Conductivity Of Medium Research Articles

Synergistic color-changing and conductive photonic cellulose nanocrystal patches for sweat sensing with biodegradability and biocompatibility.

Given the ongoing requirements for versatility, sustainability, and biocompatibility in wearable applications, cellulose nanocrystal (CNC) photonic materials emerge as excellent candidates for multi-responsive wearable devices due to their tunable structural color, strong electron-donating capacity, and renewable nature. Nonetheless, most CNC-derived materials struggle to incorporate color-changing and electrical sensing into one system since the self-assembly of CNCs is incompatible with conventional conductive mediums. Here we report the design of a conductive photonic patch through constructing a CNC/polyvinyl alcohol hydrogel modulated by phytic acid (PA). The introduction of PA significantly enhances the hydrogen bonding interaction, resulting in the composite film with impressive flexibility (1.4 MJ m-3) and progressive color changes from blue, green, yellow, to ultimately red upon sweat wetting. Interestingly, this system simultaneously demonstrates selective and sensitive electrical sensing functions, as well as satisfactory biocompatibility, biodegradability, and breathability. Importantly, a proof-of-concept demonstration of a skin-adhesive patch is presented, where the optical and electrical dual-signal sweat sensing allows for intuitive visual and multimode electric localization of sweat accumulation during physical exercises. This innovative interactive strategy for monitoring human metabolites could offer a fresh perspective into the design of wearable health-sensing devices, while greatly expanding the applications of CNC-based photonic materials in medicine-related fields.

Carbon quantum dot-assisted VO2(D) welding on holey graphene for zinc-ion battery cathode materials

Superior-quality zinc-ion batteries utilizing nanopseudocapacitor materials and flexible, three-dimensional, highly conductive porous carbon materials are current research hotspots. But the inadequate dispersion between the system components and the dissolution of the pseudocapacitive materials severely limit the further application of VO2-watery zinc-ion battery components (ZIBs). In this work, we create a novel type of independent VO2(D) covered with carbon quantum dots and assist in its welding on holey graphene (CVH). Composite structures of graphene-supported VO2(D) were designed by a simple solvothermal reaction and ultrasonic self-assembly. The CQD coating acts as a conductive medium, facilitating charge transfer to the surface and also mechanically stabilizing the cathode during volume changes, while the CQD acts as a “bridge” to form an intimate interfacial relationship with the HG. The introduction of HG not only provides more sites of activity and longitudinal transport pathways for electron and ion diffusion, but also makes the overall structure more stable and effective in eliminating the effect of volume change and realizing large pseudocapacitance. The electrochemical results show that CVH has an ultra-strong specific capacity of 443 mA h g−1 at 0.1 A/g, and a capacity retention of 332 mAh g−1 after 1000 cycles at 0.5 A/g. Excellent electrochemical performance for Zn2+ ion storage is found in CVH. This unusual structure may help us understand developing ZIB cathodes better while also offering fresh perspectives on high-performance batteries.

Synergistic enhancement of the robustness of multifunctional polyurethane via an ionic noncovalent cross-linking network and aromatic disulfides

The preparation of functional polyurethane materials with high strength, toughness, and excellent self-healing ability is currently challenging. In this study, a multifunctional bi-dynamic supramolecular crosslinked network PU elastomer was successfully prepared by introducing ionic bonds and aromatic disulfide bonds into a PU matrix. The resulting ionic PU elastomers exhibited impressive mechanical properties, including high tensile strength (39.9 ± 4.4 MPa) and excellent elongation at break (1930 ± 345 %). They also demonstrated efficient self-healing capability (94.4 %), recyclability and processability. The distribution of hydrophilic ion bonds within the polymer networks enabled the elastomers to possess water-induced shape memory and antibacterial activity. Additionally, the hydrophilicity of the elastomers provided a self-cleaning ability when used as a coating material. The covalent bonding of the cations with the PU matrix prevented the leaching of bactericidal substances, ensuring good biocompatibility of the ionic PU. Furthermore, a double-layered self-healing composite flexible sensor was developed using the ionic PU as the substrate and carboxylated carbon nanotubes (CNTs-COOH) as the conductive medium to detect human motion. These multifunctional ionic PU elastomers offer great potential for the design and preparation of robust materials with self-healing ability for various applications across multiple fields.

