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In this paper, we demonstrate the optimal multi-modes for glucose droplet (GD) sensing depending on sample (glucose droplet) positions in a half-wavelength ( $\lambda $ /2) microstrip resonator. Using two different GD positions, i.e., an edge and a center position, in the resonator, the resonant behavior of microwave multi-modes for GD sensing was investigated. GDs with three different concentrations, i.e., 0.1, 0.2, and 0.3 g/ml, were tested in the present experiment. With increasing GD concentration, the ${S}_{21}$ -level of the edge-positional GD gradually was declined at all resonant modes. For a center-positional GD, the frequency not only was deviated into the high-frequency region, but its ${S}_{21}$ -level also gradually was declined for the second and fourth modes. Based on the experimental results, the resonant behavior indicated the edge-(center-) positional GD had the resolution (~0.01/gmL−1 or ~0.05 dB/gmL−1) at the second (second) and third (fourth) modes, respectively. Furthermore, we showed that the edge-positional GD sensing is more suitable when the resonator is associated with an active circuit system, and simultaneous sensing is also possible for different positions in multi-modes.

The optical spin Hall effect, which describes the spin-dependent and transverse shift of light, has been steadily investigated with the development of sensing applications such as polarization-dependent sensors, material interface analysis, and refractive index spectroscopy. However, practical optical spin Hall effect sensing platforms have not been reported since the previous reports have only focused on passive platforms. Here, we propose a biosensing platform using chitosan-coated all-dielectric metamaterials, which can detect the relative humidity of the surroundings by analyzing the displacement of the spin Hall effect. The chitosan coating provides a high sensitivity of relative humidity with a dynamic optical spin Hall effect in all-dielectric metamaterials. The maximum displacement of the split beam is calculated as 350 nm when the relative humidity changes by 60%, resulting in 8.75 nm shift per 1% of relative humidity change. This mechanism can be further exploited for a biosensing platform since the chitosan-coated all-dielectric metamaterials are biocompatible, biodegradable, and hydrophilic. Considering the chitosan-coated all-dielectric metamaterials have high feasibility with low-cost, high-throughput nanoimprinting methods, the dynamic optical spin Hall effect-based metamaterials will be a candidate of a promising real-time and ultra-sensitive sensing platform for detecting biomolecules.

In this study, the microwave, i.e. 0.5–10 GHz, transmission characteristics of carbon nanofiber (CNF) with three different micrometer-scale thicknesses were experimentally investigated using a coplanar waveguide transmission line. In the experimental results, when the film of CNF was thick, the signal transmission level (S21-magnitude) was significantly lower and its phase (S21-phase) was shifted toward the low-frequency region. Based on the obtained S21-parameter (S21-magnitude and S21-phase), the electric permittivity (e) of CNF was extracted and showed clear differences depending on the thickness, i.e., ethin = 1.20 (0.28), emiddle = 1.84 (0.60), ethick = 6.30 (1.15) at 0.5 GHz (7.8 GHz). From the analysis of electromagnetic fields, the microwave conductivity (σmw) of CNF linearly increased with the increasing thickness, i.e., σmw/thin = 0.35 (S/m), σmw/middle = 0.58 (S/m), σmw/thick = 0.75 (S/m), due to enhanced electromagnetic field coupling between the film of CNF and the CPW line. As a result, we demonstrated that the film of CNF has a significant attenuation effect on signal transmission in the microwave regime, depending on micrometer-scale changes in film thickness.

In this paper, a microwave fluidic glucose sensor based on dual complementary split ring resonators (CSRRs) with a switching circuit is proposed for non-invasive and continuous glucose concentration detection. A CSRR has been designed to detect subtle changes in the dielectric constant of glucose solutions, and the electric field distribution is utilized to determine the effective sensing region. In a well-controlled environment, the glucose concentration can be detected by tracking the transmission coefficient of the designed CSRR. However, because the variations in dielectric constant with the glucose concentration are very small, the environmental factors (i.e., ambient temperature and relative humidity) can be dominant compared to the glucose concentration. To qualify the effect of the environmental factors, the variation in the transmission coefficient of the CSRR has been measured when the ambient temperature condition is varied from 293 K to 313 K and the relative humidity is varied from 30% to 90% inside temperature- and humidity-controlled chamber. Moreover, the environmental effects are calibrated out using two identical CSRRs with the switching circuit: one detects changes in the glucose concentration, while the other operates as a reference for environmental factors. After the elimination of the environmental effects, glucose concentrations in the range of 0 mg/dL to 400 mg/dL have been measured, and the sensitivity is 0.008dB/(100mg/dL). In addition, the reproducibility of the proposed sensor is verified by repeated measurements. It is demonstrated that the proposed sensor can detect glucose concentrations under practical environmental conditions.

