Particulate matter (PM) is reported as dangerous and can cause respiratory and health issues. Regulations, based on PM concentration, have been implemented to limit human exposition to air pollution. An innovative system with Surface Acoustic Wave (SAW) sensors combined to 3 Lpm cascade impactor was developed in our team for real time mass concentration measurements. In this study, we compare the PM sensitivity of two types of SAW sensors. The first one consists of delay lines based on Rayleigh waves propagating on a Lithium Niobate Y-X 128° substrate and the second one is a based-on Love waves on AT-Quartz. The aerosols were generated from NaCl for PM2.5 and from Silicon carbide for PM10. The sensor’s response was compared to a reference sensor based on optical measurement. The sensitivity of the Rayleigh wave based sensor is clearly lower than the Love wave sensor for both PM. Although less sensitive, Rayleigh wave sensors are very promising for the development of self-cleaning sensors using RF power due to their high electromechanical factor. To check the performance of our system in real conditions, we tested the sensitivity to PM from cigarette smoke using Rayleigh SAW. The PM2.5 stage shows a phase shift while the PM10 does not respond. This result agrees with previous studies which report that the size of particles from cigarette smoke varies between 0.1 to 1.5 µm. A good correlation between the reference sensor’s response and the phase variation of SAW sensors was obtained.

Magnetic nanofibers can be fabricated by adding nanoparticles in polymer solution using the electrospinning method. The advantages of such nanofibers include a large surface-to-volume ratio and high porosity, which makes them promising for sensing applications. In addition, carbonization of such nanofibers increases electrical conductivity. In this study, the chemical and morphological properties of magnetic nanofiber mats prepared from polyacrylonitrile (PAN)/magnetite and carbonized at 500, 600, 800 and 1000 ℃. Resulting surface morphologies with some agglomerations are discussed. Addition of nanoparticles increased average fiber diameter and improved dimensional stability.

In this paper the properties of zinc oxide (ZnO) low-dimensional conductive oxide nanostructures in the aspect of their potential applications in microelectronics, in toxic gas sensors as well as checking whether they can be also used in water treatment has been determined. ZnO nanostructured porous thin films deposited by DC reactive sputtering (RS) have been deposited on Si substrates at different temperature conditions. For the surface properties and chemical morphology analysis the X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) have been used. Thanks to those methods, it is possible to obtain information on changes in the structure caused by the adsorption of various gases from the atmosphere, mainly C pollution from air, but also from the water. Investigated ZnO thin films were also tested for their photocatalytic properties performed in UV light. For this purpose the methylene blue as a dye pollutant to evaluate the activity of the nanostructures has been used. Within this work it has been observed that the ZnO thin films, which were used, react in the selected environment and their presence reduces the amount of dye. This shows that in addition to sensor properties, properly selected zinc oxide nanostructures, used so far in toxic gas sensors, can also be used in the process of water purification and treatment, which is crucial in protecting the natural environment primarily from various types of dyes or also medicines.

We have presented methods for the wireless powering of photobioreactors and photocatalytic reactors before. Wireless powering for the internal illumination of those reactors is necessary due to the limited penetration depth of photons in those media. In order to control the processes in those reactors, several sensors are necessary. In the case of photobioreactors for the cultivation of photosynthetic active microorganisms or cells, the quantities to be measured are e.g., oxygen and carbondioxide concentration, illumination, optical density and temperature. In the case of photocatalytic reactors this can also be chemical concentrations. Classically, the sensors are installed in the reactors through a drill hole. This clearly has the drawback that the desired quantity can only be measured at one point inside the reactor and the spatial distribution is unknown. Here, we present methods to develop wireless sensor systems to overcome these problems. The floating sensors are wirelessly powered by the magnetic field mentioned above. The sensor signals are transmitted via on-off modulation among other methods which are being tested. The modulation frequency is located a factor of 1.3 above the excitation frequency in order to avoid interference by harmonics. Additionally, standard frequencies like 433 MHz are under consideration, as used by similar projects. The drawback of those high frequency standard protocols is the high damping factor in electrically conducting media. The traceability of our floating sensors is another important aspect. This goal is reached by evaluating the received sensor signal amplitude with an array of receiving coils.

Organic electrochemical transistors (OECTs) have emerged as versatile electrophysiological sensors due to their high transconductance, biocompatibility, and transparent channel material. High maximum transconductances were demonstrated facilitating extracellular recordings from electrogenic cells. However, this often requires large channel dimensions which impedes high transistor densities. To improve the device performance and density, we used interdigitated OECTs (iOECTs), which feature high transconductances at small device areas. Superior device performance was achieved by systematically optimizing the electrode layout regarding channel length, number of electrode digits, and electrode width. Interestingly, the maximum transconductance does not straightforwardly scale with the channel width-to-length ratio, which is different from planar OECTs. We used optimized iOECTs for recording action potentials of cardiomyocyte-like HL-1 cells. Furthermore, we embedded the iOECTs in a matrix of polyimide to achieve flexible and transparent bioelectronic devices. These sensors exhibited electrical characteristics similar to those of solid-substrate devices even after experiencing extremely high bending strain. Finally, we used these devices to detect neurotransmitter dopamine and ATP, which play an important role not only for signal transmission in the central nervous system but also for cardiovascular, neurodegenerative, and immune deficiency diseases. Our novel aptasensor possessed ultralow detection limits, which were several orders of magnitude lower than those of the same aptasensors using an amperometric transducer principle. Our results demonstrate that interdigitated OECTs meet two requirements of both electrophysiological and biochemical sensors, namely high device performance and small channel dimensions, and might represent the optimal transducer to integrate these two types of sensors on one chip.

