Topographical mimicry of the extracellular matrix, particularly the hierarchical fibrillar structure of collagen, has emerged as an essential factor in guiding cellular phenotype and function. In many tissues, collagen fibrils are not only organized in hierarchical bundles but are also twisted, imparting crucial tensile strength to these structures. Here, we present a fabrication method that enables the generation of such twisted structures by introducing controlled rotation of polymer melt-loaded syringes during Melt Electrofibrillation. By adjusting the rotational speed, higher twist angles in braid-like structures can be generated, replicating the full range of twist angles observed in vivo. Moreover, this advancement not only facilitates the formation of twisted fibrillar bundles with enhanced mechanical properties that resist delamination but also allows their direct printing into stable scaffolds. Experimental evaluation with three mesenchymal cell types on the scaffolds demonstrated cellular alignment and elongation along the fibril angles, as well as expression of lineage-specific transcription factors and matrix genes. This creation of three levels of hierarchy in a single step-fibrillation, twisting, and scaffold generation-thus paves the way to replicate the ultrastructure and mechanical properties of twisted collagen structures in a biomimetic manner, providing a structurally faithful scaffold platform for various tissue types.

Abstract This study investigates the structural, electronic, and elastic properties of commensurate twisted MoS 2 /MoSe 2 heterobilayers across five specific twist angles through first-principles calculations. We identify a critical angle (30°) that yields an exceptionally flat interface, characterized by a minimal interlayer spacing variation of only 0.017 Å. This distinctive planar morphology originates from a high-symmetry moiré superlattice with spatially uniform stacking configurations. Furthermore, we reveal that the variation in interlayer binding energy is governed by the lattice corrugation, reflected by a larger difference between maximum and minimum bilayer thicknesses. A more pronounced corrugation enables the system to maximize the fractional area of strongly coupled, low-energy stacking domains (e.g., AB-1) while minimizing that of weakly coupled, high-energy regions (e.g., AA). Electronically, the system exhibits a twist-angle-dependent transition between direct and indirect band gaps, while maintaining a robust type-II band alignment across all angles, with band edges localized in the MoSe 2 and MoS 2 layers, respectively. Elastic properties remain nearly unchanged at twist angles greater than 9°. But the Young's moduli of these heterobilayers surpass those of silicene and phosphorene. These findings highlight the potential of twisted MoS 2 /MoSe 2 heterobilayers as a tunable platform for advanced optoelectronic devices.

Twisted bilayer graphene (tBLG) has emerged these years with the growing research interests in the strongly correlated insulating phase, unconventional superconducting transition, and their tunable electronic properties. Hydrostatic pressure can effectively modulate the interlayer interactions in tBLG, thereby altering its electronic band structure and related physical properties. Herein, a pressure-engineering strategy has been developed to regulate the carrier transport behavior of a 2D tBLG nanodevice, fabricated via our established approach for in situ electrical measurements under high pressure. The obtained electrical results revealed that the tBLG (twist angle 1.3 ± 0.1°) device presented semiconducting behavior under different pressures. The strongly correlated state emerged in tBLG under hole doping within a rather narrow pressure window (∼4.1 GPa). Additionally, the extracted activation energy reached a maximum around 2.0 GPa. These findings provide valuable insights into pressure-tuned effective magic angle and further delving into the electronic properties of 2D twisted electronic systems.

Abstract The study aims at the utilization of ceramic insulator manufacturing industry waste in standard strength concrete (SSC) for infrastructural applications which addresses the Sustainable Development Goal (SDG‐11). The ceramic waste powder (CWP) from the electrical insulator industry has been used in the present study. From the x‐ray fluorescence analysis, it was found that the ceramic electrical insulator waste powder shows a significant increase in pozzolanic chemical composition. As many studies have been done on the mechanical and durability properties of concrete using CWP, the focus on the torsion resistance of ceramic waste reinforced standard strength concrete (RSSC) beams has not been thoroughly examined. In this study, six beams of 1.50 m span were cast and tested using the Materials Testing System loading frame. The ultimate torsional moment, angle of twist, torsional stiffness, curvature ductility and fracture width of each beam specimen were evaluated and compared. The experimentally found ultimate torque was compared theoretically using a space truss analogy and IS 456‐2000. The average increase in ultimate torsional moment and curvature ductility of ceramic waste RSSC beams was found to be 23.35% and 4.50%, respectively, when compared with the control RSSC.

