Solid Contact Research Articles

Comparative Study of Potassium Ion-Selective Electrodes with Solid Contact: Impact of Intermediate Layer Material on Temperature Resistance

This paper presents a comparative study on the temperature resistance of solid-contact ion-selective electrodes, depending on the type of solid-contact material. Five types of potassium electrodes, with a valinomycin-based model membrane, were developed using different types of mediation layers, namely a conductive polymer (poly(3-octylthiophene-2,5-diyl) and a perinone polymer), multi-walled carbon nanotubes, copper(II) oxide nanoparticles, and a nanocomposite consisting of multi-walled carbon nanotubes and copper(II) oxide. We examined how the measurement temperature (10 °C, 23 °C, and 36 °C) affects the sensitivity, measurement range, detection limit, selectivity, as well as the stability and reversibility of the electrode potential. Electrodes modified with a nanocomposite (GCE/NC/ISM) and a perinone polymer (GCE/PPer/ISM) showed the best resistance to temperature changes. An almost Nernst response and a stable measurement range and the lowest detection limit values for each temperature were obtained for them. The introduction of mediation layers significantly improved the stability and potential reversibility of all the modified electrodes relative to the unmodified electrode (GCE/ISM). Still, it was the GCE/PPer/ISM and GCE/NC/ISM that stood out from the others, with stability of 0.11 and 0.12 µV/s for 10 °C, 0.05 and 0.08 µV/s for 23 °C, and 0.06 and 0.09 µV/s for 36 °C, respectively.

The Evolution of Nanoscale Third Body Layer Revealed by Graphite Structural Superlubric Contact.

Revealing the evolution of nanoscale third bodies confined between sliding surfaces is essential to understanding the friction and electrical properties for solid contacts. Here, with graphite/graphite contacts in structural superlubricity, a state of no wear and ultralow friction, we in situ reveal the morphological evolution of a third body layer introduced by air through measuring friction and conductance during cyclic hold-slide tests. The directional transport of confined molecules causes apparent elastic deformation of the third body layer, leading to local graphite/graphite direct contact. Together with a proposed quantum tunneling effective thickness (deff) model, a constant volume of third bodies with a sub-nm thickness is observed. Our work provides a feasible approach to investigate the kinetics of substances under nanoscale confinement.

Development of a hydroponic device using potassium Ion-Selective electrode and neural network technology

The rapid development of modern agricultural biotechnology and information technology has become a key driver of modern agricultural growth. The demand for ion detection is prevalent in all aspects of agriculture. This study details the research on an ion sensor agricultural system using potassium (K) ion-selective electrodes (ISEs). The main emphasis is on the application of artificial neural networks (ANNs) for driving ISE development of accuracy. ISEs based on solid contact with metal oxides, specifically manganese dioxide, are studied. Moreover, the design details of an ion signal acquisition device using the NI-9205 acquisition card and LabVIEW are presented. Finally, based on experimental results of nutrient solution samples, ANNs show better performance than the multiple linear regression method. The mean relative error of K-ISE detection was maintained within 4%. This study thoroughly discusses ISE technology to promote its adoption in agriculture.

Modeling of the roughness effect in normal contact of deformable solids

Modeling of the roughness effect in normal contact of deformable solids

The fluid mechanics of spray cleaning: when the stress amplification at the contact lines of impacting droplets nano-scraps particles

In spray cleaning, a multitude of small drops, violently accelerated by a high-speed gas stream, strike a dirty surface. This process is extremely effective: very little dirt can resist it. This is true even for dirt particles whose characteristic size is less than 100 nm. Spray cleaning is classically modelled by balancing particle adhesion with either inertial stress or viscous shear near the surface, the latter being calculated using droplet size and velocity as the characteristic length and velocity. This results in dimensionless numbers that are often well below one, suggesting that the mechanical stress exerted on the surface by the drop impact that detaches the particle is not well captured. Using quantitative nanoscale measurements, we show that the remarkable efficiency of spray cleaning results from the forced spreading of each droplet on the surface, which generates an unsteady and inhomogeneous shear confined to a boundary layer entrained in the wake of the liquid–solid contact line. In the very first moments of impact, the boundary layer is extremely thin, yielding a gigantic stress: the contact line of the spreading droplets sweeps all the surface particles away. We propose a quantitative model of spray cleaning based on this unsteady surface stress, which agrees well with (i) experimental data obtained with spray droplets of $34\ \mathrm {\mu }$ m mean radius impacting the surface to be cleaned at a mean velocity ranging between 30 and 70 m s $^{-1}$ and contamination by nanoparticles of varying nature and shape and (ii) data in the literature on spray cleaning.

