Conductive Patterns Research Articles

Bifurcating paths: The relation between preferential pathways, channel splitting, under sampled regions, and tortuosity on the Darcy scale

Transport in porous media on the Darcy scale can be both Fickian and non-Fickian, an outcome dependent on the degree of homogeneity of the hydraulic conductivity pattern, as well as the boundary conditions and flow rate. The non-Fickian manifestation is generally associated with heterogeneous media, which promotes the formation of preferential pathways that funnel the transport. Yet this funneling occurs in both weakly and strongly heterogeneous domains, through a mechanism that is yet to be fully characterized. We model Darcy-scale transport using a particle tracking code (PT) that samples a 2D, lognormally distributed conductivity field with a variance representing a range of homogeneous to heterogeneous domains. We find that the resulting preferential pathways tend to split into more pathways (bifurcations), leaving regions into which particles do not invade, which we refer to as “under sampled regions” (USR), while forming a tortuous path. The fraction of bifurcations decreases downstream, reaching an asymptotic value, with a trend that can be fitted as a power-law of the variance. We show that the same power-law exponent relating the bifurcations to the variance holds true for the USR fraction, tortuosity, and fractal dimension with the same variance. An extension of our work is also presented for varying correlation length of the conductivity spatial distribution. We further expand our analysis to a case of impermeable fraction in a uniform conductivity field and show that the power-law fit still holds.Key PointsPreferential pathways at the Darcy scale can be characterized by their bifurcations, and USR formation formed by their tortuous path.The bifurcation fraction, USR, tortuosity, and fractal dimension scale with the conductivity heterogeneity.The same power law exponent captures the scaling of bifurcation fraction, USR, tortuosity, and fractal dimension.

Analysis of drug-induced and spontaneous cardioversions reveals similar patterns leading to termination of atrial fibrillation.

The mechanisms leading to the conversion of atrial fibrillation (AF) to sinus rhythm are poorly understood. This study describes the dynamic behavior of electrophysiological parameters and conduction patterns leading to spontaneous and pharmacological AF termination. Five independent groups of goats were investigated: (1) spontaneous termination of AF, and drug-induced terminations of AF by various potassium channel inhibitors: (2) AP14145, (3) PA-6, (4) XAF-1407, and (5) vernakalant. Bi-atrial contact mapping was performed during an open chest surgery and intervals with continuous and discrete atrial activity were determined. AF cycle length (AFCL), conduction velocity and path length were calculated for each interval, and the final conduction pattern preceding AF termination was evaluated. AF termination was preceded by a sudden episode of discrete activity both in the presence and absence of an antiarrhythmic drug. This episode was accompanied by substantial increases in AFCL and conduction velocity, resulting in prolongation of path length. In 77% ± 4% of all terminations the conduction pattern preceding AF termination involved medial to lateral conduction along Bachmann's bundle into both atria, followed by anterior to posterior conduction. This finding suggests conduction block in the interatrial septum and/or pulmonary vein area as final step of AF termination. AF termination is preceded by an increased organization of fibrillatory conduction. The termination itself is a sudden process with a critical role for the interplay between spatiotemporal organization and anatomical structure.

Effect of interfacial electronic structure on conductivity and space charge characteristics of core-shell quantum dots/polyethylene nanocomposite insulation

To investigate the effect of the interface electronic structure of core-shell quantum dots on the conductivity and space charge characteristics of polyethylene insulation, nanocomposite insulations, namely CdSe@ZnS/LDPE and ZnSe@ZnS/LDPE, are synthesized. The study focuses on elucidating the evolution patterns of DC conductivity and space charge in the nanocomposite insulation, and analyzing the effect of the interfacial electronic structure of core-shell quantum dots on the distribution of charge traps. Comparative analysis reveals that in contrast to LDPE insulation, ZnSe@ZnS/LDPE nanocomposite insulation demonstrates a substantial reduction in DC conductivity by 47.2% and a decrease in space charge accumulation by 40.3% under the conditions of elevated temperature and strong electric field. The increase of trap energy level means an enhanced trap effect on charger carriers. According to density functional theory, the band structure characteristics of core-shell quantum dots integrated with polyethylene are computationally assessed. The findings underscore that the band misalignment at the core-shell interface and the shell-insulation interface induces shifts in the conduction band bottom and at the valence band top, respectively. These shifts impose a confinement effect on electrons and holes, with the extent of this effect escalating with the augment of the difference in band gap between the core layer and the shell layer. Consequently, this phenomenon curtails carrier migration, thereby inhibiting space charge accumulation under the conditions of elevated temperature and strong electric fields.