Probing and manipulating the intriguing nonlinear optical responses in new two-dimensional (2D) van der Waals ferroelectrics are of great significance to the development of 2D material-based nonlinear optical devices. Herein, the simultaneous detection of second-harmonic generation (SHG) and third-harmonic generation (THG) optical responses in a recently discovered 2D in-plane ferroelectric material, NbOI2 is reported, as well as the giant modulation of SHG and THG in NbOI2 by integrating with atomically thin MoS2. Both experimental and theoretical results show that NbOI2, ranging from few-layer to thick-layer dimensions, exhibits robust SHG and THG responses with pronounced dependence on excitation polarization and wavelength. This behavior is attributed to the anisotropic band structure and excitonic resonance effects in NbOI2. By interfacing a few-layer NbOI2 with a monolayer MoS2, the amplitude and polarization of both SHG and THG signals are effectively modulated, which can be further tailored by excitation wavelength and twist angle. The nonlinear optical control in MoS2/NbOI2 heterostructures is correlated with polar symmetry coupling, which is well modeled via nonlinear electromagnetic theory. This study thus provides a new material platform based on van der Waals ferroelectric heterostructures for dynamic control of nonlinear light intensity and polarization, paving the path for developing advanced nonlinear photonic nanodevices.

ABSTRACT Twist angle between adjacent two‐dimensional (2D) materials can provide an exotic degree of freedom and lead to superior properties such as fascinating electronic structure, tunable bandgaps, and excellent carrier transport. The electronic and optical properties, and quantum capacitance of AA1 and AA2 stackings of twisted III‐nitride bilayers AlN, BN, and GaN at a 21.79° twist angle are investigated by density functional theory (DFT). Compared with no‐twisted systems, the twisted angle drastically reduces the band gaps of bilayer systems. The stacking mode is sensitive to the electronic structures of twisted bilayer AlN, but insensitive to the electronic structures of twisted bilayers BN and GaN. Flat bands of twisted bilayers AlN and GaN are introduced after atomic reconstruction and mainly originate from N‐p states, especially for AA2 stackings of twisted bilayers AlN and GaN. Twisted bilayer BN has the strongest absorptions of 16.4% for AA1 stacking and 14.8% for AA2 stacking in the ultraviolet region. Electrical conductivity is insensitive to stacking modes, and twisted bilayer GaN possesses the strongest electrical conductivity. Different stacking modes have little impact on the electrode type of twisted bilayer materials. All systems are cathode materials at the whole voltage. Effective mass and work function are further studied.

Flat bands with narrow energy dispersion can give rise to strongly correlated electronic and topological phases, especially when located at the Fermi level. Whilst flat bands are experimentally realized in 2D twisted van der Waals heterostructures, they are highly sensitive to twist angle, necessitating complex fabrication techniques. Geometrically frustrated kagome lattices have emerged as an attractive alternative platform as they can natively host flat bands that are observed experimentally in quasi-2D bulk-crystal kagome metals. An outstanding experimental question is whether flat bands can be realized in ultra-thin metals, with opportunities for stronger electron-electron interactions through tuning of the surrounding dielectric environment. Here, angle-resolved photoelectron spectroscopy, scanning tunnelling microscopy, and band structure calculations are used to show that ultra-thin films of the kagome metal Mn3Sn host a robust dispersionless flat band with a bandwidth of 50 meV. Furthermore, chemical tuning of the flat band to near the Fermi level via manganese defect engineering is demonstrated. The realization of tunable kagome-derived flat bands in an ultra-thin kagome metal represents a promising platform to study strongly correlated and topological phenomena, with applications in quantum computing, spintronics and low-energy electronics.

Twisted bilayer graphene (TBG) hosts strongly correlated phases at the magic angle (∼1.1∘), but these effects are suppressed at larger, more experimentally accessible twist angles where the electronic bands are typically dispersive. We demonstrate that perpendicular pressure can restore this flatband physics in large-angle TBG by systematically enhancing interlayer coupling. These pressure-induced flatbands exhibit strong electronic localization in AA-stacked regions, mimicking the magic-angle case. In a magnetic field, these flatbands give rise to an integer quantum Hall effect with a characteristic zero-energy plateau. At higher twist angles, this behavior evolves, and additional asymmetric plateaus emerge due to broken particle-hole symmetry. This topological correspondence is confirmed by the Hofstadter butterfly spectrum, which reveals the requisite low-energy gaps that align with the Hall conductivity plateaus. Our results establish a fundamental limit to this effect: while pressure extends magic-angle behavior to moderate twists, moiré correlations weaken beyond a critical angle of∼6∘. Ultimately, our work establishes pressure as a powerful tuning knob to engineer correlated and topological phases in moiré systems, offering an experimentally robust alternative to precise twist-angle control.

