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Microwave Sensors for Non-invasive Characterization and Monitoring Applications

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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Physical Sensors".

Deadline for manuscript submissions: closed (30 November 2023) | Viewed by 26980

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Special Issue Editor

Dr. Cristiano Palego

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Guest Editor

School of Computer Science and Electronic Engineering, Bangor University, Bangor, UK
Interests: microelectronics; bioelectronics; energy harvesting; microwave engineering

Special Issue Information

Dear Colleagues,

The rapid evolution of integrated circuits with high performance well into the millimeter waves is revolutionizing microwave sensing technology. The proliferation of microwave chip components and subsystems at an increasingly competitive cost is not only affecting naturally related sectors such as wireless sensor networks and radar communications; it is also propelling innovative approaches in dielectric material and micro-device characterization while showing new opportunities for minimally invasive biosample detection and autonomous radar monitoring. The presented contributions will show how the increasing convergence between microelectronics, microfluidics, and microwave sensing technologies is now driving a similar miniaturization trend as in mobile communications with a potentially broader societal impact. The anticipated applications in point-of-care and personalized medicine become even more relevant amid the emergence of 5G and Internet of Things technology. The shift toward multiphysics sensors and big data settings additionally makes microwave sensors a key enabler in the development of smart/sustainable urban or healthcare environments and unobtrusive autonomous monitoring.

This Special Issue addresses novel ideas, technologies, and challenges related to microwave sensing. It gathers the latest developments from ongoing and rapidly evolving research projects with a special emphasis on dielectric characterization of material and samples, microwave biosensing, and unobtrusive monitoring of moving targets spanning from healthcare to agritech applications. Potential topics include but are not limited to the following:

Autonomous, minimally invasive monitoring;
Biosensors for cell and/or subcellular sensing;
CMOS integrated circuit, on-chip systems, lab-on-chip;
Dielectric characterization and impedance sensing;
Localization, angle-of-arrival, and received signal strength indicator detection;
Novel microwave measurement and readout (e.g., machine learning enhanced) approaches;
Radar, doppler, and micro-doppler signatures;
Wireless sensing in sensor networks and Internet of Things settings;
Wearable and implantable microwave devices.

Dr. Cristiano Palego
Guest Editor

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Keywords

autonomous monitoring
biosensors
CMOS integrated circuit
dielectric characterization
localization
impedance sensing
microwave measurement
radar
wireless sensing
wearable electronics

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Published Papers (11 papers)

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17 pages, 6300 KiB

Open AccessArticle

Challenges in Developing a Real-Time Bee-Counting Radar

by Samuel M. Williams, Nawaf Aldabashi, Paul Cross and Cristiano Palego

Sensors 2023, 23(11), 5250; https://doi.org/10.3390/s23115250 - 1 Jun 2023

Cited by 4 | Viewed by 2344

Abstract

Detailed within is an attempt to implement a real-time radar signal classification system to monitor and count bee activity at the hive entry. There is interest in keeping records of the productivity of honeybees. Activity at the entrance can be a good measure of overall health and capacity, and a radar-based approach could be cheap, low power, and versatile, beyond other techniques. Fully automated systems would enable simultaneous, large-scale capturing of bee activity patterns from multiple hives, providing vital data for ecological research and business practice improvement. Data from a Doppler radar were gathered from managed beehives on a farm. Recordings were split into 0.4 s windows, and Log Area Ratios (LARs) were computed from the data. Support vector machine models were trained to recognize flight behavior from the LARs, using visual confirmation recorded by a camera. Spectrogram deep learning was also investigated using the same data. Once complete, this process would allow for removing the camera and accurately counting the events by radar-based machine learning alone. Challenging signals from more complex bee flights hindered progress. System accuracy of 70% was achieved, but clutter impacted the overall results requiring intelligent filtering to remove environmental effects from the data. Full article

(This article belongs to the Special Issue Microwave Sensors for Non-invasive Characterization and Monitoring Applications)

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13 pages, 4275 KiB

Open AccessArticle

Broadband Electrical Spectroscopy to Distinguish Single-Cell Ca²⁺ Changes Due to Ionomycin Treatment in a Skeletal Muscle Cell Line

by Caroline A. Ferguson, Carmen Santangelo, Lorenzo Marramiero, Marco Farina, Tiziana Pietrangelo and Xuanhong Cheng