Alzheimer’s (AD) and Parkinson’s (PD) disease are two of the most life-threatening neuro-degenerative diseases. Due to the complex nature of the diseases, diagnosis of AD and PD in the initial stages is very difficult. Recently, studies concentrating on detection of diseases with the help of breath biomarkers have proven to be effective. In this work, we detect two reported volatile organic compound (VOC) breath biomarkers of AD and PD namely styrene (STY) and propyl benzene (PBZ) using quartz tuning fork (QTF) based sensors. These QTFs are modified using polymer films to achieve selectivity. We demonstrate that polymer modified QTF based sensors can detect these analytes with high accuracy even at low (ppm) concentrations. The polymer was selected based on results obtained from Force Spectroscopy studies where we detect the change in elastic modulus of the polymer film upon interaction with the VOCs. Based on the working principle of the sensor, few parameters like recovery time (RcT), response time (RpT) and drop in frequency (Δf) among others can be utilized for better classification. The data collected from the sensor is used to classify the behaviour of the two analytes using machine learning techniques with approximately 90–95% accuracy.

Human body produces volatile organic compounds (VOCs) due to various biological processes. Recent research indicates that these VOCs can be utilized to monitor the health of an individual’s body. Metabolism is such a biochemical process that varies according to the lifestyle of a person. Researchers have found that metabolic rate can be recorded by detecting the amount of acetone release in an individual’s breath. In this work, we demonstrate the use of a polymer modified quartz tuning fork (QTF) based sensor to detect various levels of acetone (5–400ppm). As per reports, different levels of acetone expelled in breath can correspond to presence of distinct diseases in a human being. Initially, we tested free standing polymer films for change in elastic modulus (E_m) using Atomic Force Spectroscopy. Since the combination of polystyrene and cellulose acetate (PS+CA) showed good change in E_m, this material was selected to modify the QTF-based sensors. The sensor was able to detect various concentrations of acetone with high accuracy. After testing, various machine learning algorithm were utilized to better improve classification.

In the series of recently published works, we demonstrated that plasmon assisted microscopy of nano-objects (PAMONO) technique can be successfully employed for the sizing and quantification of single viruses, virus-like particles, microvesicles and charged non-biological particles. This approach enables label-free, but specific detection of biological nano-vesicles. Hence, the sensor, which was built up utilizing plasmon-assisted microscopy, possesses relative versatility and it can be used as a platform for cell-based assays. However, one of the challenging tasks for such a sensor was the ability to reach a homogeneous illumination of the whole surface of the gold sensor slide. Moreover, in order to enable the detection of even relatively low concentrations of nano-particles the focused image area had to be expanded. Both tasks were solved via modifications of previously described PAMONO-sensor set up. Taken together, our latest findings can help to develop a research and diagnostic platform based on the principles of the surface plasmon resonance (SPR)-assisted microscopy of nano-objects.

We evaluated the minimum concentration and minimum size of magnetic particles (MPs) within which modern ultra-sensitive magnetic field sensors (MFS) can detect them. Calculations showed that magnetite MPs with specific magnetization with characteristic sizes of ≥50 nm and a concentration of CV ~ 0.1 vol.% Can be detected at a distance l ≤ 0.1 mm using MFS with a magnetic field resolution of SB ≥1nT. However, at such a close distance it is impossible to non-invasively approach the biological object of study. On the other hand, the same MPs are easily detected at l ≤ 30 mm using supersensitive MFS based on the phenomena of superconductivity (SQUID) or superconductivity and spintronics (combined MFS (CMFS)). These sensors require cryogenic operating temperatures (4–77 K), and SB ~ 10–100 fT are realized in them. Note that superparamagnetic particles or carbon nanotubes (CNTs) can also be non-invasively detected by SQUID or CMFS sensors, assuming that their concentration in the material is CV ≥ 0.0000001 vol.%. It is believed that CNTs may contain catalytic iron particles or encapsulated magnetic nanoparticles in nanotubes. Thus, modern supersensitive magnetic field sensors with SB ≤ 100 fT make it possible to detect MPs in nanoscale, submicron, and micron sizes in biological objects. They can be used for non-invasive control of organs, implants, prostheses and drug carriers in the necessary parts of the body. Particularly important is the non-invasive control of CNTs in functional biocompatible nanomaterials, which have good prospects for widespread use in medical practice.

Pyroelectric infrared sensors are often based on lead-containing materials, which are harmful to the environment and subject of governmental restrictions. Ferroelectric Hf_1−xZr_xO₂ thin films offer an environmentally friendly alternative. Additionally, CMOS integration allows for integrated sensor circuits, allowing for scalable and cost-effective applications. In this work, we demonstrate the deposition of pyroelectric thin films on area-enhanced structured substrates via thermal atomic layer deposition. Scanning electron microscopy indicates a conformal deposition of the pyroelectric film in the holes with a diameter of 500 nm and a depth of 8 μm. By using TiN electrodes and photolithography, capacitor structures are formed, which are contacted via the electrically conductive substrate. Ferroelectric hysteresis measurements indicate sizable remanent polarization of up to 331 μC cm⁻², which corresponds to an area increase of up to 15 by the nanostructured substrate. For pyroelectric analysis, a sinusoidal temperature oscillation is applied to the sample. Simultaneously, the pyroelectric current is monitored. By assessing the phase of the measured current profile, the pyroelectric origin of the signal is confirmed. The devices show sizable pyroelectric coefficients of −475 μC m⁻² K⁻¹, which is larger than that of lead zirconate titanate (PZT). Based on the experimental evidence, we propose Hf_1−xZr_xO₂ as a promising material for future pyroelectric applications.