In this paper, a microwave fluidic glucose sensor based on a microwave resonator coupled with an interferometric system is proposed for sensitivity enhancement. The proposed glucose sensor consists of two parts: a sensing part and a sensitivity enhancement part. The former is composed of a rectangular complementary split ring resonator (CSRR), and the latter is composed of a variable attenuator, a variable phase shifter, two hybrid couplers, and an RF power detector. Because the variation in the electrical properties, which is utilized in the microwave detection scheme, with glucose concentration over the possible concentration range in the human body is very small, improvement of the sensitivity is critical for practical use. Thus, the effective sensing area of the rectangular CSRR is determined by considering the electric field distribution. In addition, magnitude and phase conditions for the effective sensitivity enhancement are derived from a mathematical analysis of the proposed interferometric system. In the present experiment, aimed at demonstrating the detection performance as a function of the glucose concentration in the range of 0 mg/dL to 400 mg/dL, the sensitivity is significantly improved by 48 times by applying the derived conditions for effective sensitivity enhancement. Furthermore, the accuracy of the proposed glucose sensor for glucose concentrations at a step of 100 mg/dL is verified by the Clarke error grid. Based on the measurement results, the proposed glucose sensor is demonstrated to be applicable to noninvasive and continuous monitoring in practical environments.

In this paper, a relative humidity monitoring sensor based on an active resonator with PEDOT:PSS is studied in the microwave regime. The proposed active resonator is patterned on a printed circuit board and excited by electromagnetic field coupling. The active resonator consists of two parts: a passive core resonator and an active circuit. The passive core resonator senses the humidity via the PEDOT:PSS conducting polymer film, which is located in the area of the passive core resonator with the strongest electric field. The active circuit compensates for the loss of the passive core resonator to enhance the quality factor and thus improve the sensitivity of the relative humidity sensor. By combining the passive core resonator with the active circuit, the active resonator exhibits a high quality factor (2887), which is 90 times that of the passive core resonator alone. Moreover, the sensitivity of the proposed humidity sensor is improved when using the active resonator. To verify the performance of the proposed humidity sensor, a commercial sensor is placed alongside the proposed sensor in a well-controlled environment chamber. According to the experimental results, as the relative humidity increases, the transmission coefficient (S21) increases, while the resonance frequency decreases. As a result, the sensor exhibits an increase in S21 of 3.58 dB and a decrease in the resonance frequency of 8.85 MHz when the relative humidity changes from 30% to 85%.

The invasive alien leaf‐footed bug Leptoglossus gonagra (Fabricius 1775), native to the Americas, is herein recorded from South Korea for the first time. Forty nymphs and adults were collected on 22 September 2016 from arable lands of two separate sites. These individuals were identified based on the analysis of morphological characters and cytochrome oxidase c subunit 1 sequences. A neighbor‐joining tree indicated the existence of two clades: Group A from Brazil, and Group B from Asia and Oceania. Mean genetic distance between clades was 8.11%, range 7.60–8.57%. Within clades, mean genetic distance was 0.42% (0.17–0.83%) in Group A and, 0.45% (0.00–0.83%) in Group B. Colonies of 2nd‐final instar nymphs and adults were found, on top of leaves, flowers, fruits, and between the stems of pumpkins (Cucurbita moschata). Nymphs and adults damaged host plants by sucking their leaves, stems, fruits, and buds. After the first discovery in 2016, we were unable to find the bugs again (in 2017–2019). Therefore, the invasion of this species seems to have occurred only temporarily, during the warm season. We suggest that the species may have failed to overwinter as it is normally distributed in regions warmer than Korea. Nevertheless, possible appearances of this species must be continuously monitored as it is a potential pest of various plants cultivated in South Korea.

