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25 pages, 1764 KiB

Open AccessReview

Fiber Bragg Grating Sensors: Design, Applications, and Comparison with Other Sensing Technologies

by Alaa N. D. Alhussein, Mohammed R. T. M. Qaid, Timur Agliullin, Bulat Valeev, Oleg Morozov and Airat Sakhabutdinov

Sensors 2025, 25(7), 2289; https://doi.org/10.3390/s25072289 - 4 Apr 2025

Viewed by 863

Abstract

Fiber Bragg grating (FBG) sensors have emerged as advanced tools for monitoring a wide range of physical parameters in various fields, including structural health, aerospace, biochemical, and environmental applications. This review provides a comprehensive overview of FBG sensor technology, focusing on their operating [...] Read more.

Fiber Bragg grating (FBG) sensors have emerged as advanced tools for monitoring a wide range of physical parameters in various fields, including structural health, aerospace, biochemical, and environmental applications. This review provides a comprehensive overview of FBG sensor technology, focusing on their operating principles, key advantages such as high sensitivity and immunity to electromagnetic interference, and common challenges like temperature-strain cross-sensitivity and the high cost of interrogation systems. Additionally, this review compares FBG sensors with other sensing technologies and highlights recent innovations in design, packaging, and implementation techniques. Finally, future research directions are discussed to enhance the performance, scalability, and long-term reliability of FBG-based sensing systems. Full article

(This article belongs to the Special Issue Feature Review Papers in Physical Sensors)

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42 pages, 7190 KiB

Open AccessReview

Recent Advances in Nanomaterial-Based Self-Healing Electrodes Towards Sensing and Energy Storage Applications

by Oresegun Olakunle Ibrahim, Chen Liu, Shulan Zhou, Bo Jin, Zhaotao He, Wenjie Zhao, Qianqian Wang and Sheng Zhang

Sensors 2025, 25(7), 2248; https://doi.org/10.3390/s25072248 - 2 Apr 2025

Viewed by 476

Abstract

Nanomaterial-based self-healing electrodes have demonstrated significant potential in sensing and energy storage applications due to their ability to withstand electrical breakdowns at high electric fields. However, such electrodes often face mechanical challenges, such as cracking under stress, compromising stability and reliability. This review [...] Read more.

Nanomaterial-based self-healing electrodes have demonstrated significant potential in sensing and energy storage applications due to their ability to withstand electrical breakdowns at high electric fields. However, such electrodes often face mechanical challenges, such as cracking under stress, compromising stability and reliability. This review critically examines nanomaterial-based self-healing mechanisms, focusing on properties and applications in health monitoring, motion sensing, environmental monitoring, and energy storage. By comprehensively reviewing research conducted on dimension-based nanomaterials (OD, 1D, 2D, and 3D) for self-healing electrode applications, this paper aims to provide essential insights into design strategies and performance enhancements afforded by nanoscale dimensions. This review paper highlights the tremendous potential of harnessing dimensional nanomaterials to develop autonomously restoring electrodes for next-generation sensing and energy devices. Full article

(This article belongs to the Special Issue Feature Review Papers in Physical Sensors)

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27 pages, 2386 KiB

Open AccessReview

Brief Review of Vibrothermography and Optical Thermography for Defect Quantification in CFRP Material

by Zulham Hidayat, Nicolas P. Avdelidis and Henrique Fernandes

Sensors 2025, 25(6), 1847; https://doi.org/10.3390/s25061847 - 16 Mar 2025

Viewed by 618

Abstract

Quantifying defects in carbon-fiber-reinforced polymer (CFRP) composites is crucial for ensuring quality control and structural integrity. Among non-destructive evaluation techniques, thermography has emerged as a promising solution for defect detection and characterization. This literature review synthesizes current advancements in active thermography methods, with [...] Read more.

Quantifying defects in carbon-fiber-reinforced polymer (CFRP) composites is crucial for ensuring quality control and structural integrity. Among non-destructive evaluation techniques, thermography has emerged as a promising solution for defect detection and characterization. This literature review synthesizes current advancements in active thermography methods, with a particular focus on vibrothermography and optical thermography, in identifying defects such as delaminations and barely visible impact damage (BVID) in CFRP composites. The review evaluates state-of-the-art techniques, highlighting the advanced applications of optical thermography. It identifies a critical research gap in the integration of vibrothermography with advanced image-processing methods, such as computer vision, which is more commonly applied in optical thermography. Addressing this gap holds significant potential to enhance defect quantification accuracy, improve maintenance practices, and ensure the safety of composite structures. Full article