On the Possibility of Protecting Metals From Electrochemical Corrosion without an External Power Source

Key words: electrolyte,electric current, electrode potential, cathode, anode, electrochemical protection, galvanic circuit Electrochemical corrosion of metals is one of the most common and dangerous types of corrosion, causing enormous damage to the national economy. This type of corrosion occurs in all cases, in which metals and alloys come into contact with conductive media. Anodic and cathodic electrochemical protection are the techniques for shielding metal structures from electrochemical corrosion. In these methods, the metal structure being protected is connected to an external direct current source, and depending on the direction of movement of the electrode potential of the metal (in this case, positive or negative), anodic and cathodic electrochemical protections are distinguished. The use of an external power source makes the process energy-intensive and unprofitable. This work is based on our previous studies, in which we showed that electrochemical systems, consisting of two electrodes of the same type and a conductive medium also operate in galvanic battery mode and are characterized by low galvanic currents. Given these conditions, we connected the protected object in this medium to another metal of the same name that was either smaller or larger in certain situations in order to prevent electrochemical corrosion of metals, provided that a proper galvanic circuit was formed. Studies have shown that the corrosion losses of the electrodes in the studied acid environment amounted to only 0.035 g, while the control electrode to – 0.0468 g. Approxiamtely 2 or 3 hours after the start of the experiment, the galvanometer detects the absence of current in the circuit and the system goes into a stable passive state. The mentioned circumstance makes it possible to apply a new method of protecting metals from electrochemical corrosion, which allows it to be carried out without the use of an external current source.

Printable Counter Electrode with Metal Nitride as the Conductive Medium for Perovskite Solar Cells.

Perovskite solar cells (PSCs) with a booming high power conversion efficiency (PCE) are on their road toward industrialization. A proper design of the counter electrode (CE) with low cost, high conductivity, chemical stability, and good interface contact with the other functional layer atop the perovskite layer is vital for the overall performance of PSCs. Herein, the application of titanium nitride (TiN) is reported as a conductive medium for the printable CE in hole-conductor-free mesoscopic PSCs. TiN improves the conductivity of the CE and reduces the resistivity from 20 to 10 mΩ∙cm. TiN also improves the wettability of the CE with perovskite and enhances the back interface contact, which promotes charge collection. On the other hand, TiN is chemically stable during processing and undergoes no distinguishable chemical reaction with halide perovskite. Devices with TiN as the conductive media in the CE deliver a champion PCEof 19.01%. This work supplies a considerable choice for the CE design of PSCs toward industrial applications.

A biomimetic flexible sensor inspired by Albuca namaquensis for simultaneous high stretchability and strength

In the realm of intelligent human-machine interaction, the expansive potential of robust flexible wearable electronic devices emerges prominently. However, the practicality of such flexible electronic devices is often constrained within scenarios involving substantial mechanical strains, such as high-intensity (>100 MPa) and high tensile (>1000%) deformation, particularly in articulation-rich joint regions. Specifically, the substrates of flexible sensors confront challenges in reconciling elongation rates and tensile strengths, for which a cogent strategy is currently lacking to address the aforementioned mechanical parameter requisites. To address this quandary, the present study employs a paradigm of microscale materials that synergistically integrate rigid-flexible coupling enhancements, coupled with a biomimetic progressively asymptotic stretch optimization approach at the macroscale structural level. Through an inside-out methodology, we have ingeniously devised a biomimetic flexible sensory electronic device that seamlessly integrates sensing media and load-bearing capabilities, uniquely poised for simultaneous deployment within high-intensity and high-stretchability scenarios. By employing a judicious combination of rigidly supporting styrene monomers and the polymerized three-dimensional scaffold, formed through the coupling of elastomeric sustaining ethylene-butadiene monomers, with the high-strength, highly conductive discrete medium of graphene, we have achieved the successful synthesis of a substrate boasting a mechanical strength of 121.4 MPa alongside an impressive 1109% elongation capacity. This substrate exhibits a remarkable electrical conductivity up to 106 S*m−1. Furthermore, drawing inspiration from the serpentine architecture of the Albuca namaquensis, a two-tiered gradient stretching approach has been harnessed, resulting in an approximate 2.8-fold enhancement in stretchability. Leveraging the ingeniously designed GSBS sensor, an online testing platform for human-machine interaction capable of accommodating substantial deformations at joint interfaces is established. Through this innovation, we have effectively orchestrated the synchronization and emulation of extensive tensile movements between mechanical prosthetics and human articulations.

