Conduction Channel Research Articles

Construction and Application of a Neuromorphic Circuit With Excitatory and Inhibitory Post-Synaptic Conduction Channels Implemented Using Dual-Gate Thin-Film Transistors

Construction and Application of a Neuromorphic Circuit With Excitatory and Inhibitory Post-Synaptic Conduction Channels Implemented Using Dual-Gate Thin-Film Transistors

Depletion Strategies for Crystallized Layers of Two-Dimensional Nanosheets to Enhance Lithium-Ion Conductivity in Polymer Nanocomposites.

The assembly of long-range aligned structures of two-dimensional nanosheets (2DNSs) in polymer nanocomposites (PNCs) is in urgent need for the design of nanoelectronics and lightweight energy-storage materials of high conductivity for electricity or heat. These 2DNS are thin and exhibit thermal fluctuations, leading to an intricate interplay with polymers in which entropic effects can be exploited to facilitate a range of different assemblies. In molecular dynamics simulations of experimentally studied 2DNSs, we show that the layer-forming crystallization of 2DNSs is programmable by regulating the strengths and ranges of polymer-induced entropic depletion attractions between pairs of 2DNSs, as well as between single 2DNSs and a substrate surface, by exclusively tuning the temperature and size of the 2DNS. Enhancing the temperature supports the 2DNS-substrate depletion rather than crystallization of 2DNSs in the bulk, leading to crystallized layers of 2DNSs on the substrate surfaces. On the other hand, the interaction range of the 2DNS-2DNS depletion attraction extends further than the 2DNS-substrate attraction whenever the 2DNS size is well above the correlation length of the polymers, which results in a nonmonotonic dependence of the crystallization layer on the 2DNS size. It is demonstrated that the depletion-tuned crystallization layers of 2DNSs contribute to a conductive channel in which individual lithium ions (Li ions) migrate efficiently through the PNCs. This work provides statistical and dynamical insights into the balance between the 2DNS-2DNS and 2DNS-substrate depletion interactions in polymer-2DNS composites and highlights the possibilities to exploit depletion strategies in order to engineer crystallization processes of 2DNSs and thus to control electrical conductivity.

Design of the intensification method with the help of FracCADE software

The object of research in the work is the FracCADE software, with which it is possible to simulate the process of hydraulic fracturing and well field, on which the intensification method is designed. This hydraulic fracturing simulator was developed by Schlumberger Ltd. based on proven physical principles of hydraulic fracturing to optimize the treatment process and proven in practice. The system includes a range of hydraulic fracturing models, from 2D models to extensive 3D simulations with lateral communication. It includes a number of complementary modules for fracturing fluid and proppant optimization, injection scheduling, real-time monitoring, pressure equalization, production forecasting and economic evaluation. Some models allow simulating the geometry of the fracture, solving proppant concentration problems, and simulating possible shielding due to proppant covering the fracture or the dehydration process. Hydraulic fracturing remains one of the main engineering tools for increasing the productivity of wells. The effect is achieved due to: – creation of a conductive channel (fracture) through the damaged (contaminated) zone around the well, in order to penetrate beyond its boundaries; – spreading of the channel (fracture) in the formation to a considerable depth in order to further increase the productivity of the well; – creation of a channel (fracture), which would allow changing, influencing the fluid flow in the formation. In the latter case, fracturing really becomes an effective tool that allows to manage the operation of the reservoir (in particular, change its filtering characteristics) and implement long-term strategic development programs. The concept of hydraulic fracturing is quite simple. In general, for relatively simple geology, the physical foundations of fracturing theory are fairly well developed and tested. For the most part, the difficulties boil down to two problems: the real geological conditions and the complex multidisciplinary nature of the fracturing process itself. The process of designing fracturing in order to achieve a certain result is closely related to rock mechanics (which affects the geometric parameters of the fracture), fluid hydromechanics (in which the tasks of controlling the flow of the working fluid and placing the proppant in the fracture are solved) and chemistry, which determines the behavior of materials, which are used during hydraulic fracturing. Moreover, the hydraulic fracturing project must take into account the physical limitations imposed by the specifics of the real deposit and well. In addition, to achieve the desired results, the fracturing operation must be carried out in strict accordance with the calculations (that is, a complete cycle in which each operation plays its role).

