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. 2016 Oct 28;16(11):1802.
doi: 10.3390/s16111802.

Complementary Split-Ring Resonator-Loaded Microfluidic Ethanol Chemical Sensor

Ahmed Salim  1 , Sungjoon Lim  2
Affiliations

Complementary Split-Ring Resonator-Loaded Microfluidic Ethanol Chemical Sensor

Ahmed Salim et al. Sensors (Basel). .

Abstract

In this paper, a complementary split-ring resonator (CSRR)-loaded patch is proposed as a microfluidic ethanol chemical sensor. The primary objective of this chemical sensor is to detect ethanol's concentration. First, two tightly coupled concentric CSRRs loaded on a patch are realized on a Rogers RT/Duroid 5870 substrate, and then a microfluidic channel engraved on polydimethylsiloxane (PDMS) is integrated for ethanol chemical sensor applications. The resonant frequency of the structure before loading the microfluidic channel is 4.72 GHz. After loading the microfluidic channel, the 550 MHz shift in the resonant frequency is ascribed to the dielectric perturbation phenomenon when the ethanol concentration is varied from 0% to 100%. In order to assess the sensitivity range of our proposed sensor, various concentrations of ethanol are tested and analyzed. Our proposed sensor exhibits repeatability and successfully detects 10% ethanol as verified by the measurement set-up. It has created headway to a miniaturized, non-contact, low-cost, reliable, reusable, and easily fabricated design using extremely small liquid volumes.

Keywords: complementary split ring resonator (CSRR); ethanol sensor; microfluidic channel; patch.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) Top view of CSRR-loaded patch fed by quarter-wave stub and microstrip line before loading PDMS; (b) Zoom-in image of the CSRRs slot; (c) Bird’s-eye view of the proposed sensor with the microfluidic channel; (d) Top view of channel alignment with CSRRs slot.
Figure 2
Figure 2
Comparison of resonant frequency and loaded Q-factor with and without CSRRs. E-field distributions with and without the CSRR are illustrated at 4.72 GHz and 8.01 GHz, respectively.
Figure 3
Figure 3
Simulated S11 of the CSRR-loaded patch resonator at different (a) slot length of a; (b) slot width of c; and (c) gap of g.
Figure 3
Figure 3
Simulated S11 of the CSRR-loaded patch resonator at different (a) slot length of a; (b) slot width of c; and (c) gap of g.
Figure 4
Figure 4
E-field distribution of CSRR-loaded patch at resonant frequency of 4.72 GHz (without microfluidic channel).
Figure 5
Figure 5
Simulated S11 of the proposed sensor with the empty and DI water-filled channel when LC is varied from 3 mm to 7 mm.
Figure 6
Figure 6
Side view of three layers of proposed CSRR-loaded patch as a microfluidic chemical sensor.
Figure 7
Figure 7
Simulated S-parameters of the proposed CSRR-loaded patch using empty channel (air), DI water, and 100% ethanol.
Figure 8
Figure 8
(a) Fabricated prototype of CSRR-loaded microfluidic patch as ethanol chemical sensor; (b) Side view with nanoport assembly.
Figure 9
Figure 9
Comparison of simulated and measured S-parameters of the proposed microfluidic CSRR-loaded patch using air (empty channel), DI water, and 100% ethanol.
Figure 10
Figure 10
(a) Measured S-parameters; (b) Resonant frequency of ethanol with different concentrations, from 0% (DI water) to 100% with the fitting curve of y = 2.9 × 10−3 x + 3.32 in GHz.
See this image and copyright information in PMC

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