Eng. Proc., 2022, I3S 2022

Electroactive polymer (EAP) strain sensors have gained appreciable attention as a potential candidate for their application in the area of soft electromechanical devices and have been widely used in soft robotics, healthcare, augmented reality, and wearable devices. In this research, a systematic comparison has been made by fabricating the electronic and ionic types of capacitive EAP strain sensors. To accomplish this, a combination of silicone rubber sandwiched between silver-coated stretchable fabric electrodes is used as an electronic type of EAP sensor, while a conducting and stretchable freestanding film consisting of Styrene-ethylene-butylene-styrene (SEBS) rubber and dedocyl benzene sulfonate acid (DBSA) doped polyaniline composite film sandwiched between carbon grease electrodes is chosen as an ionic type of EAP sensor. Mechanical characterization in terms of the uniaxial tensile testing was performed on both types of sensors using our custom-made tensile testing system, while capacitance under reversible stretching and relaxation under variable strains was measured using a computer-controlled XY-stage and an electrometer. Constitutive equations based on various existing mathematical models were used for analyzing stress–strain curves obtained from uniaxial tensile testing for predicting the mechanical behaviour of the sensor in multiaxial loading. The stress–strain curve for the electronic type of EAP sensor fit with Ogden’s second term, while Yeoh’s third term demonstrated a very good agreement for the ionic type of sensors. It was found that the observed capacitance was drastically enhanced for the ionic sensors, which was almost 1000 times higher compared to that observed for the electronic EAP based sensors. Conducting fabric used as stretchable top and bottom electrodes limit the elasticity of the sensor, while the ionic type of sensor can be stretchable up to >200% compared to the fabric-based sensor. Full article

This study concerns printed, disposable voltammetric electrodes for bioanalytical applications. Sensing electrodes’ electrochemically active surface area was found to relate to the screen-printing pastes’ rheology and manufacturing parameters. The sensors’ response was examined for constant carbon content in the electrode material and varying additions of surfactants and solvents, as well as the forces affecting the printing process. The printing pastes employed graphene nanoplatelets with the addition of carbon black as the functional phase and various polymers (PMMA, TPU, and others) as the composite matrix. Technological parameters examined included: the pressure and movement rate during the printing cycle, screen mesh density, curing, and ozonizing time. The rheological properties determined for each paste were: static viscosity, zero viscosity, and yield stress. To estimate active surface area values, sensors were immersed in redox couple solution and employed for CV measurements at varying scan rates. Finally, the active surface area was calculated according to the transformed Randles–Sevcik equation. The results were compared to electron transfer resistance and surface roughness. Correlation analysis was performed for the above parameters. The obtained statistical relationships will allow fine-tuning of the printed sensors’ performance as well as the faster development of new applications of this technology in analytical devices. Full article

A very simple to realize, low-cost, and highly sensitive plasmonic sensor, based on a polymeric light-diffusing fiber (LDF), is presented. The proposed surface plasmon resonance (SPR) sensor is realized by sputtering a gold nanofilm on an LDF made of PMMA. More specifically, a plastic LDF manufactured by GLOBAL ENGINEERING NETWORK SRL (Dosson di Casier, Italy) is used to realize this sensor. The optical fiber is an uncladded POF, with a simil-PMMA core of about 1600 μm in diameter and a removable jacket of about 400 μm (total diameter of about 2 mm). The SPR sensor is achieved by removing the jacket with a mechanical stripper and covering the exposed LDF surface with a 60 nm-thick gold film with a length of about 120 mm. The obtained sensor’s sensitivity varies linearly with the refractive index, and it ranges from about 1000 (nm/RIU) to almost 3000 (nm/RIU) in the considered refractive index range (from 1.332 RIU to 1.392 RIU). The obtained sensitivity values are comparable with those achieved using other SPR optical fiber sensors, but with the advantage of having a very simple production process, which does not require optical fiber modifications (such as the polishing process, tapering process, etc). So, the proposed LDF-based plasmonic sensor could be used to realize novel kinds of optical biosensors and chemical sensors. Full article

A large number of electromagnetic sensors for measuring soil moisture available on the market, differing in their method of measurement, price, shape, measurement volume, durability, etc., mislead the potential user. They cannot compare the right measurement equipment because there is no easy and reliable way to do so. The response of the sensors depends on the measurement frequency used, soil salinity, density, and texture, just to name a few. The growing concern for the sustainable use of water resources for agricultural, industrial, and domestic purposes and the growing market for the right measuring tools are putting pressure on users making the right choice. The article presents the issues and efforts of working towards standardization of electromagnetic measurements of soil moisture, especially in the field of the selection of measurement methods and reference materials that would enable the comparison of the performance of dielectric sensors available on the market. Work on the standardization of electromagnetic soil moisture measurements requires the cooperation of an interdisciplinary group of scientists and producers. The work done so far is an initial attempt to synchronize research in some international laboratories, learn about mutual research methods, and formulate research tasks for the future. Key questions about the concept development process leading to standard testing and evaluation practices for electromagnetic soil moisture measurements are still unanswered. Full article

Carbon dots (CDs) have recently emerged as a new class of fluorescent nanomaterial that can be prepared and modified in order to determine sensitivity to a variety of chemical and biological analytes. This versatility originates from different strategies of synthesis, top–down or bottom–up, that provide the means to perform heteroatom doping and the modulation of surface- and edge-attached functional groups. In particular, their great affinity with heavy-metal ions in water has stimulated a great number of studies on the response to these toxic species. Although most investigations have exploited the fluorescent emission of CDs, much less has been reported on the variations in optical absorbance, which could be more suitable for colorimetric detection in simple and cheap visual-based devices. Previous studies on top–down undoped CDs have demonstrated how slight modifications in synthesis could turn simultaneous sensitivity to As(III), Cd (II), Cu(II), and Pb(II) into a selective response to Cr(VI), due to exposure of the functional groups on the surface and the formation of hydrogen bonds. In this study, we report on the sensitivity of bottom–up nitrogen-and-sulfur co-doped CDs (NS-CDs) prepared using a simple one-pot hydrothermal method. We show how tuning the pH of the sensing solution greatly reduced the interference effects of Fe(III) and enhanced sensitivity to Cu(II) through the emergence of a distinct absorption band at 660 nm. This was attributed to the formation of cuprammonium complexes through N-containing functional groups. The concurrent response to Co(II) in a different spectral region also suggests the possibility of dual-species multiple sensitivity. The NS-CDs were characterized using TEM, STEM-coupled EDX analysis, NMR, and IR spectroscopy. The response to Cu(II) was linear in the concentration range of 1–100 µM with a limit of detection of 100 nM. Interestingly, the present system neither requires any other reagents nor any previous assay treatment. Full article

Diabetes mellitus is a group of metabolic diseases characterized by hyperglycemia resulting from a defect in the production or function of insulin, secreted by β cells of the pancreatic islets. Pancreatic islets are spherical cell aggregates (100–200 μm) which consist of several cell types. What is most important for improving research in the field of diabetes is the development of a model that reflects in vivo conditions. Here, we present a study based on the Islet-on-a-chip system, which was designed to create fully functional pseudo-islets (three-dimensional aggregates of α and β cells). This PDMS/PDMS Islet-on-a-chip system consists of two elliptical cell-culture chambers. In each of the chambers, there are 15 round microtraps (280 μm × 280 μm), each of them composed of seven circular micropillars, which force cell aggregation by limiting the growth surface. We designed this device to facilitate the screening of potential therapeutic agents, so here, we examined the effect of the newly discovered compound named 5-PAHSA on the developed model. Due to the appropriate design of the microfluidic system, it was possible to simultaneously culture, observe, and analyze the cell proliferation, viability, and hormone expression after incubation using selected concentrations of 5-PAHSA. It was noticed that after incubation with 5-PAHSA, the degree of proliferation increased in relation to both the control and the previous day of incubation. After analysis of the fluorescence intensity levels, the highest expression of insulin was observed after 48h of incubation with 100 μm of 5-PAHSA. These observations were confirmed by analyzing the amounts of secreted insulin under low (LG, 2.5 mM) and high (HG, 16.5 mM) glucose conditions using the ELISA test. Based on these results, it can be concluded that 5-PAHSA has potential properties for use as a therapeutic agent in diabetes, and the developed microsystem can be used for rapid drug screening. Full article