Ammonium Bicarbonate Templated 3D PDMS/rGO@CoFe2O4 Composite Foams for Effective Electromagnetic Interference Shielding and Thermal Insulation

In the past 50 years, the electronic and communication industries have grown exponentially, which has caused major concerns about electromagnetic (EM) pollution. In recent years, more thrust has been given to development of polymer composites to lessen electromagnetic interference (EMI) pollution. In the present work, porous polydimethylsiloxane (PDMS) composite foams based on cobalt ferrite (CoFe2O4) and reduced graphene oxide (rGO) are produced through the ammonium bicarbonate template approach. The resulting foams possess increased EMI shielding effectiveness via the absorption‐dominated mechanism due to the fact that PDMS foam functions as a three‐dimensional (3D) network, rGO offers the requisite conductive channel, and CoFe2O4 produces the necessary magnetic loss. The total EMI shielding effectiveness (SE) of PDMS/rGO composite foams without CoFe2O4 is 24 dB, however, with different weight percentages of CoFe2O4 added (3%, 6%, and 9%), the EMI SE increases to 41 dB for 3 mm thickness. The heat insulation performance of the material is also studied, and the measured thermal conductivity is 0.0391 Wm−1 K−1, which is very low value. The attributes of the composite foam underscore its excellent thermal insulation performance and its capacity for EMI shielding, rendering it highly suitable for diverse applications across various fields.

Enhancement mechanism of the comprehensive performance of all-solid-state polymer electrolytes by halloysite nanotubes: Construction of efficient lithium-ion conduction channels

Considering the current issues with poly(ethylene oxide)-based all-solid-state polymer electrolytes (PEO-ASSPEs) employed in lithium-ion batteries (LIBs), such as low ionic conductivity, low lithium-ion transference number, narrow electrochemical stability window, and poor cyclic stability. This study introduces oxygen-vacancy-rich halloysite nanotubes (HNTs) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) into the PEO matrix to fabricate a flexible composite polymer electrolyte (CPEs) via a solvent-free method. The interaction between HNTs and LiTFSI in the PEO matrix serves to mitigate the ionic solvation effect, increase the number of free lithium-ion, and reduce the lithium-ion migration energy barrier. Additionally, the internal framework formed by the mutual stacking of HNTs reduces the number of entanglements in polymer molecular chains, enhances the mobility of the chains, and generates a continuous interface effect, forming fast lithium-ion transport channels. The CPEs prepared in this study are in conformity with the Vogel-Tammann-Fulcher (VTF) empirical equation. The CPE containing 10 wt% HNTs exhibits a high ionic conductivity (7.15 × 10−4 S cm−1) at 25 °C, a high lithium-ion transference number (0.600), a wide electrochemical stability window (5.5 V), and excellent cyclic performance (capacity retention of 82.02 % after 100 cycles at 0.1C), satisfying the electrochemical performance requirements for ASSPEs in LIBs.

Experiments of Failure and Damage in ITO-Coated PC/FPC with ACF Bonding due to Bending Fatigue

Anisotropic conductive film (ACF) is frequently used in the packaging manufacture for fine-pitch conductivity and interconnection, maintaining the electrical and mechanical connections between micro-electrodes. A key determinant of good conductivity is the deformation, fatigue, and breakage of conductive particles within the ACF packaging. This study aims to measure the resistance changes of specific conductive channels and observe the microscopic fatigue damage of compressed ACF conductive particles through the fabrication of Flex Printed Circuits (FPC) / Indium Tin Oxide-coated Polycarbonate (ITO-coated PC) specimens and the setup of bending experiments. The results show that the deformation, fatigue, and breakage of conductive particles will quantitatively affect electrical conductivity performance. By microscopically observing the breakage morphology of conductive particles before and after bending, it can be found that bending in the ACF packaging area further exacerbates the previously compressed and broken conductive particles, with cracks continuing to grow and shatter.