Ultra-wideband Patch Antenna with Inhomogeneous Artificial Magnetic Conductor and Nearly Constant Radiation Pattern for Breast Tumor Detection

Ultra-wideband Patch Antenna with Inhomogeneous Artificial Magnetic Conductor and Nearly Constant Radiation Pattern for Breast Tumor Detection

Shellac-mediated laser-induced reduced graphene oxide film on paper and fabric: exceptional performance in flexible fuel cell, supercapacitor and electrocardiography applications

Natural biopolymer (shellac and dewaxed shellac) supported one-step laser-induced conductive rGO patterns (lowest sheet resistance of ∼2.3 Ω Sq.−1). Enormous potential applications in wearable, flexible, energy storage and biomedical fields.

Patternable, high-precision, controllable wettability copper layers for 3D resin-based weather-resistant electronics and 3D liquid manipulation.

The realization of 3D patterned metal layers with manipulable surface wettability has significant potential, especially in integrating microelectronics with weather resistance and multifunctional liquid manipulation. However, developing a facile and efficient method to bring it to fruition remains a great challenge. In this work, we proposed a novel 3D selective metallization strategy that combines stereolithography 3D printing with laser-induced selective metallization (LISM). Utilizing 355 nm UV or 1064 nm lasers, this strategy can prepare 3D conductive copper patterns (or circuits) with controlled wettability on various 3D-printed resin parts. The copper layer surface prepared via LISM formed microstructures similar to the papillae on the surface of a lotus leaf, and it spontaneously exhibited superhydrophobicity (156.6°) after aging in the air at room temperature. Superhydrophobic 3D circuits with self-cleaning, corrosion-resistant, and anti-condensation performance were successfully fabricated. By further treating the copper layer with a 355 nm UV laser, we realized the transformation of the superhydrophobic copper layer to a superhydrophilic state, enabling us to prepare high-precision superhydrophilic patterns or channels. A 3D self-driven flow channel was fabricated to successfully realize 3D liquid manipulation and small-scale chemical experiments.

Embedded printing of graphene sponge sensors for sleep monitoring

This study presents an approach for developing sleep monitoring sensors with excellent satisfactory softness, sensitivity and stability by embedding three-dimensional graphene conductive network patterns onto sponges.

Small Fenestra Stapedotomy in Comparison to Large Fenestra Stapedectomy in Improving Hearing Loss Caused by Otosclerosis: A Retrospective Study

Background: A retrospective study done on all otosclerotic patients who underwent stapes surgery between January 2019 and June 2022 in the department of otorhinolaryngology in a tertiary care hospital in North India. Material and Methods: Fifty four patients were enrolled in the study. The inclusion criteria of the study included patients in the age group of 18–55 years with conductive hearing loss and an intact tympanic membrane and an air–bone gap (ABG) of more than 30 dB. Diagnosis of otosclerosis is based on clinical history of progressive hearing loss and audiometric evaluation. Pure Tone Average shows typical conductive hearing loss pattern. Aim and Objective: Preoperative and 6 months postoperative audiological evaluation was conducted to understand the difference in hearing. The same surgical technique was used in all the cases, except that the dimension of the foot plate removed was different. Results: The mean age of patients in years who underwent stapes surgery was 31.6 ± 6.4 years. Out of the 54 patients, 24 (44.44%) were male and 30 (55.56%) were female. The number of patients who underwent large fenestra stapedectomy was 30 (55.56%) and who underwent small fenestra stapedotomy was 24 (44.44%). There was a significant improvement in the hearing parameters (PTA and ABG) in both the groups after surgery, but there was no significant difference between the small fenestra and large fenestra groups in terms of improvement in PTA and ABG. Conclusion: In conclusion, both small fenestra stapedotomy and large fenestra stapedectomy are safe and effective procedures for improving conductive hearing loss in otosclerosis patients.