Abstract Due to the non‐complementarity of extra‐nuclear electrons, ReS 2 shows anisotropic optical property and deliver polarization‐sensitive photodetection without using complex optical components. However, the low polarization sensitivity does not satisfy to accurate identification. Herein, by employing the symmetry breaking via twisting atomic configuration, the anisotropic optical and photoresponse is improved from both the intralayer and interlayer. By twisting the ReS 2 layers, the dark current decreases by three‐orders to ≈10 pA caused by the interlayer van der Waals gap. Moreover, twisting engineering not only suppress the dark current but also improve the in‐plane optical anisotropy. The optical anisotropic factors of 60°‐twisted ReS 2 and 90°‐twisted ReS 2 are 2.5 and 6.4, respectively, which indicate that the twist angle can alter the relative orientation of the Re‐Re chains and the interface coupling intensity. Furthermore, the device exhibits polarization sensitivity, that the 90°‐twisted ReS 2 exhibited well polarization ratio of 26.8 which is much larger than the value of 5.9 in 60°‐twisted ReS 2 . Moreover, the 90°‐twisted ReS 2 homojunctions as polarization‐sensitive photodetectors in complex visual recognition tasks is validated demonstrating that the captured polarization information significantly enhances image recognition efficiency (98.6%), confirming its practical application potential in artificial intelligence visual perception tasks.

Abstract Moiré superlattices hosting flat bands and correlated states have emerged as a focal topic in condensed matter research. Through first-principles calculations, we investigate three-dimensional flat bands in alternating twisted NbSe 2 moiré bulk structures. These structures exhibit enhanced interlayer interactions compared to twisted bilayer configurations. Our results demonstrate that moiré bulks undergo spontaneous large-scale structural relaxation, resulting in the formation of remarkably flat energy bands at twist angles ≤ 7.31°. The k z -dependent dispersion of flat bands across different moiré bulks reveals their intrinsic three-dimensional character. The presence of out-of-plane mirror symmetry in these moiré bulk structures suggests possible interlayer triplet superconducting pairing mechanisms that differ from those in twisted bilayer systems. Our work paves the way for exploring potential three-dimensional flat bands in other moiré bulk systems.

When a ribbon or tube is twisted far enough it forms buckles and wrinkles. Its new geometry can be strikingly ordered or hopelessly disordered. Here we study this process in a tube with hybrid boundary conditions: one end a cylinder and the other end crimped flat like a ribbon, so that the sample resembles a toothpaste tube. The resulting irregular structures and mechanical responses can be dramatically different from those of a ribbon. However, when we form two creases in the tube prior to twisting, we obtain an ordered structure composed of repeating triangular facets oriented at varying angles and a more elastic torque response, reminiscent of the creased helicoid structure of a twisted ribbon. We measure how the torque and structural evolution depend on parameters such as material thickness and the twist angle. When only part of the tube is precreased, the ordered structures are confined to this segment. Surprisingly, in some tubes made from thicker sheets, an ordered structure forms without precreasing. This study provides insights into controlling the buckling of thin shells, offering a potential pathway for designing ordered structures in soft materials.

Abstract Moiré superlattices in van der Waals heterostructures offer a novel approach to manipulating the Bloch wavefunction texture, influencing nonlinear electromagnetic responses like photocurrents. Twisted anisotropic ReS 2 , with its lower symmetry and inclusion of more independent non‐zero nonlinear conductivity tensor elements, emerges as a promising platform for exploring nonlinear photoresponses distinct from highly symmetric hexagonal lattices. This study systematically investigates several novel anisotropic moiré superlattices based on the twisted ReS 2 homojunctions using second harmonic generation (SHG) and nonlinear photoelectric response measurements. It is found that the texture patterns of these anisotropic moiré superlattices are highly dependent on the twist angle. Especially, the photocurrents exhibit sensitivity to both wavelength and incident direction excited by left‐ and right‐circularly polarized light. In addition, due to the chiral moiré interface and the contribution of the Berry curvature dipole (BCD), twisted ReS 2 homojunctions demonstrate an exceptional circular photogalvanic effect (CPGE) as well. By exploiting the unique photoresponse to polarization, image recognition using vortex beam within a single twisted ReS 2 device is achieved. This work not only underscores the potential of quantum geometry through anisotropic moiré superlattices but also provides valuable insights for the development of advanced intelligent optoelectronic devices.