Simulation of two-phase flow in 3D fractured reservoirs using a projection-based Embedded Discrete Fracture Model on Unstructured tetrahedral grids (pEDFM-U)

The modeling of fluid flow in heterogeneous, anisotropic and fractured porous media is relevant in many applications, including hydrocarbon and groundwater extraction, dispersion of contaminants, hydrogen or carbon dioxide (CO2) storage. Thus, accurate and scalable simulation of fluid flow through these formations continues to be a great challenge. The presence of fractures that are explicitly modeled, ranging from flow barriers to highly conductive channels, significantly increases the complexity of the numerical simulation. The Embedded Discrete Fracture Model (EDFM) produces results that can be as accurate as those obtained using equidimensional Discrete Fracture Models (DFM) at a much lower computational cost for highly conductive fractures, but it is not adequate for impermeable barriers. In contrast, the pEDFM (projection-based Embedded Discrete Fracture Model) produces accurate results for both, channels and barriers by using additional matrix-fracture connectivities. In its current versions, it is restricted to cartesian and corner-point grid geometries and to the classical Two Point Flux Approximation (TPFA) scheme. In this work, for the first time, the pEDFM is extended to handle unstructured tetrahedral meshes (pEDFM-U). In addition, interface fluxes are approximated by using the Multipoint Flux Approximation method with a Diamond stencil (MPFA-D). This allows for simulation of highly heterogeneous and anisotropic geo-models. The developed method is robust and can deal with full permeability tensors on arbitrary tetrahedral meshes. The advective terms are discretized considering an implicit First Order Upwind (FOU) method. Our method is implemented within the DARSim (Delft Advanced Reservoir Simulation) open-source simulator framework. Through several test cases, the proposed method showed to be robust and capable to accurately capture the effects of both high and low permeability fractures for general tetrahedral meshes, under arbitrary heterogeneous and anisotropic permeability tensors for the rock matrix.

Mechanosensitive channel MscL gating transitions coupling with constriction point shift.

The mechanosensitive channel of large conductance (MscL) acts as an "emergency release valve" that protects bacterial cells from acute hypoosmotic stress, and it serves as a paradigm for studying the mechanism underlying the transduction of mechanical forces. MscL gating is proposed to initiate with an expansion without opening, followed by subsequent pore opening via a number of intermediate substates, and ends in a full opening. However, the details of gating process are still largely unknown. Using in vivo viability assay, single channel patch clamp recording, cysteine cross-linking, and tryptophan fluorescence quenching approach, we identified and characterized MscL mutants with different occupancies of constriction region in the pore domain. The results demonstrated the shifts of constriction point along the gating pathway towards cytoplasic side from residue G26, though G22, to L19 upon gating, indicating the closed-expanded transitions coupling of the expansion of tightly packed hydrophobic constriction region to conduct the initial ion permeation in response to the membrane tension. Furthermore, these transitions were regulated by the hydrophobic and lipidic interaction with the constricting "hot spots". Our data reveal a new resolution of the transitions from the closed to the opening substate of MscL, providing insights into the gating mechanisms of MscL.

MXene and AgNW based flexible transparent conductive films with sandwich structure for high-performance EMI shielding and electrical heaters

With the popularization of 5G technology and the development of science and technology, flexible and transparent conductive films (TCF) are increasingly used in the preparation of optoelectronic devices such as electromagnetic shielding devices, transparent flexible heaters, and solar cells. Silver nanowires (AgNW) are considered the best material for replacing indium tin oxide to prepare TCFs due to their excellent comprehensive properties. However, the loose overlap between AgNWs is a significant reason for the high resistance. This article investigates a sandwich structured conductive network composed of AgNW and Ti3C2Tx MXene for high-performance EMI shielding and transparent electrical heaters. Polyethylene pyrrolidone (PVP) solution was used to hydrophilic modify PET substrate, and then MXene, AgNW, and MXene were assembled layer by layer using spin coating method to form a TCF with a sandwich structure. One-dimensional AgNW is used to provide electron transfer channels and improve light penetration, while two-dimensional MXene nanosheets are used for welding AgNWs and adding additional conductive channels. The flexible TCF has excellent transmittance (85.1 % at 550 nm) and EMI shielding efficiency (27.1 dB). At the voltage of 5 V, the TCF used as a heater can reach 85.6 °C. This work offers an innovative approach to creating TCFs for the future generation.