The properties of specialty optical fiber technology are determined by many aspects, such as the choice of material from which optical fibers are made, the refractive index profile, or the optical fiber manufacturing method. Typical optical fibers are made from ultrapure silicon dioxide (SiO₂), called fused silica, in a process called chemical vapor deposition (CVD). The differences between refractive indexes are most often obtained by doping silica glass with selected inorganic compounds, mainly germanium dioxide (GeO₂), which increases the refractive index, and fluorine, which lowers it accordingly. The proper design of the dopant profile in the optical fiber core and in the layer surrounding the core is crucial for nonlinear optical fibers with shaped dispersion characteristics. Such optical fibers can be used for the generation of nonlinear phenomena, such as supercontinuum generation (broadband light source) or soliton self-frequency shift. As part of the research, structures of nonlinear optical fibers with flattened normal dispersion in the near-infrared range were designed through the use of numerical simulations in COMSOL Multiphysics. The theoretical chromatic dispersion characteristics and dependence of the effective mode field area on the wavelength were obtained from the theoretical structures. Based on the designed optical fiber structures, a series of nonlinear optical fibers were produced, which were characterized by a high concentration of GeO₂ in the core and the presence of a fluorine-doped layer around the core. The influence of geometrical parameters, e.g., the width of the fluorine-doped layer (ratio of the radius of the fluorosilicate layer to the radius of the core), and the imperfections resulting from the technological aspects on the optical properties of manufactured optical fibers, with a particular emphasis on chromatic dispersion and the effective mode field area, was determined experimentally. Theoretical optical fiber models, along with their calculated properties (chromatic dispersion and effective mode field area), were compared with real measurements. Full article

In the conventional real-time polymerase chain reaction (RT-PCR) technique, DNA amplification is confirmed by quantitatively analyzing the increase in the fluorescence brightness using a fluorescent label. However, when using a fluorescence label-based technology, an optical structure enabling the accurate and expensive fluorescence detection is required, and the pretreatment of the sample is required to attach a visible fluorescence marker. In order to overcome this problem, many technologies have been studied for label-free detection using electrical sensors. Impedance has the characteristic of being highly correlated with the concentration of the sample solution and the fragment length of the DNA. If a change in the amount of DNA can be detected by a change in impedance during the PCR process, a detection device with a small and simple structure can be implemented without including an optical detection unit. In this paper, we propose a PCR chip and detection system based on impedance spectroscopy. Two types of chips were made using two types of flexible printed circuit boards (PCBs) with different electrode shapes, double-sided tape, and a plastic film. The system for driving the PCR process includes a microcontroller and is configured to control temperature and process measured values. The DNA sample solutions, diluted to various concentrations, were injected into the two types of chips, and the impedance values for each concentration were measured. The measured values were analyzed for each concentration and electrode type. As a result, it was found that although there is a difference in the size of the measured value depending on the type of chip, it is possible to distinguish between them by concentration. Full article

In recent years, the use of hyperthermia to induce the cellular activity of hippocampal neurons, which in vitro and in vivo experiments have shown to evoke a promising neural activity, has been explored. This is due to the hyperthermia effect, which improves the neurotransmission process, and this could be related to the fact that cells and neurons are temperature sensitive. However, if the temperature exceeds the physiological range (35–39 °C), abnormalities can occur as well as life-threatening health complications; for that reason, it is essential to have an accurate temperature monitor for such a technique. For that reason, the use of a non-invasive biosensor to monitor temperature changes remotely and that has a high temporal resolution is essential. In this work, the temperature-sensing properties of fluoroindate glasses doped with Er³⁺ and Yb³⁺ were examined with the aim of evaluating their potential as a wireless temperature sensor. The main advantage of the use of such a matrix is its low phonon energy, high refractive index, and transparency in the infrared spectra region. Their glass structure was analyzed using X-ray power diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), and Raman spectroscopy, while their ability as a non-invasive temperature sensor was evaluated using radiative transition analysis, along with calculation of absorption, emission, and effective emission cross sections. Finally, adequate functional models of temperature sensing were established for Er, Yb co-doped glass systems utilizing temperature dependences of luminescence spectra. Full article

Even outside of the instance of a global pandemic, the proper cleaning of professional work wear is crucial—thus, laundry technology becomes more and more efficient and automated. A bottleneck in the professional laundry process of working garments is the detection of foreign items in pockets and belts; undetected items may not only stain the clothes, but also harm the laundry machines and cause malfunctions or damages. However, the process of locating them is also potentially dangerous, as state-of-the-art is the manual scanning of every piece of garment to find items such as scissors, highlighters, syringes, screwdrivers, scalpels, paper notepads, and sweets. Some of the found objects are completely harmless, but several bare a high potential of injury for the worker involved in the laundry process. Due to the variety of the objects’ materials—plastics, paper, metal, and glass—the items are very challenging to detect with conventional sensors, such as cameras or metal detectors. In non-destructive testing, X-ray transmission (XRT) proved to be a powerful tool for detecting items inside of objects that can not be found by superficial sensors. Unfortunately, XRT does not allow for the distinction between thick objects with low X-ray mass attenuation coefficient and thin objects of stronger attenuation. Thus, similar gray values may be detected, for instance, for components of clothes, such as reflective stripes and pens. In this case, a segmentation by simple thresholding would be hopeless. In contrast, dual energy XRT allows for the obtainment of quantitative information concerning the chemical composition of the scanned materials, which helps to identify objects. In this study, different kinds of working garments were loaded with realistic foreign items in order to show the potential of dual energy XRT in the laundry industry. Full article

A³B⁵ materials used in the construction of a superlattice have properties that enable the design of devices (to include avalanche photodiodes) optimized for use in infrared detection. These devices are used in the military and medicine industries, and in other areas of science and technology. This paper presents a theoretical assessment and analysis of the impact of stresses on an InAs/InAsSb type-II superlattice (T2SL) grown on a GaSb buffer layer, considering band gap energy and effective masses at a temperature of 150 K. The theoretical research was carried out with the use of the commercial platform “SimuApsys” (Crosslight). The method kp 8·8 (k = 0.06) was adopted in T2SL modeling. Luttinger coefficients (γ₁, γ₂ and γ₃) were assessed assuming the Kane coefficient F = 0. The band gap energy of InAsSb ternary materials was determined assuming that the bowing parameter for the above-mentioned temperature was b_g = 0.75 eV. The cut-off wavelength values were estimated on the basis of theoretically determined absorption coefficients (α). The energy gap was calculated according to the following formula: E_g = 1.24/λ_cut-off. From the analysis of theoretical results, it can be concluded that the stresses in T2SL cause the E_g shift, which also has an impact on the influence on the change of the effective masses m_e and m_h, which play an important role in the optical and electrical parameters of the detection structure. The simulated theoretical parameters T2SL at 150 K are comparable to those measured experimentally. Full article

