Search Results (29)

Controlling spin dynamics conventionally requires external magnetic fields, strong electric bias, or material-specific spin–orbit interactions, while the temporal reference frame remains fixed. Here we introduce curved-time spintronics, a framework in which a synthetic lapse field, implemented through GHz surface-acoustic-wave (SAW) modulation, reshapes the effective flow of time experienced by spinor, magnonic, and photon–spin degrees of freedom. Using a curved-time Schrödinger–Pauli model, we show that it renormalizes the Larmor frequency, modifies SOC-driven splittings, and produces helicity-dependent spin precession under circularly polarized excitation. Strikingly, a spatial lapse gradient induces a Hall-like transverse drift even when in the absence of any external electric field or intrinsic Berry curvature, demonstrating that time geometry alone can generate transverse transport. Time-domain simulations confirm curvature-driven Hall response across graphene, carbon nanotubes, and generic Dirac platforms, establishing a material-agnostic, field-free mechanism for transverse spin manipulation. We further predict curvature-dependent spin diffusion, temporal magnon focusing, and helicity-selective entanglement generation, and propose pump–probe detection via ultrafast Kerr rotation synchronized to SAW-driven lapse modulation. These results position engineered time geometry as a new spintronic control axis, enabling Hall-like effects, spin transport, and chiral phase manipulation without relying on intrinsic material properties, magnetic fields, or electric gating. Full article

To mitigate the interlayer defects and weak interfacial adhesion inherent in FFF-printed parts, thereby facilitating subsequent supercritical foaming applications, a microwave-assisted interlayer healing strategy is developed for FFF-printed, supercritical CO₂-foamed thermoplastic polyurethane (TPU) by incorporating aminated helical multi-walled carbon nanotubes (AS-MWCNTs). Owing to their unique helical morphology, AS-MWCNTs exhibit enhanced microwave absorption and localized heating capability, enabling selective thermal activation at interlayer regions within the foamed architecture. Microwave irradiation induces localized softening of the TPU matrix and promotes polymer chain mobility and interdiffusion across layer interfaces, while preserving the cellular morphology and bulk foamed structure. By optimizing AS-MWCNT loading, substantial improvements in interlayer bonding strength, energy absorption, and overall mechanical performance are achieved. This work provides an effective strategy to restore interlayer integrity in supercritical CO₂-foamed, additive manufactured elastomers and offers insights into the design of microwave-responsive, self-healing cellular materials. Full article

Artificial muscles translate the biological principles of motion into soft, adaptive, and multifunctional actuation. This review accordingly highlights research into natural actuation strategies, such as skeletal muscles, muscular hydrostats, spider silk, and plant turgor systems, to reveal the principles underlying energy conversion and deformation control. Building on these insights, polymer-based artificial muscles based on these principles, including pneumatic muscles, dielectric elastomers, and ionic electroactive systems, are described and their capabilities for efficient contraction, bending, and twisting with tunable stiffness and responsiveness are summarized. Furthermore, the abilities of carbon nanotube composites and twisted yarns to amplify nanoscale dimensional changes through hierarchical helical architectures and achieve power and work densities comparable to those of natural muscle are discussed. Finally, the integration of these actuators into soft robotic systems is explored through biomimetic locomotion and manipulation systems ranging from jellyfish-inspired swimmers to octopus-like grippers, gecko-adhesive manipulators, and beetle-inspired flapping wings. Despite rapid progress in the development of artificial muscles, challenges remain in achieving long-term durability, energy efficiency, integrated sensing, and closed-loop control. Therefore, future research should focus on developing intelligent muscular systems that combine actuation, perception, and self-healing to advance progress toward realizing autonomous, lifelike machines that embody the organizational principles of living systems. Full article

Graphene Nano-Carbons (GNCs) have a huge potential, but current production methods limit their exploration and use. Many GNCs will be explored here with a focus on CNTs (Carbon NanoTubes) (which have some of the highest strengths of any known material, conductivity, EMF absorptivity, and many other useful properties. Manufacturing them abundantly, inexpensively, and in eco-friendly ways remains a significant challenge. Two CNT/GNCs production methods are compared and reviewed. Traditional Chemical Vapor Deposition (CVD) production heats organic reactants with metal catalysts to form GNC/CNTs. As of now, the CVD CNT production has been limited by the high-energy costs, costs per weight comparable to precious metals, and a high CO₂-footprint. C2CNT is an electrochemical methodology that overcomes the constraints of CVD, while producing high-quality CNT/GNCs. C2CNT is a molten carbonate CO₂-electrolysis that makes GNCs. The C2CNT process also selectively produces a wider variety of CNTs (including helical, magnetic, and doped) and GNCs with higher product specificity than CVD by fine-tuning electrolysis parameters. The wide variety of CNTs/GNCs that can be produced by each of these methods is reviewed and discussed. The goal of this perspective is to compare GNC production methods. Full article

