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We investigated the design and characterization of a Lab-On-a-Chip (LoC) cell detection system primarily designed to support immunotherapy in cancer treatment. Immunotherapy uses Chimeric Antigen Receptors (CARs) and T Cell Receptors (TCRs) to fight cancer, engineering the response of the immune system. In recent years, it has emerged as a promising strategy for personalized cancer treatment. However, it requires bioreactor-based cell culture expansion and manual quality control (QC) of the modified cells, which is time-consuming, labour-intensive, and prone to errors. The miniaturized LoC device for automated QC demonstrated here is simple, has a low cost, and is reliable. Its final target is to become one of the building blocks of an LoC for immunotherapy, which would take the place of present labs and manual procedures to the benefit of throughput and affordability. The core of the system is a commercial, on-chip-integrated capacitive sensor managed by a microcontroller capable of sensing cells as accurately measured charge variations. The hardware is based on standardized components, which makes it suitable for mass manufacturing. Moreover, unlike in other cell detection solutions, no external AC source is required. The device has been characterized with a cell line model selectively labelled with gold nanoparticles to simulate its future use in bioreactors in which labelling can apply to successfully engineered CAR-T-cells. Experiments were run both in the air—free drop with no microfluidics—and in the channel, where the fluid volume was considerably lower than in the drop. The device showed good sensitivity even with a low number of cells—around 120, compared with the 107 to 108 needed per kilogram of body weight—which is desirable for a good outcome of the expansion process. Since cell detection is needed in several contexts other than immunotherapy, the usefulness of this LoC goes potentially beyond the scope considered here. [ABSTRACT FROM AUTHOR]

In this paper calculating the technological errors that arise when using capacitive sensors to measure the air gap (AG) in hydrogen generators, in particular, those caused by the inaccuracy of their installation on the machine. The results of the analysis of the error caused by the skew of the plane of the sensor electrodes relative to the constructive boring of the stator core are given. It was found that the skew of the electrodes could significantly affect the accuracy of the measurements, which in turn affects the efficiency and reliability of the hydrogen generator. A detailed assessment of the influence of this skew on the measurement results was carried out using a sensor consisting of a system of N copla-nar parallel strip electrodes located perpendicular to the core boring. A calculation scheme has been developed for the quantitative assessment of the error, which allows determining the value of the error taking into account analytical dependencies. Numerical methods were used to assess the influence of skew on the accuracy of measurements, and the results were obtained for a sensor designed for a capsule hydrogen generator of the SGK538/160-70M type. Based on the obtained results, practical recommendations have been developed to reduce the impact of skew error on measurement accuracy. Ref. 11, fig. 6.

Cooperative robots that perform safety functions as part of cooperative work with humans have been recently drawing attention. Proximity and tactile sensors that can be retrofitted to a robot's surface are important safety measures for existing robots that are not manufactured as cooperative robots to be used as cooperative robots. In this paper, a string‐like self‐capacitance‐based proximity and tactile sensor that can be easily wrapped around various types of existing robots is proposed. The novel and useful point in this paper is that it can be easily mounted on various robots by a flexible string‐like proximity and tactile sensor. The sensor module can be adjusted to the required length by connecting different numbers of modules depending on the mounting surface. As a demonstration, six prototype sensor modules were connected by each connector and wrapped around a robotic arm. The sensor modules on the robot's surface could detect an object within its proximity range and detect the rough pressure after contact. In addition, the robotic arm with the sensor modules could be controlled in real time using the data obtained from the sensor that are object detection data at proximity range. These results confirm that the proposed sensor module can be used in the proximity and tactile sensors of existing robots. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Limited or absent haptic feedback is reported as a factor hindering the continued adoption of surgical robots. This article presents a proof of concept for vibrotactile feedback integrated into a continuum robot to explore whether such feedback improves spatial perception in surgical settings. The robot is equipped with a capacitive sensor for noncontact endoscope localization, enabling spatial awareness of the robot’s tool center point (TCP) within the surgical environment. The data from the sensor is processed and transmitted to a bracelet worn by the user, which generates vibrotactile feedback. The bracelet contains four vibration motors providing tactile cues for navigation and positioning of the robot’s TCP. All subsystems are integrated into a unified system to deliver vibrotactile feedback to the user. When the user maneuvers the TCP of the robot near an object, they receive vibrotactile feedback via the bracelet. Thereby, the intensity of vibration increases as the TCP approaches the object, and the direction of the obstacle is mapped on the bracelet. Initial functional tests were performed and prove the functionality of the proposed system.

The gravimetric method is one of the most accurate for determining soil water content (SWC). Several low-cost sensors have been developed to simplify measuring water content in soil by measuring soil moisture. However, the sensor must be calibrated to determine soil moisture parameters accurately. In this research, comparative analysis, and calibration of resistive and capacitive low-cost sensors were carried out. The calibration method for each sensor uses the gravimetric water content (GWC) and volumetric water content (VWC) methods. Measuring changes in SWC using sensors is performed in real time based on internet of things (IoT). Based on the measurements of the capacitive, resistive type 1, and resistive type 2 sensors with three repetitions, the linear regression R2 values were obtained at 0.980, 0.827, and 0.942, respectively. Furthermore, a stability test is carried out to see how stable the sensor is when making measurements over a long period. The result is that the capacitive, resistive type 1, and resistive type 2 sensors have errors 1.971×10- 4, 7.001×10-4, and 6.270×10-4 . Based on the results obtained, capacitive sensors have the highest level of accuracy and stability. Furthermore, capacitive sensors are applied to IoT-based agriculture with long range (LoRa) as communication data. [ABSTRACT FROM AUTHOR]