Visual tracking of multiple objects is a challenging task that has gained considerable attention recently. The process involves several steps: detection, data association, and re-identification, each with its own set of challenges. Trending methods usually combine some of these steps and report impressive results in tracking benchmarks while running at practical speeds. In this work, we develop an online, real-time multi-object tracking approach that is also able to perform consumer tracking in indoor retail stores, without further tuning its design philosophy. Our model can utilize multi-modal inputs, such as RGB and thermal images when available, to improve its performance while maintaining acceptable speeds at 20FPS. Our key contribution to motion forecasting replaces the standard Kalman filters with an LSTM network to properly model long-term dependencies and target tracking. Numerical experiments of our method on the widely used MOT16 benchmark demonstrate its effectiveness. Additionally, qualitative results in in-house retail image data confirm the method’s capacity for practical multi-consumer tracking. Our proposed system is part of a research project aiming to capture retail consumers’ preferences, as a function of their relative position with respect to particular areas of a store that have been mapped according to the shelves, which are visible for each view area of the installed RGB and thermal cameras. Additionally, the system relies on accurate estimation of consumer age and gender using only body images in a multi-task deep learning framework in order to further taxonomize consumer preferences into age and gender groups. By these means, useful consumer meta-data can be extracted, ready to be employed for marketing campaign customization, which might improve sales and the consumer experience altogether. Full article

Landmines and explosive remnants of war pose a global humanitarian problem and cause numerous casualties long after the conflict has ended. The current approaches for locating landmines, such as metal detection, which require one’s physical presence at the minefield, involve high risk to personnel; these methods are also costly, time-consuming, and have a high rate of false-positive results. There is no currently viable technology for the remote detection of buried explosive devices. A possible solution to this may be the use of genetically engineered microorganisms, molecularly “tailored” to emit an optical signal in the presence of trace explosives escaping for the landmine and accumulating in the soil above it. This optical signal, imaged from a remote location, can then be used to generate a physical map of the mine’s location. A few years ago, we have described the remote detection of buried landmines using alginate-encapsulated fluorescent microbial (Escherichia coli) bioreporters spread over the tested minefield. Since then, we have modified the system to one based on bioluminescent (rather than fluorescent) bacteria and have employed several synthetic biology approaches to significantly enhance their major performance parameters: higher signal intensity, faster response time, and lower detection threshold of the target explosives. These molecular approaches and their effect on sensor performance will be described. Full article

Several techniques can be used for the detection and analysis of odors. Among them, electronic noses emerged as a rapid and non-invasive diagnostic tool with various applications ranging from the food industry to medical diagnosis or forestry and agriculture. The concept of an electronic nose consists of using an array of nonspecific gas sensors equipped with machine learning pattern recognition algorithms. A few devices based on MOX (metal-oxide) commercially available sensors (Figaro Inc., Osaka, Japan) have been constructed in our laboratory. The operation of developed devices consisted of measuring sensors’ conductivity, carried out as a response to changing operation conditions by moving sensors from clean air to the vicinity of the sample where volatile organic components are present. Additionally, the sensors’ operation in various working temperatures was exploited. Our goal was to develop an inexpensive and effective tool for the early detection of tree diseases caused by pathogenic oomycetes such as fungi. The devices were tested, both on pure cultures of cultivated organisms, and in interaction with infected plants. Distinguishing between the pathogenic oomycetes Phytophthora plurivora and Pythium intermedium, and the fungi Fusarium oxysporum and Rhizoctonia solani, by detecting the odors of their volatile secondary metabolites has been reported. Information about which pathogen we are dealing with in forest nurseries allows us to design an appropriate plant protection strategy (e.g., selecting appropriate pesticides). Experiments aiming to detect the fungal infection of tree seeds during storage were also performed on English oak (Quercus robur) acorns and silver fir (Abies alba) seeds. Additionally, studies of ash (Fraxinus excelsior) dieback caused by Hymenoscyphus fraxineus pathogenic fungi using a PEN3 electronic nose device (portable electronic nose, Airsense Analytics GmbH, Schwerin, Germany) were performed by measuring infected roots and soil. Full article

Alteration of the polarisation state of light is an appealing source of contrast which has been used in polarised light microscopy of very thin sections for many decades, and has applications in geology, materials, and biology. The polarisation-sensitive (PS) version of optical coherence tomography (OCT), in contrast, probes a sample volume (rather than a thin section) and identifies the presence, relative arrangement, and orientation of sub-wavelength-sized fibrous structures. In biology, PS-OCT is sensitive to structures such as collagen fibres or muscle cells, and the shape of individual scatterers, such as cells. PS-OCT has been in existence since the early 1990s, but it has yielded less to date than its early promise suggested. The received signal is complicated by the cumulative influence of the propagation path on the contrast, and the complex physics of polarised light–hard and soft tissue interactions. Thus, image interpretation has been challenged by the lack of one-to-one correspondence between PS images and OCT structural images. Nonetheless, applications have been pursued, including in glaucoma, tumour and burns assessment, and wound monitoring. In this work, I will describe what has changed recently to overcome the existing challenges, focusing on our recent work, and why we expect polarisation-based contrast to yield great advances over the coming years. Full article

Today, multispectral optical sensors are extensively studied in non-contact and remote imaging systems. However, our previous experimental studies have shown that the changes in the reflective properties of chicken eggshells allow for the classification of their origin as either healthy or Mycoplasma synoviae (MS)-infected hens. MS is a pathogen affecting poultry that may have a significant economic impacts on poultry breeding. In this work, we present the portable optical fiber reflectometer, which can be used for early MS detection in a flock by the measurement of back-reflected light in a multispectral system. The designed reflectometer consists of control and optical modules. The control module is responsible for the light source and photodetector modulation, the synchronization and the power supply, as well as data recording. The main part of this module is a microcontroller used to ensure flexibility in creating the research sequence during operation. The optical module is based on a fiber bundle with six light outputs and a single detection line. The loose end of the fiber bundle is integrated with an optical head, which shapes the illuminating beam to obtain measurement conditions. The same optical head collects a back-reflected beam that propagates through the detection line to the detector. The application of the optical fiber decreases the weight of the whole system and enables the flexible operation of the optical head, making this system portable. In order to classify the test objects, the collected data were subjected to numerical analysis by means of machine learning. Full article

The rapid progress in the field of chemical sensors has made it possible to carry out quick, accurate, and precise monitoring of interactions between biological compounds, enabling the development of models describing the processes that occur at the cellular level. Measurement techniques utilizing biosensors coupled with optical detection play a special role in this type of research. Label-free techniques, such as surface plasmon resonance, are particularly useful for studying intermolecular interactions in real time and for determining the thermodynamic parameters that characterize them. The study presented in this work concerns the use of the surface plasmon resonance (SPR) technique to evaluate the biological activity and potential mutagenicity of recombinant insulin analogs exhibiting a prolonged period of action (compared to human insulin)—these are innovative drug candidates for the treatment of diabetes. The project’s aim was achieved by the analysis of kinetic parameters describing the interactions of cell surface receptors with a wide range of recombinant proteins with amino acid sequences that differ from the natural hormone in only a few positions. The presented results include the construction of the receptor layer with immobilized membrane receptors, obtained by their covalent conjugation with -COOH terminated SPR chips. The selection of appropriate parameters of the conjugation process with the use of carbodiimide chemistry could obtain good-quality layers with a sensitivity that enabled the direct monitoring of the receptor’s interactions with insulin and its analogues. The research covers the optimization of the receptor layer to reach high-ligand surface density. The results of molecular modelling with the use of the kinetic curves obtained for the interaction of insulin and long-acting analogues were also shown. Determined kinetic parameters (especially KD) became the starting point for the comparative characteristics of studied proteins’ interactions with an insulin receptor. Full article