This study presents an exact analytical investigation into the static response of helical single-walled carbon nanotube (SWCNT) beams based on Eringen’s differential nonlocal elasticity theory, which captures nanoscale effects arising from interatomic interactions. A key contribution of this work is the derivation of the governing equations for helical SWCNT beams, based on the nonlocal Euler–Bernoulli theory, followed by their exact analytical solution using the initial value method. To the best of the authors’ knowledge, this represents the first closed-form formulation for such complex nanostructures using this theoretical framework of nonlocal elasticity theory. The analysis considers both cantilevered and clamped–clamped boundary conditions, under various concentrated force and moment loadings applied at the ends and midpoint of the helical beam. Displacements and rotational components are expressed in the Frenet frame, enabling direction-specific evaluation of the deformation behaviour. Parametric studies are conducted to investigate the influence of geometric parameters—such as the winding angle ($\alpha$) and aspect ratio ($R/d$) and the nonlocal parameter ($R/\gamma$). Results show that nonlocal elasticity theory consistently predicts higher displacements and rotations than the classical local theory, revealing its importance for accurate modelling of nanoscale structures. The proposed analytical framework serves as a benchmark reference for the modelling and design of nanoscale helical structures such as nano-springs, actuators, and flexible nanodevices. Full article

The electrochemical conversion of CO₂ into high-purity Graphene NanoCarbon (GNC) materials provides a compelling path to address climate change while producing economically valuable nanomaterials. This work presents the progress and prospects of new large-scale syntheses of GNC allotropes via the C2CNT (CO₂ to Carbon Nano Technology) process. The C2CNT molten carbonate electrolysis technique enables the formation of Carbon NanoTubes (CNTs), Magnetic CNTs (MCNTs), Carbon Nano-Onions (CNOs), Carbon Nano-Scaffolds (CNSs), and Helical CNTs (HCNTs) directly from atmospheric or industrial CO₂. We discuss the morphology control enabled through variations in electrolyte composition, temperature, current density, and nucleation additives. We present results from scaled operations reaching up to 1000 tons/year CO₂ conversion and propose design approaches to reach megaton scales to support climate mitigation and GNC mass production. The products demonstrate high crystallinity, as evidenced by Raman, XRD, SEM, and TGA analyses, and offer promising applications in electronics, construction, catalysis, and medical sectors. Full article

Membrane technology has emerged as an effective solution for the purification of oily wastewater, particularly in the separation of oil-in-water (O/W) emulsions. However, challenges, such as membrane fouling and the development of robust ceramic membranes with superior stability, continue to limit their widespread application. In this work, helical carbon nanotubes (HCNTs) with interlocking structures were grown in ceramic support channels through the airflow-induced chemical vapor deposition (CVD) method to fabricate membrane material with high hydrophilicity and underwater oleophobicity. The influence of CVD parameters on the growth of HCNTs and the membrane separation performance for O/W emulsions were studied systematically. The optimal HCNTs-SiC composite membrane was prepared at 600 °C, featuring a pore size of 0.95 μm and flux of 229.29 L·m⁻²·h⁻¹. This membrane demonstrated exceptional purification efficiency (99.99%) for a 500 ppm O/W emulsion, along with a stable flux of 32.48 L·m⁻²·h⁻¹ under a transmembrane pressure (TMP) of 1.5 bar. Furthermore, the unique membrane structure and surface heterogeneity contributed to its long service life and excellent recovery capability. This work provides a novel strategy for designing high-performance ceramic membranes for oil–water separation, offering potential solutions to current limitations in membrane technology. Full article

