Feature Review Papers in Physical Sensors

Dear Colleagues,

This Special Issue aims to publish high-quality review papers in the field of physical sensors. Contributions may focus on all types of physical sensors, based on the magnetic, semiconducting, dielectric, conducting and superconducting properties of various materials, and thus may refer to magnetic, electric, optic, acoustic and other types of physical sensors, used in the industry, biomedicine, defense, transportation, etc.

Manuscripts should include the current state of the art and perspectives in the field, illustating the advances offered by the authors. All types of reviews will be considered as long as they meet the journal’s standards. We encourage researchers from various fields to contribute reviews highlighting the latest developments in their field or to invite relevant experts and colleagues to do so.

Prof. Dr. Evangelos Hristoforou
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• sensors based on magnetic properties
• sensors based on semiconducting properties
• sensors based on dielectric properties
• sensors based on conducting properties
• sensors based on superconducting properties
• magnetic sensors
• optic sensors
• acoustic sensors
• electric sensors
• industrial applications
• defense applications
• transportation applications
• biomedical applications
• multidisciplinary

Title: Magnetostrictive Delay Lines: Arrangements, Properties, Materials & Sensing Applications
Authors: Eleni Mangiorou, Spyros Angelopoulos, Aphrodite Ktena, Evangelos Hristoforou
Affiliation: Laboratory of Electronic Sensors, National TU of Athens, Zografou Campus, Athens, Greece 15780
Abstract: The paper illustrates a review on magnetostrictive delay lines (MDL), reffering to materials, topological arrangements, materials used and of course different families of sensors. At first, almost all topological arrangements based on MDLs are illustrated, followed by the most important engineering properties that should be examined for sensing applications. Then, the possible materials and their methodological characterization is illustrated. Then, the position-displacement-tactile, stress-force-pressure and field sensors based on MDLs are presented, with some distinct applications. Finally, an analytical model of the MDL operation is also provided.

Title: Implantable passive sensors for biomedical applications
Authors: Emmanouel Hourdakis1 and Panagiotis Kassanos2
Affiliation: 1 School of Electrical and Computer Engineering (ECE), National Technical University of Athens (NTUA), Greece 2 The Hamlyn Centre, Institute of Global Health Innovation, Imperial College London, London, UK, SW7 2AZ*
Abstract: In recent years, implantable sensors are being extensively researched since they allow localized sensing at an area of interest (e.g. within the vicinity of a surgical site or other implant) unintrusive and potentially continuous sensing, enabling greater specificity, early warning capabilities, and thus timely clinical intervention. Wireless communication schemes such as RF, inductive coupling or ultrasounds are being used to allow the wireless remote interrogation of the implanted sensor and, if needed, bidirectional communication between the implanted device and 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, when several sensors and sensors operating with different modalities are used in implanted sensor arrays, while also allowing lower detection limits and the possibility to encode patient sensitive information. 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 for detection without the need for a local energy source or active electronics. They also offer significant advantages in the areas of sensor node and system complexity, cost and size. These offset their inherent lower detection limit capabilities, in many applications. In this review, implantable passive sensor technologies will be discussed along with their communication schemes. Materials, detection strategies and applications of passive sensors will be described. Advantages over active sensor technologies will be highlighted, as well as critical aspects related to packaging (hermeticity) and biocompatibility.