Immunotherapy is an innovative cancer treatment that activates the immune system, enabling natural anti-cancer defense mechanisms. Although the large-scale use of immunological treatment is yet to happen, immunotherapy already plays a practical role in cancer treatment. Lung cancers have been selected as the main subject of interest. The aim of the presented research is to explore an innovative methodology for the rapid determination of protein antigens by means of miniaturized immunosensing platforms. One of the key elements of such a diagnostic approach is the determination of programmed death-ligand 1 (PDL1) and/or human epidermal growth factor receptor (HER2) expression directly on cancer cells or in biofluid samples. As a principle, the developed method should act as a support or an alternative to the assessment of tissue sections after immunohistochemical staining or classical enzyme-linked immunosorbent assays (ELISAs). The idea covers the utilization of biosensing platforms based on flexible substrates, e.g., poly (ethylene terephtalate) foils or antibody-binging membranes made of nitrocellulose/poly (vinylidene fluoride) for the sensitive detection of lung cancer biomarkers. As a result, it would be possible to globally assess the occurrence of biomarkers (e.g., PDL1 epitopes). The detection process consists of instrumental readout using optical techniques (spectrophotometry or fluorometry). The main goals of the presented research will be: (i) the characterization of antibody-protein antigen interactions and the selection of the best immunosensing formats; (ii) the selection of the most attractive epitopes as sensing targets; and (iii) the characterization of the analytical performance of the developed immunosensing platforms for the detection of PDL1 and/or HER2 biomarkers. Taking into account the benefits, we believe that the proposed research will allow us to broaden the knowledge about cancer diagnostics and allow us to propose a quantitative methodology for determining various epitopes of cancer cells. Full article

Thermo-optical properties of liquid materials are very important in many practical applications. The temperature dependence of the refractive index (RI) is usually sufficient to fully characterize a given material, however, for some applications an extinction coefficient (EC) temperature dependence has a great influence on the optical properties of the sensor’s transducer. Our previous studies have shown that light wave propagation properties in a large mode area (LMA) photonic crystal fiber (PCF) partially filled with liquid strongly depend not only on its RI, but also on the state of matter—either liquid or solid—which also determines its EC. Therefore, high absorption of the filling material significantly reduces the intensity of light passing through the PCF. In the presented work we studied commercial PCF (LMA-10) partially filled with liquid paraffin. Recorded light transmission within the temperature range of 20–120 °C allowed us to observe changes in the propagation conditions of such a hybrid PCF transducer, when the light transmission was supported either by index-guiding and bandgap-guiding mechanisms, depending on the paraffin’s RI. Furthermore, as the RI of the paraffin approached the RI of the PCF, we observed a lack of the transmission and then the propagation changed between the index-guiding and the bandgap-guiding conditions. The transmission in the bandgap-guiding region was reduced in comparison with the transmission in the index-guiding region. This can be caused by the difference of EC of paraffin in the two guiding regions. In our numerical simulations we analyzed the influence of this parameter on the transmission losses by changing the values of the EC to match them with the experimental results. Hence, we were able to obtain its value, which was not previously reported. The presented studies provide not only an insight into the material properties of paraffin, but also pave the way for PCF-based RI sensors. Full article

High time resolution and extreme radiation hardness are key for detectors to be operated in future particle accelerators and in space or medical applications. With respect to these relevant properties, we report here on performances of pixel sensors prepared on mono- and poly-crystalline synthetic Chemical Vapor Deposited (CVD) diamonds, by fast laser modification via multiphoton absorption from a 50 fs, 800 nm, Ti:Sa source. The research has been carried out in the framework of the Timespot experiment of the Italian National Institute for Nuclear Physics (INFN) aimed to achieve both high spatial resolution (55 μm pitch) and very high time resolution (tens of picoseconds) with very radiation tolerant detectors. Timespot exploits the recent 3D electrode architecture to enhance both time resolution and radiation hardness with respect to standard planar silicon and diamond detectors. We present here a major step forward in material engineering and fabrication procedure, yielding a time resolution improvement of our devices from the initial 280 ps to the present 80 ps, bringing this figure of merit very close to that allowed by the more mature 3D silicon technology. Recent results will be presented, and strategies for further improvements will be discussed. Since diamond is known to be a very radiation-tolerant material, it is considered very promising for implementing devices planned for very fast response and radiation hardness. We present results on a thorough study of polycrystalline and monocrystalline diamond sensors irradiated up to a fluence level of 10¹⁶ n_eq (1 MeV)/cm². The superior radiation hardness of the 3D architecture is demonstrated with respect to the planar detectors. We have also verified that the radiation hardness increases with increasing bulk electrode density. The results are discussed and compared with other radiation hardness studies carried out on 3D diamond sensors. Full article

With the advancements in remote sensing, satellite images have become a popular data modality and are widely used in many applications. Among others, satellite images are used by surveyors and engineers for urban planning and asset management, e.g., for rapidly growing cities, urban sprawl, and informal settlement. A preliminary step in satellite image analysis is identifying the regions of interest or target objects in the scene and extracting them from irrelevant objects for further processing. This image segmentation task is challenging due to various factors, e.g., occlusions, lighting conditions, and noises. To address these issues, many researchers have proposed different approaches, e.g., UNET, which is regarded as a state-of-the-art method. However, it has high memory consumption, low accuracy, and poor quality prediction when applying satellite images. Thus, we propose a multi-channel decomposition semantic segmentation method, MNET, for object classification. We used the dataset obtained by MBRSC satellites and divided the scene objects into six classes (vegetation, water, road, building, land, unused). The study area is in Dubai. We compared our approach with UNET++, U2NET, and 2D-VNET. Experimental findings show that: (1) MNET outperforms others with a mIoU score of 79.4%, whereas UNET gives 75.1%, and (2) accurate patch generation is a crucial part of the model performance, as ignoring less informative patches during training increases the accuracy by 5%. In conclusion, our proposed method offers a lightweight structure, is a computationally less expensive model, and is simple to deploy in industry applications. In this work, we conducted an extensive analysis of domain transferability, class bias, and class co-occurrence. We also compared the best and worst predictions with a number of current methods. We believe that our MNET can also benefit other domains, such as in floodwater detection using Interferometric Synthetic Aperture Radar (InSAR) data, building extraction, and crop segmentation, due to the prediction accuracy and memory consumption efficiency of MNET. Full article

Metastasis of cancer cells to various organs in the human body is a significant oncological problem. The mechanisms that activate the invasion of cancer cells are not well understood. The research on the processes of cancer invasion is limited under laboratory conditions, because there are still few biotechnological solutions developed to conduct advanced, three-dimensional (3D) cell cultures in vitro. It is necessary to develop new tools for cell engineering that will allow the study of the processes related to cancer metastases and that will enable the analysis of interactions between non-malignant and cancer cells. In this work, a new body-on-a-chip microfluidic system was designed. The microsystem was made of two layers of biocompatible poly(dimethyl siloxane) (PDMS) and a thin, porous PDMS membrane, which was the surface of cell growth. The developed microsystem enabled 3D culture of several types of non-malignant and cancer cells under microfluidic conditions. Four types of cells were cultured simultaneously in the microsystem: non-malignant lung cells (MRC-5), breast fibroblasts (HMF) and co-culture of ovarian fibroblasts (HOF) and ovarian cancer cells (A2780). Additionally, the use of cellular co-culture allowed the imitation of the physiological structure of cancer tissue, composed of a cancerous parenchyma and a non-cancerous stroma. The multi-organ cell culture model was characterized by viability tests: AlamarBlue assay and differential fluorescence staining with propidium iodide and calcein-AM. The changes in the morphology of lung cells and breast fibroblasts because of interaction with ovarian cancer model were also observed using microscopic methods. The cancer cells can create new inflammatory disease outbreaks as a result of interaction with the microenvironment created by non-malignant cells. Therefore, in the next stage of research, the body-on-a-chip system will be used for analyzing the invasion of ovarian cancer cells by monitoring pro-inflammatory factors in the microenvironment created by non-malignant cells of other organs. Full article

