Low Impedance Research Articles

Direct synthesis of a lithium carboxymethyl cellulose binder using wood dissolving pulp for high-performance LiFePO4 cathodes in lithium-ion batteries

Lithium carboxymethyl cellulose (CMC-Li) is a promising novel water-based binder for lithium-ion batteries. The direct synthesis of CMC-Li was innovatively developed using abundant wood dissolving pulp materials from hardwood (HW) and softwood (SW). The resulting CMC-Li-HW and CMC-Li-SW binders possessed a suitable degree of substitutions and excellent molecular weight distributions with an appropriate quantity of long- and short-chain celluloses, which facilitated the construction of a reinforced concrete-like bonding system. When used as cathode binders in LiFePO4 batteries, they uniformly coated and dispersed the electrode materials, formed a compact and stable conductive network with high mechanical strength and showed sufficient lithium replenishment. The prepared LiFePO4 batteries exhibited good mechanical stability, low charge transfer impedance, high initial discharge capacity (∼180 mAh/g), high initial Coulombic efficiency (99 %), excellent cycling performance (<3% loss over 200 cycles) and good rate capability, thereby outperforming CMC-Na and the widely used cathode binder polyvinylidene fluoride.

ECG signal quality in intermittent long-term dry electrode recordings with controlled motion artifacts.

Wearable long-term monitoring applications are becoming more and more popular in both the consumer and the medical market. In wearable ECG monitoring, the data quality depends on the properties of the electrodes and on how they interface with the skin. Dry electrodes do not require any action from the user. They usually do not irritate the skin, and they provide sufficiently high-quality data for ECG monitoring purposes during low-intensity user activity. We investigated prospective motion artifact-resistant dry electrode materials for wearable ECG monitoring. The tested materials were (1) porous: conductive polymer, conductive silver fabric; and (2) solid: stainless steel, silver, and platinum. ECG was acquired from test subjects in a 10-min continuous settling test and in a 48-h intermittent long-term test. In the settling test, the electrodes were stationary, whereas both stationary and controlled motion artifact tests were included in the long-term test. The signal-to-noise ratio (SNR) was used as the figure of merit to quantify the results. Skin-electrode interface impedance was measured to quantify its effect on the ECG, as well as to leverage the dry electrode ECG amplifier design. The SNR of all electrode types increased during the settling test. In the long-term test, the SNR was generally elevated further. The introduction of electrode movement reduced the SNR markedly. Solid electrodes had a higher SNR and lower skin-electrode impedance than porous electrodes. In the stationary testing, stainless steel showed the highest SNR, followed by platinum, silver, conductive polymer, and conductive fabric. In the movement testing, the order was platinum, stainless steel, silver, conductive polymer, and conductive fabric.

Study on the detonation wave propagation of shaped charge with three-layer liner and its driving characteristics to liner

With the continuous improvement of various armor protection technologies, the armor protection performance has increased significantly, and then the damage performance requirements of armor-piercing ammunition have also increased. In order to improve the penetration ability of the liner, a new three-layer liner structure is designed in this paper. The jet forming process was simulated by AUTODYN software. The mechanism of shaped jet forming of three-layer liner was studied. The reason why the penetration depth of three-layer liner was higher than that of ordinary liner was explained. The influence of three-layer liner on the propagation of detonation wave and the change of pressure when detonation wave acted on liner were found, which provided a new idea for improving the penetration depth of jet. The influence of liner material, cone angle and stand-off on jet forming and penetration was also studied by orthogonal optimization experiment, and the structural parameters with the best penetration performance were obtained. The results show that the pressure at the convergence point increases first and then decreases during the formation of the jet of the three-layer liner. The pressure at the convergence point when the three-layer liner material is from low impedance to high impedance from the outside to the inside is much larger than the pressure at the convergence point from high impedance to low impedance. When the three-layer liner material is Al 2024-Copper–Tantalum from the outside to the inside, the pressure at the convergence point of the three-layer liner at different times is higher than that of the double-layer liner and the single-layer liner. Reasonable matching of different impact impedance materials in the three-layer liner can greatly improve the pressure value of the detonation wave acting on the cone liner. The maximum pressure at the convergence point on the axis is 39.10 GPa, which is 22.00% higher than that of the double-layer liner at the convergence point, and 53.03% higher than that of the single-layer liner at the convergence point. The orthogonal design test scheme is simulated and analyzed. The penetration depth is taken as the observation index, and the range analysis is adopted. The results show that the material matching of the three-layer liner has the greatest influence on the depth of the jet penetrating the target plate, followed by the cone angle of the three-layer liner. Relatively speaking, the stand-off has the least influence on the result. Reasonable matching of materials with different impact impedances in the three-layer liner can maximize the penetration depth of the jet into the target plate.

