A Study of Optimal Design of Multi-channel Quartz Crystal Microbalance
Date Issued
2008
Date
2008
Author(s)
Liao, Shao-An
Abstract
Single-electrode quartz crystal microbalance (QCM) has been a commercialized bio-senser in recent years. However, with the advantage of being able to perform multi-sensing, the idea of multi-channel quartz crystal microbalance (MQCM) has been proposed. Multi-channel quartz crystal microbalance has at least two electrodes, which offer multi-sensing. In this thesis, single electrode design was first modified based on the n-m model. This design enables better energy trapping efficiency and avoids decreased sensitivity while reducing the electrode dimension. Nevertheless, the influence from flexural wave is still strong. The mesa design was then applied to increase the effective mass density of the electrode region by increasing the thickness of the region. Two designs were then implemented to the dual-channel quartz crystal microbalance. Interference between the electrodes is the main concern of dual-channel quartz crystal microbalance. The dimensions of each electrode were therefore chosen not to be close. Similar dimension of two electrodes will result in the overlap of resonance frequencies so that the sensitivity of the device is decreased. Besides, the size of quartz plate is fixed and two electrodes must be fit in, the dimension of each electrode was thus set to be as small as possible to avoid close proximity and thus the coupling between electrodes. With the optimized parameters, a MQCM was manufactured using lithography. The signal output was measured by Agilent 4294a Impedance Analyzer. First, the resonance frequency of each electrode was measured. Later, water drop was loaded onto electrode 1 and the resonance frequencies of both electrodes were measured. The same process was repeated for water drop loaded onto electrode 2. It was found no significant frequency shift on electrode 1 occurred when water drop (mass) was loaded on electrode 2 and vice versa.
Subjects
energy trapping effect
quartz
quartz crystal microbalance
piezoelectric material
mesa design
Type
thesis
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