A circular capacitive rainfall sensor can operate from non-touch mode to touch mode; that is, under the action of enough rainwater, its movable electrode plate can form a circular contact area with its fixed electrode plate. Therefore, the weight of rainwater is borne by only its movable electrode plate in non-touch mode operation but by both its movable and fixed electrode plates in touch mode operation, and the total capacitance of its touch mode operation is much larger than that of its non-touch mode operation. Essential to its numerical design and calibration is the ability to predict the deflection shape of its moveable electrode plate to determine its total capacitance. This requires the analytical solution to the fluid–structure interaction problem of its movable electrode plate under rainwater. In our previous work, only the analytical solution for the fluid–structure interaction problem before its movable electrode plate touches its fixed electrode plate was obtained, and how to numerically design and calibrate a circular non-touch mode capacitive rainfall sensor was illustrated. In this paper, the analytical solution for the fluid–structure interaction problem after its movable electrode plate touches its fixed electrode plate is obtained, and how to numerically design and calibrate a circular touch mode capacitive rainfall sensor is illustrated for the first time. The numerical results show that the total capacitance and rainwater volume when the circular capacitive rainfall sensor operates in touch mode is indeed much larger than that when the same circular capacitive rainfall sensor operates in non-touch mode, and that the average increase in the maximum membrane stress per unit rainwater volume when the circular capacitive rainfall sensor operates in touch mode can be about 20 times smaller than that when the same circular capacitive rainfall sensor operates in non-touch mode. This is where the circular touch mode capacitive rainfall sensor excels. [ABSTRACT FROM AUTHOR]

With the increasing focus on irrigation management, it is crucial to consider cost-effective alternatives for soil water monitoring, such as multi-point monitoring with low-cost soil moisture sensors. This study assesses the accuracy and functionality of low-cost sensors in a sandy loam (SL) soil amended with biochar at rates of 15.6 and 31.2 tons/ha by calibrating the sensors in the presence of two nitrogen (N) and potassium (K) commercial fertilizers at three salinity levels (non/slightly/moderately) and six soil water contents. Sensors were calibrated across nine SL-soil combinations with biochar and N and K fertilizers, counting for 21 treatments. The best fit for soil water content calibration was obtained using polynomial equations, demonstrating reliability with R 2 values greater than 0.98 for each case. After a second calibration, low-cost soil moisture sensors provide acceptable results concerning previous calibration, especially for non- and slightly saline treatments and at soil moisture levels lower than 0.17 cm3cm−3. The results showed that at low frequencies, biochar and salinity increase the capacitance detected by the sensors, with calibration curves deviating up to 30% from the control sandy loam soil. Due to changes in the physical and chemical properties of soil resulting from biochar amendments and the conductive properties influenced by fertilization practices, it is required to conduct specific and continuous calibrations of soil water content sensor, leading to better agricultural management decisions. [ABSTRACT FROM AUTHOR]

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Cellulose nanofibers (CNFs) are part of organic crystallization macromolecular compounds that can be found in bacteria's capsular polysaccharides and plant fibers. CNFs have a lot of potential as suitable matrices and advanced materials, and there have been a lot of studies done on them so far, both in terms of modifying them and inventing uses for them. In this paper, CNFs/reduced graphene oxide (GO) (rGO) nanocomposites were developed to create renewable, flexible, and cheap humidity sensors. The composite film's performance as a humidity sensor was evaluated by analyzing the variations in capacitance at different humidity levels. The synthesized composite film underwent characterization using various analytical techniques, including scanning electron microscopy (SEM), UV (ultraviolet)/Vis (visible) spectrophotometry, Fourier transform infrared spectroscopy (FTIR), and thermomechanical analysis (TMA). The sensing mechanism is elucidated based on hydrophilic functional groups within the composite material. It has been observed that 3 wt% rGO/CNF composite is the best suited for humidity sensing among all other samples. [ABSTRACT FROM AUTHOR]

In contrast to conventional non-destructive testing (NDT) and non-destructive evaluation (NDE) methodologies, including radiography, ultrasound, and eddy current analysis, coplanar capacitive sensing technique emerges as a novel and promising avenue within the field. This paper endeavors to elucidate the efficacy of coplanar capacitive sensing, also referred to as capacitive imaging (CI), within the realm of NDT. Leveraging extant scholarly discourse, this review offers a comprehensive and methodical examination of the coplanar capacitive technique, encompassing its fundamental principles, factors influencing sensor efficacy, and diverse applications for defect identification across various NDT domains. Furthermore, this review deliberates on extant challenges and anticipates future trajectories for the technique. The manifold advantages inherent to coplanar capacitive sensing vis-à-vis traditional NDT methodologies not only afford its versatility in application but also underscore its potential for pioneering advancements in forthcoming applications. [ABSTRACT FROM AUTHOR]

This paper presents a compact design of a coplanar capacitive sensor based on a printed circuit board (PCB) to apply in non-contact and non-destructive thin film thickness measurement. The capacitive sensor design is structured by two coplanar capacitors, including a reference coplanar capacitor and a sensing coplanar capacitor. Using this structure, the thin film thickness could be estimated through the imbalance voltage produced between the two signals from the reference capacitor and sensing capacitor. The size of the proposed sensor is 9.99 × 9.99 mm and the capacitor electrodes structured by shapes of spiral, interdigital, and round are studied and optimized. Those electrode structures have been modelled and simulated and the simulation results reveal that the spiral structure gives the best performance. The experiment was conducted using plastic thin films with thickness ranging from 10 to 230 µm and dielectric constants ranging from 1.375 to 3.19 to investigate the working principle of the sensor. Experiment results show the approximate linearity of the output voltage corresponding to the various thickness at measurement range from 0 to 90 µm. The sensitivity of the sensor is 13.5 and 29 mV/µm corresponding to the 1.375 and 3.19 dielectric constants of the thin films, respectively. The proposed coplanar capacitive sensor is fabricated based on the PCB platform and shows good performance with a minimum cost. The experiment results demonstrate that this sensor has a high potential to be applied in several biomedical and industrial thin film thickness measurement applications. [ABSTRACT FROM AUTHOR]