In this paper, we characterize the thin conducting polymer film, PEDOT: PSS, using a microstrip line in a humid environment at microwave frequencies. To characterize the thin film alone over the microstrip line, a de-embedding technique of thru-reflect-line (TRL) calibration is utilized. After the de-embedding procedure, the thin film is modeled with a transmission line, and the film’s R, L, G, and C parameters are extracted from measured S-parameters. In addition, the characteristics of the thin film has been tested in terms of electrical conductivity with increasing relative humidity (RH). In the future, it is expected that this work can contribute to the improvement of stability as well as performance of conducting polymer-based electronic sensing devices.

In this paper, we propose a humidity sensor based on a negative resistance oscillator using conducting polymer (CP) PEDOT:PSS film at room temperature. The proposed humidity sensor basically consists of a microstrip line and a negative resistance circuit, which creates a negative resistance for high-frequency oscillation. The microstrip line has a circuit structure that is connected through a via hole between the ground plane and the signal line with a CP thin film. From our experimental results, we find that the oscillation frequency of the sensor gradually decreases as the relative humidity (RH) increases. Owing to the conductivity variation of the CP film with the RH value, the oscillation frequency of the sensor sensitively changes in real time. Therefore, we suggest that our microwave-oscillator-based sensor scheme is a good candidate for the design of a robust and stable humidity sensor.

This review paper focuses on radio-frequency (RF) biosensors for real-time and continuous glucose sensing reported in the literature, including our recent research. Diverse versions of glucose biosensors based on RF devices and circuits are briefly introduced, and their performances are compared. In addition, the limitations of the developed RF glucose biosensors are discussed. Finally, we present perspectives on state-of-art RF biosensing chips for point-of-care diagnosis and describe their future challenges.

This study aims to investigate the microwave properties of coplanar waveguide (CPW)-based poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) conducting polymer line in an ethanol gas atmosphere, with the frequency range of 0.5&ndash, 2 GHz. For an ethanol-exposed PEDOT:PSS line (test sample), the transmission coefficient (S21) decreased immediately, moreover, the microwave effective conductivity (&sigma, m/w) decreased simultaneously, compared with the ethanol-free PEDOT:PSS line (reference sample). The immediate variations in &Delta, S21 ( = S21,ethanol &minus, S21,free) and &Delta, &sigma, m/w ( = &sigma, m/w,ethanol &minus, m/w,free) were approximately 10.2 dB and 2.7 &times, 104 S/m, respectively. Furthermore, in the analysis of the circuit model of the PEDOT:PSS line, the characteristic impedance and distributed elements, i.e., resistance (R) and inductance (L) per length, of the test sample increased, compared with the reference sample. However, upon stopping the exposure to ethanol gas, the microwave properties of the test sample instantaneously recovered to those of the reference sample. According to these critical observations, we could confirm that the coplanar waveguide with a PEDOT:PSS line shows a significant difference in the diverse microwave properties, through rapid response to the ethanol gas at room temperature.

Although data-based healthcare innovation has been spotlighted in South Korea in recent years, previous studies have made little effort to systematically predict various possible future outcomes in the data-driven healthcare economy. This study investigated possible future such scenarios in South Korea by conducting a general morphological analysis (GMA). Seven key factors were identified that will drive the data-driven healthcare economy: the acceptability of data utilization, the level of data literacy, the status of healthcare data regulation, the healthcare data system, medical costs, the convergence of ICT and biotechnology, and the utilization of data in medical services. The main findings are as follows: Four possible scenarios for the data-driven healthcare economy in South Korea were identified. The first scenario suggested mostly optimistic prospects and close associations between factorial values on the various spectra. The second scenario was similar to the first one, except for medical costs. However, the third scenario contrasted with the first, as it entailed relatively pessimistic factorial values. Finally, most of the elements of the current healthcare status quo were maintained in the fourth scenario. This study makes not only an academic contribution, but also has policy implications based on the four scenarios.

