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Special Issue "Selected Papers from 16th International Conference on Optical and Electronic Sensors (COE 2020)"

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

Deadline for manuscript submissions: 31 December 2021.

Special Issue Editors

Prof. Dr. Katarzyna Zakrzewska
E-Mail Website
Guest Editor
Faculty of Computer Science, Electronics and Telecommunications, AGH University of Science and Technology, al. A. Mickiewicza 30, 30-059 Krakow, Poland
Interests: solid-state physics; thin films; materials science; chemical engineering; renewable energy; chemical sensors
Prof. Dr. Artur M. Rydosz
E-Mail Website
Guest Editor
Department of Electronics, AGH University of Science and Technology, 30-059 Krakow, Poland
Interests: metal oxide thin films; nanomaterials; gas sensors; acetone detection; exhaled breath analysis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The 16th International Conference on Electronic and Optical Sensors, COE’2020, could not have taken place as planned in spring of 2020 due to the unexpected development of the COVID-19 pandemic. However, this Special Issue already includes seven papers related to the research, the results of which were supposed to be presented during the event, which was regretfully canceled.

Eventually, it was possible to arrange a three-day online COE’2020 international meeting on from 27 to 29 September 2021, with more than a hundred participants from 11 countries. Eight fascinating  plenary lectures were delivered by distinguished scientists, namely Elisabetta Comini (Italy), Rupert Schreiner (Germany), Lars Österlund (Sweden), Don N. Futaba (Japan), Susana Cardoso de Freitas (Portugal), Bilge Saruhan-Brings (Germany), Marcel Bouvet (France), and Eduard Llobet (Spain). The program of the conference offered 52 oral presentations including 21 invited talks. Three contributions from young speakers—Bartosz Dzikowski (Warsaw University of Technology), Bartosz Kawa (Wroclaw University of Science and Technology), and Julia Mazurków (AGH UST, Krakow)—have been awarded. The conference was sponsored by the Polish Ministry of Education and Science, MEN, within the framework of the Excellent Science (Doskonała Nauka, DNK/SP/462114/2020) project. Six companies—Prevac, Elsta Elektronika, EV Group, Vakpol, OEM Automatic, and Radionika—have supported the conference since its beginning.

The 16th International Conference on Optical and Electronic Sensors, COE’2020, was organized by three faculties of AGH University of Science and Technology, Kraków, Poland: Computer Science, Electronics and Telecommunications; Materials Science and Ceramics; and Electrical Engineering, Automatics, Computer Science and Biomedical Engineering. The President of AGH UST, JM Rector prof. dr. hab. inż. Jerzy Lis, has granted his honorary patronage and became the Chair of the Honorary Committee of this event.

The conference has a long tradition dating back to 1990 when the first COE was initiated by the sensor community in Poland under auspices of the Polish Sensor Society, PTTS.  Since 2014, COE has attained the status of an international conference. Two past COE conferences were hosted by Gdansk University of Technology in 2016 and Warsaw University of Technology in 2018.

The scope of the conference covered the most important issues: new sensor materials; nanosensors; nano- and micro-systems, including MEMS, MOEMS, RF MEMS, and NEMS; sensor networks; biosensors and lab-on-chip devices; semiconducting and electrochemical gas sensors; optical and magnetic sensors; sensors of physical quantities; the theory and modelling of sensing behavior; and the application of sensors, especially in medicine as well as in emerging topics such as wearable electronics, the Internet of Things (IoT), and the Internet of Energy (IoE).

On the behalf of the Scientific Committee, International Advisory Board, and the Technical Committee  of COE’2020, I kindly invite you to submit the manuscripts devoted to the results of your current research to this Special Issue of Sensors.

Prof. Dr. Katarzyna Zakrzewska
Prof. Dr. Artur M. Rydosz 
Guest Editors

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 papers will be 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 2200 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.