Ultralow Resistivity of the Graphite/Au van der Waals Heterostructure in the Structural Superlubric State.

Structural superlubricity, a state of zero wear and ultralow friction between two sliding solid contact surfaces, offers transformative potential for NEMS/MEMS switches, relays, logic devices, and sensors. Ultralow resistivity in two-dimensional (2D)/three-dimensional (3D) van der Waals heterostructures is critical for most applications. Using high-vacuum thermal evaporation of Au, we fabricate defect-free single-crystal graphite/Au van der Waals heterostructures in the SSL state, achieving a record-low resistivity of 2.542 × 10-12 Ω m2, which is 6 times lower than that of prior reports. The resistance remains stable under varying loads and speeds, attributed to the all-atom contact and defect-free single-crystal graphite. Thermal evaporation of Au preserves the single-crystal graphite 2D lattice, enabling lower resistivity. The 2D/3D SSL heterostructure is simpler, more stable, and broadly more applicable than 2D/2D systems. It establishes the electrical foundation for applying superlubric technology in micro-nano devices and provides a platform for studying fundamental behaviors at 2D/3D sliding interfaces, including electron friction, phonon dissipation, and electron transfer.

An Experimentally Designed Sertaconazole Sensor for Selective and Enhanced Potentiometric Response: Determination in Cream, Plasma & in Presence of Other Imidazoles

AbstractA two‐step experimental design was followed to develop a potentiometric solid contact ion‐selective electrode for sertaconazole (STN) determination. A full factorial design was first employed in screening for the best cation exchanger, ionophore and conducting polymer. Amounts of the selected cation exchanger; tetrakis[3,5‐bis(trifluoromethyl)phenyl] borate (TFPB), and ionophore; calix[6]arene (CX6), incorporated in STN sensing membrane were then optimized with the aid of face centered composite design. Calibration slope, detection limit and electrode selectivity in presence of another imidazole‐classified drug; econazole, were the selected responses in both designs. The optimized ion‐sensing membrane, containing 1.0 mg TFPB and 9.9 mg CX6, showed enhanced responses compared to the primarily screened ones. This optimized electrode exhibited a linear response over a concentration range of 1.0×10−6‐−1.0×10−3 M with a Nernstian slope of 57.50 mV/decade. The detection limit was lowered by about one order of magnitude via this optimization to equal 3.16×10−7 M. The proposed electrode was successfully challenged for STN determination in the presence of other imidazoles. It was then used for STN determination in cream and spiked plasma as an example of biological fluid. Our proposed potentiometric method was finally compared to the reported chromatographic ones in terms of sensitivity, and greenness evaluation by the widely applicable Analytical GREEnness (AGREE) tool. The comparison revealed the superiority of our method in terms of sensitivity and sustainability.

Forces and grain–grain contacts in bidisperse beds sheared by viscous fluids

In a recent paper [Gonzalez et al., “Bidisperse beds sheared by viscous fluids: Grain segregation and bed hardening,” Phys. Fluids 35, 103326 (2023)], we investigated the motion of grains within a granular bed sheared by a viscous fluid and showed how segregation and hardening occur in the fluid- (bedload) and solid-like (creep) regions. In this paper, we inquire further into the mechanisms leading to grain segregation in a bidisperse bed, and how the forces are distributed. For that, we carried out numerical simulations at the grain scale by using computational fluid dynamics–discrete element method, with which we were able to track the positions, velocities, forces, and solid contacts underwent by each grain. We show that during the upward motion of large grains the direct action of fluid forces is significant in the middle and upper parts of the bedload layer, while only contact forces are significant in the creep layer and lower part of the bedload layer. We also show that in all cases the particles experience a moment about a −45° contact point (with respect to the horizontal plane) when migrating upward, whether entrained by other contacts or directly by the fluid. In addition, we show the variations in the average solid–solid contacts, and how forces caused either by solid–solid contacts or directly by the fluid are distributed within the bed. Our results provide the relationship between force propagation and reorganization of grains in sheared beds, explaining mechanisms found, for example, in river beds and landslides.