Free ion impurities in liquid crystals significantly impact the dynamic electro-optic performance of liquid crystal displays, leading to slow switching times, short-term flickering, and long-term image sticking. These ionic contaminants originate from various sources, including LC cell fabrication, electrode degradation, and organic alignment layers. This study demonstrates that doping LCs with a small concentration of helical carbon nanotubes effectively reduces free ion concentrations by approximately 70%. The resulting reduction in ionic impurities lowers the rotational viscosity of the LC, facilitating faster electro-optic switching. Additionally, the purified LC exhibits enhanced dielectric anisotropy, further improving its performance in display applications. These findings suggest that helical carbon nanotubes doping offers a promising approach for mitigating ion-related issues in liquid crystals without the need for additional chemical treatments, paving the way for an efficient liquid crystal display technology. Full article

The atomic structure, electronic, phonon, and optical properties of chalcogen helical chains (S, Se, Te) were studied using line symmetry groups and DFT calculations. The whole possible range of torsion deformations (from 0° to 180°), as well as the range of axial deformations (from 0.6 to 1.6) were considered. For the studied chains, the atomic and electronic structures at the energy minima were found. It was shown that for the considered chalcogen chains, the minimum of electronic energy is in the region of rotation angles ~103–107°. The electronic structure of all chains was considered in the helical Brillouin zone, which made it possible to trace its evolution up to the extreme torsional deformations: 0° (linear chain) and 180° (zigzag chain). A method for obtaining the dispersion of phonon states in the helical Brillouin zone has been developed based on the results of calculations by the CRYSTAL17 program. This allowed us to trace the evolution of phonon dispersion curves under torsion deformations up to their extreme values. Based on the known selection rules for helical polymers, the energies of optical, IR, and Raman transitions were obtained. This allows one to predict the optical properties of atomic chalcogen chains—both in a free state and inside carbon nanotubes. Full article

This study investigates the mechanisms driving current generation, power output, and charge storage in carbon nanotube springs under mechanical strain, addressing the gap between experimental observations and theoretical modeling, particularly in asymmetric electrical responses. Leveraging the Dirac equation in curved spacetime, we analyze how curvature-induced scalar and pseudo-gauge potentials shape two-dimensional electron gases confined to carbon nanotube springs. We incorporate applied mechanical strain by introducing time-dependent variations in the Lamé coefficient and curvature parameters, enabling the analysis of mechanical deformation’s influence on electrical properties. Our model clarifies asymmetric electrical responses during stretching and compression cycles and explains how strain-dependent power outputs arise from the interplay between mechanical deformation and curvature effects. Additionally, we demonstrate mechanisms by which strain influences charge redistribution within the helically coiled structure. We develop a new equivalent circuit model linking mechanical deformation directly to electronic behavior, bridging theoretical physics with practical electromechanical applications. The analysis reveals asymmetric time-dependent currents, enhanced power output during stretching, and strain-dependent charge redistribution. Fourier analysis uncovers dominant frequency components (primary at $\Omega$, harmonic at $2\Omega$) explaining these asymmetries. Theoretical investigations explain the mechanisms behind the curvature-driven time-dependent current source, the frequency-dependent peak power, the characteristics of open-circuit voltage with strain, and the asymmetric electrical property response under applied strain as the generated current and the charge distribution within the carbon nanotube springs. These findings highlight carbon nanotube springs applied to energy harvesting, wearable electronics, and sensing technologies. Full article

Helical carbon nanotubes (HCNTs) with different geometrical properties were constructed and incorporated into nanocomposites for the investigation of the anti-crack mechanism. The interfacial mechanical properties of the nanocomposites reinforced with straight carbon nanotubes and various types of HCNTs were investigated through the pullout of HCNTs in the crack propagation using molecular dynamics (MD). The results show that the pullout force of HCNTs is much higher than that of CNTs because the physical interlock between HCNTs and matrices is much stronger than the van der Waals (vdW) interactions between CNTs and matrices. Remarkably, HCNTs with a large pitch length can not only effectively prevent the initiation of breakages but also hinder the growth of cracks, while HCNTs with a small diameter and tube radius cannot even effectively prevent the initiation of cracks, which is similar to straight CNTs. Moreover, the shear resistance of HCNTs increases with the increase in the helix angle, which remains at a high level when the helix angle reaches the critical value. However, HCNTs with a small helix angle and large diameter can carry out more polymer chains, while snake-like HCNTs and HCNTs with a small diameter and helix angle can hardly carry out any polymer chain during the pullout process and show similar interfacial properties to the straight CNTs. Full article