Published Papers (10 papers)

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Research

Article
Electrochemical Characterization of Modified Glassy Carbon Electrodes for Non-Enzymatic Glucose Sensors
Sensors 2021, 21(23), 7928; https://doi.org/10.3390/s21237928 - 27 Nov 2021
Viewed by 263
Abstract
The diversity of materials proposed for non-enzymatic glucose detection and the lack of standardized protocols for assessing sensor performance have caused considerable confusion in the field. Therefore, methods for pre-evaluation of working electrodes, which will enable their conscious design, are currently intensively sought. [...] Read more.
The diversity of materials proposed for non-enzymatic glucose detection and the lack of standardized protocols for assessing sensor performance have caused considerable confusion in the field. Therefore, methods for pre-evaluation of working electrodes, which will enable their conscious design, are currently intensively sought. Our approach involved comprehensive morphologic and structural characterization of copper sulfides as well as drop-casted suspensions based on three different polymers—cationic chitosan, anionic Nafion, and nonionic polyvinylpyrrolidone (PVP). For this purpose, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy were applied. Subsequently, comparative studies of electrochemical properties of bare glassy carbon electrode (GCE), polymer- and copper sulfides/polymer-modified GCEs were performed using electrochemical impedance spectroscopy (EIS) and voltammetry. The results from EIS provided an explanation for the enhanced analytical performance of Cu-PVP/GCE over chitosan- and Nafion-based electrodes. Moreover, it was found that the pH of the electrolyte significantly affects the electrocatalytic behavior of copper sulfides, indicating the importance of OHads in the detection mechanism. Additionally, diffusion was denoted as a limiting step in the irreversible electrooxidation process that occurs in the proposed system. Full article
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Communication
Method of Step Detection and Counting Based on Measurements of Magnetic Field Variations
Sensors 2021, 21(23), 7775; https://doi.org/10.3390/s21237775 - 23 Nov 2021
Viewed by 168
Abstract
Basic human activity recognition (HAR) and analysis is becoming a key aspect of tracking and identifying daily habits that can have a critical impact on healthy lifestyles by providing feedback on health status and warning of deterioration. However, current approaches for detecting basic [...] Read more.
Basic human activity recognition (HAR) and analysis is becoming a key aspect of tracking and identifying daily habits that can have a critical impact on healthy lifestyles by providing feedback on health status and warning of deterioration. However, current approaches for detecting basic activities such as movements or steps rely on solutions with multiple sensors which affect their size and power consumption. In this paper, we propose a novel method that uses only a single magnetic field sensor for basic step detection, unlike the well-known multisensory solutions. The approach presented here is based on real-time analysis of magnetic field sensor measurements to detect and count steps during a walking activity. The approach is implemented in a system that integrates a digital magnetic field sensor with software blocks: filter, steady state detector, extrema detector with classifier, and threshold comparator implemented in an embedded platform. Outdoor experiments with volunteers of different ages and genders walking at variable speeds showed that the proposed detection method achieves up to 98% accuracy in step detection. The obtained results show that a single magnetic field sensor can be used to detect steps, and in general offers the possibility of simplifying the current solutions by reducing the device dimensions, the cost of a system and its power consumption. Full article
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Article
Mode Sensitivity Exploration of Silica–Titania Waveguide for Refractive Index Sensing Applications
Sensors 2021, 21(22), 7452; https://doi.org/10.3390/s21227452 - 09 Nov 2021
Viewed by 375
Abstract
In this paper, a novel and cost-effective photonic platform based on silica–titania material is discussed. The silica–titania thin films were grown utilizing the sol–gel dip-coating method and characterized with the help of the prism-insertion technique. Afterwards, the mode sensitivity analysis of the silica–titania [...] Read more.