An experimental investigation into the characteristics of ammonia dissociation in a Bubbling Fluidised Bed

Ammonia (NH3) dissociation is of an initial and very important step during its combustion process. This study therefore systematically investigates the effect of reaction temperature (650–950 °C), fluidisation number (0.83–2.50) and static bed depth (0–25 mm) on NH3 dissociation in a laboratory-scale Bubbling Fluidised Bed (BFB). By analysing the concentrations of H2 and N2 in the effluent using gas chromatography, results show that the conversion ratio of NH3 in BFB was merely 0.26%–0.29% at 650 °C but increased significantly to 18.1%–25.3% at 950 °C. This highlights the importance of temperature in promoting NH3 dissociation. However, as fluidisation number increased from 1.0 to 2.5, attributing to a decrease in gas – solid contact time, the conversion ratio of NH3 decreased correspondingly from the highest 20.7%–5.7%. Moreover, as static bed depth increased from 15 mm to 25 mm, the conversion ratio of NH3 increased slightly from 21.5% to 26.8%, both of which were found to be higher than that without bed particles. Clearly, NH3 dissociation is enhanced by the bed material depth but is also dependent on the gas – solid contact time. In addition, by measuring the temperature distribution in the BFB reactor, a temperature drop of ca. 20 °C near the distributor was confirmed, showing a strong effect of endothermicity during NH3 dissociation. These would provide an improved comprehension on the mechanisms of NH3 dissociation and offer theoretical guidance for optimising the combustion processes in BFB burning NH3.

Bistability-enhanced elastocaloric cooling device based on a natural rubber foil

A novel solid-state elastocaloric cooling device is presented, making use of a bistable actuation mechanism for loading of a natural rubber (NR) foil refrigerant. The thicknesses of the foil refrigerants are 290 and 650 μm in an initial undeformed state, while their lateral size is 9 × 26.5 mm2. Owing to the large surface-to-volume ratio of the NR foils, heat transfer to the heat sink and source is accomplished by a solid–solid mechanical contact. The loading mechanism consists of a rotating lever arm providing for stable positions at contact to the heat sink and source, which allows for significant power saving during elastocaloric cycling. In addition, the negative biasing associated with bistability favors good thermal contact at the end positions, which improves heat transfer resulting in a maximum temperature span ΔTdevice of 4.2 K in the strain range of 300%–700% under adiabatic conditions. The coefficient of performance of the device COPdevice reaches values up to 5.7 for foil refrigerants of 290 μm thickness. The maximum cooling power is 214 mW corresponding to a specific cooling power of 3.4 Wg−1.

Impact of Ultrasonic Welding Parameters on Weldability and Sustainability of Solid Copper Wires with and without Varnish.

This article contains an advanced analysis of the properties of solid wire electrical contacts produced by ultrasonic welding, both with and without varnish. The main disadvantage of ultrasonic welding of thin wires is the inability to achieve acceptable peel force and tensile strength, which is mainly due to the deformation and thinning of the wires. This study deals with ultrasonic welding using a ring of thin solid copper wires that minimises the deformation and thinning of the wires. The influence of welding parameters such as energy, pressure and amplitude were systematically analysed. Based on these parameters, the optimum welding programme and control method was determined to weld unvarnished and varnished wires. The investigations included electrical resistance tests, optical microscopy, micro-hardness measurements, peel tests and tensile tests, and the measurement of energy consumption. The results showed no significant differences in microstructure and hardness between varnished and unvarnished joints. Ultrasonic joints of varnished wires achieved lower electrical conductivity (by 38%), lower tensile strength (by 3%) and higher peel strength (by 7%), while the welding process was more sustainable in terms of energy (by 6.6%) and time consumption (without preprocessing).