A real-time humidity sensor based on a microwave resonator coupled with a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) conducting polymer (CP) film is proposed in this paper. The resonator is patterned on a printed circuit board and is excited by electromagnetic field coupling. To enhance the sensitivity of the sensor, the CP film is located in the area with the strongest electric field in the resonator. To investigate the performance, the proposed sensor is placed alongside a reference sensor in a humidity chamber, and humidity is injected at room temperature. The experimental results indicate that the electrical properties of the resonator with the CP film, such as the transmission coefficient (S21) and resonance frequency, change with the relative humidity (RH). Specifically, as the RH changes from 5% to 80%, S21 and the resonance frequency change simultaneously. Moreover, the proposed sensor exhibits great repeatability in the middle of the sensing range, which is from 40% to 60% RH. Consequently, our resonator coupled with the CP film can be used as a real-time humidity-sensing device in the microwave range, where various radio-frequency devices are in use.

This Chapter describes the methods of a proximity coupling RF vital sensor. The methods are mainly divided into two categories: the chest wall sensor and the wrist pulse sensor. For each part, the theoretical considerations, simulation results, and experimental results on methods for efficiently enhancing the sensitivity of the sensors are described in detail. In addition, we introduce an autoregressive (AR) model which is one of the parametric spectral analyses suitable for vital sign detection.

In this paper, the advances in radio-frequency (RF)/microwave biosensors based on graphene nanomaterials including graphene, graphene oxide (GO), and reduced graphene oxide (rGO) are reviewed. From a few frontier studies, recently developed graphene nanomaterials-based RF/microwave biosensors are examined in-depth and discussed. Finally, the prospects and challenges of the next-generation RF/microwave biosensors for wireless biomedical applications are proposed.

In this paper, a proximity coupling RF sensor based on injection-locked phase-locked loop (PLL) for wrist pulse detection is proposed. The sensor is composed of two main parts: a free-running oscillator and a PLL synthesizer containing a voltage-controlled oscillator. The free-running oscillator is built with a two-port microstrip line resonator (inter-digital electrodes), which acts as part of a transducer that can transform the expansion or contraction of the radial artery into an impedance variation. Measurements show that the impedance variation of the resonator due to changes in the radial artery causes a frequency change of up to 0.74 MHz in the free-running oscillator. For the PLL part, the frequency change can be transformed to a variation in dc voltage by injection of the modulated signal from the wrist pulse into a phase-locked oscillator. The variation of the loop-control voltage, in one cycle of the pulse, is approximately 10–15 mV peak-to-peak. Our sensor is demonstrated to be an effective noncontact and noninvasive scheme for wrist pulse detection.

In this review, the advances in radio-frequency (RF) /microwave chemical gas sensors using conducting polymers are discussed. First, the introduction of various conducting polymers is described. Only polyaniline (PANi), polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT), which are mainly used for gas sensors in RF/microwave region, are focused in this review. Sensing mechanism of the three conducting polymers are presented. And the RF/microwave characteristics and RF/microwave applications of the three conducting polymers are discussed. Moreover, the gas sensors using conducting polymers in RF/microwave frequencies are described. Finally, the the challenges and the prospects of the next generation of the RF/microwave based chemical sensors for wireless applications are proposed.

The purpose of this study is to investigate the effects of the natural river conservation work and to find remedies for them, targeting Jangsu-cheon with high frequency of use by citizens among the rivers in Incheon Metroplitan City, Korea; for this, this study conducted investigations and analyses of Jangsu-cheon completed in December, 2008. As a result of investigating 3 spots for the water system of Jangsu-cheon over a total of 3 years (2009, 2010, 2014), it was found that benthic macro-invertebrates of a total of 3 phyla, 5 classes, 11 orders, 26 families, 56 species, and 980 specimens were distributed there. When they were analyzed by year, 18 families and 30 species in 2009, right after the natural river conservation work, and 22 families and 37 species in 2010, 2 years after the work, were found, with 7 species increasing in number; after that, as a result of the investigation in 2014, 22 families and 38 species were found, which tells the river has entered the stabilization stage since the recovery in 2010.Therefore, this study could identify: the water environment of the river was improved due to the natural river conservation work for Jangsu-cheon; in addition, Jangsu-cheon showed good ecological environment due to the continuous maintenance of the good wetlands in Incheon Grand Park in the upper area of the river; and the natural river conservation work of Jangsu-cheon created positive effects.