(This article belongs to the Special Issue Feature Review Papers in Physical Sensors)

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41 pages, 8971 KiB

Open AccessReview

Scientific Machine Learning for Guided Wave and Surface Acoustic Wave (SAW) Propagation: PgNN, PeNN, PINN, and Neural Operator

by Nafisa Mehtaj and Sourav Banerjee

Sensors 2025, 25(5), 1401; https://doi.org/10.3390/s25051401 - 25 Feb 2025

Viewed by 954

Abstract

The governing Partial Differential Equation (PDE) for wave propagation or the wave equation involves multi-scale and multi-dimensional oscillatory phenomena. Wave PDE challenges traditional computational methods due to high computational costs with rigid assumptions. The advent of scientific machine learning (SciML) presents a novel [...] Read more.

The governing Partial Differential Equation (PDE) for wave propagation or the wave equation involves multi-scale and multi-dimensional oscillatory phenomena. Wave PDE challenges traditional computational methods due to high computational costs with rigid assumptions. The advent of scientific machine learning (SciML) presents a novel paradigm by embedding physical laws within neural network architectures, enabling efficient and accurate solutions. This study explores the evolution of SciML approaches, focusing on PINNs, and evaluates their application in modeling acoustic, elastic, and guided wave propagation. PINN is a gray-box predictive model that offers the strong predictive capabilities of data-driven models but also adheres to the physical laws. Through theoretical analysis and problem-driven examples, the findings demonstrate that PINNs address key limitations of traditional methods, including discretization errors and computational inefficiencies, while offering robust predictive capabilities. Despite current challenges, such as optimization difficulties and scalability constraints, PINNs hold transformative potential for advancing wave propagation modeling. This comprehensive study underscores the transformative potential of PINN, followed by recommendations on why and how it could advance elastic, acoustic, and guided wave propagation modeling and sets the stage for future research in the field of Structural Health Monitoring (SHM)/Nondestructive Evaluation (NDE). Full article

(This article belongs to the Special Issue Feature Review Papers in Physical Sensors)

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21 pages, 1853 KiB

Open AccessReview

Dielectric Permittivity in Copper Leaching: A Review

by Marcos Andreu, Robert Zwick and Moe Momayez

Sensors 2025, 25(3), 794; https://doi.org/10.3390/s25030794 - 28 Jan 2025

Viewed by 797

Abstract

The leaching process for copper extraction has garnered significant attention due to its critical role in meeting the rising demand for copper, driven by global trends towards decarbonization and electrification. The accurate measurement of variables is essential for process control, prompting the development [...] Read more.

The leaching process for copper extraction has garnered significant attention due to its critical role in meeting the rising demand for copper, driven by global trends towards decarbonization and electrification. The accurate measurement of variables is essential for process control, prompting the development of advanced sensor technologies. This paper reviews the applications of dielectric permittivity measurements in the mining industry, focusing on their potential to enhance the monitoring and optimization of copper leaching processes. It evaluates the suitability of permittivity-based sensors, analyzing their advantages and limitations, and discusses the implications for process control and economic optimization. The study highlights the integration of permittivity measurements into existing monitoring systems, aiming to improve efficiency, reduce environmental impact, and increase ore recovery rates. This comprehensive review provides insights into the current state of permittivity measurement technologies and their future prospects in the context of copper leaching. Full article

(This article belongs to the Special Issue Feature Review Papers in Physical Sensors)

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37 pages, 6344 KiB

Open AccessReview

IR Sensors, Related Materials, and Applications

by Nikolaos Argirusis, Achilleas Achilleos, Niyaz Alizadeh, Christos Argirusis and Georgia Sourkouni

Sensors 2025, 25(3), 673; https://doi.org/10.3390/s25030673 - 23 Jan 2025

Cited by 1 | Viewed by 3239

Abstract

Infrared (IR) sensors are widely used in various applications due to their ability to detect infrared radiation. Currently, infrared detector technology is in its third generation and faces enormous challenges. IR radiation propagation is categorized into distinct transmission windows with the most intriguing [...] Read more.