This paper presents a novel capacitive sensor-based device for detecting type-2 diabetes through blood analysis. The proposed methodology measures changes in the complex permittivity of red blood cells (RBCs) caused by elevated glucose levels, affecting their rheological and electrical properties, such as viscosity, volume, relative permittivity, dielectric loss, and AC conductivity. These changes, well-documented in the literature, alter the bio-impedance signature of RBCs, serving as an indicator for type-2 diabetes. The study examines various concentrations of normal and diabetic RBCs within a frequency range of 50 kHz to 200 kHz, chosen for its relevance to bio-impedance responses. Experimental results show that healthy RBCs in a 200 μL PBS solution have a complex permittivity (ɛmix) of 65.12 and conductivity (σmix) of 0.63 S/m, while diabetic RBCs measure 73.44 and 0.68 S/m, respectively. Additionally, the complex permittivity decreases as the cell concentration increases for both normal and diabetic RBCs. At 100% cell concentration, the average bio-impedance for diabetic blood cells is 50.3 kΩ, compared to 56.7 kΩ for healthy blood cells over the entire frequency range. The standard deviation of bio-impedance (Zmix) between 50 kHz and 200 kHz highlights the difference between healthy and diabetic RBCs, with 200 kHz measurements proving more reliable. To detect these bio-impedance changes, an interdigitated electrode (IDE) capacitive sensor with 40 capacitive elements was simulated. The complex bio-impedance (Zmix) was measured within the 50 kHz–200 kHz frequency range, providing clear differentiation between healthy and diabetic blood cells. Simulation using Finite Element Method (FEM) through COMSOL® software supports these findings, showcasing the sensor’s efficacy in type-2 diabetes detection.

Abstract Hepatocellular carcinoma (HCC) stands as the most prevalent form of primary liver cancer, predominantly affecting patients with chronic liver diseases such as hepatitis B or C-induced cirrhosis. Diagnosis typically involves blood tests (assessing liver functions and HCC biomarkers), imaging procedures such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), and liver biopsies requiring the removal of liver tissue for laboratory analysis. However, these diagnostic methods either entail lengthy lab processes, require expensive imaging equipment, or involve invasive techniques like liver biopsies. Hence, there exists a crucial need for rapid, cost-effective, and noninvasive techniques to characterize HCC, whether in serum or tissue samples. In this study, we developed a spiral sensor implemented on a printed circuit board (PCB) technology that utilizes impedance spectroscopy and applied it to 24 tissues and sera samples as proof of concept. This newly devised circuit has successfully characterized HCC and normal tissue and serum samples. Utilizing the distinct dielectric properties between HCC cells and serum samples versus the normal samples across a specific frequency range, the differentiation between normal and HCC samples is achieved. Moreover, the sensor effectively characterizes two HCC grades and distinguishes cirrhotic/non-cirrhotic samples from tissue specimens. In addition, the sensor distinguishes cirrhotic/non-cirrhotic samples from serum specimens. This pioneering study introduces Electrical Impedance Spectroscopy (EIS) spiral sensor for diagnosing HCC and liver cirrhosis in clinical serum—an innovative, low-cost, rapid (

In this work, polypyrrole (PPy) is synthesized, characterized, and employed as an active sensing material for the fabrication of humidity sensors. An 80 nm thick layer of PPy is spin coated on the pre-patterned thermally deposited silver (Ag) electrodes spaced 50 µm apart to fabricate Ag/PPy/Ag surface-type sensor. Atomic force microscopy analysis revealed granular microstructure morphology in the thin films of PPy. Additionally, X-ray diffraction (XRD), ultraviolet–visible (UV-Vis) and Fourier transformed infrared (FTIR) spectra of PPy are analyzed to study its crystallinity, optical bandgap and bond dynamics to confirm the molecular composition of PPy. The fabricated Ag/PPy/Ag sensor is characterized by varying the humidity levels between a broad range [0–95% relative humidity (RH)] at different frequencies of 120 Hz and 1 kHz. The prepared sensor showed promising sensing features such as higher sensitivity 233 nF/%RH (at 120 Hz), 83 pF/%RH (at 1 kHz), quick response time (5.20 ± 0.2 s) and recovery times (6.43 ± 0.2 s), a wide working range of relative humidity (20–95%RH) and low hysteresis gap (1.57%) with outstanding recyclability. This study reveals the potential of PPy as the best candidate for humidity sensing applications. [ABSTRACT FROM AUTHOR]

Around the world, managing and classifying solid waste is one of the most important challenges to sustaining economic growth and preserving the environment. The objective of this paper is to propose the use of Smart Ecological Points as a strategy to address the problem of solid waste management systems at the source, which has become one of the biggest problems globally, and Colombia is no exception. This article describes the current state of the problem in the country and presents a prototype of a low-cost Smart Ecological Point supported by the use of an experimental capacitive sensor and machine learning algorithms, which will reduce the time necessary for the classification of recyclable and non-recyclable waste, increasing the percentage of waste that can be reused and minimizing health risks by reducing the probability of being contaminated at the source, an aspect that is very common when waste is sorted manually. According to the results obtained, it is evident that the proposed prototype made an adequate classification of waste, generating the possibility of it being manufactured with existing technology in order to promote adequate waste classification at the source. [ABSTRACT FROM AUTHOR]