Investigation into the Mitigation of Crevice Corrosion of Aluminum–Copper Contacts in Seawater by Regulating the Contact Surface Roughness

Crevice corrosion for dissimilar metal contacts is a key problem in engineering applications. This work has attempted to prevent the ingress of corrosive media into the crevice between aluminum alloy and copper by controlling the roughness (machining accuracy) of the contact surfaces. Both electrochemical and alternating dry/wet immersion tests were used to investigate the corrosion resistance of aluminum alloy–copper contacts with different contact surface roughness. Considering the relationship between the contact surface roughness and the liquid–solid contact angle and the crevice width, a finite element model based on fluid dynamics theory is established to analyze the effect of the contact surface roughness on the seawater infiltration depth in the contact crevice. The distribution of corrosion products on the aluminum alloy and copper surfaces is observed by optical microscope and scanning electron microscope. The phase composition of the corrosion products is analyzed by X‐ray diffraction technique. The results show that the corrosion resistance of the contact improves as the roughness of the contact surface decreases. This is attributed to the fact that the infiltration of seawater is retarded due to the decrease in the crevice width and increase in the contact angle with the decrease in the contact surface roughness.

Solid Contact Microfabricated Electrode for Point-of-Care Electrochemical Determination of a Parasitic Infection Managing Medication Based on a Transducer Layer Prussian Blue Analogue Decorated with Multi-Walled Carbon Nanotubes

Point-of-care diagnostics (POC), often known as on-site testing has evolved as a quick and accurate methodology for analyzing and therapeutic monitoring of drugs. The aim of this study is to provide cost-effective, simple, portable, reliable, and ecofriendly methodology for determination of Tinidazole (TD); potentiometric sensors are found to be an ideal fit for achieving these goals. An advanced microfabricated ion selective electrode is provided employing two-steps procedure. The first is selecting the most selective ionophore for TD determination while the second is to improve the stability and detection limit upon doping the nanoparticles as ion to electron transducer layer between the microfabricated copper electrode and the ion selective media as it can decrease potential drift from 8.0 to ∼1.0 mV h−1. Nernstian potentiometric results were obtained for TD in range of concentration 1.0 × 10−3 to 1.0 × 10−8 M, its slope was −57.43 mV/decade with lower detection limits 2.55 × 10−9 M. Essential values of the adopted sensor are fast and stable response time (9 ± 2 s). The provided potentiometric approach succeeds to asses TD in its pure and pharmaceutical forms, furthermore in different biological fluids with satisfactory results.

Optimization of the polyaniline solid contact in potentiometric sensors for detection of paralytic shellfish toxins in mussels

The present study optimized the properties of the electropolymerized polyaniline (PANI) solid inner contact for a potentiometric chemical sensor by varying the thickness of the polymer layer. A potentiometric sensor for detecting one of the paralytic shellfish toxins, decarbamoyl saxitoxin (dcSTX), in mussel extracts was selected as a case study. The plasticized PVC membrane composition, developed in previous work for the detection of this toxin, was used. The structure and electrical properties of PANI layers of different thicknesses were studied using scanning electron microscopy and electrochemical impedance spectroscopy. The effect of PANI solid contact thickness on the characteristics of the potentiometric sensor, including sensitivity, detection limit, and selectivity to dcSTX in buffer solutions and mussel extracts, was evaluated. The formation of a water layer at the inner solid contact and PVC membrane interface was investigated using electrochemical impedance spectroscopy and a water test. PANI layer thickness 1.1 µm was found to be optimal for solid inner contact for potentiometric sensor with PVC membrane providing highest sensitivity and selectivity.

3D-Printed Transducers for Solid Contact Potentiometric Ion Sensors: Improving Reproducibility by Fabrication Automation.