ПРИНЦИПЫ, ОБЩАЯ СХЕМА И ОБОСНОВАНИЕ ЭФФЕКТИВНОСТИ ТЕПЛОПЕРЕДАЧИ ПРИ ПРОИЗВОДСТВЕ МЯСНЫХ ПРОДУКТОВ ПИТАНИЯ

The article studies flow chart development for production line of liquid packaged broths in the form of a finished fast-food product. It reports on the results of analytical justification of technological operations and heat transfer process of meat cooking in liquid packaged broths production. The research was based on theoretical analysis of thermal conductivity patterns from hydrodynamic and capacitive properties of medium and processed product. Based on the results of the study, closed flow line was developed, being an integral structured system. It includes all technological process operations and their interaction in complex in liquid packaged broth production. Optimization of continuous process operations ensures high sterility, liquid broth quality and resource economy.

High-density and high-coverage composite atrial activation maps: an in-silico validation study.

Repetitive atrial activation patterns (RAAPs) during complex atrial tachycardia could be associated with localized mechanisms that can be targeted. Clinically available electroanatomical mapping systems are limited by either the spatial coverage or electrode density of the mapping catheters, preventing the adequate visualization of transiently occurring RAAPs. This work proposes a technique to overcome this shortcoming by stitching spatially overlapping conduction patterns together to a larger image- called a composite map. Simulated stable mechanisms and meandering reentries are sequentially mapped (4x4 grid, 3mm spacing) and then reconstructed back to the original sizes with the proposed recurrence plot-based algorithm. The reconstruction of single linear waves presents minimal errors (local activation time (LAT) difference: 3.2 [1.6-4.9] ms, conduction direction difference: 5.2 [2.3-8.0] degrees). Errors significantly increase (p<0.05) for more complex patterns, being the highest with unstable reentries (LAT difference: 10.3 [3.5-16.2] ms, conduction direction difference: 18.2 [6.7-29.7] deg). In a second part of the analysis, 111 meandering reentries are reconstructed. Mapping 30 locations overlappingly around each reentry core was found to be the optimal mapping strategy. For this optimal setting, LAT, conduction direction, and core localization errors are low (6.1 [4.2-8.6] ms, 11.2 [8.6-15.5] deg and 4.1 [2.9-4.9] mm, respectively) and are weakly correlated with the degree of the meander ( ρ=0.41, ρ=0.40 and ρ=0.20, respectively). Our findings underline the feasibility of generating composite maps by stitching spatially overlapping recordings. Composite maps can be instrumental in personalized ablation strategies.

Sustainable bioelectronics fabrication through photo-induced swelling of green hydrogels

Electrical circuit manufacture for flexible electronics is a very specialized printing process in which electrically functional inks are printed onto a substrate. In almost all cases, the substrate assumes a passive role in ink distribution, which has been the conventional methodology used up until now. Herein we have discovered that a sodium carboxymethyl cellulose (CMCNa) hydrogel substrate demonstrates heightened susceptibility to UV photo-irradiating and because of molecular-level bond lability that leads to a macroscopic improved swelling (“writing” action). The localized photo-activated events lead to temporary 3D contours on the hydrogel substrate where conductive ink is held in valleys to allow the formation of conductive traces. A self-distribution of ink in the valleys is achieved which, moreover, is a type of mask-based photolithography or digital image generation. The process can be employed for polymeric inks such as PEDOT:PSS to obtain ink patterns without need of complex inkjet printers or other conventional printers. The drying causes recession of the temporary swollen hydrogel contours and returns the surface to flattened format. The process works at lower ink solids of 0.125 % and has shown that 1.15 J/mm2 of UV energy is capable of creating an electrically isolated conductive pattern. Initial water content of the system plays an important role in which 20 g/g of absorbed water/substrate is sufficient for acceptable pattern generation.