In the paper the impact of the skewness of the surface where the electrodes (sensitive the elements) of the runout capacitive sensor are located on its conversion function is considered. The sensor is designed for the usage in control and diagnostics systems of the actual technical condition of high-power hydro generators. During the assembly runout capacitive sensors may be installed with deviations relatively the normal to the surface, which is controlled, or as a result of technological errors the surface of the sensors may be located under certain angle to the shaft axis, also deviations may occur as a result of vibration or other impacts in the process of operation. It is noted that the response function of the runout capacitive sensor is greatly influenced by the deviation of the planes of electrodes location relatively the axis of the shaft surface. To assess the effect of influence of the skew error on the runout capacitive sensors response function stability, a calculation scheme was used and simulations were conducted in the Comsol Multiphysics environment. The research conducted enabled to obtain response functions for runout capacitive sensors with plane-parallel electrodes at different skewness angles of the surface of the electrodes location. Results of the experimental studies proved the correctness of the analytical propositions and data, obtained as a result of computer simulation The results of the analysis of the obtained response functions enabled to determine that the skewness influences the value of the informative component of the capacitance of the output value of response function of the runout capacitive sensors informative capacity of the output value of runout capacitive sensors and leads to the shift of the graph of the response function on additive component. [ABSTRACT FROM AUTHOR]

Hepatocellular carcinoma (HCC) stands as the most prevalent form of primary liver cancer, predominantly affecting patients with chronic liver diseases such as hepatitis B or C-induced cirrhosis. Diagnosis typically involves blood tests (assessing liver functions and HCC biomarkers), imaging procedures such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), and liver biopsies requiring the removal of liver tissue for laboratory analysis. However, these diagnostic methods either entail lengthy lab processes, require expensive imaging equipment, or involve invasive techniques like liver biopsies. Hence, there exists a crucial need for rapid, cost-effective, and noninvasive techniques to characterize HCC, whether in serum or tissue samples. In this study, we developed a spiral sensor implemented on a printed circuit board (PCB) technology that utilizes impedance spectroscopy and applied it to 24 tissues and sera samples as proof of concept. This newly devised circuit has successfully characterized HCC and normal tissue and serum samples. Utilizing the distinct dielectric properties between HCC cells and serum samples versus the normal samples across a specific frequency range, the differentiation between normal and HCC samples is achieved. Moreover, the sensor effectively characterizes two HCC grades and distinguishes cirrhotic/non-cirrhotic samples from tissue specimens. In addition, the sensor distinguishes cirrhotic/non-cirrhotic samples from serum specimens. This pioneering study introduces Electrical Impedance Spectroscopy (EIS) spiral sensor for diagnosing HCC and liver cirrhosis in clinical serum—an innovative, low-cost, rapid (< 2 min), and precise PCB-based technology without elaborate sample preparation, offering a novel non-labeled screening approach for disease staging and liver conditions. [ABSTRACT FROM AUTHOR]

An outstanding event related to the understanding of the physics of mechanical sensors occurred and was announced in 1954, exactly seventy years ago. This event was the discovery of the piezoresistive effect, which led to the development of semiconductor strain gauges with a sensitivity much higher than that obtained before in conventional metallic strain gauges. In turn, this motivated the subsequent development of the earliest micromachined silicon devices and the corresponding MEMS devices. The science and technology related to sensors has experienced noteworthy advances in the last decades, but the piezoresistive effect is still the main physical phenomenon behind many mechanical sensors, both commercial and in research models. On this 70th anniversary, this tutorial aims to explain the operating principle, subtypes, input–output characteristics, and limitations of the three main types of mechanical sensor: strain gauges, capacitive sensors, and piezoelectric sensors. These three sensor technologies are also compared with each other, highlighting the main advantages and disadvantages of each one. [ABSTRACT FROM AUTHOR]

The demand for fiber-reinforced polymers (FRPs) has significantly increased in various industries due to their attributes, including low weight, high strength, corrosion resistance, and cost-efficiency. Nevertheless, FRPs, such as glass and Kevlar fiber composites, exhibit anisotropic properties and relatively low interlaminar strength, rendering them susceptible to undetected damage. The integration of real-time damage detection processes can effectively mitigate this issue. This paper introduces a novel method for fabricating embedded capacitive sensors within FRPs using a coating technique. The study encompasses two types of fibers, namely glass and Kevlar fiber/epoxy composites. The physical vapor deposition (PVD) technique is employed to coat bundle fibers with conductive material, thus creating embedded electrodes. The results demonstrate the uniform distribution of nanoparticles of gold (Au) along the fibers using PVD, resulting in a favorable resistance of approximately ≈100 Ω. Two sensor configurations are explored: axial and lateral embedding of the coated yarn (electrodes) to investigate the influence of load direction on the coating yarn. Axial-sensor configuration specimens undergo tensile testing, showcasing a linear response to axial loads with average sensitivities of 1 for glass and 1.5 for Kevlar fiber/epoxy composites. Additionally, onset damage is detected in both types of fiber composites, occurring before final fracture, with average stress at the turning point measuring 208 MPa for glass and 144 MPa for Kevlar. The lateral-sensor configuration for glass fiber-reinforced polymer (GFRP) exhibits good linearity towards strain until failure, with average gauge factors of 0.25 and −2.44 in the x and y axes, respectively. [ABSTRACT FROM AUTHOR]