Utilizing Shear Piezoelectricity of Chiral Lead‐Free Metal Halides for Electromechanical Sensing

AbstractChiral hybrid metal halides have emerged as a promising class of piezoelectric materials owing to their ease of synthesis, low acoustic impedance, and solution processibility. However, many known chiral halides crystalize in structures with only shear piezoelectricity which is less facile to be utilized compared with the longitudinal piezoelectricity, largely preventing their practical utility. In addressing this problem, chiral lead‐free S‐MPBiCl5 and R‐MPBiCl5 (MP = 2‐methylpiperazinium) with shear piezoelectricity are synthesized and the thin films orientating along the polarization direction are fabricated. These orientated films, characterized by numerous grains and compact grain boundaries, can effectively facilitate the grain boundary sliding to convert normal stress into shear stress, thus facilely activating the shear piezoelectricity. The resulting devices can accurately identify the position and type of ultrasound sources without the need for a complex acoustic impedance matching layer. Moreover, these devices can successfully sense delicate variations in momentum caused by table tennis balls. The findings open up a new pathway to utilize shear piezoelectricity that is normally considered unuseful of metal halides and other molecular piezoelectrics.

Enhanced diffusion kinetics in Y-doped SnO2 anodes for low-temperature lithium-ion batteries: A combined theoretical and experimental study

In recent years, there has been an increasing demand for lithium-ion batteries suitable for low temperatures in various fields. SnO2, with its high theoretical specific capacity, has emerged as an ideal candidate for low-temperature lithium-ion batteries. However, tin oxide exhibits inherent issues such as poor conductivity and limited cycle reversibility. Enhancing the diffusion rate of lithium ions in tin oxide is crucial for improving its low-temperature performance. We use first-principles calculations based on Density Functional Theory (DFT) to investigate the doping models of various transition metal elements (Sc, Y, Ti, Zr, V, Nb, Gr, Mo, Mn, Fe, Co, Ni) with a rational ratio of 4 % in SnO2. The results indicate that Y doping decreases the band gap of SnO2 by 0.253 eV, leading to a significant reduction in the Li-ion diffusion barrier of α-Sn. Furthermore, the synthesized SnO2 doped with Y (Y-SnO2) electrode exhibited excellent cyclic stability as an anode and achieved a high reversible capacity of 672 mAh g−1 at −10°C, surpassing that of the pure SnO2 (450 mAh g−1). Moreover, it demonstrated a higher diffusion coefficient of lithium ions and lower charge transfer impedance at both low and room temperatures.

Research on the Performance Improvement Method for Lithium-Ion Battery in High-Power Application Scenarios