Analyzing the macroscopic/mesoscopic mechanical properties and fatigue damage of graphene oxide/microcapsule self-healing concrete

Concrete materials used in transmission projects in Northwest China require specific properties, such as crack resistance, fatigue resistance, and low impedance. To meet these requirements, microcapsules with repair properties were synthesized using a physical method. Graphene oxide was employed as a conductive medium and reinforcing material to prepare standard concrete composite parts. Furthermore, the stress state and cracking behavior of the microcapsules in concrete were simulated through the Python-based secondary development of ABAQUS. An orthogonal test design was conducted to determine the optimal graphene oxide, microcapsule, and water–cement ratios. Based on the orthogonal test results, fatigue testing was conducted to assess the fatigue strength, fatigue life, and crack development behavior of the concrete under combined dynamic and static loading. The results show that the thickness of the microcapsule wall material directly influences the fracture extension and practicability of the concrete. Including a certain amount of graphene oxide can enhance the strength of the concrete, reduce its resistivity, and compensate for the microcapsule-induced early strength loss. The optimal graphene oxide/microencapsulated concrete ratios were determined as 3 % microcapsule admixture, 0.1 % graphene oxide admixture, and 0.45 water–cement ratio. Notably, at low stress levels, graphene oxide and microcapsules act synergistically to enhance concrete fatigue resistance. Graphene oxide/microencapsulated concrete exhibits higher residual fatigue strength than ordinary concrete; however, the difference in their fatigue resistance diminishes as the number of cycles increases.

Performance analysis of atomic magnetometer and bandwidth‐extended loop antenna in resonant phase‐modulated magnetic field communication system

AbstractTelecommunications through an electrically conductive medium require the use of carrier bands with very‐low and ultralow frequencies to establish radiofrequency links in harsh environments. Recent advances in atomic magnetometers operating at very‐low frequencies have facilitated the reception of digitally modulated signals. We demonstrate the transmission and reception of quadrature phase‐shift keying (QPSK) signals using a multi‐resonant loop antenna and atomic magnetometer, respectively. We report the measured error vector magnitude according to the symbol rate for QPSK modulation and analyze the bandwidth of a receiver based on the atomic magnetometer. The multi‐resonant loop antenna noticeably enhances the bandwidth by over 70% compared with a single‐loop antenna. QPSK modulation for a carrier frequency of 20 kHz and symbol rate of 150 symbols per second verifies the feasibility of demodulation, and the measured error vector magnitude and signal‐to‐noise ratio are 7.29% and 30.9 dB, respectively.

Tunable open Janus functional thermal device based on moving thermal conductive medium

The Janus functional thermal device (JFTD) can produce different thermal modulation effects on the heat flow incident from different directions. To solve the problems of material anisotropy and non-interaction with the external environment in the thermal target region of the previous JFTD, an open JFTD is proposed by using a moving thermal conductive medium in four rectangular modules on the background thermal conductive plate. The thermal target region within the proposed open JFTD is an isotropic thermal conductive medium (e.g., the same as the background medium), which can be connected to the external region. The simulated results show that the proposed open JFTD performs as a thermal concentrator for the heat flows with incident angles between 0° and the critical angle and a thermal cloak for the heat flows with incident angles between the critical angle and 90°, which can be applied to the separate processing of multiple heat flows from different directions in various integrated systems.