We demonstrate proprioceptive feedback control of a one degree of freedom soft, pneumatically actuated origami robot and an assembly of two robots into a two degree of freedom system. The base unit of the robot is a 41 mm long, 3-D printed Kresling-inspired structure with six sets of sidewall folds and one degree of freedom. Pneumatic actuation, provided by negative fluidic pressure, causes the robot to contract. Capacitive sensors patterned onto the robot provide position estimation and serve as input to a feedback controller. Using a finite element approach, the electrode shapes are optimized for sensitivity at larger (more obtuse) fold angles to improve control across the actuation range. We demonstrate stable position control through discrete-time proportional-integral-derivative (PID) control on a single unit Kresling robot via a series of static set points to 17 mm, dynamic set point stepping, and sinusoidal signal following, with error under 3 mm up to 10 mm contraction. We also demonstrate a two-unit Kresling robot with two degree of freedom extension and rotation control, which has error of 1.7 mm and 6.1°. This work contributes optimized capacitive electrode design and the demonstration of closed-loop feedback position control without visual tracking as an input. This approach to capacitance sensing and modeling constitutes a major step towards proprioceptive state estimation and feedback control in soft origami robotics. [ABSTRACT FROM AUTHOR]

The capability of dielectric measurements was significantly increased with the development of capacitive one-side access physical sensors. Complete samples give no opportunity to study electric susceptibility at a partial coverage of the one-side access sensor's active area; therefore, partial samples are proposed. The electric susceptibility at the partial coverage of a circular one-side access sensor with cylinders and shells is investigated for polyurethane materials. The implementation of the relative partial susceptibility permitted us to transform the calculated susceptibility data to a common scale of 0.0–1.0 and to outline the main trends for PU materials. The partial susceptibility, relative partial susceptibility, and change rate of relative partial susceptibility exhibited dependence on the coverage coefficient of the sensor's active area. The overall character of the curves for the change rate of the relative partial susceptibility, characterised by slopes of lines and the ratio of the change rate in the centre and near the gap, corresponds with the character of the surface charge density distribution curves, calculated from mathematical models. The elaborated methods may be useful in the design and optimization of capacitive OSA sensors of other configurations of electrodes, independent of the particular technical solution. [ABSTRACT FROM AUTHOR]

Gait phase monitoring wearable sensors play a crucial role in assessing both health and athletic performance, offering valuable insights into an individual's gait pattern. In this study, we introduced a simple and cost-effective capacitive gait sensor manufacturing approach, utilizing a micropatterned polydimethylsiloxane dielectric layer placed between screen-printed silver electrodes. The sensor demonstrated inherent stretchability and durability, even when the electrode was bent at a 45-degree angle, it maintained an electrode resistance of approximately 3 Ω. This feature is particularly advantageous for gait monitoring applications. Furthermore, the fabricated flexible capacitive pressure sensor exhibited higher sensitivity and linearity at both low and high pressure and displayed very good stability. Notably, the sensors demonstrated rapid response and recovery times for both under low and high pressure. To further explore the capabilities of these new sensors, they were successfully tested as insole-type pressure sensors for real-time gait signal monitoring. The sensors displayed a well-balanced combination of sensitivity and response time, making them well-suited for gait analysis. Beyond gait analysis, the proposed sensor holds the potential for a wide range of applications within biomedical, sports, and commercial systems where soft and conformable sensors are preferred. [ABSTRACT FROM AUTHOR]

Researchers have typically studied the brain by monitoring characteristic signals, such as electrophysiology and neurotransmitters by implanted electronics. Here, real‐time monitoring of dynamic deformations of the brain tissue in vivo, is demonstrated, as a new characteristic parameter that is reflective of brain states. As a proof of concept, a thin capacitive deformation sensor is fabricated and implanted between the skull and cortex, and the sensor is shown to effectively monitor dynamic deformations of the cortical surface in the rat brain as induced by respiration and heartbeat under different degrees of anesthesia. This brain monitoring approach based on deformation signals opens up a new direction for understanding the brain. [ABSTRACT FROM AUTHOR]

This study presents a biosensor fabricated based on integrated passive device (IPD) technology to measure microbial growth on solid media in real-time. Yeast (Pichia pastoris, strain GS115) is used as a model organism to demonstrate biosensor performance. The biosensor comprises an interdigital capacitor in the center with a helical inductive structure surrounding it. Additionally, 12 air bridges are added to the capacitor to increase the strength of the electric field radiated by the biosensor at the same height. Feasibility is verified by using a capacitive biosensor, and the change in capacitance values during the capacitance detection process with the growth of yeast indicates that the growth of yeast can induce changes in electrical parameters. The proposed IPD-based biosensor is used to measure yeast drop-added on a 3 mm medium for 100 h at an operating frequency of 1.84 GHz. The resonant amplitude of the biosensor varies continuously from 24 to 72 h due to the change in colony height during vertical growth of the yeast, with a maximum change of 0.21 dB. The overall measurement results also fit well with the Gompertz curve. The change in resonant amplitude between 24 and 72 h is then analyzed and reveals a linear relationship with time with a coefficient of determination of 0.9844, indicating that the biosensor is suitable for monitoring yeast growth. Thus, the proposed biosensor is proved to have potential in the field of microbial proliferation detection. [ABSTRACT FROM AUTHOR]

Based on the well logging requirements of horizontal stripper wells, the flow characteristics of the oil-water two-phase flow in the invisible horizontal tri-electrode capacitive sensor (HTCS) measurement pipeline are studied. First, an experimental device and a numerical validation model of a horizontal 20 mm glass pipeline are established to study the flow characteristics of the oil-water two-phase flow. Then, the flow characteristics of the horizontal oil-water two-phase flow in the measurement pipeline under different horizontal inclination angles are studied and the flow patterns and inclination angles suitable for the new tri-electrode capacitive sensor are discussed. Finally, using the horizontal oil-water two-phase flow loop platform of the largest oil and gas testing center in China, the dynamic response of the new capacitive sensor is studied under different inclination angles, flow rates, and water-cut conditions, and the dynamic response law is analyzed based on the simulation results.