With the development of technology, high-power lithium-ion batteries are increasingly moving towards high-speed discharge, long-term continuous output, instantaneous high-rate discharge, and miniaturization, and are being gradually developed towards the fields of electric tools, port machinery and robotics. Improving the power performance of batteries can be achieved from multiple dimensions, such as electrochemical systems and battery design. In order to improve the power performance of lithium-ion batteries, this paper proposes design methods from the perspective of electrochemical systems, which include increasing the high-rate discharge capacity and low impedance of the battery. This article also studies the preparation of high-power lithium-ion batteries. This article aims to improve the rate performance of batteries by studying high-performance cathode materials, excellent conductive networks, and high-performance electrolytes. This article successfully screened high-performance cathode materials by comparing the effects of different particle sizes of cathode materials on electrode conductivity and battery internal resistance. By comparing the effects of electrolyte additives under pulse cycling, high-quality electrolyte additive materials were selected. By comparing the effects of different types, contents, and ratios of conductive agents on electrode conductivity, battery internal resistance, high-quality conductive agents, and appropriate ratios were selected. Finally, a 10 Ah cylindrical high-power lithium-ion battery with a specific energy of 110 Wh/kg, pulse discharge specific power of 11.3 kW/kg, an AC internal resistance of ≤0.7 m Ω, a 10C full capacity discharge cycle of over 1700, a 30C full capacity discharge cycle of over 500, and a continuous discharge capacity of 10C–30C, and a pulse discharge capacity of over 100C was prepared.

Triazine-based porous aromatic polymer coating with ultra-low interface impedance for stable Zn anode

Aqueous zinc-ion batteries (AZIBs) have superiorities such as high safety, low redox potential and low cost, but they still have the disadvantages of uncontrollable zinc dendrite growth, severe corrosion, and hydrogen evolution reactions. This study synthesized a porous organic polymer based on anthraquinone and triazine units (C-PAT) and used it as a protective coating for zinc anode of AZIBs. Profiting by high hydrophobicity of C-PAT, the electrode-electrolyte interface corrosion was reduced, thus achieving a stable Zn anode with low interface impedance. The symmetrical battery assembled with Zn anode modified with C-PAT could stably cycle for 1820 h maintaining a lower polarization voltage of 33 mV at 0.25 mA cm−2. The full battery (C-PAT@Zn//NHVO) shows a high initial capacity of 358.2 mAh g−1 at 1 A g−1 and displays an impressive cycling performance with high reversible capacity of 191.5 mAh g−1 after 300 cycles. This study could provide a new course for the application of porous organic polymers as the protective coatings of Zn anode to obtain long-life AZIBs.

Impact of Impedance Levels on Recording Quality in Flexible Neural Probes.

Flexible neural probes are attractive emerging technologies for brain recording because they can effectively record signals with minimal risk of brain damage. Reducing the electrode impedance of the probe before recording is a common practice of many researchers. However, studies investigating the impact of low impedance levels on high-quality recordings using flexible neural probes are lacking. In this study, we electrodeposited Pt onto a commercial flexible polyimide neural probe and investigated the relationship between the impedance level and the recording quality. The probe was inserted into the brains of anesthetized mice. The electrical signals of neurons in the brain, specifically the ventral posteromedial nucleus of the thalamus, were recorded at impedance levels of 50, 250, 500 and 1000 kΩ at 1 kHz. The study results demonstrated that as the impedance decreased, the quality of the signal recordings did not consistently improve. This suggests that extreme lowering of the impedance may not always be advantageous in the context of flexible neural probes.

On‐Skin Paintable Water‐Resistant Biohydrogel for Wearable Bioelectronics

AbstractTo achieve accurate monitoring of bioelectrical signals, it is essential to use customizable bioelectrodes that can self‐adapt to the skin's surface topography. Ion‐conducting hydrogel has received significant attention in this field due to its softness, adhesion, and skin‐like mechanical properties. However, these bioelectrodes currently suffer from degradation of adhesion, electrical conductivity, and skin‐compliance when exposed to aqueous environments. This significantly limits the application of bioelectrodes. Herein, a customizable biohydrogel that can be applied on skin or fabric by solvent volatilization for liquid ink‐gel film conversion is reported. The biohydrogel's distinct characteristic of transitioning between a liquid and hydrogel phase establishes superb conformal contact and dynamic compliance with the epidermis. This effectively eliminates motion artifacts and results in lower contact impedance and noise in both static and dynamic states when compared to existing bioelectrodes. The biohydrogel is applied to the cotton fabric to create electrocardiogram (ECG) monitoring garments. These garments enable the acquisition of ECG signals with high accuracy in aqueous environment for over 72 h. Besides, the biohydrogel‐based garments outperform the commercial gel electrodes by 83.5% in signal‐to‐noise ratio. Additionally, the cotton/biohydrogel electrode facilitates multi‐channel, high‐fidelity recording of ECG signals, enabling high‐performance capture and classification of ECG waveforms across multiple channels.