Infrared (IR) sensors are widely used in various applications due to their ability to detect infrared radiation. Currently, infrared detector technology is in its third generation and faces enormous challenges. IR radiation propagation is categorized into distinct transmission windows with the most intriguing aspects of thermal imaging being mid-wave infrared (MWIR) and long-wave infrared (LWIR). Infrared detectors for thermal imaging have many uses in industrial applications, security, search and rescue, surveillance, medical, research, meteorology, climatology, and astronomy. Presently, high-performance infrared imaging technology mostly relies on epitaxially grown structures of the small-bandgap bulk alloy mercury–cadmium–telluride (MCT), indium antimonide (InSb), and GaAs-based quantum well infrared photodetectors (QWIPs), contingent upon the application and wavelength range. Nanostructures and nanomaterials exhibiting appropriate electrical and mechanical properties including two-dimensional materials, graphene, quantum dots (QDs), quantum dot in well (DWELL), and colloidal quantum dot (CQD) will significantly enhance the electronic characteristics of infrared photodetectors, transition metal dichalcogenides, and metal oxides, which are garnering heightened interest. The present manuscript gives an overview of IR sensors, their types, materials commonly used in them, and examples of related applications. Finally, a summary of the manuscript and an outlook on prospects are given. Full article

(This article belongs to the Special Issue Feature Review Papers in Physical Sensors)

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24 pages, 19605 KiB

Open AccessReview

Field-Programmable Gate Array (FPGA)-Based Lock-In Amplifier System with Signal Enhancement: A Comprehensive Review on the Design for Advanced Measurement Applications

by Jose Alejandro Galaviz-Aguilar, Cesar Vargas-Rosales, Francisco Falcone and Carlos Aguilar-Avelar

Sensors 2025, 25(2), 584; https://doi.org/10.3390/s25020584 - 20 Jan 2025

Viewed by 1528

Abstract

Lock-in amplifiers (LIAs) are critical tools in precision measurement, particularly for applications involving weak signals obscured by noise. Advances in signal processing algorithms and hardware synthesis have enabled accurate signal extraction, even in extremely noisy environments, making LIAs indispensable in sensor applications for [...] Read more.

Lock-in amplifiers (LIAs) are critical tools in precision measurement, particularly for applications involving weak signals obscured by noise. Advances in signal processing algorithms and hardware synthesis have enabled accurate signal extraction, even in extremely noisy environments, making LIAs indispensable in sensor applications for healthcare, industry, and other services. For instance, the electrical impedance measurement of the human body, organs, tissues, and cells, known as bioelectrical impedance, is commonly used in biomedical and healthcare applications because it is non-invasive and relatively inexpensive. Also, due to its portability and miniaturization capabilities, it has great potential for the development of new point-of-care and portable testing devices. In this document, we highlight existing techniques for high-frequency resolution and precise phase detection in LIA reference signals from field-programmable gate array (FPGA) designs. A comprehensive review is presented under the key requirements and techniques for single- and dual-phase digital LIA architectures, where relevant insights are provided to address the LIAs’ digital precision in measurement system configurations. Furthermore, the document highlights a novel method to enhance the spurious-free dynamic range (SFDR), thereby advancing the precision and effectiveness of LIAs in complex measurement environments. Finally, we summarize the diverse applications of impedance measurement, highlighting the wide range of fields that can benefit from the design of high performance in modern measurement technologies. Full article

(This article belongs to the Special Issue Feature Review Papers in Physical Sensors)

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57 pages, 5777 KiB

Open AccessReview

Implantable Passive Sensors for Biomedical Applications

by Panagiotis Kassanos and Emmanouel Hourdakis

Sensors 2025, 25(1), 133; https://doi.org/10.3390/s25010133 - 28 Dec 2024

Viewed by 1955

Abstract

In recent years, implantable sensors have been extensively researched since they allow localized sensing at an area of interest (e.g., within the vicinity of a surgical site or other implant). They allow unobtrusive and potentially continuous sensing, enabling greater specificity, early warning capabilities, [...] Read more.

In recent years, implantable sensors have been extensively researched since they allow localized sensing at an area of interest (e.g., within the vicinity of a surgical site or other implant). They allow unobtrusive and potentially continuous sensing, enabling greater specificity, early warning capabilities, and thus timely clinical intervention. Wireless remote interrogation of the implanted sensor is typically achieved using radio frequency (RF), inductive coupling or ultrasound through an external device. Two categories of implantable sensors are available, namely active and passive. Active sensors offer greater capabilities, such as on-node signal and data processing, multiplexing and multimodal sensing, while also allowing lower detection limits, the possibility to encode patient sensitive information and bidirectional communication. However, they require an energy source to operate. Battery implantation, and maintenance, remains a very important constraint in many implantable applications even though energy can be provided wirelessly through the external device, in some cases. On the other hand, passive sensors offer the possibility of detection without the need for a local energy source or active electronics. They also offer significant advantages in the areas of system complexity, cost and size. In this review, implantable passive sensor technologies will be discussed along with their communication and readout schemes. Materials, detection strategies and clinical applications of passive sensors will be described. Advantages over active sensor technologies will be highlighted, as well as critical aspects related to packaging and biocompatibility. Full article