Enhanced performance in doped micro-nano porous organic thin-film transistors

Molecular doping, as an effective technique for controlling the electrical property of organic semiconductors (OSCs) by introducing additional charges, has been proven to adjust important device parameters in organic thin-film transistors (OTFTs). Doping highly crystalline OSCs without disrupting structural order is a crucial challenge, as it significantly affects the charge carrier mobility. Here, we demonstrate a molecular doping method without disrupting the molecular ordering to improve the charge carrier mobility of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) based OTFTs via a simple thermal spin-coating method. The key is to introduce micro-nano pores into C8-BTBT thin-film for channel doping, which is achieved by mixing with the unsubstituted BTBT as it can be easily removed from the thin-film through an ordinary annealing process. Micro-nano pores allow the dopant molecules (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, F4-TCNQ) to access the conductive channel of OTFT, which is beneficial for charge injection. Indeed, we further discover that F4-TCNQ doped porous C8-BTBT thin-films exhibit better charge mobility than those of neat and F4-TCNQ doped C8-BTBT films in OTFTs. This work proposes an effective way to expose OSC conjugated core to the dopant, which not only improves the charge transfer reaction between organic/dopant semiconductor through cofacial stacking, but also reduces the trap density and contact resistance.

Investigation of Heat Source Layout Optimization by Using Deep Learning Surrogate Models

Abstract The heat source layout optimization (HSLO) is typically used to facilitate superior heat dissipation in thermal management. However, HSLO is characterized by numerous degrees-of-freedom and complex interrelations between components. Conventional optimization methodologies often exhibit limitations such as high computational demands and diminished efficiency, particularly for complex scenarios. This study demonstrates the application of deep learning surrogate models based on the feedforward neural network (FNN) to optimize heat source layouts. These models provide rapid and precise evaluations, with diminished computational loads and enhanced efficiency of HSLO. The proposed approach integrates coarse and fine search modules to traverse the layout space and pinpoint optimal configurations. Parametric examinations are taken to explore the impact of refinement grades and conductive ratios, which dominate the optimization problem. The pattern changes of the conductive channel have been presented. Moreover, the critical conductive ratio has been found, below which the conductive material can no longer contribute to heat dissipation. The outcomes elucidate the fundamental mechanisms of HSLO, providing valuable insights for thermal management strategies.

Direct and Continuous Monitoring of Multicomponent Antibiotic Gentamicin in Blood at Single-Molecule Resolution.

Point-of-care monitoring of small molecules in biofluids is crucial for clinical diagnosis and treatment. However, the inherent low degree of recognition of small molecules and the complex composition of biofluids present significant obstacles for current detection technologies. Although nanopore sensing excels in the analysis of small molecules, the direct detection of small molecules in complex biofluids remains a challenge. In this study, we present a method for sensing the small molecule drug gentamicin in whole blood based on the mechanosensitive channel of small conductance in Pseudomonas aeruginosa (PaMscS) nanopore. PaMscS can directly detect gentamicin and distinguish its main components with only a monomethyl difference. The 'molecular sieve' structure of PaMscS enables the direct measurement of gentamicin in human whole blood within 10 min. Furthermore, a continuous monitoring device constructed based on PaMscS achieved continuous monitoring of gentamicin in live rats for approximately 2.5 h without blood consumption, while the drug components can be analyzed in situ. This approach enables rapid and convenient drug monitoring with single-molecule level resolution, which can significantly lower the threshold for drug concentration monitoring and promote more efficient drug use. Moreover, this work also lays the foundation for the future development of continuous monitoring technology with single-molecule level resolution in the living body.

Rapid ion conduction enabled by synergism of oriented liquid crystals and Electron-Deficient boron atoms in multiblock copolymer electrolyte for advanced Solid-State Lithium-Ion battery