Cryogenic fluid such as liquid hydrogen is used as the propellant for rockets. Cryogenic fluids are easy to boil and become gas-liquid two phase flow. Cavitation instability that occurs in cryogenic fluid has been a serious problem in pumps of rockets. However, this phenomenon is not fully understood. Therefore, revealing cavitation instability is an urgent matter. Previous research suggests that cavitation instability is likely to occur in conical diffusers. In this research, application of non-contact capacitive void fraction sensor to a tapered tube was attempted to measure the volume fluctuation of cavitation instability. The sensor was designed based on electric field analysis (EFA). EFA was conducted with two types of electrodes, and two fluid models. The result suggested that parallel type electrode was superior to spread out type electrode. However, low sensitivity of the sensor at the edge of electrode remained as a problem. To confirm the effect of the low sensitivity at the edge, the additional EFA was conducted. According to the results, the accuracy was the poorest when gas phase concentrated at the edge. Furthermore, flow experiment was performed to verify the accuracy of the void fraction sensor. Void fraction was measured in five flow patterns and the measurement was compared with void fraction calculated by using Smith's equation and Thom's equation. The result of the experiment corresponded with the void fraction from each equation within the margin of error. [ABSTRACT FROM AUTHOR]

In accordance with the international research experience, the maximum allowable normalized vibration displacement values for each group of machines from 15 kW to 500 MW to their respective vibration state are given. The importance of determining the nature of the vibration signal and choosing the appropriate tools for its evaluation is formulated. The analysis of the sequence of the conversion of the vibration displacement into the output voltage by a capacitive sensor, which has a long measuring circle and therefore a large error compared to the direct measurement conversion of the vibration displacement into a time interval, was carried out. Structural diagram and a mathematical model for measuring the conversion of vibration displacement into capacitor capacity are proposed. Analytical and graphical dependence of the capacity of the parametric sensor on the displacement of the plates under the action of vibration displacement in the justified range of their possible change from 20 to 120 μm was obtained. It was established that in this range of changes in vibration displacement, the capacity of the capacitor changes within such limits from 3 to 18 nF. A mathematical model for measuring the transformation of vibration displacement into a time interval was obtained and a graphical dependence of the duration of the time interval τ on the change in the displacement a of the plates under the action of vibration displacement in the set range of movement of the capacitor plates from 20 to 120 μm was given. It is shown that the value of the time constant in this range varies from 100 to 325 μs. A scheme of a capacitive measuring transducer of vibration displacement in a time interval and time diagrams explaining the principle of its operation are proposed. It is shown that the quantization error will not exceed 0.1 % during further measurement conversion into a binary code. The error from the insensitivity zone of the comparator is of the same order. The use of such an approach will allow formalizing further research into the measuring channels of vibration monitoring systems of electromechanical systems and complexes [ABSTRACT FROM AUTHOR]

An accurate humidity measurement is essential in various industries, including product stability, pharmaceutical and food preservation, environmental control, and precise humidity management in experiments and industrial processes. Crafting effective humidity sensors through precise material selection is crucial for detecting minute humidity levels across various fields, ultimately enhancing productivity and maintaining product quality. Metal–organic frameworks (MOFs), particularly zeolitic imidazolate frameworks (ZIFs), exhibit remarkable properties and offer a wide range of applications in catalysis, sensing, and gas storage due to their structural stability, which resembles zeolites. The previous research on MOF-based humidity sensors have primarily used electrical resistance-based methods. Recently, however, interest has shifted to capacitive-based sensors using MOFs due to the need for humidity sensors at low humidity and the resulting high sensitivity. Nevertheless, further studies are required to optimize particle structure and size. This study analyzes ZIF-8, a stable MOF synthesized in varying particle sizes, to evaluate its performance as a humidity sensor. The structural, chemical, and sensing properties of synthesized ZIF-8 particles ranging from 50 to 200 nanometers were examined through electron microscopy, spectroscopic, and electrochemical analyses. The fabricated copper electrodes combined with these particles demonstrated stable and linear humidity sensing capabilities within the range of 3% to 30% relative humidity (RH). [ABSTRACT FROM AUTHOR]

The design, especially the numerical calibration, of a circular touch mode capacitive pressure sensor is highly dependent on the accuracy of the analytical solution of the contact problem between the circular conductive membrane and the rigid plate of the sensor. In this paper, the plate/membrane contact problem is reformulated using a more accurate in-plane equilibrium equation, and a new and more accurate analytical solution is presented. On this basis, the design and numerical calibration theory for circular touch mode capacitive pressure sensors has been greatly improved and perfected. The analytical relationships of pressure and capacitance are numerically calculated using the new and previous analytical solutions, and the gradually increasing difference between the two numerical calculation results with the gradual increase in the applied pressure is graphically shown. How to use analytical solutions and analytical relationships to design and numerically calibrate a circular touch mode capacitive pressure sensor with a specified pressure detecting range is illustrated in detail. The effect of changing design parameters on capacitance–pressure analytical relationships is comprehensively investigated; thus, the direction of changing design parameters to meet the required or desired range of pressure or capacitance is clarified. [ABSTRACT FROM AUTHOR]