Reactive Aerosol Jet Printing of 2D and 3D Ag Patterns

Printed electronics is a rapidly growing field that involves the use of printing technologies to create electronic devices such as sensors, displays, and solar cells 1. Unlike traditional electronics, which rely on rigid and bulky components, printed electronics can be obtained on flexible and lightweight substrates such as plastic and paper, allowing the development of novel applications such as wearable electronics, smart packaging, and medical sensors. Printing technologies uniquely feature miniaturization and patterning capability at low-cost and high-throughput production. Among them, screen-printing, inkjet printing (IJP) and aerosol jet printing (AJP) are the most employed to fabricate conductive metallic patterns of Ag, Au, Cu and other metal nanoparticles (NPs). These printing techniques typically requires concentrated ink of metal NPs. However, specially in the case of IJP and AJP the synthesis of very small NPs (d < 100 nm) as well as proper ink formulation and long-time stability are major limitations to printing conductive metallic patterns 2.In this work, we propose an innovative method to produce 2D and 3D patterns and structures of Ag NPs by reactive Aerosol Jet Printing (r-AJP) on different substrates, using a custom-built aerosol jet printer. Ag NPs were in-situ reduced coupling two aerosol streams carrying the Ag precursor and a reducing agent, respectively. The process is fast, scalable and cheap. The electrical properties, in terms of both linear and areal electrical conductivity, of the r-AJP silver structures metallization patterns were investigated. Furthermore, the effect of both process parameters and precursor solution physical properties on printed Ag structure and morphology was assessed by x-ray diffraction (XRD) and scanning electron microscopy (SEM) in order to define the optimized condition for high definition 2d and 3D patterns by r-AJP. Bibliography P. Martins et al., Advanced Functional Materials, 33, 2213744 (2023).Y. Sui and C. A. Zorman, J. Electrochem. Soc., 167, 037571 (2020).

Coaxial Electrohydrodynamic Printing of Microscale Core-Shell Conductive Features for Integrated Fabrication of Flexible Transparent Electronics.

Reliable insulation of microscale conductive features is required to fabricate functional multilayer circuits or flexible electronics for providing specific physical/chemical/electrical protection. However, the existing strategies commonly rely on manual assembling processes or multiple microfabrication processes, which is time-consuming and a great challenge for the fabrication of flexible transparent electronics with microscale features and ultrathin thickness. Here, we present a novel coaxial electrohydrodynamic (CEHD) printing strategy for the one-step fabrication of microscale flexible electronics with conductive materials at the core and insulating material at the outer layer. A finite element analysis (FEA) method is established to simulate the CEHD printing process. The extrusion sequence of the conductive and insulating materials during the CEHD printing process shows little effect on the morphology of the core-shell filaments, which can be achieved on different flexible substrates with a minimum conductive line width of 32 ± 3.2 μm, a total thickness of 53.6 ± 4.8 μm, and a conductivity of 0.23 × 107 S/m. The thin insulating layer can provide the inner conductive filament enough protection in 3D, which endows the resultant microscale core-shell electronics with good electrical stability when working in different chemical solvent solutions or under large deformation conditions. Moreover, the presented CEHD printing strategy offers a unique capability to sequentially fabricate an insulating layer, core-shell conductive pattern, and exposed electrodes by simply controlling the material extrusion sequence. The resultant large-area transparent electronics with two-layer core-shell patterns exhibit a high transmittance of 98% and excellent electrothermal performance. The CEHD-printed flexible microelectrode array is successfully used to record the electrical signals of beating mouse hearts. It can also be used to fabricate large-area flexible capacitive sensors to accurately measure the periodical pressure force. We envision that the present CEHD printing strategy can provide a promising tool to fabricate complex three-dimensional electronics with microscale resolution, high flexibility, and multiple functionalities.

An ultra‐thin frequency‐selective surface with inductive loading for X‐band shielding applications

SummaryA novel band‐stop frequency‐selective surface (FSS) for X‐band electromagnetic shielding is reported in this study. The single‐layer, single‐sided FSS has frequency‐dependent conductive patterns developed on a polyimide substrate that provides strong rejection to the entire X‐band frequencies. The unit cell FSS has an octagonal loop configuration. Each side of the octagonal loop is alternatively loaded with thick conductive patches and stub lines to reject 8 − 12 GHz with |S21| ≤ −15 dB. The size of the unit cell FSS is 0.167λo × 0.1673λo where λo is the free space wavelength calculated at the center frequency. Owing to the rotational symmetry, the FSS unit cell exhibits mode‐independent characteristics. The bending characteristics of the FSS are analyzed, and the inferences show that the FSS properties remain unchanged under flat and bent cases. The ultra‐thin FSS offers stable frequency response for normal and oblique incidences up to 80°. The designed FSS is fabricated and tested under laboratory conditions to validate the simulation results.

