A Helmholtz Resonator with Spiral Neck for Analyte Concentration Measurement in Low Frequency Range

Yugang Chen,Yong-Hwa Park,Bomi Lee

doi:10.3390/app10113676

Abstract

Helmholtz resonators (HR) have been proven to have feasibility for sensor applications with good performance. However, for biosensor application, when the amount of test sample is limited, the operating frequency tends to be very high, which may bring challenges of resonance excitation and frequency measurement. In this paper, a modified HR was proposed for biosensor application at a lower frequency, by designing the neck of the HR as a type of an Archimedes spiral, which can increase the neck length as much as possible without occupying much space. The resonant frequency of the proposed HR was derived by treating it as an HR with a straight neck with the equivalent length. An analytical example was calculated and verified by acoustic finite element analysis, and the results clearly showed that the frequency decreases in comparison to that of the conventional HR. Based on the underlying theory, the measurement principle was proposed and the experiment setup was established using a 3D-printed structure. The experiment was done using test solutions with different glucose concentrations, whose results showed consistency with the analytical results and noticeable frequency increases with the glucose concentration. Prospective results of the proposed HR after miniaturization show an operating frequency around 3 kHz when the amount of test sample is 0.1 mL, which will facilitate use of the common acoustic power source and acoustic pressure sensors in the sensing system.

Highlights

Over the past several decades, dynamic-mode cantilever sensors have been studied extensively with broad applications in various fields due to their fast response and low fabrication cost
When the amount of test sample is limited, the operating frequency tends to be much higher, which brings challenges in resonance excitation and frequency measurement
The neck of the proposed Helmholtz resonator (HR) in this paper is designed along the Archimedes spiral, which is the trajectory of a point moving with constant velocity on a rotating straight line with constant angular velocity in the horizontal plane

Summary

Introduction

Over the past several decades, dynamic-mode cantilever sensors have been studied extensively with broad applications in various fields due to their fast response and low fabrication cost. With the development of microfabrication technology, high sensitivity and resolution are realized [1] This kind of sensor mostly detects the resonant frequency shift induced only by the added mass effect, so sensitivity improvements are usually realized by decreasing the size or operating at higher order modes [2,3], which may bring manufacturing complexities and frequency measurement difficulties. To conquer these deficiencies, sensing architecture based on Helmholtz resonance was proposed in our previous paper as a new type of biosensor [4], which shows a higher sensitivity at a similar operating frequency compared with the sensor using a cantilever beam. We aim to design a new type of Helmholtz resonator (HR) to lower the resonant frequency

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Conclusion