Title: Mobile device with IoT capabilities for the detection and quantification of refrigerants using infrared sensors
Authors: Nikolaos Argirusis *(1), Georgia Sourkouni (2), and Christos Argirusis (2),(3)
Affiliation: (1) mat4nrg GmbH, Burgstätter Str. 42, 38678 Clausthal-Zellerfeld, Germany (2) Clausthal Centre of Materials Technology (CZM), Clausthal University of Technology, Leibnizstr. 9, 38678 Clausthal-Zellerfeld, Germany (3) School of Chemical Engineering, National Technical University of Athens, 15773 Zografou, Greece
Abstract: Climate change is primarily caused by the combustion of fossil fuels, with greenhouse gas (GHG) emissions also playing a significant role. Worldwide, the release of greenhouse gases causes a rise in average temperature, reduction in ice mass resulting in sea level rise, and occurrence of extreme climate events. An increase of 1.4 °C in surface temperature since the 1900s, with a particularly high increase of 0.18 °C in June 2023. Fluorinated greenhouse gases (FGGs) are classified as worldwide pollutants. Fluorinated greenhouse gases often have a high global warming potential compared to other greenhouse gases. Chlorofluorocarbons (CFCs) have been historically utilized in propellants for packaging materials, aerosol solvents, and refrigerants, and have been identified as possible factors in ozone depletion. The Montreal Protocol of 1987 aimed to phase out the usage of CFCs. This led to the substitution of CFCs with hydrofluorocarbons (HFCs). New types of refrigerants have been developed to comply with updated environmental laws, with the goal of reducing the impact on the ozone layer. Detecting the existence and concentration of new and older refrigerant gases is crucial for assessing system functionality and determining whether they can be recycled or need to be disposed of. Additional justifications for the necessity of quantitative measurements of these gases include the manufacturing of air conditioning components, leak detection is conducted to ensure they are free of leaks. Testing is also carried out on newer systems to see if they are functioning at peak efficiency and with the correct mixing ratios. Fast Fourier transform spectroscopy enables the detection and measurement of substances. These tools are fragile, cumbersome, costly, and typically require a skilled technician to operate them in the field. Thus, a portable, user-friendly, and cost-effective detection device would be beneficial. Fast Fourier transform spectroscopy enables the detection and measurement of substances. These tools are delicate, unwieldy, costly, and typically require a skilled technician to operate them in the field. Thus, a portable, user-friendly, and cost-effective detection device would be beneficial. Compact devices equipped with infrared sensor arrays provide data to machine learning algorithms for analyzing measurement findings. This article provides an in-depth analysis of the categorization of refrigerant gases in Internet of Things (IoT) gas detection devices. We demonstrate the functionality in effectively differentiating between important refrigerant gases like R32 and R134, with low delay, through practical tests. Data was collected utilizing a diverse range of prevalent refrigerant gases. This study utilizes data collected from the refrigerants R32 and R134a. Hence, comprehensive IR spectra of the specific refrigerants are required. The IR spectra were collected using a custom-made 3D-printed tubular reactor equipped with two BaF2 windows, suitable for use in the beamline of a Bruker IR-Spectrometer. Data were collected by exposing the IR-sensor to controlled gas environments with varying amounts of refrigerant gases using accurately produced gas mixtures. Prior to each experiment, the sensors were calibrated to guarantee precise and uniform measurements. Following the measurement, data was immediately sent to an Internet of Things (IoT) platform and shared with business-to-business (B2B) clients.

Title: Open magnetic circuit measurement methods for the non-destructive evaluation of steel strip mechanical properties
Authors: Anastassios Skarlatos
Affiliation: Commissariat à l’Énergie Atomique et aux Énergies Alternatives (CEA), Laboratory for Integration of Systems and Technology (LIST), Université Paris-Saclay, F-91120 Palaiseau, France
Abstract: Magnetic characterisation measurements usually involve a closed magnetic circuit with a ribbon-type specimen. This experimental arrangement assures the maximisation of the magnetic flux that crosses the material and its collimation in a single direction. Two characteristic examples of such setups are the Epstein frame and the single or double yoke circuit also known as single sheet tester. These setups however require a special preparation of the specimen in the sense that a ribbon sample must be detached from the piece under study, which makes them quasi-destructive and hence impractical for in-situ characterisation. This is the reason why a number of different devices has been developed for the nondestructive characterisation of ferromagnetic materials. These methods find the application in the industry for the control of finished or semi-finished products in form of planar sheets. Common feature of these methods is that they involve open-circuit measurements, in the sense that the applied magnetic flux is closed in the air in form of stray field. A second feature of these methods, closely related with the first, is that they provide only indirect information hysteresis curve via a number of well-chosen identifiers due to the incapability of the setup to provide a complete hysteresis curve measurements. In this review article, an overview of the different available methods will be presented and a detailed discussion of the involved identifiers and their pertinence for characterisation of specific magnetic and mechanical features will be provided. Some well-known industrial realisations of these setups such as the IMPOC, HACOM, PropertyMon and the 3MA will be also given. The article will conclude with a brief discussion of model-based inversion methods for recovering the full hysteresis curve from such partial information, a subject of ongoing research.