Chemical sensors based on metal oxides (MOx) are one of the most promising gas sensing devices due to their high sensitivity to numerous gases, fast response, miniaturization, and simple production. The detection principle of these sensors is a conductivity change of the MOx-sensing material due to the chemical reactions of gases with surface molecules. Cross sensitivities and interference to humidity, however, are still significant drawbacks of these sensors. The functionalization of MOx-sensing films with catalytic nanoparticles (NP) is a highly promising technology for optimizing sensor performance. The huge variety of potential MOx–NP combinations requires efficient screening technologies to find proper hybrid material mixtures which enable the controlled adjustment of the sensor response to specific target gases. This is of high importance for the realization of a multi-gas sensor device capable of the clear discrimination of single gas components from a gas mixture. In this work we introduce our approach for the efficient screening of hybrid MOx–NP material combinations. We have developed a specific Si-platform chip along with a gas measurement setup which enables the simultaneous characterization of 16 chemical sensor structures in parallel. The Si-chips feature an array of Ti/Pt electrodes for contacting ultrathin MOx-sensing films, which are deposited by spray pyrolysis, and structured by photolithography to a size of 50 × 100 µm². On these platform chips we tested three different MOx (SnO₂, ZnO, and CuO) before and after functionalization with mono- and bimetallic NPs (such as Au, Pt, Pd, and NiPt) on several test gases (CO, HCmix, toluene, CO₂). Measurements were performed in a background gas of synthetic air at different relative humidity levels (25–75%) and at different operating temperatures up to 350 °C. We present the sensing performance results of various MOx-NP combinations, exhibiting an optimized response to specific target gases. Full article

Tapered optical fibers, due to their specific optical properties, are great sensing elements. During the elongation of an optical fiber, a tapered waist forms, which allows the electromagnetic wave to propagate in the whole volume of this structure; simultaneously, some part of this wave leaks out of the taper as an evanescent wave. In fiber-based surface plasmon resonance sensors, the evanescent field of propagating modes in a fiber penetrates a thin metal layer and, thus, the surface plasmons are excited at a metal/dielectric interface. Additionally, to control and strengthen the SPR effect, liquid crystal cladding with controllable refractive indices by voltage has been applied. This research focused on an electric field sensor based on a tapered optical fiber probe. The manufactured sensor consisted of gold- and silver-coated thin films in the tapered waist area of an optical fiber with the low-refractive-index liquid crystal named 3092A as cladding. The Au and Ag layers with thicknesses from 10 to 30 nm were deposited using the sputtering method. Because of the significant influence of liquid crystal molecules’ initial arrangement on light propagation, three types of liquid crystal cells, orthogonal, parallel, and twist, were considered. Measurements were performed at room temperature, and the steering voltage ranged U from 0 to 200 V in a wide optical range. The obtained results allowed us to establish resonant peaks, the depths and positions of which depended on the metallic layer used, liquid crystal cell type, and voltage, and could be controlled by the mentioned factors. Full article

Based on the modification of biological substances, either directly from the patient to be treated or from healthy donors, Advanced Therapy Medicinal Products (ATMPs) are promising therapeutic solutions (among others, CAR T-cells represent the current and best-known ATMPs). However, at a few hundred thousand USD per dose, these products suffer from their prohibitive price, limiting the number of treated patients. The reasons for this can be summarized as follows. The whole process takes place in sterile facilities and requires trained staff (as well as onerous equipment) who perform sampling for the numerous rounds of quality control performed throughout production. Production can last more than one week, and each round of sampling further increases the risk of contamination and the need to fight against them. Therefore, there exists a need for online control of the content of the bioreactor during production, especially focused on concentration measurements and quality assessments. Meanwhile, the real-time detection of possible contamination would allow production to be stopped as soon as a problem arises, hence saving days of useless cultures and reducing the cost of global production. In this conference, we present simple and real-time white-light spectroscopy to simultaneously monitor T-cell growth, estimate the production quality and detect contamination. The mathematical description of the absorption spectra shape allows us to achieve these goals. The contactless nature of white-light spectroscopy prevents sampling of the bioreactor’s content, and consequently, reduces the risk of concomitant contamination. The possible integration of such online methods in bioreactors is also proposed with the ulterior motive of democratizing the use of ATMPs for as many people as possible. Full article

The presented research shows the effect of mixing Fe₃O₄ nanoparticles with higher alkanes on the propagation of the light wave in a biconical, adiabatic optical fiber taper. A fiber optic taper makes it possible to directly influence the light parameters inside the taper without the necessity of leading the beam out of the structure. The mixture of alkanes and Fe₃O₄ nanoparticles forms a special cladding surrounding the fiber taper, which can be controlled by temperature and magnetic fields. The results show changes in beam intensity and polarization properties, such as the azimuth; ellipticity, depending on mixture temperature, aggregation of nanoparticles, and different applied magnetic fields. The taper is made of a standard single-mode telecommunication fiber, pulled out to a length of 25.0 ± 0.5 mm. The diameter of the tapers is around 8.0 ± 0.3 μm. Such a taper causes the beam to leak out of a waist structure and allows the addition of external beam-controlling cladding material. The built-in sensor containing nanoparticles operates according to the on-off principle, as well as with changes in the nanoparticles’ position around the taper. Nanoparticles added to the alkanes cause an increase in hysteresis via a heating and cooling process. Magnetic particles can change their positional influence on the light propagation and polarization parameters. Such a mixture also creates a significant shift in the temperature characteristics during the heating process, in which the mixture changes its physical state with the simultaneous slight shifting of the characteristics during cooling. The data covers a wide spectral range of 500 to 1700 nm. Temperature tests for the selected lengths in the visible and infrared range are determined. Full article

We report a novel, miniaturized gas sensor configuration with ppbv (parts-per-billion by volume) sensitivity, where detection of the gas sample concentration is realized inside a Nd:YVO₄/YVO₄/Air-Gap structure (2 × 2 × 14 mm³) of the double-beam, monolithic diode-pumped solid-state laser (DPSSL) resonator operating at 1064 nm. Both generated probe and reference beams are passed through an ultra-compact sensing volume (4 μL) of the air-gap section filled with gas molecules. Simultaneously, an auxiliary laser beam is targeted on the absorption line of a measured gas sample and focused on a 1064 nm probe beam only. Due to the absorption effect, excited gas molecules are heated locally, resulting in a negligible change in a gas refractive index (RI), which is inherent to the photothermal effect (PT). Hence, the PT-induced variations of the gas RI inside the laser resonator are modulating the optical path-length of the probe beam, which resulted in a significant optical frequency shift of the probe beam against the reference one. The optical frequency changes were measured by applying the heterodyne detection technique, where both 1064 nm beams were coupled onto the near-infrared (near-IR) high-speed photodiode (PD), resulting in a beat note signal readout down-converted into the radio-frequency (RF) domain. The RF mixer was used to shift the beat note in frequency accordingly to the frequency modulation (FM) demodulator range. The demodulator converts the beat note frequency changes into a proportional voltage signal. To provide better gas sensor properties, a typical wavelength modulation spectroscopy (WMS) technique was additionally used. The solid-state laser intra-cavity photothermal sensor (SLIPS) is a unique approach to gas spectroscopy, which provides tens of ppbv sensitivity, more than 5000 signal-to-noise (SNR) ratio, baseline-free measurements, miniature, versatile and non-complex sensor setup based on inexpensive DPSSL technology. The SLIPS has no limitation in terms of the excitation wavelength because only one near-IR detector for signal retrieval is needed. Full article

Molecular diagnosis evaluates changes in molecules occurring in cells through numerical and imaging. The expression of genes and disease genes are studied to present directions for the prevention and treatment of infectious diseases. Real-time polymerase chain reaction is a technology that amplifies the amount of a small-target genetic material. Real-time PCR (Polymerase Chain Reaction) detection technology based on fluorescence measurement detects DNA amplification and measures fluorescence brightness. Existing real-time PCR systems require complex configurations and many optical components. As a result, the size of the optical system device is large, and there are limitations in cost and assembly. In addition, imaging devices, such as large and expensive high-performance cameras, are required to measure fluorescence. Recently, due to the continuous development of cameras for smartphones, many cameras with a small size and good performance are being developed. In this paper, we propose a low-cost compact fluorescence detection device using a parallel light lens. The proposed system has a simple optical structure, and the cost of the system can be reduced and miniaturized. This system has the same field of view using a fresnel lens. In addition, a small and inexpensive CMOS (Complementary Metal–Oxide Semiconductor) camera (Arducam, Nanjing, China) and LED were placed in the same direction to the greatest extent possible in the center of the fresnel lens. For an accurate analysis, an image processing method was used to compensate. As a result of comparative experiments using double distilled water (DDW) and a reference fluorescence solution (FAM), the proposed system confirmed that stable fluorescence detection was possible. Full article