A wavelet analysis method to retrieve thermal conductivity and radiative properties of intense extinction and low conductive medium

The accurate acquisition of the physical properties of strongly extinction materials limits their application development. In order to solve the problem of large errors in the high temperature measurement of these materials, this paper constructs an inversion model for the radiative and conductive coupled heat transfer through wavelet decomposition coefficients, and compares it with traditional methods. The radiative and conductive coupled heat transfer model is solved by finite volume method and Monte Carlo method. Daubechies nine wavelet is used for signal wavelet analysis. It has been discovered that the wavelet decomposition parameters of the temperature field are mainly concentrated in the 4–8 wavelet frequency band of wavelet, it can separate from the random error that is mainly concentrated in the 1–3 frequency band of wavelet. Most of physical properties like the heating power, convective heat transfer coefficient, material thermal conductivity, extinction coefficient has a great impact on the waveform and amplitude of wavelet detail coefficient and approximation coefficient, and the change trend of approximation coefficient and detail coefficient amplitude is consistent with the trend of temperature field. However, the effect of scattering albedo on wavelet parameters is tiny. Through inversion, it is found that the inversion model based on wavelet decomposition parameters of 5–7 frequency band has higher accuracy when random error exists.

Leveraging Commercial Microfluidic Chips for Zeta Potential Characterization

Bacteria zeta potential, ζ, is one of the key parameters for the deposition of bacteria on an electrode, also called electrophoretic deposition (EPD) and depends on the strain, suspension composition and pH. Measuring directly with a zetasizer is challenging due to the non-spherical shape of bacteria and the need for a lower conductivity medium which could affect the value of ζ. Electrokinetic measurements are usually performed with microchannels in PDMS [1] or in PMMA [2], both of which require expensive tools for the fabrication of either the mold or the microchannel itself. Reducing the cost and time needed to perform such measurements would enable the broader use of this technique. We anticipate solving this challenge with commercially available microfluidic chips as will be outlined in this study.Under an electric field E in a microchannel, the electrokinetic velocity of particles in a fluid is linked to two phenomena: electrophoresis (EP) due to the zeta potential of the particle and electroosmosis (EO) due to the zeta potential of the channel wall. PMMA microchannels (Microfluidic ChipShop) with 200 µl reservoirs together with a voltage sequencer (Labsmith) controlled with LabVIEW were used to characterize the velocity of 1 µm and 2 µm polystyrene beads with different surface functionalizations (nonfunctionalized polystryrene (PS), Sulfate-modified (SU-modified), Carboxylate-modified (CO-modified) and Amine-modified (AM-modified) from Invitrogen and Magsphere suspended in 10 mM HEPES (pH 7) by applying different voltages between the inlet and outlet platinum electrodes for 90 s. Recorded time-lapse fluorescent image sequences were analyzed with ImageJ and TrackMate. Electrokinetic velocities obtained by Particle Tracking Velocimetry (PTV) at different voltages were fitted with a linear fit with a high coefficient of determination allowing the extraction of the different particle zeta potentials, which are in good agreement with the control measurements performed with a Zetasizer Ultra (Malvern Panalytical) [3]. Further, this methodology was used to characterize a prevalent strain of E. coli, yielding values in agreement with the literature.The use of commercially available microfluidic chips in electrokinetic characterization could alleviate the need for microfabrication and allow the wider adoption of this characterization method. These measurements are ultimately critical to better understand the role of the zeta potential in EPD of microbes for an array of applications.[1] S. Antunez-Vela, et al., Anal Chem, 2020[2] Q. Wang et al., Science Advances, 2019[3] J. Cottet, et al. In preparation

Multicolor electrochromic fabric with a simple structure of PEDOT:PSS/DMSO

Smart textiles with highly controllable and tunable color changes have attracted considerable attention because of their promising practical application functionality, such as military clothes, sensors, decorations, and protective purposes like information encryption and alert, including thermochromism, photochromism, electrochromism, etc. Among them, the color variation of stimulus-responsive fabric triggered by electricity is more conveniently and effectively controlled than the color change that relies on stimuli like temperature and ultraviolet radiation. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfo-nate) (PEDOT:PSS) are one kind of the most promising electrochromic materials. Currently, electrochromic fabrics (ECFs) based on PEDOT:PSS is still hindered by relatively poor conductive efficiency and complex structure. Here, we developed a multicolor ECFs with a simplified structure using polyester (PET) fabric, PEDOT:PSS/dimethy sulfoxide (DMSO), ionic liquids as an electrochromic container, a conductive color-changing layer and ion transfer medium, respectively. Therein, PEDOT:PSS enhanced conductivity by changing the conformation with DMSO. The conductive solution PEDOT:PSS/DMSO was coated on the flexible PET substrates and then treated with ionic liquids as a conductive layer and redox reactions functional layer to realize the color-changing. These ECFs exhibited impressive electrochromic behavior with color-changing between light blue and dark blue. Moreover, the device was endowed with hydrophobicity and self-cleaning by spraying commercially available hydrophobic agents. To overcome the monochromatic color-changing capacity of traditional ECFs, subtractive principle was introduced to design multicolor electrochromic fabric. Multicolor electrochromic along with excellent flexibility, stability, and lightweight features, are practical for camouflage applications, such as the reversible yellow-green conversion that can adapt to land and grass fighting scenes. We believe the simple-structured multicolor electrochromic fabric would be promising for flexible display in any textile-based markets, such as adaptive camouflage.