Sensors 2023, 23(9), 4358; https://doi.org/10.3390/s23094358 - 28 Apr 2023

Cited by 1 | Viewed by 1799

Abstract

Many skeletal muscle diseases such as muscular dystrophy, myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), and sarcopenia share the dysregulation of calcium (Ca²⁺) as a key mechanism of disease at a cellular level. Cytosolic concentrations of Ca²⁺ can signal dysregulation in organelles including the mitochondria, nucleus, and sarcoplasmic reticulum in skeletal muscle. In this work, a treatment is applied to mimic the Ca²⁺ increase associated with these atrophy-related disease states, and broadband impedance measurements are taken for single cells with and without this treatment using a microfluidic device. The resulting impedance measurements are fitted using a single-shell circuit simulation to show calculated electrical dielectric property contributions based on these Ca²⁺ changes. From this, similar distributions were seen in the Ca²⁺ from fluorescence measurements and the distribution of the S-parameter at a single frequency, identifying Ca²⁺ as the main contributor to the electrical differences being identified. Extracted dielectric parameters also showed different distribution patterns between the untreated and ionomycin-treated groups; however, the overall electrical parameters suggest the impact of Ca²⁺-induced changes at a wider range of frequencies. Full article

(This article belongs to the Special Issue Microwave Sensors for Non-invasive Characterization and Monitoring Applications)

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13 pages, 40819 KiB

Open AccessArticle

Elastic Textile Wristband for Bioimpedance Measurements

by Giuseppina Monti, Federica Raheli, Andrea Recupero and Luciano Tarricone

Sensors 2023, 23(6), 3351; https://doi.org/10.3390/s23063351 - 22 Mar 2023

Cited by 1 | Viewed by 1804

Abstract

In this paper, wristband electrodes for hand-to-hand bioimpedance measurements are investigated. The proposed electrodes consist of a stretchable conductive knitted fabric. Different implementations have been developed and compared with Ag/AgCl commercial electrodes. Hand-to-hand measurements at 50 kHz on forty healthy subjects have been carried out and the Passing–Bablok regression method has been exploited to compare the proposed textile electrodes with commercial ones. It is demonstrated that the proposed designs guarantee reliable measurements and easy and comfortable use, thus representing an excellent solution for the development of a wearable bioimpedance measurement system. Full article

(This article belongs to the Special Issue Microwave Sensors for Non-invasive Characterization and Monitoring Applications)

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22 pages, 14096 KiB

Open AccessArticle

Detection of Semi-Solid Materials Utilizing Triple-Rings CSRR Microwave Sensor

by Ahmed Jamal Abdullah Al-Gburi, Norhanani Abd Rahman, Zahriladha Zakaria and Merih Palandoken

Sensors 2023, 23(6), 3058; https://doi.org/10.3390/s23063058 - 12 Mar 2023

Cited by 18 | Viewed by 2941

Abstract

This article proposes the design, fabrication and measurement of a triple-rings complementary split-ring resonator (CSRR) microwave sensor for semi-solid material detection. The triple-rings CSRR sensor was developed based on the CSRR configuration with curve-feed designed together, utilizing a high-frequency structure simulator (HFSS) microwave studio. The designed triple rings CSRR sensor resonates at 2.5 GHz, performs in transmission mode, and senses shift in frequency. Six cases of the sample under tests (SUTs) were simulated and measured. These SUTs are Air (without SUT), Java turmeric, Mango ginger, Black Turmeric, Turmeric, and Di-water, and detailed sensitivity analysis is conducted for the frequency resonant at 2.5 GHz. The semi-solid tested mechanism is undertaken using a polypropylene (PP) tube. The samples of dielectric material are filled into PP tube channels and loaded in the CSRR centre hole. The e-fields near the resonator will affect the interaction with the SUTs. The finalized CSRR triple-rings sensor was incorporated with defective ground structure (DGS) to deliver high-performance characteristics in microstrip circuits, leading to a high Q-factor magnitude. The suggested sensor has a Q-factor of 520 at 2.5 GHz with high sensitivity of about 4.806 and 4.773 for Di-water and Turmeric samples, respectively. The relationship between loss tangent, permittivity, and Q-factor at the resonant frequency has been compared and discussed. These given outcomes make the presented sensor ideal for detecting semi-solid materials. Full article

(This article belongs to the Special Issue Microwave Sensors for Non-invasive Characterization and Monitoring Applications)

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12 pages, 5734 KiB

Open AccessArticle

Development of the Tele-Measurement of Plasma Uniformity via Surface Wave Information (TUSI) Probe for Non-Invasive In-Situ Monitoring of Electron Density Uniformity in Plasma Display Fabrication Process

by Si-Jun Kim, Min-Su Choi, Sang-Ho Lee, Won-Nyoung Jeong, Young-Seok Lee, In-Ho Seong, Chul-Hee Cho, Dae-Woong Kim and Shin-Jae You