3D printing technology has become attractive in the development of electrochemical sensors as it offers automation in fabrication, customization on-demand, and reproducibility, among other features. Nonetheless, to date, solid contact potentiometric ion sensors have remained overlooked using this technology. Thus, the novelty of this work relies on demonstrating for the first time the usefulness of the multimaterial 3D printing approach to manufacture potentiometric ion-selective electrodes. The significance is indeed twofold. First, we discovered that by using the polyethylene terephthalate glycol (PETg) and polylactic acid-carbon black (PLA-CB) filaments together with a rational electrode design containing a well to accommodate the ion-selective membrane, a tight seal among all of the sensing materials is obtained. Importantly, this has mainly impacted the electrode-to-electrode reproducibility (ERSD0 ± 3 mV). Second, 75 ready-to-use electrodes can be printed in less than 3.5 h in a completely automated manner at a cost of ∼0.32 €/sensor. This feature may positively impact the suitability of further scaled-up production as well as the possibility of application in low-resource contexts. Overall, the presented outcomes are expected to encourage certain research directions to adopt using multimaterial 3D-printing approaches for producing highly reproducible solid contact potentiometric ion-selective electrodes, but are not restricted to them.

Novel usage of perinone polymer as solid contact in ion-selective electrodes

The paper presents the use of a new perinone polymer (PPer) as an intermediate layer and the development of a new type of potassium ion-selective electrodes with solid contact. The PPer layer was applied to the surface of a glassy carbon electrode using potentiodynamic polymerization from an electrolyte solution containing perinone precursors (Per). Subsequently, the surface of the electrode after application of the polymer was examined using a microscope and an optical profilometer. To check the quality of the prepared ion-selective electrodes, a series of tests were carried out and the analytical and electrical parameters of the electrodes were determined. Electrode modifications using PPer improved the electrode parameters, especially the stability and reversibility of the potential, compared to the control electrode covered only with an ion-sensitive membrane. The best electrode was the electrode modified with PPer applied in 10 cycles, which, as a result of the modification, allowed better parameters to be obtained – slope 58.86 mV/decade, LOD 1.2 × 10−6 M, linearity range 5 × 10−6 – 1 × 10−1 M. A very low short-term potential drift value of 2.7 × 10−4 mV/s was obtained as well as an extremely satisfactory SD value of 1.1 mV from E0 measurements. The modification also improved electrical properties and gave a negative result of the water layer test.

Polymer‐Sorbent Direct Air Capture Contactors with Complex Geometries 3D‐Printed via Templated Phase Inversion

AbstractLow‐cost direct air capture (DAC) systems require efficient gas–solid contactors. These contactors provide rapid rates of heat and mass transport with minimal pressure drops. Triply periodic minimal surfaces (TPMS) are a class of geometries that are shown to have heat transfer properties that exceed those of other geometries, and these benefits are expected to manifest in mass transfer as well due to the analogies between heat and mass transfer. However, creating TPMS contactors is difficult using conventional manufacturing techniques such as injection molding. Non‐solvent‐induced phase separation (NIPS) of a polymeric ink containing the adsorbent is one way to construct adsorption contactors with excellent mass transport rates, but contactors have to date only been fabricated in simple geometries (e.g., films, fibers). This study demonstrates that NIPS of polymeric inks occurs within a simultaneously‐dissolving, water‐soluble, 3D‐printed template. This templated phase inversion (TPI) technique can create seemingly unlimited macroscopic architectures, including TPMS contactors, using a variety of potential DAC adsorbents, including zeolite, silica, activated carbon, and metal–organic frameworks. SEM, micro‐computed tomography, and nitrogen adsorption experiments reveal the microscopic pore structures and macroscopic geometries of the resulting sorbent contactors. TPMS DAC contactors with poly(ethyleneimine)/silica adsorbents are shown to have CO2 capture performances that rival or exceed other contactor geometries.

Miniature and cost‐effective self‐powered triboelectric sensing system toward rapid detection of puerarin concentration

