Preparation And Characterization Of An On-Chip Spherical Glass Resonant Densitometer

Microfluidics technology manipulates microfluids and integrates sample preparation, reaction, separation, detection and other basic functions into a small chip with high analysis efficiency, high precision and high sensitivity using a small amount of samples. On-line precise detection of microfluids density is critical for disease detection and monitoring in microfluidics. However, current liquid densitometers are hard to be integrated onto a microfluidic chip. Most of liquid densitometers are composed of cantilever beams, which are directly immersed in the tested liquids, leading to performance degradation of densitometers. Other densitometers include embedded silicon microchannels and resonators, which are opaque, leading to measurement error caused by bubble in the tested liquids. Micro online liquid densitometers, with high precision and low cost, have become a hotspot for research.In this study, a novel glass spherical resonator, taken as an online densitometer in a microfluidic chip, was designed and prepared by a chemical foaming process. The online integrated micro spherical resonant densitometer is based on the principle that the density shifts of the liquid included in the glass spherical resonator would lead to the shifts of the resonant frequency of the glass spherical resonator.First of all, modal analysis and harmonic frequency response analysis of the glass spherical resonator were performed by ANSYS. Results showed obvious displacement in the vertical direction on the top of the glass spherical resonator in the boucing mode, which indicated that top areas of the glass spherical resonator and its boucing mode are preferences of the vibration tests. The effect of liquid density on the resonant frequency of the glass spherical resonator in the microfluidic chip was studied. Results showed that the change of liquid density would lead to the change of the resonant frequency of the glass spherical resonator. Results also showed that the resonant frequency increased with the decrease of the liquid density. Liquid density and resonant frequency were in a linear relationship in a small density variation.Secondly, a chemical foaming process was proposed and theory of glass spherical resonator preparation was studied. Then, the designed microfluidic chip with glass spherical resonator and microchannels was prepared. Results showed that glass spherical resonator prepared by the chemical foaming process had controllable sizes with smooth surfaces and uniform structures.Finally, vibration tests of the liquid filled glass spherical resonator were conducted by using Laser Doppler Vibrometer (LDV). Results showed that the resonant frequency decreased with the increase of the liquid density. Results also showed that liquid density and resonant frequency were in a linear relationship in a small density variation, which corresponded well with the simulation results.The hemispherical glass shell resonator for on line densitometer demonstrated in this thesis is expected to have awide application in microfluidics in future.