Sensors 2023, 23(5), 2521; https://doi.org/10.3390/s23052521 - 24 Feb 2023

Cited by 2 | Viewed by 2062

Abstract

The importance of monitoring the electron density uniformity of plasma has attracted significant attention in material processing, with the goal of improving production yield. This paper presents a non-invasive microwave probe for in-situ monitoring electron density uniformity, called the Tele-measurement of plasma Uniformity via Surface wave Information (TUSI) probe. The TUSI probe consists of eight non-invasive antennae and each antenna estimates electron density above the antenna by measuring the surface wave resonance frequency in a reflection microwave frequency spectrum (S

_{11}

). The estimated densities provide electron density uniformity. For demonstration, we compared it with the precise microwave probe and results revealed that the TUSI probe can monitor plasma uniformity. Furthermore, we demonstrated the operation of the TUSI probe beneath a quartz or wafer. In conclusion, the demonstration results indicated that the TUSI probe can be used as an instrument for a non-invasive in-situ method for measuring electron density uniformity. Full article

(This article belongs to the Special Issue Microwave Sensors for Non-invasive Characterization and Monitoring Applications)

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9 pages, 423 KiB

Open AccessCommunication

Proposal: Apparatus for Sensing the Effect of Surface Roughness on the Surface Resistance of Metals

by Kostiantyn Torokhtii, Andrea Alimenti, Pablo Vidal García, Nicola Pompeo and Enrico Silva

Sensors 2023, 23(1), 139; https://doi.org/10.3390/s23010139 - 23 Dec 2022

Cited by 5 | Viewed by 1517

Abstract

The root mean square surface roughness

R_{q}

of metals is detrimental in several microwave applications.

R_{q}

characterization methods are thus largely used and of great interest. In this work, a new dielectric loaded resonator (DR) design is proposed to evaluate the [...] Read more.

The root mean square surface roughness

R_{q}

of metals is detrimental in several microwave applications.

R_{q}

characterization methods are thus largely used and of great interest. In this work, a new dielectric loaded resonator (DR) design is proposed to evaluate the surface resistance variations of samples with different

R_{q}

. The new design is thought to make the measurement accuracy, usually strongly affected by the measurement repeatability, suitable for this study. We analyze the measurement method’s sensitivity and accuracy in order to assess the possibility of using this new DR design for highly accurate surface resistance measurements sensitive to

R_{q}

variations. Full article

(This article belongs to the Special Issue Microwave Sensors for Non-invasive Characterization and Monitoring Applications)

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13 pages, 12363 KiB

Open AccessArticle

Nanoscale Characterization of Graphene Oxide-Based Epoxy Nanocomposite Using Inverted Scanning Microwave Microscopy

by C. H. Joseph, Francesca Luzi, S. N. Afifa Azman, Pietro Forcellese, Eleonora Pavoni, Gianluca Fabi, Davide Mencarelli, Serena Gentili, Luca Pierantoni, Antonio Morini, Michela Simoncini, Tiziano Bellezze, Valeria Corinaldesi and Marco Farina

Sensors 2022, 22(24), 9608; https://doi.org/10.3390/s22249608 - 8 Dec 2022

Cited by 5 | Viewed by 1728

Abstract

Scanning microwave microscopy (SMM) is a novel metrological tool that advances the quantitative, nanometric, high-frequency, electrical characterization of a broad range of materials of technological importance. In this work, we report an inverted near-field scanning microwave microscopy (iSMM) investigation of a graphene oxide-based epoxy nanocomposite material at a nanoscopic level. The high-resolution spatial mapping of local conductance provides a quantitative analysis of the sample’s electrical properties. In particular, the electrical conductivity in the order of ∼

10^{- 1}

S/m as well as the mapping of the dielectric constant with a value of ∼4.7 ± 0.2 are reported and validated by the full-wave electromagnetic modeling of the tip–sample interaction. Full article

(This article belongs to the Special Issue Microwave Sensors for Non-invasive Characterization and Monitoring Applications)

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16 pages, 4240 KiB

Open AccessArticle

Cervical Tissue Hydration Level Monitoring by a Resonant Microwave Coaxial Probe

by Heungjae Choi, Emilia Barker, Ali A. Abduljabar, Dilly Anumba and Adrian Porch

Sensors 2022, 22(23), 9527; https://doi.org/10.3390/s22239527 - 6 Dec 2022

Viewed by 2119

Abstract

Cervical tissue hydration level is one of the most important parameters to monitor in the early diagnosis of preterm birth. Electrical-impedance-spectroscopy-based techniques are often used, but they suffer from limited accuracy. Open microwave coaxial probes have been widely used as a broadband dielectric characterization technique for human tissue samples due to their versatility, but with limited accuracy due to their nonresonant nature. In this work, a resonant microwave open coaxial probe with multiple harmonic resonances is proposed as a sensing platform for tissue-hydration-level monitoring. The mechanical design was analyzed and verified by finite-element full 3D electromagnetic simulation and experiments. Dominant sources of errors and the ways to mitigate them were discussed. In vitro experiments were carried out on human cervix samples to verify the precision and accuracy by comparing the results to a commercial skin-hydration sensor. The proposed sensor shows mean fractional frequency shift of (3.3 ± 0.3) × 10⁻⁴ per unit % over the entire data. This translates into an absolute frequency shift (

