.1. Micromachined or MEMS flow sensors: The measurement of fluid flow rates is an essential requirement in both industrial and commercial applications. It has been estimated by Hayward [1] that there are more than one hundred different types of flow sensors with a mode of operation based on almost any physical domain. Although several large-scale flowmeter types are commercially available, the continuous development of the three-dimensional techniques of microfabrication and MEMS, with consequent cost reduction and quality improvement, has rapidly extended the market of micromachined or MEMS flow sensors. In particular, applications of micromachined or MEMS sensors to monitor gas and liquid flows hold immense potential because of their valuable characteristics, such as low-energy consumption, relatively good accuracy, the ability to measure very small flow, small size and so on.After the first integrated silicon-based sensor for gas flow measurement [2] appeared in 1974, a higher growth of research works in the field of micromachined or MEMS flow sensors took place in the eighties and about a decade was needed to develop the integration of many microfluidic devices into a single chip [3,4].Based on the working principles, the micromachined or MEMS flow sensors can be distinguished into two groups [5]. The first group contains flow sensors based on heat exchange, named 'thermal flow sensors'; whereas all the other flowmeters based on different working principles rather than thermal exchange, are thus named as 'non-thermal flow sensors', which are also divided into several subgroups depending on the principle of measurement used like cantilever flow sensors, differential pressure-based flow sensors, resonating flow sensors and laser Doppler flowmeters. Amplitude change enhancement by vibration mode localisation:The micro resonator sensor [6-10] is used to detect external stimulus, that is, force, mass, molecular as well as atomic adsorption and so on. The amount of relative change...

Enhancing amplitude changes by mode localization in trio cantilevers with mass perturbation

“…Both analytical and experimental results show that higher amplitudes could be obtained for the two side (outermost) cantilevers due to the symmetrical design. A coupled aluminium nitride coated single crystal silicon (AlN/SCS) two-cantilever array [28], applicable to ultra-sensitive resonating flow-meters, has been also analytically studied by applying an external force of 100 Pa.…”