Enhanced microwave absorption of g-C3N4/poly(vinylidene difluoride)/carbon black composites

The two-dimensional (2D) nanostructures have been widely applied as microwave absorption materials due to their unique structural features towards electromagnetic wave absorption. Herein, we have prepared graphitic carbon nitride (g-C3N4) nanosheets with a facile synthesis process, and then it was composited with a minimal amount of polyvinylidene difluoride (PVDF) and carbon black (CB) to enhance the microwave attenuation of g-C3N4 and to present an eco-friendly and cost-effective microwave absorbing material (MAM) as g-C3N4/PVDF/CB. The designed g-C3N4/PVDF/CB composite delivers a maximum return loss of −30.93 dB at 11.44 GHz, corresponding to an absorption efficiency of over 99.92%, with an average return loss of −17.29 dB. However, the dielectric performances were also elucidated with independent contributions of dielectric constant, tangent loss, and conductivity towards the microwave absorption performances. The integration of absorption medium PVDF and conductive medium CB to g-C3N4 offers the excellent absorption ability of g-C3N4/PVDF/CB. Hence, in the exploration of new MAM, g-C3N4/PVDF/CB may be an attractive microwave-absorbing material with strong dielectric parameters and excellent absorption effects.

Разработка математической модели для учета влияния морской среды на распространение магнитного поля в системах беспроводной связи

The article proposes a mathematical model for taking into account the influence of an electrically conductive medium on the propagation of a magnetic field in the problem of implementing wireless communication under water, that is, in an environment with high attenuation of the electrical component of the electromagnetic field. The results of modeling the dependence of the attenuation on the distance of the amplitude of the magnetic field strength in free space and in an absorbing medium at a frequency of 3 MHz are presented. It is planned to conduct experimental studies to refine the model.

Processing GPR Surveys in Civil Engineering to Locate Buried Structures in Highly Conductive Subsoils

Many studies have illustrated the great benefit of ground-penetrating radar (GPR) in civil engineering. However, in some cases, this geophysical survey method does not produce the desired results due to the electromagnetic characteristics of the subsoil. This study presents the results obtained in two locations near Linares (southern Spain), evaluating the detection of structures buried in conductive host materials (0.02 S/m in site 1 and 0.015 S/m in site 2) characterized by strong signal attenuation. Accounting for the study depth, which was 1.5 m, a 500 MHz shielded GPR antenna was used at both sites. At the first site, a controlled experiment was planned, and it consisted of burying three linear elements. An iron pipe, a PVC pipe, and a series of precast blocks were buried at a depth of 0.5 m in a subsoil composed of highly conductive clayey facies. To eliminate additional multiples caused by other superficial structures and increasing the high-frequency content, the predictive deconvolution flow was applied. In the 3D processing, the cover surfaces technique was used. Once the acquired GPR signals was analyzed and the optimal processing flow established, a second site in which different infrastructures in a conductive host medium formed by marly facies was explored. The 2D flow and 3D processing applied in this work allows to detect and see the continuity of some structures not visible for the default processing.

Instability of supersonic solitary waves in a generalized elastic electrically conductive medium

Instability of supersonic solitary waves in a generalized elastic electrically conductive medium

Propagation of Powerful Nano- and Subnanosecond Video Pulses in a Medium with Various Thermodynamic Characteristics

A conservative model is proposed for a weakly conductive material medium with changing thermodynamic characteristics during the propagation of a pulse in it. Equations are obtained that describe the change in the shape of the profile of a video pulse propagating in a medium, as well as in nonlinear transmission lines with a temperature dependence of the permittivity. It is shown that if the temperature coefficient of the permittivity is negative, then the peak power of the pulse can increase with time; otherwise, the temperature dependence of the permittivity leads to an increase in attenuation.