In this paper, a novel and cost-effective photonic platform based on silica–titania material is discussed. The silica–titania thin films were grown utilizing the sol–gel dip-coating method and characterized with the help of the prism-insertion technique. Afterwards, the mode sensitivity analysis of the silica–titania ridge waveguide is investigated via the finite element method. Silica–titania waveguide systems are highly attractive due to their ease of development, low fabrication cost, low propagation losses and operation in both visible and near-infrared wavelength ranges. Finally, a ring resonator (RR) sensor device was modelled for refractive index sensing applications, offering a sensitivity of 230 nm/RIU, a figure of merit (FOM) of 418.2 RIU−1, and Q-factor of 2247.5 at the improved geometric parameters. We believe that the abovementioned integrated photonics platform is highly suitable for high-performance and economically reasonable optical sensing devices. Full article
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Communication
Nitrogen Dioxide Sensing Using Multilayer Structure of Reduced Graphene Oxide and α-Fe2O3
Sensors 2021, 21(3), 1011; https://doi.org/10.3390/s21031011 - 02 Feb 2021
Cited by 2 | Viewed by 880
Abstract
Multilayers consisting of graphene oxide (GO) and α-Fe2O3 thin layers were deposited on the ceramic substrates by the spray LbL (layer by layer) coating technique. Graphene oxide was prepared from graphite using the modified Hummers method. Obtained GO flakes reached [...] Read more.
Multilayers consisting of graphene oxide (GO) and α-Fe2O3 thin layers were deposited on the ceramic substrates by the spray LbL (layer by layer) coating technique. Graphene oxide was prepared from graphite using the modified Hummers method. Obtained GO flakes reached up to 6 nanometers in thickness and 10 micrometers in lateral size. Iron oxide Fe2O3 was obtained by the wet chemical method from FeCl3 and NH4OH solution. Manufactured samples were deposited as 3 LbL (GO and Fe2O3 layers deposited sequentially) and 6 LbL structures with GO as a bottom layer. Electrical measurements show the decrease of multilayer resistance after the introduction of the oxidizing NO2 gas to the ambient air atmosphere. The concentration of NO2 was changed from 1 ppm to 20 ppm. The samples changed their resistance even at temperatures close to room temperature, however, the sensitivity increased with temperature. Fe2O3 is known as an n-type semiconductor, but the rGO/Fe2O3 hybrid structure behaved similarly to rGO, which is p-type. Both chemisorbed O2 and NO2 act as electron traps decreasing the concentration of electrons and increasing the effective multilayer conductivity. An explanation of the observed variations of multilayer structure resistance also the possibility of heterojunctions formation was taken into account. Full article
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Article
Nonenzymatic Glucose Sensors Based on Copper Sulfides: Effect of Binder-Particles Interactions in Drop-Casted Suspensions on Electrodes Electrochemical Performance
Sensors 2021, 21(3), 802; https://doi.org/10.3390/s21030802 - 26 Jan 2021
Cited by 1 | Viewed by 767
Abstract
The constant progress in novel nanomaterials synthesis has contributed to the rapid development of nonenzymatic glucose sensors. For working electrodes preparation, drop casting proved to be the most convenient and thus most widely applied method. However, appropriate interpretation of obtained electrochemical signal requires [...] Read more.
The constant progress in novel nanomaterials synthesis has contributed to the rapid development of nonenzymatic glucose sensors. For working electrodes preparation, drop casting proved to be the most convenient and thus most widely applied method. However, appropriate interpretation of obtained electrochemical signal requires in-depth knowledge of limitations related to this technique. In this study, we prepared solutions based on commonly reported polymers for nanostructures immobilization and investigated their influence on copper sulfides distribution on the electrode. Characterization of suspensions properties and behavior of particles during droplet drying revealed that nonionic polyvinylpyrrolidone (PVP) was favorable for electrodes modification with copper sulfides in comparison with Nafion and chitosan. It ensured homogeneity of the suspension as well as the uniform coverage of the electrode surface with particles, what resulted in increased active surface area and, therefore, higher signal from glucose addition. On the other hand, when cationic chitosan was used as a binder, suspensions were agglomerated and, within dry deposits, a coffee-ring effect was observed. Appropriate adjustment of material and polymer interactions led to enhanced electrode electrochemical performance. Full article