Examining Performance Loss Mechanisms in Lithium-Ion Batteries with the High-Voltage Mn-Rich Spinel Positive Electrodes

The high-voltage spinel, with the nominal composition of LiNi0.5-xMn1.5+xO4 (LNMO), could be a sustainable alternative to the layered-oxide positive electrodes used in lithium-ion batteries. However, commercial acceptance has been limited as LNMO cells display rapid performance loss during cycling. To examine reasons for this loss we prepared cells with LNMO-based positive and either graphite or lithium titanate (LTO) based negative electrodes. Our initial cells displayed high impedance and rapid impedance rise during cycling. Adding single walled carbon nanotubes in the positive lowered initial cell impedance but impedance increased during cycling because of coating delamination from the Al foil. Using a primed Al current collector solved the delamination problem: cells with this current collector showed only a small impedance rise. Regarding capacity, cells with the LTO negative showed higher initial capacities and smaller fade. Our data indicate that cell capacity retention is determined by reduction reactions at the negative electrode that lower capacity and oxidation reactions at the positive electrode that increase capacity: both types of reactions deplete the cell electrolyte during extended cycling. All things considered, species generated at high voltages, either in the electrolyte or at the LNMO electrode, drive cell capacity fade.

Parylene-based stretchable neural electrodes with serpentine interconnects

Parylene C has rapidly gained popularity as a flexible and biocompatible material for next generation chronic probes. However, the mechanical strains attributed to the intracranial pressure and micromotion may compromise the longevity and biostability of implanted neural devices. To obtain conformable bioelectronic interfaces, it is essential to incorporate serpentine metal interconnects in flexible neural electrodes to achieve stretchability. In this paper, the influence of straight segments on the mechanical behavior of serpentine-shaped Parylene C probes has been investigated by finite element analysis. The etching performance of Parylene C with different masks are compared and the optimum masking material is the SiO2 film grown at a low temperature by inductively coupled plasma chemical vapor deposition (ICP-CVD). In vitro electrochemical measurements verify excellent electrode function with a low impedance of 13±0.4 kΩ at 1 kHz, which is beneficial for high-resolution neural recording.

Optimization of TiN/TiOxNy Laminated Electrode Films for High-Performance Gene Sequencing Chip

With continuous advancement of the fourth generation nanopore gene sequencing technology, the requirements for performance of the electrode films in gene sequencing chips are increasing. This study utilized the high vacuum reactive magnetron sputtering method to examine the impact of working pressure on the electrical, electrochemical, crystal structure, chemical composition, and surface morphology of TiOxNy thin films in detail. The findings revealed that the TiN thin film deposited at 0.4 Pa exhibited the lowest resistivity of 391.9 μΩ·cm. Additionally, the TiOxNy thin film deposited at 1.6 Pa demonstrated the highest volumetric specific capacitance of 35.37 mF·cm−2·μm−1 at 5 mV·s−1. Utilizing the optimal parameters, TiOxNy laminated electrode thin films were in situ grown. Through measurements and analysis, it was found that the TiOxNy electrode thin film effectively achieves a 29.35% improvement in specific capacitance compared to the single layer TiOxNy electrode thin film. The integration of a TiN current collector with low resistivity effectively reduced the internal resistance of the electrode system and decreased the response time to 0.038 s. The features of low impedance and high specific capacitance of TiOxNy laminated thin films offer promising prospects for the preparation of gene sequencing chip with high throughput.