We report on the calibration and testing of a fiber Bragg grating (FBG)-based 2D-shape sensing strip for real-time monitoring of the position and orientation of the human spine during gait. The strip is evaluated for its use as an input for control of an exoskeleton for patients with spinal cord injury. By measuring the torsion and bending of the back, walking movements can be reconstructed. The 3D-printed strip has nine embedded fiber Bragg gratings that are located at specific places with respect to the vertebral column. Three FBGs are placed opposite to the thoracic vertebrae T6–T9, these FBGs are sensitive for measuring the bending of the spine during the gait cycle. Torsion is measured at two locations: at thoracic vertebra, T3 and at lumbar vertebra, L3. At these locations, the width of the strip is reduced to have a larger sensitivity for torsion. The strain at each FBG is measured using an interrogator. This leads to the radius of curvature and torsion as a function of time. The Frenet-Serret formulae are used to calculate the shape of the strip during the gait cycle. We have calibrated this FBG strip for curvature by bending it at known radius of different curvatures. We found a linear dependence between the strain and curvature. For torsion calibration we have rotated the strip with a stepper motor at different angles and monitored the strain. We, again, found a linear dependence with a small hysteresis. We mounted the strip on a healthy test subject and monitored their gait cycle. The FBG strip shows similar results when compared to a motion capture system based on multiple cameras. Although the fixation of the strip to a garment or on the back directly strongly influences the measured response, it does show a periodic and reproducible signal during the gait cycle. Full article

Optofluidics is a constantly developing research area that combines known technologies from chemistry and photonics. Various systems have been created, which are used in biology and chemistry as well as in other subjects. The combination of materials such as polydimethylsiloxane (PDMS) and liquid crystal (LC) provides a number of possibilities to create functional structures. The properties of LC allow systems to be developed in PDMS, e.g., lenses with different focal lengths depending on the polarization of light or multiplexers have been proposed. Appropriately controlling LC molecule orientation is a crucial element in creating tunable systems. The motivation of this research is to determine the proper arrangement of an electrode array to control the orientation of liquid crystal molecules and thus the refractive index. The performed tests allowed the initial parameters to be determined to produce LC:PDMS structures with a periodic orientation of LC molecules. As the channel sizes have to be micrometer-scale, a proper electrode arrangement has to be developed. The materials from which electrodes can be created are also limited due to PDMS properties as well as the size of the channels. The plan is to create a tunable LC:PDMS structure with LC molecules in a periodic reorientation, which would allow the system to function as a tunable Bragg grating. It would be the first achievement of this kind, and it would open up new possibilities for the combination of liquid crystal and PDMS in photonic systems. Full article

Evacuating large passenger ships is a complex and safety-critical process. During an evacuation, the passengers are assisted by exit signs, the public announcement system and the crew, the latter providing instructions for mustering and abandonment. In addition, passengers are required to wear lifejackets that are made of buoyant or inflatable material used to keep them safe in the water. The timely mustering and guidance of passengers to their embarkation stations is of the utmost importance and greatly affects the evacuation time in the case of an emergency. This is especially important in extreme conditions and hazards, such as fire and flooding. Within the context of the project SafePass, a smart lifejacket is designed and implemented, which integrates indoor localization technology and a haptic navigation system that can assist passengers during evacuation. The indoor localization technology reports the passengers’ location within the ship, while the navigation system can negotiate a route and navigate the passenger using vibration motors attached to the smart lifejacket. These actuators vibrate to provide haptic cues to the passenger to navigate them to their destination in low visibility conditions and in the case they are left behind or lost. The smart lifejacket can also help the crew to locate stray passengers, thus increasing the safety of passengers and reducing the evacuation time as a whole. Full article

Energy consumption has increased exponentially over the last decades. This fact reflects the price of the electrical energy. Consequently, the scientific community has concentrated on generation procedures from renewable sources. In this sense, the efficiency of conventional photovoltaic cells and the emergence of new organic and hybrid materials have substantially improved photovoltaic generation and its Power Conversion Efficiency (PCE). The interest in organic cells has been justified by their beneficial properties: ease of processing, low cost, flexibility, and low weight. Recently, the increasing PCE evolution has been higher than that of the classical technologies, reaching values up to 17.5%. Notwithstanding that, there are still several challenges to deal with. Amongst them, there is the lifetime of these devices. In certain contexts, the fabrication conditions and their associated parameters constrain the time degradation of the physical properties of the organic device. This study assessed how time degradation affects organic cells, in which certain fabrication parameters were varied. In particular, this work evaluated cells with the following structure: ITO/PEDOT:PSS/P3HT:PCBM/Al. The analysis focused on parameters such as PEDOT:PSS solution volume, P3HT:PCBM solution ratio, solution temperature, and layered dopants. The results obtained in terms of PCE, V_oc, and I_sc provide insights on the possible dependences for the lifetime degradation. Finally, in light of the results, this work proposed several analytical models that aid in the fitting of the degradation curves for the studied materials and their fabrication parameters. Full article

Chemical sensors should provide fast and reliable information on an analytes. One possible technology used in contemporary sensor research is the so-called lab on paper, in which appropriate chemical indicators are immobilized on a specially designed paper chip with hydrophilic and hydrophobic paths. The difference in the wettability of the basic material is used to deliver a liquid sample to an appropriate place of the chip via the indicator. The sample is transported by capillary forces. This article presents a new design of a lab-on-paper chemical sensor for the detection of explosive materials. The chemical sensors were based on Whatman chromatography paper, which was covered with a wax layer. A precise wax pattern was deposited using a Xerox wax printer Colorqube 8700. Afterwards, the chromatography paper was heated up to 170 °C for 2 min. In this way, the wax layer penetrates the paper and creates a hydrophobic barrier. A solution of gold nanoparticles (with diameters of 20 nm) was modified using cysteamine. The paper-based chemical sensor was modified using such a solution. The sensing pads were then covered with 0.1 M NaOH solution. The changes in the color of the sensing pad were dependent on the explosive material. The designed sensor was tested with samples of 2,4,6-trinitrotoluene (TNT). Full article

In recent years, the classic geometries of sensors based on surface plasmon resonance (SPR) have been adapted for use in optical fibers (both extrinsic and intrinsic configurations), thus providing a simple approach to low-cost plasmonic sensing. For instance, polymer optical fibers (POFs) are particularly advantageous due to their excellent flexibility, ease of manipulation, great numerical aperture, large diameter and, last but not least, the fact that plastic can withstand smaller bend radii than glass. In bio-chemical applications, a very specific medium (receptor layer) for the selective binding of the considered analyte is deposited on a gold layer of the SPR platform. A simple and low-cost experimental setup, consisting of a halogen lamp and a spectrometer, can be arranged to measure the light spectrum transmitted through the SPR-POF sensors. Interesting applications have been devised and successfully implemented by exploiting these low-cost plasmonic POF platforms combined with different receptors, such as molecularly imprinted polymers (MIPs), chemical receptors, and bio-receptors (aptamers and antibodies). For example, by exploiting SPR in a D-shaped POF probe with different receptors, interesting results have been achieved in medical diagnostics for cancer bio-markers detection, the monitoring of antigens in celiac disease, L-nicotine detection, thrombin detection, and SARS-CoV-2 virus and pancreatic amylase detection. A survey of these medical applications is presented, highlighting the advantages and limitations of each application and revealing possible future implementations of the platform as a point-of-care device. Full article