Synthesis and properties of a ternary transition metal compound as positive electrode for high-performance supercapacitors

A nanostructured NixFeyCuz(CO3)(OH)2 electrode with a large surface area was deposited on a Ni-foam substrate using a facile hydrothermal method. The well-organized microscopic and free-standing nano-sized ternary metal compounds exhibited high electrical conductivity and competent ion transport ability. This composite is particularly attractive for high-performance power-storage systems owing to its binder-free nature and exceptional value as a current-carrying electrode. Ternary electrodes containing three transition metals have a higher entropy than binary electrodes, which reduces the movement distance of ions on the electrode surface and enhances key electrochemical advantages, thereby providing a high specific capacitance with durability and cycling stability when coated with a highly conductive electrochemical pattern. The NixFeyCuz(CO3)(OH)2 compound demonstrated remarkable specific surface area of 106 m2 g−1 and high specific capacities of 271.8 and 75.2 mAh g−1 at current densities of 3 and 15 A g−1. In addition, an asymmetric supercapacitor fabricated with the NixFeyCuz(CO3)(OH)2 compound as the positive electrode and graphene as the negative electrode exhibited a high energy density of 55.1 W h kg−1 at power and current densities of 398.5 W kg−1 and 2 A g−1, respectively, as well as a remarkable cycling stability of 84.3 %, which was maintained following 10,000 long cycles.

Selective Metallization on 3D Substrates for MIMO Antennae

Multiple-input multiple-output (MIMO) antenna technology owes its low weight and energy-saving electronic applications to the use of polymer substrates. Applying metallization to obtain conductive substrates involves spraying untreated molds with a gel to form a temporary protective coating. The coating is then partially removed with a laser to expose areas for metallization. After that, the exposed areas are modified with a palladium-tin (Pd-Sn) colloidal catalyst to enhance the adhesion between the insulating surface and copper deposition. It’s with these three steps that the modified areas become selective to metallization. It’s observed that copper deposited incessantly at a high speed of 5 μm/hr after above treatment, and formed a dense layer with a low resistivity. The conductive patterns plated on the 3D substrate render the MIMO antenna system applicable to wireless local area network (WLAN) with two switchable frequencies, as evidenced by the simulation tests in which the antennae had ECC values below 0.2, a VSWR of 3 to 1, and a radiation efficiency around 50% at 2.4 GHz and 37% at 5.8 GHz. The electroless plating technology used above adds to a duplicable MIMO-antenna manufacturing process of low temperature and cost.

Preliminary simulation of spatial distribution patterns of soil thermal conductivity in permafrost of the Arctic

ABSTRACTThe Arctic amplification (AA) has exacerbated permafrost degradation, posing a serious threat to infrastructure security and other areas. Therefore, it is crucial to accurately assess the current status and future changes of permafrost, and reliable soil thermal conductivity (STC) is an important prerequisite for permafrost prediction. However, few methods and products are available for regional-scale STC simulations in permafrost of the Arctic, which lead to greater uncertainty in the simulation of land surface temperatures. This study conducted a preliminary STC simulation based on the XGBoost method. The results show that the average STC during the freezing period is between 0.71∼0.73 W·m−1K−1, and around 0.67 W·m−1K−1 during the thawing period; The variation of STC between the thawing and freezing period ranged from −0.34–0.23 W·m−1K−1, with an average value of −0.02 W·m−1K−1; The areas where STC of the thawing period is smaller than that of the freezing period are mainly concentrated in the marginal areas near the sea on the continental side of North America and in the typical areas of plains, lowlands, and plateaus on the continental side of Eurasia. The areas with large STC during the thawing period are concentrated in mountainous areas.