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Article
Sensors in the Autoclave-Modelling and Implementation of the IoT Steam Sterilization Procedure Counter
Sensors 2021, 21(2), 510; https://doi.org/10.3390/s21020510 - 13 Jan 2021
Viewed by 764
Abstract
Surgical procedures involve major risks, as pathogens can enter the body unhindered. To prevent this, most surgical instruments and implants are sterilized. However, ensuring that this process is carried out safely and according to the normative requirements is not a trivial task. This [...] Read more.
Surgical procedures involve major risks, as pathogens can enter the body unhindered. To prevent this, most surgical instruments and implants are sterilized. However, ensuring that this process is carried out safely and according to the normative requirements is not a trivial task. This study aims to develop a sensor system that can automatically detect successful steam sterilization on the basis of the measured temperature profiles. This can be achieved only when the relationship between the temperature on the surface of the tool and the temperature at the measurement point inside the tool is known. To find this relationship, the thermodynamic model of the system has been developed. Simulated results of thermal simulations were compared with the acquired temperature profiles to verify the correctness of the model. Simulated temperature profiles are in accordance with the measured temperature profiles, thus the developed model can be used in the process of further development of the system as well as for the development of algorithms for automated evaluation of the sterilization process. Although the developed sensor system proved that the detection of sterilization cycles can be automated, further studies that address the possibility of optimization of the system in terms of geometrical dimensions, used materials, and processing algorithms will be of significant importance for the potential commercialization of the presented solution. Full article
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Article
SnO2/TiO2 Thin Film n-n Heterostructures of Improved Sensitivity to NO2
Sensors 2020, 20(23), 6830; https://doi.org/10.3390/s20236830 - 29 Nov 2020
Cited by 2 | Viewed by 728
Abstract
Thin-film n-n nanoheterostructures of SnO2/TiO2, highly sensitive to NO2, were obtained in a two-step process: (i) magnetron sputtering, MS followed by (ii) Langmuir-Blodgett, L–B, technique. Thick (200 nm) SnO2 base layers were deposited by MS and [...] Read more.
Thin-film n-n nanoheterostructures of SnO2/TiO2, highly sensitive to NO2, were obtained in a two-step process: (i) magnetron sputtering, MS followed by (ii) Langmuir-Blodgett, L–B, technique. Thick (200 nm) SnO2 base layers were deposited by MS and subsequently overcoated with a thin and discontinuous TiO2 film by means of L–B. Rutile nanopowder spread over the ethanol/chloroform/water formed a suspension, which was used as a source in L–B method. The morphology, crystallographic and electronic properties of the prepared sensors were studied by scanning electron microscopy, SEM, X-ray diffraction, XRD in glancing incidence geometry, GID, X-ray photoemission spectroscopy, XPS, and uv-vis-nir spectrophotometry, respectively. It was found that amorphous SnO2 films responded to relatively low concentrations of NO2 of about 200 ppb. A change of more than two orders of magnitude in the electrical resistivity upon exposure to NO2 was further enhanced in SnO2/TiO2 n-n nanoheterostructures. The best sensor responses RNO2/R0 were obtained at the lowest operating temperatures of about 120 °C, which is typical for nanomaterials. Response (recovery) times to 400 ppb NO2 were determined as a function of the operating temperature and indicated a significant decrease from 62 (42) s at 123 °C to 12 (19) s at 385 °C A much smaller sensitivity to H2 was observed, which might be advantageous for selective detection of nitrogen oxides. The influence of humidity on the NO2 response was demonstrated to be significantly below 150 °C and systematically decreased upon increase in the operating temperature up to 400 °C. Full article
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Article
Modeling and Implementation of TEG-Based Energy Harvesting System for Steam Sterilization Surveillance Sensor Node
Sensors 2020, 20(21), 6338; https://doi.org/10.3390/s20216338 - 06 Nov 2020
