| Summary: | 碩士 === 國立中興大學 === 物理學系所 === 100 === In this study, microwave resonators are used to real-time detect blockade events of particle flowing through a pore. The resonators are reflective microstrip resonators(MSRs) and double split ring resonators(DSRRs), fabricated on printed circuit boards(PCB). By monitoring the microwave reflection or transmission, we demonstrated the detection of 0.25 mm-in-diameter particles suspended in water through the pore, which is 0.8 mm in diameter at the position where the microwave electric field is strongest.
The microwave measurement is reliable since it is consistent with ion current measurement, which is a direct observation of the particle blockade. Also, the change in microwave signal is larger as the particle size increases. Sensitivity for amplitude and phase have different trend in their carrier frequency: for phase, the resonant frequency is the most sensitive operating point while for the amplitude, the most sensitive point is slightly off the resonance. If using the phase detection at the resonant frequency, we found MSRs more sensitive than DSRRs. This is because of the different electric field direction in the sensing area.
For detecting smaller particles, the microwave resonator and pore size should be reduced by micro fabrication techniques. Thus we tried to fabricate resonators on various substrates, and found that MS resonators made on 50 μm-thick polyimide substrates displayed a good resonant property.
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