In this paper, the electrical characteristics of interdigital capacitor with single-layer and multi-layer graphene were compared and analyzed in the microwave region. In equivalent circuit, a capacitor coupled with graphene showed the clear difference in electrical components such as resistance, inductance, and capacitance. In particular, for the capacitor with single-layer graphene, additional induc-tance and resistance occurred and the electrode resistance was also increased. Meanwhile, the self-resonance frequency of capacitor was shifted toward lower frequency region and its transmitted characteristic was considerably improved at frequency ranging from 0.4 to 4 GHz. The electrical characteristics of the capacitor with multi-layer graphene were somewhat different than the bare capacitor. In conclusion, we could confirm that single-layer graphene greatly influenced the electrical characteristics and performances of interdigital capacitor compared to multi-layer graphene.Key words: Graphene, Interdigital Capacitor, Self-Resonance Frequency, S-Parameter mR2015nopq(r stVuq) vwEHx`av wy Revised December 21, 2015 ; Accepted December 21, 2015. (ID No. 20151016-078)„Corresponding Author: Hee-Jo Lee (e-mail: hjlee@daegu.ac.kr)

In this study, the electrical characteristics of interdigital capacitors with single-layer and multi-layer graphene are compared and analyzed in the microwave region. In equivalent circuit, a capacitor coupled with graphene shows the clear difference in electrical components such as resistance, inductance, and capacitance. In particular, for the capacitor with single-layer graphene, additional inductance and resistance is occurred and the electrode resistance is also increased. Meanwhile, the self-resonance frequency of capacitor is shifted toward lower frequency region and its transmitted characteristic is considerably improved at frequency ranging from 0.4 to 4 GHz. The electrical characteristics of the capacitor with multi-layer graphene are somewhat different than the bare capacitor. In conclusion, we can confirm that single-layer graphene greatly influences the electrical characteristics and performances of interdigital capacitor compared to multi-layer graphene.

In this paper, a radio-frequency circuit model of an interdigital capacitor (IDC) with a multilayer graphene (MLG) width variation is proposed. The circuit model with three sample configurations, i.e., a bare IDC, IDC-MLG with a width of 5 μm, and IDC-MLG with a width of 20 μm, is constructed via a fitted method based on the measured samples. The simulated results of the circuit model are validated through the RF characteristics, e.g., the capacitance and the self-resonance frequency, of the measured samples. From the circuit model, all samples show not only a similar capacitance behavior but also an identical self-resonance frequency of 10 GHz. Moreover, the R, L, and C values of MLG with a 5 μm width (MLG with a 20 μm width) alone are approximately 0.8 kΩ (0.5 kΩ), 0.5 nH (0.9 nH), and 0.3 pF (0.1 pF), respectively. As a result, we find that the simulated results are in good agreement with RF characteristics of the measured samples. In the future, we expect that the proposed circuit model of an IDC with...

In this paper, we investigate on the capacitance behavior of radio-frequency interdigital capacitor with single- and multi-layer graphenes, 5-μm wide and 20-μm long, grown by chemical vapor deposition. From the obtained results, the self-resonance frequency of the capacitor alone is unaffected by adding single- and multi-layer graphenes. However, the capacitor with single-layer graphenes shows a lower capacitance peak compared to the two other configurations due to an increase of overall resistance by the single-layer graphene. As a result, we find that the performance of the overall capacitor can be dependent on the resistance of graphenes.

In this paper, we demonstrate the sensing feasibility of the proposed high-Q resonator using a phosphate-buffered saline droplet at microwave frequencies. In the experimental results, the resonant frequency, signal level, and Q-factor of the S21-parameter with and without a 1-μl droplet were changed to about 230 MHz, 32 dB, and 1500, respectively. The resonator system was found to be suitable for droplet sensing with a small volume due to its small and compact scheme. This resonator system is expected to play an important role in droplet sensing with different dielectric constants.