Soret-Dufour Mechanisms on the Thermal Loading of Catteneo-Christov Theories on Magnetohydrodynamic (MHD) Casson Nanofluid Dynamics Over a Stretching Sheet

The dynamics of Casson nanofluid with chemically reactive and thermally conductive medium past an elongated sheet were investigated in this study. The thermal loading of the fluids is considered while experimenting the Cattaneo-Christov theories with MHD boundary layer flow. The Rosseland approximation is used on the radiative heat flux because the fluids are optically thin. Partial differential equations were used in the flow model (PDEs). These PDEs were converted to ordinary differential equations (ODEs). The Runge-kutta method and firing techniques were used to solve the altered equations numerically. Graphs were used to depict the effect of relevant flow parameters, while computations on engineering values of relevance were tabulated. The velocity profile was found to degenerate when the visco-inelastic parameter (Casson) was set to a higher value. The boundary layer distributions degenerate when the unsteadiness parameter (A) is increased. The findings revealed that, the plastic dynamic viscosity of the Casson fluid causes reduction to the velocity profile. This paper is unique because it examined the simultaneous thermal loading of two non-Newtonian fluids (Casson-Williamson) nanofluids with experimentation of Cattaneo-Christov theories. To the very best of our knowledge, no study has explored study of this type in literature.

High-Volume-Rate 3-D Ultrasound Imaging Using Fast-Tilting and Redirecting Reflectors.

Three-dimensional ultrasound imaging has many advantages over 2-D imaging such as more comprehensive tissue evaluation and less operator dependence. However, developing a low-cost and accessible 3-D ultrasound solution with high volume rate and imaging quality remains a challenging task. Recently, we proposed a 3-D ultrasound imaging technique: fast acoustic steering via tilting electromechanical reflectors (FASTER), which uses a fast-tilting acoustic reflector to steer ultrafast plane waves elevationally to achieve high-volume-rate 3-D imaging with conventional 1-D transducers. However, the initial FASTER implementation requires a water tank for acoustic wave conduction and cannot be conveniently used for regular handheld scanning. To address these limitations, here, we developed a novel ultrasound probe clip-on device that encloses a fast-tilting reflector, a redirecting reflector, and an acoustic wave conduction medium. The new FASTER 3-D imaging device can be easily attached to or removed from clinical ultrasound transducers, allowing rapid transformation from 2-D to 3-D imaging. In vitro B-mode studies demonstrated that the proposed method provided comparable imaging quality to conventional, mechanical-translation-based 3-D imaging while offering a much faster volume rate (e.g., 300 versus ∼ 10 Hz). We also demonstrated 3-D power Doppler (PD) and 3-D super-resolution ultrasound localization microscopy (ULM) with the FASTER device. An in vivo imaging study showed that the FASTER device could clearly visualize the 3-D anatomy of the basilic vein. These results suggest that the newly developed redirecting reflector and the clip-on device could overcome key hurdles for future clinical translation of the FASTER 3-D imaging technology.

Research on the Principle of Anisotropy of Soil Conductivity

Soil conductivity characteristics are the main factors affecting the safety of power system grounding engineering, while the complex distribution of soil resistivity and its anisotropy often cause deviations in the evaluation of the actual grounding. This paper establishes the anisotropy model of soil resistance based on a microscopic perspective, improves the discrimination method of resistance anisotropy, and proposes the conjecture that the variation of resistivity anisotropy is caused by the difference of conductive medium connectivity in different directions. In this paper, the probability distribution of resistivity and the resistance anisotropy ratio are found to be distorted in specific water content intervals, and the trend of the distortion rate is consistent with it, combined with the critical conditions of sudden changes in soil resistivity. Moreover, the correctness of the conjecture is verified in this research. It is also found that there is more than a single conductive mutation interval in the soil, and one of them is at low water content in the high porosity model due to differences in the connectivity of the soil skeleton in all directions. This method can be applied to other studies of soil anisotropy, such as percolation, by changing the conditions and parameters.