Thixotropy and printability study of intense pulsed light sinterable copper paste formulations for flexible substrates

At present, most of the reported articles on IPL sintering of flexible copper paste focus mainly on the effects of IPL sintering parameters and copper powder modification methods on conductive copper patterns, which ignores the influence of thixotropy, printing and other properties that are of great concern in industrial production on the conductive copper pattern. In this article, four resin materials with distinctive mechanical properties, heat resistance, and stability are selected to develop a flexible copper paste formulation for IPL sintering. By focusing on the thixotropy and printing properties of different flexible copper pastes formulations, we found the relationship between these two properties and the performance of conductive copper patterns. The results show that thixotropy property affects the printing property, and the printing property affects the density and boundary definition of the conductive copper pattern film layer after sintering, thus affecting the conductivity. Finally, we obtained a flexible copper paste formulation suitable for IPL sintering with a printed line width of 35.47 μm, a line space of 31.55 μm, and a square resistance of 15.7 mΩ/◻.

Fabrication of conductive Ag/AgCl/Ag nanorods ink on Laser-induced graphene electrodes on flexible substrates for non-enzymatic glucose detection

An unusual strategy was designed to fabricate conductive patterns for flexible surfaces, which were utilized for non-enzymatic amperometric glucose sensors. The Ag/AgCl/Ag quasi-reference ink formulation utilized two reducing agents, NaBH_{4} and ethylene glycol. The parameters of the ink, such as sintering time and temperature, NaBH_{4} concentration, and layer number of coatings on flexible laser-induced graphene (LIG) electrodes were investigated. The conductive Ag/AgCl/Ag ink was characterized using electrochemical and surface analysis techniques. The electrocatalytic activity of Ag/AgCl/Ag NRs can be attributed to their high surface area, which offer numerous active sites for catalytic reactions. The selectivity and sensitivity of the electrodes for glucose detection were investigated. The XRD analysis showed (200) oriented AgCl on covered Ag NRs, and with the addition of NaBH_{4}, the intensity of the peaks of the Ag NRs increased. The wide linear range of non-enzymatic sensors was attained from 0.003 to 0.18 mM and 0.37 to 5.0 mM, with a low limit of detection of 10 upmuM and 20 upmuM, respectively.The linear range of enzymatic sensor in real sample was determined from 0.040 to 0.097 mM with a detection limit of 50 upmuM. Furthermore, results of the interference studies demonstrated excellent selectivity of the Ag/AgCl/Ag NRs/LIG electrode. The Ag/AgCl/Ag NRs on the flexible LIG electrode exhibited excellent sensitivity,long-time stablity,and reproducibility. The efficient electroactivity were deemed suitable for various electrochemical applications and biosensors.

Temperature and frequency dependent response of electrical conduction and dielectric relaxation mechanism in CuCr2O4 tetragonally distorted spinel chromite

Herein, the polycrystalline CuCr2O4 (CCO) electro-ceramic was prepared via the sol-gel self-combustion route. The X-ray powder diffraction analysis at room temperature revealed that the CCO chromite was synthesized in a single phase tetragonally distorted normal spinel structure with I41/amd space group. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) investigated the polycrystalline nature of the compound. The microstructural analysis by field emission scanning electron microscopy (FESEM) explored the surface morphology of micron-sized grains (Gs) distinguished by well-pronounced grain boundaries (GBs) available for electrical response of the material. The color mapping images of elements by energy-dispersive X-ray spectroscopy (EDS) divulged the homogeneous distribution of elements in the compound. The surface chemistry of the compound was studied by X-ray photoelectron spectroscopy (XPS). This information helped in understanding the electronic states of the ions contributing to the electrical networks and mechanisms responsible for the charge transport within the CCO system. The dielectric relaxation and electrical transport properties were analyzed using complex impedance spectroscopy (CIS) over the experimental range of frequency and temperature from 40 Hz to 1 MHz and 243–493 K, respectively. The experimental complex impedance data were analyzed by RGQGRGBQGB equivalent circuit model which resolved the electro-active contributions of bulk and interface of the CCO spinel to its electrical dynamics. The dispersion in AC conductivity was explained by Jonscher's double power law which provided evidence of small polaron hopping (SPH) as a dominant transport mechanism governing electrical conduction in the compound. The temperature-dependent DC conductivity pattern exhibited an Arrhenius-like behavior that followed Mott and Davis's model of SPH. The analysis of complex electrical modulus M*(ω,T) professed the localized and de-localized movements of the charge carriers. The dielectric permittivity response of CCO followed Havriliak-Negami (HN) phenomenology that divulged the existence of non-Debye type dielectric relaxation processes. The interfacial polarization was observed to be accountable for the dispersion in dielectric loss spectra.