AbstractThe detection of puerarin concentration is an essential capability to study the functional role of the Pueraria root as a natural medicine and dietary source in the treatment of cardiovascular diseases and liver protection. Current methods to detect and measure puerarin concentration, such as ultraviolet–visible spectrophotometry (UV), are bulky, require an external power supply, and are inconvenient to use. Here, we propose a triboelectric puerarin‐detecting sensor (TPDS) which is based on liquid–solid contact electrification, in which liquid–solid interactions generate rapid electrical signals in only 0.4 ms to enable real‐time detection of puerarin concentration in water droplets. The electrical signal of the TPDS decreases with an increase of puerarin concentration, and the sensitivity of the approach is 520 V·(μg/mL)−1. The TPDS represents a miniature and cost‐effective sensor that is 0.2% of the size and 0.01% of the cost of a UV spectrophotometer. Our theoretical analysis verified that the puerarin concentration in droplets can effectively regulate the electronic structure, where higher concentrations of puerarin lead to a narrower energy bandgap, which allows the TPDS to detect puerarin concentration without the need for an external power supply. The TPDS therefore provides a route for the development of a portable and self‐powered method to measure the concentration of an active ingredient in droplets through the conversion of natural energy.image

Quantitative Optimization of Handheld Probe External Pressure on Dermatological Microvasculature Using Optical Coherence Tomography-Based Angiography.

Optical Coherence Tomography (OCT)-based angiography (OCTA) is a high-resolution, high-speed, and non-invasive imaging method that can provide vascular mapping of subcutaneous tissue up to approximately 2 mm. In dermatology applications of OCTA, handheld probes are always designed with a piece of transparent but solid contact window placed at the end of the probe to directly contact the skin for achieving better focusing between the light source and the tissue, reducing noise caused by minor movements. The pressure between the contact window and the skin is usually uncontrollable, and high external pressure affects the quality of microvascular imaging by compressing the vessels and obstructing the underlying blood flow. Therefore, it is necessary to determine a pressure range to ensure that the vessels can be fully imaged in high-quality images. In this paper, two pressure sensors were added to the existing handheld OCT probe, and the imaging probe was fixed to a metal stand and adjusted vertically to change the pressure between the probe and the tested skin site, a gradient of roughly 4 kPa (with 1-2 kPa error) increase was applied in each experiment, and the impact of pressure to the vessel was calculated. The experiment involved a total of five subjects, three areas of which were scanned (palm, back of the hand, and forearm). The vessel density was calculated to evaluate the impact of external pressure on angiography. In addition, PSNR was calculated to ensure that the quality of different tests was at a similar level. The angiography showed the highest density (about 10%) when the pressure between the contact window on the probe and the test area was between 3 and 5 kPa. As the pressure increased, the vascular density decreased, and the rate of decrease varied in different test areas. After fitting all the data points according to the different sites, the slope of the fitted line, i.e., the rate of decrease in density per unit value of pressure, was found to be 4.05% at the palm site, 6.93% at the back of the hand, and 4.55% at the forearm site. This experiment demonstrates that the pressure between the skin and contact window is a significant parameter that cannot be ignored. It is recommended that in future OCTA data collection processes and probe designs, the impact of pressure on the experiment be considered.

A novel method for gas-solid contact visualization and efficiency quantification in dry fixed-bed desulfurization

A novel method for the visualization of gas–solid contact states and the quantitative evaluation of contact efficiency in the dry fixed-bed desulfurization process is proposed in this study. This method utilizes the chromogenic properties of phenolphthalein (PP) on the surfaces of various sodium salt products during the sodium bicarbonate dry desulfurization process, enabling visualization of gas–solid contact status. Samples of desulfurization products are photographed, and ImageJ software is employed for image processing to calculate color residual rates, thereby quantifying gas–solid contact efficiency. The specific operating conditions that produced the best visualization effect of gas–solid contact states were determined through experimentation, including: an appropriate PP solid content of ≤ 0.336 % for ultrafine NaHCO3 with D90 = 6.14 μm; a steam volume ratio of approximately 13.94 % to 24.46 %, a temperature inside the reactor of 110 °C–175 °C. Moreover, the fading effect of the indicative sodium-based absorbent was consistent across SO2 concentrations from 850 mg/m3 to 5100 mg/m3, with higher concentrations reducing the time needed for visualizing gas–solid contact and quantifying efficiency. The gas–solid contact efficiency (Egs = 87.85 %) calculated by the method showed a small deviation of only 0.55 % from the efficiency (E’gs = 88.4 %) calculated based on sulfur capacity, validating the method’s reliability. The study’s outcomes present a novel method for analyzing the gas–solid contact state, which can serve future efforts in the design optimization of dry fixed-bed desulfurization reactors.