(This article belongs to the Special Issue Feature Review Papers in Physical Sensors)

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14 pages, 475 KiB

Open AccessReview

Challenges and Prospects of Sensing Technology for the Promotion of Tele-Physiotherapy: A Narrative Review

by Kei Kakegawa and Tadamitsu Matsuda

Sensors 2025, 25(1), 16; https://doi.org/10.3390/s25010016 - 24 Dec 2024

Viewed by 949

Abstract

Significant developments in sensing technology have had many impacts, enhancing monitoring and assessment accuracy across diverse fields. In the field of physical therapy, sensing, which plays a pivotal role in tele-physiotherapy, rapidly expanded amid the COVID-19 pandemic. Its primary objective is to monitor [...] Read more.

Significant developments in sensing technology have had many impacts, enhancing monitoring and assessment accuracy across diverse fields. In the field of physical therapy, sensing, which plays a pivotal role in tele-physiotherapy, rapidly expanded amid the COVID-19 pandemic. Its primary objective is to monitor biological signals and patient movements at remote locations. To further enhance the effectiveness and the scope of tele-physiotherapy, it is essential to further develop sensing and data analysis technologies. However, there are usability and analysis issues that have limited its use. The development of these technologies will not only enhance the accuracy of deep learning by AI through the acquisition of big data, but also has the potential to elucidate movement characteristics associated with movement disorders or pathological conditions. Furthermore, improving sensing technologies can broaden applications extending beyond tele-physiotherapy to impact daily life. Looking forward, it holds promise for improving our understanding of disease prognosis and progression. Full article

(This article belongs to the Special Issue Feature Review Papers in Physical Sensors)

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23 pages, 321 KiB

Open AccessReview

A Review of Indoor Localization Methods Leveraging Smartphone Sensors and Spatial Context

by Jiayi Li, Yinhao Song, Zhiliang Ma, Yu Liu and Cheng Chen

Sensors 2024, 24(21), 6956; https://doi.org/10.3390/s24216956 - 30 Oct 2024

Viewed by 1677

Abstract

As Location-Based Services (LBSs) rapidly develop, indoor localization technology is garnering significant attention as a critical component. Smartphones have become tools for indoor localization due to their highly integrated sensors, fast-evolving computational capabilities, and widespread user adoption. With the rapid advancement of smartphones, [...] Read more.

As Location-Based Services (LBSs) rapidly develop, indoor localization technology is garnering significant attention as a critical component. Smartphones have become tools for indoor localization due to their highly integrated sensors, fast-evolving computational capabilities, and widespread user adoption. With the rapid advancement of smartphones, methods for smartphone-based indoor localization have increasingly attracted attention. Although there are reviews on indoor localization, there is still a lack of systematic reviews focused on smartphone-based indoor localization methods. In particular, existing reviews have not systematically analyzed smartphone-based indoor localization methods or considered the combination of smartphone sensor data with prior knowledge of the indoor environment to enhance localization performance. In this study, through systematic retrieval and analysis, the existing research was first categorized into three types to dissect the strengths and weaknesses based on the types of data sources integrated, i.e., single sensor data sources, multi-sensor data fusion, and the combination of spatial context with sensor data. Then, four key issues are discussed and the research gaps in this field are summarized. Finally, a comprehensive conclusion is provided. This paper offers a systematic reference for research and technological applications related to smartphone-based indoor localization methods. Full article

(This article belongs to the Special Issue Feature Review Papers in Physical Sensors)

22 pages, 4902 KiB

Open AccessReview

A Review of Microstrip Patch Antenna-Based Passive Sensors

by Zain Ul Islam, Amine Bermak and Bo Wang

Sensors 2024, 24(19), 6355; https://doi.org/10.3390/s24196355 - 30 Sep 2024

Cited by 4 | Viewed by 3658

Abstract

This paper briefly overviews and discusses the existing techniques using antennas for passive sensing, starting from the antenna operating principle and antenna structural design to different antenna-based sensing mechanisms. The effects of different electrical properties of the material used to design an antenna, [...] Read more.