This paper introduces an innovative method for the analysis of alcohol–water droplets on a CMOS capacitive sensor, leveraging the controlled thermal behavior of the droplets. Using this sensing method, the capacitive sensor measures the total time of evaporation (ToE), which can be influenced by the droplet volume, temperature, and chemical composition. We explored this sensing method by introducing binary mixtures of water and ethanol or methanol across a range of concentrations (0–100%, with 10% increments). The experimental results indicate that while the capacitive sensor is effective in measuring both the total ToE and dielectric properties, a higher dynamic range and resolution are observed in the former. Additionally, an array of sensing electrodes successfully monitors the droplet–sensor surface interaction. However practical considerations such as the creation of parasitic capacitance due to mismatch, arise from the large sensing area in the proposed capacitive sensors and other similar devices. In this paper, we discuss this non-ideality and propose a solution. Also, this paper showcases the benefits of utilizing a CMOS capacitive sensing method for accurately measuring ToE. [ABSTRACT FROM AUTHOR]

Abstract Researchers have typically studied the brain by monitoring characteristic signals, such as electrophysiology and neurotransmitters by implanted electronics. Here, real‐time monitoring of dynamic deformations of the brain tissue in vivo, is demonstrated, as a new characteristic parameter that is reflective of brain states. As a proof of concept, a thin capacitive deformation sensor is fabricated and implanted between the skull and cortex, and the sensor is shown to effectively monitor dynamic deformations of the cortical surface in the rat brain as induced by respiration and heartbeat under different degrees of anesthesia. This brain monitoring approach based on deformation signals opens up a new direction for understanding the brain.

We demonstrate proprioceptive feedback control of a one degree of freedom soft, pneumatically actuated origami robot and an assembly of two robots into a two degree of freedom system. The base unit of the robot is a 41 mm long, 3-D printed Kresling-inspired structure with six sets of sidewall folds and one degree of freedom. Pneumatic actuation, provided by negative fluidic pressure, causes the robot to contract. Capacitive sensors patterned onto the robot provide position estimation and serve as input to a feedback controller. Using a finite element approach, the electrode shapes are optimized for sensitivity at larger (more obtuse) fold angles to improve control across the actuation range. We demonstrate stable position control through discrete-time proportional-integral-derivative (PID) control on a single unit Kresling robot via a series of static set points to 17 mm, dynamic set point stepping, and sinusoidal signal following, with error under 3 mm up to 10 mm contraction. We also demonstrate a two-unit Kresling robot with two degree of freedom extension and rotation control, which has error of 1.7 mm and 6.1°. This work contributes optimized capacitive electrode design and the demonstration of closed-loop feedback position control without visual tracking as an input. This approach to capacitance sensing and modeling constitutes a major step towards proprioceptive state estimation and feedback control in soft origami robotics.

ObjectiveThe soil moisture content is a crucial factor that directly affected the growth and yield of crops. By using a soil measurement instrument to measure the soil's moisture content, lots of powerful data support for the development of agriculture can be provided. Furthermore, these data have guiding significance for the implementation of scientific irrigation and water-saving irrigation in farmland. In order to develop a reliable and efficient soil moisture sensor, a new capacitive soil moisture sensor based on microfabrication technology was proposed in this study. Capacitive moisture sensors have the advantages of low power consumption, good performance, long-term stability, and easy industrialization.MethodThe forked electrode array consists of multiple capacitors connected in parallel on the same plane. The ideal design parameters of 10 μm spacing and 75 pairs of forked electrodes were obtained by calculating the design of forked finger logarithms, forked finger spacing, forked finger width, forked finger length, and electrode thickness, and studying the influence of electrode parameters on capacitance sensitivity using COMSOL Multiphysics software. The size obtained an initial capacitance on the order of picofarads, and was not easily breakdown or failed. The sensor was constructed using microelectromechanical systems (MEMS) technology, where a 30 nm titanium adhesion layer was sputtered onto a glass substrate, followed by sputtering a 100 nm gold electrode to form a symmetrical structure of forked electrodes. Due to the strong adsorption capacity of water molecules of the MoS2 (molybdenum disulfide) layer, it exhibited high sensitivity to soil moisture and demonstrated excellent soil moisture sensing performance. The molybdenum disulfide was coated onto the completed electrodes as the humidity-sensitive material to create a humidity sensing layer. When the humidity changed, the dielectric constant of the electrode varied due to the moisture-absorbing characteristics of molybdenum disulfide, and the capacitance value of the device changed accordingly, thus enabling the measurement of soil moisture. Subsequently, the electrode was encapsulated with a polytetrafluoroethylene (PTFE) polymer film. The electrode encapsulated with the microporous film could be directly placed in the soil, which avoided direct contact between the soil/sand particles and the molybdenum disulfide on the device and allowed the humidity sensing unit to only capture the moisture in the soil for measuring humidity. This ensured the device's sensitivity to water moisture and improved its long-term stability. The method greatly reduced the size of the sensor, making it an ideal choice for on-site dynamic monitoring of soil moisture.Results and DiscussionsThe surface morphology of molybdenum disulfide was characterized and analyzed using a Scanning Electron Microscope (SEM). It was observed that molybdenum disulfide nanomaterial exhibited a sheet-like two-dimensional structure, with smooth surfaces on the nanosheets. Some nanosheets displayed sharp edges or irregular shapes along the edges, and they were irregularly arranged with numerous gaps in between. The capacitive soil moisture sensor, which utilized molybdenum disulfide as the humidity-sensitive layer, exhibited excellent performance under varying levels of environmental humidity and soil moisture. At room temperature, a humidity generator was constructed using saturated salt solutions. Saturated solutions of lithium chloride, potassium acetate, magnesium chloride, copper chloride, sodium chloride, potassium chloride, and potassium sulfate were used to generate relative humidity levels of 11%, 23%, 33%, 66%, 75%, 84%, and 96%, respectively. The capacitance values of the sensor were measured at different humidity levels using an LCR meter (Agilent E4980A). The capacitance output of the sensor at a frequency of 200 Hz ranged from 12.13 pF to 187.42 nF as the relative humidity varied between 11% to 96%. The sensor exhibited high sensitivity and a wide humidity sensing range. Additionally, the frequency of the input voltage signal had a significant impact on the capacitance output of the sensor. As the testing frequency increased, the response of the sensor's system decreased. The humidity sensing performance of the sensor was tested in soil samples with moisture content of 8.66%, 13.91%, 22.02%, 31.11%, and 42.75%, respectively. As the moisture content in the soil increased from 8.66% to 42.75%, the capacitance output of the sensor at a frequency of 200 Hz increased from 119.51 nF to 377.98 nF, demonstrating a relatively high sensitivity. Similarly, as the frequency of the input voltage increased, the capacitance output of the sensor decreased. Additionally, the electrode exhibited good repeatability and the sensitivity of the sensor increased significantly as the testing frequency decreased.ConclusionsThe capacitive soil moisture sensor holds promise for effective and accurate monitoring of soil moisture levels, with its excellent performance, sensitivity, repeatability, and responsiveness to changes in humidity and soil moisture. The ultimate goal of this study is to achieve long-term monitoring of capacitance changes in capacitive soil moisture sensors, enabling monitoring of long-term changes in soil moisture. This will enable farmers to optimize irrigation systems, improve crop yields, and reduce water usage. In conclusion, the development of this innovative soil moisture sensor has the potential to promote agricultural modernization by providing accurate and reliable monitoring of soil moisture levels.