Liquid crystals (LCs) with characteristics of self-orientation have exhibited superiorities in construction of ordered ion channels for rapid Li-ion transport. Herein, reversible addition-fragmentation chain transfer (RAFT) polymerization is employed to synthesize a unique type of boron-containing LCs based ABCBA type multiblock copolymers for the first time. The composite block copolymer electrolytes (BCPEs) are fabricated by introducing the copolymer electrolytes into glass fiber separator via solution-casting method. Noteworthily, LCs can not only provide ordered ion channels for efficient ion conduction, but also ameliorate the mechanical strength. Meanwhile, the nitrile groups with high polarity from LCs are able to further facilitate lithium salt dissociation and reinforce electrochemical stability of the system. Crucially, boron elements with electron deficiency can anchor anions and adsorb impurities to endow BCPEs with boosted ion transport capability and sufficient electrochemical stability. Consequently, the well-designed electrolyte shows high ionic conductivity of 1.13 × 10−4 S cm−1 (30 °C), and broadened electrochemical stability window of 4.85 V. Impressively, the assembled Li/LiFePO4 cells and even Li/LiMnxFe1-xPO4 high-voltage cells exhibit remarkable performances. This work provides a synthetic strategy of structure-controlled polymer electrolyte matrix and illustrates that the BCPEs are definitely a category of satisfactory electrolyte candidate for high-performance solid-state lithium-ion batteries.

3D interconnected graphene nanoplatelets and nickel ferrite based silicone rubber foams for effective electromagnetic interference shielding and thermal insulation performance

In the present study, porous composite foams made of silicon rubber (SR), graphene nanoplatelets (GnP), and nickel ferrite (NiFe2O4) nanoparticles were developed using the salt template approach. SR act as a 3D porous network, the conductive channel provided by graphene nanoplatelets and the magnetic and dielectric loss provided by the NiFe2O4 and the composite foam as a whole showed absorption-dominated EMI shielding due to synergism between GnP and NiFe2O4. Without NiFe2O4, the total EMI SE is 23 dB, while different NiFe2O4 weight percentages (0%, 3%, 6%, & 9%) increase the SET up to 36.7 dB. The thermal conductivity of this prepared sample is found to be 0.0313 Wm−1K−1 for 9 wt% filler content of NiFe2O4. It shows a moderately low value as compared to existing polymer composites. The resulting SR/GnP@NiFe2O4 composite foams, which are lightweight, strong, and multifunctional, have straightforward synthesis procedures and have a myriad of possible uses for EMI shielding systems and thermal insulations in the disciplines of aerospace, military engineering, electrical engineering and electronics.

Phonon-drag in a graphite channel buried in diamond

While the phonon-drag effect can induce large Seebeck coefficients, it is associated with large mean free path phonons present in the vicinity of the maximum in temperature of the lattice thermal conductivity. In this paper, we initiate a new route by searching for the mutual drag between the electron and phonon-drag gases at the interface between two different media. In that respect, the temperature studies of the conductance and Seebeck coefficient of a model system consisting of an electrically conductive graphitic channel buried beneath the surface of a diamond crystal are shown. The observed behaviour is very similar to that of graphite, with a typical negative peak associated with the phonon-drag effect. Interestingly, this phonon-drag peak of the buried graphitic channel appears at a significantly higher temperature than that in pure graphite.

Self-healing thermally conductive polymer composites based on polyvinyl alcohol with dynamic borate ester and hydrogen bonds

Traditional thermally conductive polymer materials exhibit a propensity for damage when applied in dynamic environments, which leads to shortened service life and suboptimal utilization of resources. Herein, polyvinyl alcohol (PVA)-based thermally conductive composites with a self-healing capability are prepared based on dynamic borate ester bonds and hydrogen bonds. Poly(dopamine) functionalized graphene oxide (denoted as PGO) is used as a thermally conductive filler to achieve a high thermal conductivity (TC) of 0.79 W/(m·K) for the PGO/PVA composites, which is 527% of pure PVA (0.15 W/(m·K)). The improved TC of PGO/PVA composites is mainly attributed to the reduction in interface thermal resistance and the construction of heat conduction channels. Additionally, the PGO/PVA composites display a self-healing efficiency higher than 60% at room temperature without external simulation. Furthermore, the as-prepared PGO/PVA composites exhibit excellent mechanical properties, with a tensile strength of 409 kPa and an elongation at break of 479%, respectively. This work provides a promising strategy for fabricating thermally conductive polymer composites, which can be deployed as thermal interface materials for long-term applications.

A Universal Approximation for Conductance Blockade in Thin Nanopore Membranes.