The development of optical fiber sensor technology has led to interest in the use of new elements for functionalizing the fiber end face. The modification of this part of the fiber can be conducted by forming a polymer microtip (PM). The technology of manufacturing PMs on single-mode and multi-mode fibers is widely described in the literature. Geometry and optical properties of PMs depend on technological process parameters, optical fiber type, and monomer mixture composition. PM can be considered in the context of sensor applications as a transducer that is sensitive to refractive index (RI) changes. RI sensors were an inspiration to explore the possibility of using PM to detect VOCs in air. Five selected volatile compounds were tested: trimethyl phosphate (TMP), 1,4-thioxane (THX), acetone, toluene, and aqueous ammonia. The principle of the sensor operation was based on the phenomenon of attraction and repulsion of the condensed VOCs. Attracted VOC molecules cover the PM surface and form a liquid film that changes the RI at the interface between the PM and the external material. The return loss level changes rapidly when the PM is introduced into the glass vial filled with the test compound. The proposed sensor acts as a threshold, showing only the presence of condensed VOC, but with no ability to determine its concentration and type of substance. Such a sensor can be used in warning systems to monitor leaks in volatile chemical transport lines, as well as to monitor accumulations of hazardous liquid substances that easily transit into the vapor phase. It acts as an early warning system in the event of the condensation process of the monitored dangerous chemical agent. Full article

Acrylamide (AA), C₃H₅NO, is used worldwide in the synthesis of polymers and gels for wastewater treatments and in the paper industry. Naturally, it is formed in heat-treated food, mostly during the frying and baking of potatoes, cereals, and coffee beans. Its presence in food is dangerous as it is a neurotoxic and genotoxic compound. Triggered by new EU regulations, there is a high demand for reliable and cost-effective sensors in food and home appliances. In view of this, electrochemical sensors show high potential for the detection of toxic compounds. In the present work, we show the development of electrochemical biosensor elements, since AA is a non-active molecule and direct electrochemical detection is not possible. The sensors’ receptor element is based on modified commercial screen-printed electrodes (SPEs) that offer on-site and cost-efficient sensing. As an electrochemical transducer, conductive polyaniline (PANI) decorated with Au NPs was applied, enabling high sensitivity and limit of detection below the 10⁻⁶ M range. As a biological component, enzyme amidase was selected, since it is known that it catalyzes the hydrolysis of acrylamide into carboxyl acid and ammonia. The ammonia was finally detected using chronoamperometry. The chemical interaction between PANI and ammonia is well-known and thus was used as a base for the fabrication of an amperometric sensory platform for its aqueous detection at neutral pH. To understand AA and amidase interaction and decomposition into ammonia, PANI electrochemical synthesis and redox behavior in acidic and neutral media were used to study the mechanism of AA indirect detection. Full article

Infectious diseases, such as COVID-19, continue to cause an enormous burden of death and disability in developing countries, and there is an urgent need to better understand these infectious pathogens and develop ways to control their spread. We have developed a new type of testing strategy based on electrochemical biosensing aspects, created using a microfluidic detection platform for rapid, sensitive, and specific detection of infectious SARS-CoV-2 and its variants. The target compounds, i.e., SARS-CoV-2 variants, were selected due to the current worldwide outbreak; however, the fabricated biosensing aspect may be expanded to future emerging pathogens by undemanding modifications. The biosensor platform is based on screen-printed electrodes (SPEs), modified with nanostructured polystyrene (PS)/polyaniline (PANI)-Au NP composites. The surface of modified-SPEs is later immobilized using different representative receptor elements, i.e., specific viral antibodies. Tackling PS/PANI-Au NP composites on the nanoscale enables us to exploit its outstanding conductivity, biocompatibility, and high surface area which facilitate the loading of a huge amount of viral receptor elements (Ab), thus resulting in high sensitivity, specificity, and low detection limits (i.e., at attomolar concentration levels). Such a construction is able to translate this specific covalent interaction (Ab) with its corresponding binding viral target, i.e., receptor-binding domain ((RBD) of spike (S) glycoprotein) into a measurable, concentration-dependent electrochemical response. By creating an electrochemical readout, data enable qualitative and quantitative analysis. The fabricated system represents a low-cost and efficient alternative to conventional assays for testing as it offers a simple in-situ method of analysis in much shorter time frames. Its feasible design is easy to use and can be operated by patients themselves using simple samples such as saliva, thus allowing population-scale screening. Full article

Wearable devices are being increasingly used to objectively monitor and evaluate physical variables related to human movements, such as sports. Although wearables for kinematic measurements are widely used nowadays, many dynamic studies still employ force platforms to have reliable and valid data for estimating vertical ground reaction forces (vGRFs). Not only are force platforms quite expensive, but they also cannot be easily accommodated in a practical scenario and significantly restrict the user’s freedom of movement to a small fixed area. This article presents a smart insole sensor capable of providing a reliable and valid measurement of vGRFs. Regarding the hardware, the wearable is comprised of piezoresistive force sensors distributed along with the insole, which provides plantar force distribution measurements, and an embedded system for data collection and communication worn on the lower leg. In order to make the system more affordable, we made the prototype enclosure using 3D-printing technology. Finally, to monitor the wearable outputs, the insole sensor uses a mobile application connected to the wearable via Bluetooth 4.0. The prototype underwent both unit and value calibration at the lab using gold standard force plates to guarantee accurate outputs. Regarding the software, we implemented a novel deep learning algorithm for vGRF estimation and insole sensor calibration. This research provides an advancement toward developing a wearable monitoring system for vGRF reporting in real-life scenarios. Full article

Ultra-broadband emission in the range of 1.0–2.1 mm is required in medicine (OCT), metrology, and sensing systems. Novel ideas are connected to the rare-earth co-doping of low-phonon energy glasses (further fiber core) and ultra-broad emissions obtained as a result of the superposition of particular luminescence bands. The 1.5–2 um broadband ASE in both germanate glasses and glass fibers co-doped with Tm³⁺/Ho³⁺, Yb³⁺/Tm³⁺/Ho³⁺ and Er³⁺/Tm³⁺/Ho³⁺ can be realized as a result of radiative transitions in the 1.4–2.1 mm range due to Tm³⁺: ³H₄→³F₄ (1.45 mm), Er³⁺: ⁴I_13/2→⁴I_15/2 (1.55 mm), Tm³⁺: ³F₄→³H₆ (1.8 mm), and Ho³⁺: ⁵I₈→⁵I₇ (1.55 mm) transitions and the partial donor–acceptor energy transfer and superposition of the particular emission bands. This work presents two important issues: (1) the optimization of the co-dopant concentration in germanate glasses and the construction of double-clad, multicore fibers to obtain flat broadband emission in the 1.5–2.1 mm range; (2) the development of the multicore glass–ceramic optical fibers co-doped with rare-earth and d-block metals, which enables the extension of the emission band. The effect of the rare-earth concentration on the donor–acceptor energy transfer and, finally, obtaining broadband luminescence in glasses co-doped with Er³⁺/Tm³⁺/Ho³⁺, Yb³⁺/Tm³⁺/Ho³⁺ and glass–ceramics co-doped with Ni²⁺/Er³⁺ will be presented. Constructions of the multicore characterized by broadband, eye-safe ASE will be also analyzed. Full article

Quinoxaline heterocyclic aromatic amines (HAAs) are formed during meat and fish cooking, frying, or grilling at high temperatures. They are usually generated at very low concentrations (~ng per g of a food sample). However, HAAs are classified as potent hazardous carcinogens because they may effectively damage DNA because of intercalation or strand break. Hence, chronic exposure to HAAs, even in low doses, can lead to lung, stomach, and breast cancer. HPLC is commonly applied for HAA toxins’ determination in food matrices. However, this technique is expensive, tedious, and time-consuming. Therefore, fast, simple, inexpensive, and reliable HAA determination procedures are in demand. Molecularly imprinted polymers (MIPs) are excellent examples of bio-mimicking recognition materials. Therefore, they have been used in numerous applications in selective chemosensing. Within the present research, we synthesized a nucleobase-functionalized molecularly imprinted polymer (MIP) to be used as a recognition unit for an electrochemical sensor to selectively determine 2-amino-3,7,8-trimethyl-3H-imidazo[4,5-f]quinoxaline (7,8-DiMeIQx) HAA. MIP-(7,8-DiMeIQx) film-coated electrodes were highly sensitive and selective to 7, 8-DiMeIQx. The linear dynamic concentration range of the devised capacitive chemosensor extended from 47 to 400 µM of 7, 8-DiMeIQx, and the imprinting factor was high (IF = 8.5). The MIP-(7,8-DiMeIQx) film-coated electrodes were successfully applied for 7, 8-DiMeIQx determination in meat samples. Full article