Ce doped UiO-66(Hf) electrolyte for all-solid-state lithium metal batteries

Solid electrolytes have garnered significant attention as promising candidates for all-solid-state batteries due to their excellent safety, and cycling stability. However, the development of solid electrolytes faces challenges in achieving high ionic conductivity and low interfacial impedance. In this study, we prepared a Ce doped UiO-66(Hf)-base electrolyte using a solvothermal method. The resulting electrolyte exhibited remarkable properties, including high Li-ion conductivity (3.72 × 10−3 S cm−1), a high lithium ion transfer number (tLi+ = 0.66), and stability during stripping electroplating. These impressive results can be attributed to that the shorter length of the Ce-O bond in UiO-66(Hf) compared to the Hf-O bond, which enhances the transformation of Li+ ions. The incorporation of Ce as a dopant into UiO-66(Hf) in solid electrolytes holds great promise for future applications in solid-state batteries.

Adherence to the CLOSE Protocol and Low Baseline Generator Impedance Are Independent Predictors of Durable Pulmonary Vein Isolation.

Background: Atrial fibrillation (AF) recurrence after pulmonary vein isolation (PVI) is predominantly attributed to pulmonary vein reconnection (PVR). Predictors of AF recurrence have been widely studied; however, data are scarce on procedural parameters that predict chronic PVR. We aimed to study PVR rates and predictors of PVR. Methods: We retrospectively included 100 patients who underwent repeated ablation due to AF recurrence after initial PVI with the CARTO system. PVR was determined during the repeated procedure by electrophysiological evaluation, and initial procedural characteristics predicting PVR were studied, including adherence to the CLOSE protocol, use of high power, first-pass isolation (FPI), and baseline generator impedance (BGI). Results: Thirty-eight patients underwent initial CLOSE-guided PVI, and sixty-two underwent initial non-CLOSE PVI. A repeat procedure was performed 23 ± 16 months after the initial procedure. In total, PVR was found in 192 of 373 PVs (51.5%), and all PVs were isolated in 17/100 (17%) patients. Factors associated with all PVs being isolated were adherence to the CLOSE protocol, a higher power setting, the presence of bilateral FPI, and lower BGI (88% vs. 28%, p < 0.0001; 37.5 W vs. 30 W, p = 0.0276; 88.2% vs. 40.4%, p = 0.0007; and 127.6 Ω vs. 136.6 Ω, p = 0.0027, respectively). In initial procedures with adherence to the CLOSE protocol, the FPI rate was significantly higher (73.7% vs. 25%, p < 0.0001), while there were no significant differences in terms of procedure time and left atrial dwell time (81 vs. 85 min, p = 0.83; and 60 vs. 58 min, p = 0.08, respectively). BGI ≥ 130 Ω (AUC = 0.7403, sensitivity: 77.1%, specificity: 68.8%, p = 0.0032) was associated with a significantly higher probability of PVR (OR = 6.757; p < 0.0001). In multivariable analysis, independent predictors for PVR were non-adherence to the CLOSE protocol and BGI ≥ 130 Ω. Conclusions: Our findings indicate that adherence to the CLOSE protocol and baseline generator impedance < 130 Ω during AF ablation are independent predictors of PVI durability.

Sandwich-type composited solid polymer electrolytes to strengthen the interfacial ionic transportation and bulk conductivity for all-solid-state lithium batteries from room temperature to 120 °C

The insurmountable charge transfer impedance at the Li metal/ solid polymer electrolytes (SPEs) interface at room temperature as well as the ascending risk of short circuits at the operating temperature higher than the melting point, dominantly limits their applications in solid-state batteries (SSBs). Although the inorganic filler such as CeO2 nanoparticle content of composite solid polymer electrolytes (CSPEs) can significantly reduce the enormous charge transfer impedance at the Li metal/SPEs interface, we found that the required content of CeO2 nanoparticles in SPEs varies for achieving a decent interfacial charge transfer impedance and the bulk ionic conductivity in CSPEs. In this regard, a sandwich-type composited solid polymer electrolyte with a 10% CeO2 CSPEs interlayer sandwiched between two 50% CeO2 CSPEs thin layers (sandwiched CSPEs) is constructed to simultaneously achieve low charge transfer impedance and superior ionic conductivity at 30 °C. The sandwiched CSPEs allow for stable cycling of Li plating and stripping for 1000 h with 129 mV polarized voltage at 0.1 mA cm−2 and 30 °C. In addition, the LiFePO4/Sandwiched CSPEs /Li cell also exhibits exceptional cycle performance at 30 °C and even elevated 120 °C without short circuits. Constructing multi-layered CSPEs with optimized contents of the inorganic fillers can be an efficient method for developing all solid-state PEO-based batteries with high performance at a wide range of temperatures.