The advantages and features of the use of pressure accumulators (CA) with blocks of conic springs for restoring and stabilizing the pressing pressure of the stator core of a powerful turbogenerator (TG), which are installed under the tightening nuts or instead of them on the threaded ends of the tightening prisms of the core, are described. It is shown that the measurement of the displacement of the compression disc spring in the CA makes it possible to estimate the current state of the pressing pressure. The use of a capacitive sensor of linear displacements, placed outside the CA, to control the movement of the spring block in the caseless CA is substantiated. According to the specified design parameters of the caseless CA and the value of the maximum stroke of the plate springs in it, a capacitive sensor with its specified characteristics was developed. The method of monitoring the state of the TG stator core using the CA system with capacitive sensors on each CA and the control method with the alternate use of one disk spring travel meter are described. Ref. 14, fig. 6.

Alcohol ingested by humans can be analyzed via breath tests; however, approximately 1% can be excreted via the skin. In this paper, we present a capacitive sensor using hydrophobically treated anodic aluminum oxide (AAO) capable of detecting alcohol excreted through the epidermis. The degree of hydrophobicity based on the duration of exposure to 3-aminopropyltriethoxysilane vapor comprising a small number of Si–NH2 functional groups on the AAO surface was confirmed and the optimal exposure time was confirmed to be 60 min. The hydrophobized AAO showed a 4.8% reduction in sensitivity to moisture. Simultaneously, the sensitivity of the sensor to ethanol decreased by only 12%. Lastly, the fabricated sensor was successfully operated by attaching it to an ankle-type breathalyzer. [ABSTRACT FROM AUTHOR]

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Copyright of Smart Agriculture is the property of Smart Agriculture Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, a device for measuring soil moisture at multiple depths was designed and implemented. Measuring soil moisture data allows you to set the optimal moisture environment for crop growth and helps increase production and yield through healthy growth of crops. In addition, the importance of measuring accurate soil moisture data is being emphasized to interpret and prevent natural disasters such as droughts and floods caused by climate change. However, it is difficult to measure moisture changes at the depth of crop roots by measuring moisture on the soil surface. Therefore, in this paper, a soil moisture measurement device was implemented by integrating capacitive sensors and environmental sensors. The device's features include variable measurement of moisture at a depth of approximately 10 to 60 cm rather than the soil surface, and real-time wireless transmission using Lora. When water was supplied to river sand in 10mL units as an experimental method, the measurement range of the implemented sensor was 0~70mL, and it was confirmed that the sensor responded sensitively to changes in moisture in the soil. [ABSTRACT FROM AUTHOR]

For effective measurement and collection of soil moisture information an electronic system has been designed and developed. Since soil water holding capacity varies depending on the soil structure so a sensor probe is designed with a sensing system for efficient detection of moisture in the soil. The capacitive sensor probe is designed to detect a change of capacitance response from 15 to 1200pF. According to this change of capacitance response, a series RLC network is designed to find out an optimum frequency for efficient sensing of moisture. The designed sensor probe is calibrated for three different types of soil (silt/sandy/clay) using Thermogravimetric (TG) Analysis. To process the sensing data, DataLogger (DL) algorithm has been developed and programmed in an ARM controller for monitoring and storing of data on server using IoT (Internet of Things). For the designed sensing circuit, an optimum frequency of 218 kHz is found out from the resonance curve. At this frequency, the response of electronic interfacing circuit is observed in terms of capacitance and voltage. Data obtained from linear analysis (R square: ~ 0.99, Pearson's r: ~ 0.99) shows that the designed sensor system responds appreciably to the moisture change. [ABSTRACT FROM AUTHOR]