A Compact Microwave Microfluidic Sensor Using a Re-Entrant Cavity
<p>Cross section of a re-entrant microwave cavity, showing the distribution of electric (<b>a</b>) and magnetic (<b>b</b>) fields; the position of the sample tube within the axial hole.</p> "> Figure 2
<p>Equivalent lumped circuit for the re-entrant cavity.</p> "> Figure 3
<p>Re-entrant cavity with a gap partially filled with a dielectric.</p> "> Figure 4
<p>Re-entrant cavity dimensions.</p> "> Figure 5
<p>Photograph of the machined re-entrant cavity and its component parts.</p> "> Figure 6
<p>The complete microfluidic system connected to the cavity sensor and controlled via LabVIEW code. The microscopic camera has been used for video recording.</p> "> Figure 7
<p>Simulation result for the normalized electric field (V/m) when the FEP sample tube is empty.</p> "> Figure 8
<p>Simulation result for the normalized electric field (V/m) when there is water in the FEP tube within the active gap area.</p> "> Figure 9
<p>Cross sectional view when FEP tube is empty (<b>a</b>); and when there is water in tube in the active gap area (<b>b</b>).</p> "> Figure 10
<p>Schematic diagram of the electric field lines near the sample when (<b>a</b>) the cavity is empty; and (<b>b</b>) when there is a water-filled tube.</p> "> Figure 11
<p>Measured and simulated |S<sub>21</sub>| for several solvents at 25 °C.</p> "> Figure 12
<p>(Δ<span class="html-italic">f</span>/<span class="html-italic">fr</span>) for water, methanol, ethanol, and chloroform vs <span class="html-italic">ε</span><sub>1</sub>-1 (<b>a</b>); and (Δ<span class="html-italic">f<sub>B</sub></span>/<span class="html-italic">f<sub>r</sub></span>) for the same solvents vs. <span class="html-italic">ε</span><sub>2</sub> (<b>b</b>).</p> "> Figure 13
<p>RMC perturbations due to a segmented oil: water flow. (<b>a</b>) resonant frequency (water = low frequency); (<b>b</b>) bandwidth (water = high bandwidth); and (<b>c</b>) insertion loss (water = high loss).</p> ">
Abstract
:1. Introduction
2. Theory
3. Cavity Design and Fabrication
- The electric field is parallel to the sample length, meaning that depolarization is minimal and the changes in resonator parameters (such as resonant frequency) are linearly dependent on the relative permittivity.
- The effective volume of the re-entrant cavity is very small, yielding a sensitive sample characterization.
4. Microfluidic System Design
5. Results
5.1. Simulation Results
5.2. Experimental Results
5.3. Results for Segments Flow
6. Conclusions
Author Contributions
Conflicts of Interest
References
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Resonator | |||
---|---|---|---|
Water | 78.4 | 5.16 | 8.27 |
Methanol | 32.5 | 5.60 | 51.5 |
Ethanol | 24.3 | 4.20 | 163 |
Chloroform | 4.72 | 2.50 | 7.96 |
Resonator | Simulated fr (GHz) | Measured fr (GHz) | Simulated Quality | Measured Quality | Simulated IL (dB) | Measured IL (dB) | Simulated Permittivity | Measured Permittivity | Error |
---|---|---|---|---|---|---|---|---|---|
Empty | 2.4271 | 2.4271 | 1190 | 1187 | −25.020 | −25.153 | |||
Water | 2.4161 | 2.4160 | 615 | 613 | −31.527 | −31.578 | 77.23 − j9.04 | 77.85 − j9.10 | 0.8% |
Methanol | 2.4229 | 2.4227 | 385 | 381 | −35.509 | −35.296 | 22.27 − j13.06 | 22.84 − j12.87 | 1.5% |
Ethanol | 2.4257 | 2.4255 | 483 | 480 | −33.169 | −33.117 | 7.01 − j6.97 | 7.27 − j6.96 | 1.7% |
Chloroform | 2.4263 | 2.4261 | 1125 | 1125 | −25.557 | −25.663 | 4.69 −d j0.27 | 4.81 − j0.30 | 2.5% |
Segment Type | Velocity (mm/sec.) Measured by Camera | Length (mm) from Camera | Length (mm) from Cavity |
---|---|---|---|
Water | 3.4 ± 0.2 | 18.5 ± 1.2 | 18.2 ± 0.9 |
Oil | 3.4 ± 0.2 | 35.5 ± 1.2 | 33.6 ± 1.6 |
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Hamzah, H.; Abduljabar, A.; Lees, J.; Porch, A. A Compact Microwave Microfluidic Sensor Using a Re-Entrant Cavity. Sensors 2018, 18, 910. https://doi.org/10.3390/s18030910
Hamzah H, Abduljabar A, Lees J, Porch A. A Compact Microwave Microfluidic Sensor Using a Re-Entrant Cavity. Sensors. 2018; 18(3):910. https://doi.org/10.3390/s18030910
Chicago/Turabian StyleHamzah, Hayder, Ali Abduljabar, Jonathan Lees, and Adrian Porch. 2018. "A Compact Microwave Microfluidic Sensor Using a Re-Entrant Cavity" Sensors 18, no. 3: 910. https://doi.org/10.3390/s18030910