Quantification of impedance and mechanical properties of Zeonor using scanning acoustic microscopy

This article explores the potential of Zeonor, a transparent cyclic olefin polymer, for applications in transparent acoustic/photo-acoustic transducers. Despite its widespread use in optics, microfluidics, medical devices, and electronics, Zeonor's acoustic properties remain understudied. To extend this, the current work employs scanning acoustic microscopy (SAM) to obtain its mechanical properties. The signal processing method known as maximal overlap discrete wavelet transform (MODWT) is applied to efficiently break down the acoustic responses of Zeonor. The filtered signal is now time-segmented to obtain the desired signal, containing the characterizing signal feature that predicts the acoustic impedance. Further, the longitudinal and transverse acoustic velocities of the Zeonor are determined using successive peak identification and time-of-flight observations. Moreover, an impedance map is developed using Kriging with a Gaussian variogram, that provides the spatial distribution of impedance. Utilizing these results, the article determines mechanical properties such as shear modulus, Young's modulus, and Poisson's ratio, finding good agreement with literature values. The lower acoustic impedance and optical transparency of Zeonor position it as an ideal material for high-frequency photo-acoustic transducers.

Modulating Fe/P ratios in Fe-P alloy through smelting reduction for long-term electrocatalytic overall water splitting

Owing to strong Fe-P interaction that differs the electron distribution beneath metal/phosphide interface of Fe-P alloy, the charge transfer of Fe-P alloy has been accelerated during the electrocatalytic oxidation process and improved the efficiency and durability of overall water splitting. In this work, a novel metallurgical technology in combination with smelting reduction and Single Roller Melting Spinning (SRMS) for the purpose of electrochemical overall water splitting where High-phosphorus Oolitic Iron Ore (HPOIO) has been directly used as the main raw material is developed for preparing amorphous Fe-P alloys strips. The rational modulation on the Fe/P ratio can alter the crystal structure and crystallinity of Fe-P alloy, favor electron transfer, and further trap the positively charged H+. The obtained FeP electrocatalyst exhibits 436 and 527 mV at 10 mA cm−1 with Tafel slopes of 102.3 and 77.2 mV dec−1 for HER and OER in 1.0 mol/L KOH solution, respectively, especially with long-term stability (∼207 h for HER and ∼42 h for OER). Specifically, the DFT calculation displaying structural advantages and componential superiorities exhibited that P in Fe-P amorphous alloy regulated by systematic P addition optimization might increase the energy density in the Fermi level. Furthermore, the phosphorus content brought about high active surface areas, low impedance, and variable reaction paths-caused low reaction energy barriers with the improved amorphicity and absorption and desorption of intermediates, thereby boosting the overall water splitting activity. This study displays a novel strategy to develop Fe-P amorphous alloy for the stable and efficient overall water splitting.