Cited by 2 | Viewed by 770
Abstract
The aim of this work is a proof of concept, that medical Internet of Things (IoT) sterilization surveillance sensors can be powered by using the heat during a steam sterilization procedure. Hereby, the focus was on the use of thermo-electrical generators (TEG) to [...] Read more.
The aim of this work is a proof of concept, that medical Internet of Things (IoT) sterilization surveillance sensors can be powered by using the heat during a steam sterilization procedure. Hereby, the focus was on the use of thermo-electrical generators (TEG) to generate enough power for an ultra-low-power sensor application. Power generation requirement of the sensor was 1.6 mW over the single sterilization cycle. The thermal gradient across the TEG has been achieved using a highly efficient aerogel-foam-based thermal insulation, shielding a heat storage unit (HSU), connected to one side of the TEG. The evaluation of the developed system was carried out with thermal and electrical simulations based on the parameters extracted from the TEG manufacturer’s datasheet. The developed model has been validated with a real prototype using the thermal step response method. It was important for the authors to focus on rapid-prototyping and using off-the-shelf devices and materials. Based on comparison with the physical prototype, the SPICE model was adjusted. With a thermal gradient of 12 °C, the simulated model generated over 2 mW of power. The results show that a significant power generation with this system is possible and usable for sensor applications in medial IoT. Full article
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Article
High-Temperature Hydrogen Sensing Performance of Ni-Doped TiO2 Prepared by Co-Precipitation Method
Sensors 2020, 20(21), 5992; https://doi.org/10.3390/s20215992 - 22 Oct 2020
Cited by 8 | Viewed by 790
Abstract
This work deals with the substantially high-temperature hydrogen sensors required by combustion and processing technologies. It reports the synthesis of undoped and Ni-doped TiO2 (with 0, 0.5, 1 and 2 mol.% of Ni) nanoparticles by a co-precipitation method and the obtained characteristics [...] Read more.
This work deals with the substantially high-temperature hydrogen sensors required by combustion and processing technologies. It reports the synthesis of undoped and Ni-doped TiO2 (with 0, 0.5, 1 and 2 mol.% of Ni) nanoparticles by a co-precipitation method and the obtained characteristics applicable for this purpose. The effect of nickel doping on the morphological variation, as well as on the phase transition from anatase to rutile, of TiO2 was investigated by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The resistive sensors prepared with these powders were tested toward H2 at 600 °C. The results indicate that 0.5% Ni-doped TiO2 with almost equal amounts of anatase and rutile shows the best H2 sensor response (ΔR/R0 = 72%), response rate and selectivity. The significant improvement of the sensing performance of 0.5% Ni-doped TiO2 is mainly attributed to the formation of the highest number of n-n junctions present between anatase and rutile, which influence the quantity of adsorbed oxygen (i.e., the active reaction site) on the surface and the conductivity of the material. Full article
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Article
CuO-Ga2O3 Thin Films as a Gas-Sensitive Material for Acetone Detection
Sensors 2020, 20(11), 3142; https://doi.org/10.3390/s20113142 - 02 Jun 2020
Cited by 3 | Viewed by 1262
Abstract
The p-n heterostructures of CuO-Ga2O3 obtained by magnetron sputtering technology in a fully reactive mode (deposition in pure oxygen) were tested under exposure to low acetone concentrations. After deposition, the films were annealed at previously confirmed conditions (400 °C/4 h/synthetic [...] Read more.
The p-n heterostructures of CuO-Ga2O3 obtained by magnetron sputtering technology in a fully reactive mode (deposition in pure oxygen) were tested under exposure to low acetone concentrations. After deposition, the films were annealed at previously confirmed conditions (400 °C/4 h/synthetic air) and further investigated by utilization of X-ray diffraction (XRD), X-ray reflectivity (XRR), energy-dispersive X-ray spectroscopy (EDS). The gas-sensing behavior was tested in the air/acetone atmosphere in the range of 0.1–1.25 ppm, as well as at various relative humidity (RH) levels (10–85%). The highest responses were obtained for samples based on the CuO-Ga2O3 (4% at. Ga). Full article
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