This paper briefly overviews and discusses the existing techniques using antennas for passive sensing, starting from the antenna operating principle and antenna structural design to different antenna-based sensing mechanisms. The effects of different electrical properties of the material used to design an antenna, such as conductivity, loss tangent, and resistivity, are discussed to illustrate the fundamental sensing mechanisms. Furthermore, the key parameters, such as operating frequency and antenna impedance, along with the factors affecting the sensing performance, are discussed. Overall, passive sensing using an antenna is mainly achieved by altering the reflected wave characteristics in terms of center frequency, return loss, phase, and received/reflected signal strength. The advantages and drawbacks of each technique are also discussed briefly. Given the increasing relevance, millimeter-wave antenna sensors and resonator sensors are also discussed with their applications and recent advancements. This paper primarily focuses on microstrip-based radiating structures and insights for further sensing performance improvement using passive antennas, which are outlined in this study. In addition, suggestions are made for the current scientific and technical challenges, and future directions are discussed. Full article

(This article belongs to the Special Issue Feature Review Papers in Physical Sensors)

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33 pages, 33868 KiB

Open AccessReview

Advanced Applications of Porous Materials in Triboelectric Nanogenerator Self-Powered Sensors

by Zhengyin Duan, Feng Cai, Yuxin Chen, Tianying Chen and Peng Lu

Sensors 2024, 24(12), 3812; https://doi.org/10.3390/s24123812 - 13 Jun 2024

Cited by 8 | Viewed by 2772

Abstract

Porous materials possess advantages such as rich pore structures, a large surface area, low relative density, high specific strength, and good breathability. They have broad prospects in the development of a high-performance Triboelectric Nanogenerator (TENG) and self-powered sensing fields. This paper elaborates on [...] Read more.

Porous materials possess advantages such as rich pore structures, a large surface area, low relative density, high specific strength, and good breathability. They have broad prospects in the development of a high-performance Triboelectric Nanogenerator (TENG) and self-powered sensing fields. This paper elaborates on the structural forms and construction methods of porous materials in existing TENG, including aerogels, foam sponges, electrospinning, 3D printing, and fabric structures. The research progress of porous materials in improving TENG performance is systematically summarized, with a focus on discussing design strategies of porous structures to enhance the TENG mechanical performance, frictional electrical performance, and environmental tolerance. The current applications of porous-material-based TENG in self-powered sensing such as pressure sensing, health monitoring, and human–machine interactions are introduced, and future development directions and challenges are discussed. Full article

(This article belongs to the Special Issue Feature Review Papers in Physical Sensors)

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23 pages, 7408 KiB

Open AccessSystematic Review

Sensors and Sensing Devices Utilizing Electrorheological Fluids and Magnetorheological Materials—A Review

by Yu-Jin Park and Seung-Bok Choi

Sensors 2024, 24(9), 2842; https://doi.org/10.3390/s24092842 - 29 Apr 2024

Cited by 6 | Viewed by 2206

Abstract

This paper comprehensively reviews sensors and sensing devices developed or/and proposed so far utilizing two smart materials: electrorheological fluids (ERFs) and magnetorheological materials (MRMs) whose rheological characteristics such as stiffness and damping can be controlled by external stimuli; an electrical voltage for ERFs [...] Read more.

This paper comprehensively reviews sensors and sensing devices developed or/and proposed so far utilizing two smart materials: electrorheological fluids (ERFs) and magnetorheological materials (MRMs) whose rheological characteristics such as stiffness and damping can be controlled by external stimuli; an electrical voltage for ERFs and a magnetic field for MRMs, respectively. In this review article, the MRMs are classified into magnetorheological fluids (MRF), magnetorheological elastomers (MRE) and magnetorheological plastomers (MRP). To easily understand the history of sensing research using these two smart materials, the order of this review article is organized in a chronological manner of ERF sensors, MRF sensors, MRE sensors and MRP sensors. Among many sensors fabricated from each smart material, one or two sensors or sensing devices are adopted to discuss the sensing configuration, working principle and specifications such as accuracy and sensitivity. Some sensors adopted in this article include force sensors, tactile devices, strain sensors, wearable bending sensors, magnetometers, display devices and flux measurement sensors. After briefly describing what has been reviewed in a conclusion, several challenging future works, which should be undertaken for the practical applications of sensors or/and sensing devices, are discussed in terms of response time and new technologies integrating with artificial intelligence neural networks in which several parameters affecting the sensor signals can be precisely and optimally tuned. It is sure that this review article is very helpful to potential readers who are interested in creative sensors using not only the proposed smart materials but also different types of smart materials such as shape memory alloys and active polymers. Full article

(This article belongs to the Special Issue Feature Review Papers in Physical Sensors)

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