Poly(vinylidene fluoride)-based composite membranes with continuous metal–organic framework layer for high-performance separators of lithium-ion batteries

Lithium-ion batteries (LIBs) play a critical role in modern portable electronic devices, electric vehicles, and wearable electronics. However, the formation of lithium dendrites during cycling results in serious capacity loss and safety risks owing to the heterogeneous transport and deposition of Li+. In this work, we present a poly(vinylidene fluoride) (PVDF)-based composite membrane with a continuous metal–organic framework (MOF) layer as high-performance separators in LIBs. The PVDF membranes with uniform pore structures are prepared by using superspreading strategy, facilitating the growth of continuous and controllable MOF layer inside the membranes via a simple interfacial synthesis. The as prepared PVDF-MOF composite membranes display uniform and continuous subnanochannels with connected opened metal sites (OMS), which can generate a homogeneous transport of Li+. Taking advantages of the low impedance (∼2 Ω), high ionic conductivity (0.61 mS cm−1), and high stripping peak current (0.89 mA cm−2), the PVDF-MOF composite separators efficiently prevent the uneven deposition and the generation of lithium dendrites. Moreover, the PVDF-MOF-based LIBs showed a high capacity retention rate of 81.0 % after 250 cycles. This strategy paves a new avenue for MOF-based composite separator in LIBs.

Optimization of electromagnetic absorption properties based on graphene, carbon nanotubes, and Fe3O4 multidimensional composites

AbstractExcellent electromagnetic wave loss and impedance matching are typical characteristics of superior‐performance electromagnetic wave (EMW) absorption materials. Changing the component ratios and multidimensional combinations of various absorbing materials is one of the best methods to improve absorption performance. This work used a convenient physical mixing approach to combine three wave‐absorbing materials with various dimensions to successfully prepare Graphene/carbon nanotubes/Fe3O4 (G/C/Fe3O4)/paraffin composites. One‐dimensional (1D) tube carbon nanotubes (CNTs) pierced two‐dimensional (2D) sheet graphene to form a strong three‐dimensional (3D) conductive network, enhancing interfacial polarization without introducing zero‐dimensional (0D) magnetic Nano‐Fe3O4. Nevertheless, because of their significant dielectric characteristics, the graphene/carbon nanotube (G/C) paraffin composites displayed low impedance matching and electromagnetic wave absorption properties. At a mass ratio of 1:1, the G/C/paraffin composites achieved an ideal reflection loss (RL) of −11.99 db and an impedance matching value of 0.59. Adding Fe3O4 improved the impedance matching and electromagnetic wave loss performance and promoted the formation of a non‐homogeneous interface, improving interfacial polarization and reflection. The G/C/Fe3O4/paraffin composite, with a mass ratio of 1:1:6 and a filler ratio of 20%, achieved an optimum reflection loss of −37.2 dB and an effective absorption bandwidth of 4.16 GHz. This work optimized and improved the performance of EMW materials practically and rapidly, providing a research method for the widespread application of superior‐performance electromagnetic wave absorption materials.Highlights The EMW absorption materials with various architectures. 1D CNTs pierced 2D sheet graphene to form a strong 3D conductive network. Adding Fe3O4 promoted the formation of a non‐homogeneous interface. Electromagnetic synergies and different structural combinations It achieved excellent impedance matching and electromagnetic loss performance.

Low-impedance tissue-device interface using homogeneously conductive hydrogels chemically bonded to stretchable bioelectronics.

Stretchable bioelectronics has notably contributed to the advancement of continuous health monitoring and point-of-care type health care. However, microscale nonconformal contact and locally dehydrated interface limit performance, especially in dynamic environments. Therefore, hydrogels can be a promising interfacial material for the stretchable bioelectronics due to their unique advantages including tissue-like softness, water-rich property, and biocompatibility. However, there are still practical challenges in terms of their electrical performance, material homogeneity, and monolithic integration with stretchable devices. Here, we report the synthesis of a homogeneously conductive polyacrylamide hydrogel with an exceptionally low impedance (~21 ohms) and a reasonably high conductivity (~24 S/cm) by incorporating polyaniline-decorated poly(3,4-ethylenedioxythiophene:polystyrene). We also establish robust adhesion (interfacial toughness: ~296.7 J/m2) and reliable integration between the conductive hydrogel and the stretchable device through on-device polymerization as well as covalent and hydrogen bonding. These strategies enable the fabrication of a stretchable multichannel sensor array for the high-quality on-skin impedance and pH measurements under in vitro and in vivo circumstances.