The early diagnosis of skin diseases, specifically skin cancers, might have a crucial impact on people’s health, providing information enabling the immediate implementation of the appropriate therapy and eventually saving the patient’s life. The automation of the diagnosis process based on image analysis is broadly exploited in current research. Among others, the methods of polarization analysis in imaging systems have been growing in popularity in recent years. The image processing supported by the light polarisation-sensitive device has been used in numerous imaging applications, including medical imaging, machine vision, and autonomous vehicle navigation, to name a few. The main goal of this work is to develop a new solution for a comprehensive automated skin analysis system allowing the classification of skin lesions based on multimodal image data and deep machine learning models. The main challenge of this research is to improve the sensitivity and specificity of the melanoma diagnosis and finally determine the optimal configuration of the system for the acquisition of diagnostic data. In particular, a specific setup for polarisation image analysis will be presented and discussed in the context of its sensitivity and applicability. Additionally, the method of digital analysis and classification of acquired images will be presented and discussed in detail. As part of this work, the relevance of deep learning to enhance the recognition of human skin lesions was also investigated, with a specific focus on optimizing the method of using available image datasets for the initial training of neural network models. Full article

In recent years, significant progress in polarization imaging technologies has been observed, resulting in a numerous applications of this technology in biomedical imaging, autonomous vehicle navigations, 3D surface inspection, and many others. One of the most important applications of polarizing imaging is improving the image quality in scattering media. A good example is a number of conducted research and development works on improving the quality of images in underwater vision, providing impressive application results. In this work, we focused, however, on an agriculture industry-oriented solution, addressing the challenge of high-speed, highly reliable detection of the pits in cherries. In particular, different setup configurations for polarization image analysis using liquid crystal (LC) filters were investigated, and the examination of the sensitivity of the polarization systems was performed. It should be noted here that the polarization imaging systems are usually less sensitive, and the acquired images are of insufficient quality. That is why machine learning technology was used to enhance the object detection efficiency, and the method of extracting the details of the acquired images and improving detection accuracy based on machine learning was presented. Full article

Silicon nanowire sensors have demonstrated outstanding utility in biosensing, especially for small biomolecules at extremely low concentrations. However, the sensor is less commonly applied in whole-cell monitoring, such as CAR T-cell counting during cancer treatment. The patient’s T-cells are modified to express chimeric antigen receptors (CAR), targeting specific tumor cells in CAR T-cell treatment. Therefore, the CAR T-cell level in blood is an essential parameter when it comes to determining the immune system’s reactivity to fight cancer cells. Although nanosensors are typically beneficial for early cancer diagnosis and detection, we want to expand their application and explore their usage in cancer treatment monitoring and development. Our previous works showed promising results of using nanosensors to find the most effective immunotherapy. In this work, we study the response of silicon nanowire field-effect transistors (SiNW FET) to the binding of CAR T-cells and discuss the benefits and limitations of the sensors in cell monitoring. The SiNW FETs fabricated in a top-down manner showed superior sensitivity to IgG antibodies sensing in our previous study. A peptide with a high affinity to the designed CAR T-cells immobilized on SiNW FETs to detect the cell binding. We observed distinguished signals following the number of cells binding to the sensing area. The results pave the way for using nanosensors in monitoring cancer treatment, yet they suggest some room for improvement. Full article

The need for the development of diagnostic tools, which allow for rapid and reliable analyses, is still of great importance. Recently, more and more attention has been paid to diagnostic systems, which can be used for point-of-care testing (POCT) for biomarkers and pathogens, assuring uncomplicated operations and rapid results. This presentation will cover several topics that must be considered upon designing and fabricating such devices, starting from the selection of biosensing elements and detection pathways, novel materials, and technologies, as well as appropriate analytical signal generation, data processing, miniaturization, and automatization of individual analytical steps up to cost-effectiveness. In the framework of this presentation, the electrochemical POCT system developed in our laboratory will also be presented. This system consists of: (i) disposable diagnostic cartridges containing a network of microchannels, bioreactor, specially designed carbon-based electrodes, and other elements (fabricated using a foil-to-foil technique), (ii) microelectronic reader, which can be used by doctors, nurses and paramedics under non-laboratory conditions, and (iii) a measurement data management system with accompanying infrastructure. This universal device can be applied for the determination/detection of bacterial, viral, and fungal antigens, as well as cardiovascular and hormonal biomarkers (in blood, urine, and nasal swabs and other biological samples). The applicability of the developed POCT system for the determination of certain biomarkers (e.g., C-reactive protein) will be demonstrated and evaluated. Full article

Identifying which type of lamp is installed on each public lighting pole and evaluating its luminous power is important because the new light-emitting diodes (LED)-type models are much more economical in terms of energy, and energy distribution companies need to know the consumption of public lighting energy. In Brazil, the following types of lamps exist in street lighting: incandescent, mercury vapor, sodium vapor, “mixed” lamps (composed of a mercury vapor arc tube in series with an incandescent tungsten filament), metal lamps and modern LED-type lamps. In this article, the authors describe the experimental results of the development of an automated system for recognizing lamps for public lighting based on the light pattern of each lamp, taking into account an innovative optic method, which uses the reproduction index of color (RIC) phenomenon and colored cards. Data collection in the field consisted of the task of driving a vehicle through public roads and obtaining several photos of the colored cards illuminated through the lamps of the poles and also through the use of a spectrophotometer, which is already traditionally employed for this application. Samples were obtained and used for training classifiers that use machine learning in order to identify the nature of the lamps. The tests were carried out on the city’s public roads at night, so the resulting tables also show the noise from interfering light sources (examples: lights from windows in houses and buildings, lights in stores, etc.), thus creating a very realistic scenario. The performance of the classifiers was evaluated through parameters used in artificial intelligence. Full article

Tyramine is a known biogenic amine commonly found in some fermented foods and beverages. The consumption of large amounts of food contaminated with tyramine can cause food poisoning and severe allergic reactions in the human body. A healthy person can intake about 200–800 mg in a single oral intake. However, higher concentrations of tyramine can cause food poisoning and health problems if this concentration is exceeded. In this case, it is extremely important to detect and quantify the tyramine content in food samples to ensure food quality. In the present work, we developed a poly(methylene blue) film, (PMB)-modified carbon and multi-walled carbon nanotube (MWCNT) screen-printed electrode for rapid and timely tyramine analysis. The proposed sensor was used for the oxidation of tyramine using electrochemical techniques such as cyclic voltammetry and differential pulse voltammetry (DPV). The electrochemical techniques were performed with tyramine under optimal conditions, including the supporting electrolyte, pH, working potential window, and scan rate. The PMB-modified electrode showed an oxidation potential of tyramine of 0.68 V in phosphate-buffered solution (0.1 M PBS, pH 7.4) at a scan rate of 50 mV/s. The plain screen-printed electrode showed an oxidation potential of tyramine of 0.9 V with a lower current response under the same experimental conditions. The modified method could detect tyramine over a wide linear range from 0.29 µM to 3.3 µM via DPV and 9.9 µM to 48.53 µM via cyclic voltammetry, with a low detection limit of 0.096 μM (S/N = 3). Based on the voltametric results, it was concluded that the developed modified electrodes provide accuracy, rapid analysis, selectivity, and reproducibility for tyramine analysis. Full article