Nanopore-based sensing platforms have transformed single-molecule detection and analysis. The foundation of nanopore translocation experiments lies in conductance measurements, yet existing models, which are largely phenomenological, are inaccurate in critical experimental conditions such as thin and tightly fitting pores. Of the two components of the conductance blockade, channel and access resistance, the access resistance is poorly modeled. We present a comprehensive investigation of the access resistance and associated conductance blockade in thin nanopore membranes. By combining a first-principles approach, multiscale modeling, and experimental validation, we propose a unified theoretical modeling framework. The analytical model derived as a result surpasses current approaches across a broad parameter range. Beyond advancing our theoretical understanding, our framework's versatility enables analyte size inference and predictive insights into conductance blockade behavior. Our results will facilitate the design and optimization of nanopore devices for diverse applications, including nanopore base calling and data storage.

Lithiophilic Hydrogen-Substituted Graphdiyne Aerogels with Ionically Conductive Channels for High-Performance Lithium Metal Batteries.

Lithium (Li) metal stands as a promising anode in advancing high-energy-density batteries. However, intrinsic issues associated with metallic Li, especially the dendritic growth, have hindered its practical application. Herein, we focus on molecular combined structural design to develop dendrite-free anodes. Specifically, using hydrogen-substituted graphdiyne (HGDY) aerogel hosts, we successfully fabricated a promising Li composite anode (Li@HGDY). The HGDY aerogel's lithiophilic nature and hierarchical pores drive molten Li infusion and reduce local current density within the three-dimensional HGDY host. The unique molecular structure of HGDY provides favorable bulk pathways for lithium-ion transport. By simultaneous regulation of electron and ion transport within the HGDY host, uniform lithium stripping/platting is fulfilled. Li@HGDY symmetric cells exhibit a low overpotential and stable cycling. The Li@HGDY||lithium iron phosphate full cell retained 98.1% capacity after 170 cycles at 0.4 C. This study sheds new light on designing high-capacity and long-lasting lithium metal anodes.

Signatures of Mesoscopic Transport in Single Non‐Intentionally Doped GaN‐Nanowire Field‐Effect Transistors

In this work, the fabrication and characterization of a fully functional field‐effect transistor (FET) are addressed based on a non‐intentionally doped GaN‐nanowire FET (NW–FET). Universal conductance fluctuations (UCFs) are observed at temperatures below 140 K. In contrast to other reports in literature, UCFs appear in the analyzed NW–FET only under the influence of an electrical field when applying a gate voltage, while no UCF signatures are observed when performing magnetic‐field‐dependent measurements. The reason is the considerable impact of the applied voltage on the narrow conductive channel of the non‐intentionally doped NW. The electrical field influences the Fermi level as well as the width of the depletion region, both changing the effective impurity distribution which determines the set of possible electron paths. The electric‐field‐induced variation of the set of electron paths correlates with a conductance variation, which leads to the occurrence of UCFs. Furthermore, the reliability of determining the phase coherence length from the NW–FET transfer characteristics is analyzed. It is shown that the value of is significantly affected by the choice of the gate voltage range due to the current dependence of the magnitude of the UCFs.

Quantum interference effects in a 3D topological insulator with high-temperature bulk-insulating behavior

The Bi2Se3-family of 3D topological insulators (3DTI) exhibit insulating bulk states and surface states presenting a Dirac cone. At low temperatures, the conduction channels through the bulk of the material are fully gapped, making 3DTIs perfect systems to study the 2D transport behavior of Dirac fermions. Here, we report a 3DTI Bi1.1Sb0.9STe2 with a reduced level of defects, and thus, high-temperature insulating behavior in its bulk states. The insulator-to-metal transition occurs at ∼250 K, below which the bulk contributions are negligible. Even at room temperature, the conductivity contribution from the bulk channel is less than 20%. Quantum transport properties of topological surface states are observed in the Bi1.1Sb0.9STe2 nanoflake devices, e.g., high Hall mobility (∼1150 cm2/V s at 3 K), strong Shubnikov–de Haas oscillations with π Berry phase, weak antilocalization, and electron–electron interaction. Notably, additional oscillation patterns with quasi-periodicity-in-B and field-independent amplitude features are observed. The surface dominant transport behavior up to room temperature suggests that Bi1.1Sb0.9STe2 is a room temperature topological insulator for electronic/spintronic applications.