In this study, the pristine MgO, MgO/CNT and Ni-MgO/CNT nanocomposites were processed using the impregnation and chemical vapor deposition methods and analyzed for hydrogen evolution reaction (HER) using the electrochemical water splitting process. Furthermore, the effect of nickel on the deposited carbon was systematically elaborated in this study. The highly conductive carbon nanotubes (CNTs) deposited on the metal surface of the Ni-MgO nanocomposite heterostructure provides a robust stability and superior electrocatalytic activity. The optimized Ni-MgO/CNT nanocomposite exhibited hierarchical, helical-shaped carbon nanotubes adorned on the surface of the Ni-MgO flakes, forming a hybrid metal–carbon network structure. The catalytic HER was carried out in a 1M alkaline KOH electrolyte, and the optimized Ni-MgO/CNT nanocomposite achieved a low (117 mV) overpotential value (ɳ) at 10 mA cm⁻² and needed a low (116 mV/dec) Tafel value, denotes the Volmer–Heyrovsky pathway. Also, the high electrochemical active surface area (ECSA) value of the Ni-MgO/CNT nanocomposite attained 515 cm², which is favorable for the generation of abundant electroactive species, and the prepared electrocatalyst durability was also performed using a chronoamperometry test for the prolonged duration of 20 h at 10 mA cm⁻² and exhibited good stability, with a 72% retention. Hence, the obtained results demonstrate that the optimized Ni-MgO/CNT nanocomposite is a highly active and cost-effective electrocatalyst for hydrogen energy production. Full article

Stretchable yarn/fiber electronics with conductive features are optimal components for different wearable devices. This paper presents the construction of coil structure-based carbon nanotube (CNT)/polymer fibers with adjustable piezoresistivity. The composite unit fiber is prepared by wrapping a conductive carbon CNT sheath onto an elastic spandex core. Owing to the helical coil structure, the resultant CNT/polymer composite fibers are highly stretchable (up to approximately 300%) without a noticeable electrical breakdown. More specifically, based on the difference in the coil index (which is the ratio of the coil diameter to the diameter of the fiber within the coil) according to the polymeric core fiber (spandex or nylon), the composite fiber can be used for two different applications (i.e., as strain sensors or supercapacitors), which are presented in this paper. The coiled CNT/spandex composite fiber sensor responds sensitively to tensile strain. The coiled CNT/nylon composite fiber can be employed as an elastic supercapacitor with excellent capacitance retention at 300% strain. Full article

The increasing demand for portable and wearable electronics has promoted the development of safe and flexible yarn–based batteries with outstanding electrochemical properties. However, achieving superior energy storage performance with a high active material (AM) load and long cycle life with this device format remains a challenge. In this study, a stable and rechargeable high–performance aqueous Ni–Fe yarn battery was constructed via biscrolling to embed AMs within helical carbon nanotube (CNT) yarn corridors. Owing to the high load of charge storage nanoparticles (NPs; above 97 wt%) and the outer neat CNT layer, the buffered biscrolled Ni–Fe yarn battery demonstrates excellent linear capacity (0.053 mAh/cm) and cycling stability (60.1% retention after 300 charge/discharge cycles) in an aqueous electrolyte. Moreover, our flexible yarn battery exhibits maximum energy/power densities of 422 mWh/cm³ and 7535 mW/cm³ based on the total volume of the cathode and anode, respectively, which exceed those reported for many flexible Ni–Fe batteries. Thus, biscrolled Ni–Fe yarn batteries are promising candidates for next–generation conformal energy solutions. Full article

Single-walled carbon nanotubes (SWCNTs) have superior mechanical properties which originate from a strong C-C covalent bond and unique nanostructure. Chirality, one of the helical structural parameters of SWCNTs, leads to differences in mechanical performance. In this work, molecular dynamics (MD) simulation was performed to analyze engineering Poisson’s ratio (EPR) and incremental Poisson’s ratio (IPR) of SWCNTs with different chiral angles, respectively, under tensile and compressive load, as well as the chiral effect on rigidity. We reported the minimum EPR for (4, 1) SWCNT and obtained the distribution and trend of EPR which is dependent on chiral index m. In addition, a new observation showed two exactly opposite trends of EPR existing not only in tension and compression but also in the longitudinal and radial directions. Furthermore, we found that the critical strain, over which SWCNT would be auxetic, ranged from 6% to 18% and was also chirality-dependent. Three representative SWCNTs with chiral angle of 0° (zigzag), 10.89° (chiral), and 30° (armchair) were selected for the mechanism study of auxeticity. Finally, a method of the contribution to radial strain for two main deformation modes proposed in this paper could well explain the negative IPR phenomenon. Full article