Δ f_{N})

of 252 ± 23 kHz/%, 455 ± 41 kHz/%, and 647 ± 57 kHz/% at second, fourth, and sixth harmonic resonance, respectively. Full article

(This article belongs to the Special Issue Microwave Sensors for Non-invasive Characterization and Monitoring Applications)

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21 pages, 21449 KiB

Open AccessArticle

A Novel Localization System in SAR-Demining Applications Using Invariant Radar Channel Fingerprints

by Nicholas Karsch, Hendrik Schulte, Thomas Musch and Christoph Baer

Sensors 2022, 22(22), 8688; https://doi.org/10.3390/s22228688 - 10 Nov 2022

Cited by 5 | Viewed by 1466

Abstract

In this paper, we present a novel two dimensional (2D) frequency-modulated continuous-wave (FMCW) localization method for handheld systems based on the extraction of distinguishable subchannel fingerprints. Compared with other concepts, only one subdivided radar source channel is needed in order to instantly map a one-dimensional measurement to higher-dimensional space coordinates. The additional information of the detected target is implemented with low-cost hardware component features, which exhibit distinguishable space-dependent fingerprint codes. Using the given a priori information of the hardware thus leads to a universally applicable extension for low-cost synthetic aperture radar (SAR)-demining purposes. In addition to the description of the system concept and its requirements, the signal processing steps and the hardware components are presented. Furthermore, the 2D localization accuracy of the system and the classification accuracy of the frequency-coded fingerprints are described in a defined test environment to proof the operational reliability of the realized setup, reaching a classification accuracy of 94.7% and an averaged localization error of 4.9 mm. Full article

(This article belongs to the Special Issue Microwave Sensors for Non-invasive Characterization and Monitoring Applications)

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11 pages, 4755 KiB

Open AccessArticle

An Improved Split-Ring Resonator-Based Sensor for Microfluidic Applications

by Wei Ye, Da-Wei Wang, Jing Wang, Gaofeng Wang and Wen-Sheng Zhao

Sensors 2022, 22(21), 8534; https://doi.org/10.3390/s22218534 - 5 Nov 2022

Cited by 16 | Viewed by 2982

Abstract

This study proposes an ultrahigh-sensitivity split-ring resonator-based microwave sensor for retrieving the complex permittivity of liquid samples. An interdigital capacitor structure was used to expand the sensing area and the sensitivity. A defected ground structure and A parallel dual split-ring resonator were introduced to improve the quality factor. A polydimethylsiloxane microfluidic channel substrate was placed above the interdigital capacitor structure. The channel route coincided with the interdigital gap to fully utilize the strong electric field. Ethanol–water solutions with varying ethanol fractions were injected into the channel as the testing liquid. It was demonstrated that the variation in resonant frequency can be used to retrieve the dielectric properties of liquid samples. The proposed sensor used a small liquid volume of ~0.68 μL and provided values in good agreement with the reference data. Full article

(This article belongs to the Special Issue Microwave Sensors for Non-invasive Characterization and Monitoring Applications)

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Review

Jump to: Research

18 pages, 7013 KiB

Open AccessReview

Microwave Devices for Wearable Sensors and IoT

by Alessandra Costanzo, Elisa Augello, Giulia Battistini, Francesca Benassi, Diego Masotti and Giacomo Paolini

Sensors 2023, 23(9), 4356; https://doi.org/10.3390/s23094356 - 28 Apr 2023

Cited by 9 | Viewed by 3874

Abstract

The Internet of Things (IoT) paradigm is currently highly demanded in multiple scenarios and in particular plays an important role in solving medical-related challenges. RF and microwave technologies, coupled with wireless energy transfer, are interesting candidates because of their inherent contactless spectrometric capabilities and for the wireless transmission of sensing data. This article reviews some recent achievements in the field of wearable sensors, highlighting the benefits that these solutions introduce in operative contexts, such as indoor localization and microwave sensing. Wireless power transfer is an essential requirement to be fulfilled to allow these sensors to be not only wearable but also compact and lightweight while avoiding bulky batteries. Flexible materials and 3D printing polymers, as well as daily garments, are widely exploited within the presented solutions, allowing comfort and wearability without renouncing the robustness and reliability of the built-in wearable sensor. Full article

(This article belongs to the Special Issue Microwave Sensors for Non-invasive Characterization and Monitoring Applications)

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