Hexagonal boron nitride (hBN) is an important 2D material for van der Waals heterostructures, single photon emitters, and infrared nanophotonics. The optical characterization of mono- and few-layer samples of hBN however, remains a challenge as the material is almost invisible optically. Here, phase-resolved sum-frequency microscopy is introduced as a technique for imaging monolayers of hBN grown by chemical vapor deposition (CVD) and visualizing their crystal orientation. Femtosecond mid-infrared (IR) and visible laser pulses are used for sum-frequency generation (SFG), which is imaged in a wide-field optical microscope. The IR laser resonantly excites a phonon of hBN that leads to an ≈800-fold enhancement of the SFG intensity, making it possible to image large 100×100µm2 sample areas in less than 1 s. Heterodyne detection combined with azimuthal sample rotation further provides full crystallographic information. Combined knowledge of topography and crystal orientation reveals that triangular domains of CVD-grown monolayer hBN have nitrogen-terminated zigzag edges. Overall, SFG microscopy is an ultra-sensitive tool with the potential to image crystal structure, strain, stacking sequences, and twist angles in a wide range of van der Waals structures, where locating and identifying monolayer regions and interfaces with broken inversion symmetry is of paramount importance.

Abstract When two layers of graphene are stacked at a twist angle of approximately 1.1°, strong interlayer coupling gives rise to a pair of flat bands in the twisted bilayer graphene (TBG) system, leading to strong electron-electron interactions. At half-filling of the flat bands, the system exhibits unique correlated insulating states. Here, we study the electrical transport properties of heterostructures composed of TBG and the antiferromagnetic insulator chromium oxychloride (CrOCl), proposing a strategy to modulate the correlated insulating state in TBG. During the transition from the conventional phase to the strong interfacial coupling phase, we observe kink behaviors in the charge neutrality point (CNP), correlated insulating state, and band insulating state. Under a perpendicular magnetic field, the system exhibits broadened quantum Hall plateaus in the strong interfacial coupling regime. Electrons localized within the CrOCl screen the bottom gate, making the doping of TBG less sensitive to changes in the bottom gate voltage. These phenomena are well delineated by a charge transfer model between TBG and CrOCl. Our research provides insights for future control of electronic correlations and topological states in graphene moiré systems through interfacial charge coupling.

ABSTRACT The twisted nanocavity, formed by stacking photonic crystals, enables extreme in‐plane light confinement and allows for active tuning of optical modes by adjusting the twist angle and manipulating the shape of central unit cell. Here, we present a straightforward method for constructing ultra‐compact twisted photonic crystal nanocavities with ultra‐small mode volumes for lasing emission in the 1550 nm telecom band. The fabricated twisted photonic crystal nanolasers exhibit a systematic change in lasing wavelengths depending on the lattice constant and the radius of airhole. Furthermore, to reduce the mode volume and suppress multi‐wavelength emission under high input powers, a fully degeneracy‐lifted optical mode is engineered by breaking the rotational symmetry and incorporating a slotted airhole into the twisted nanocavity. Optimized lasing performance with stable single‐mode operation and an ultra‐small mode volume of 0.052 has been achieved in the twisted slotted photonic crystal nanolaser. Our work provides a practical method for easily constructing robust nanolasers that simultaneously achieve an ultra‐small mode volume and single‐mode emission, which paves the way for developing high‐performance nanoscale coherent light sources for densely integrated photonic chips.

Manipulation of laser emission characteristics plays a key role in diverse technologies. However, compact lasers with internal beam steering functionalities remain a challenge. Here, we demonstrate how gradient moiré perovskite superlattices can facilitate dynamic laser beam steering. By combining a two-dimensional (2D) square lattice with a globally curved 1D perovskite grating, we fabricated gradient moiré photonic superlattices with continuously variable twist angles. We revealed how the moiré interlayer coupling at the high-symmetry points on the Brillouin zone boundaries can produce additional cavity modes with twist angle–controlled wave vectors. We showed that the moiré-induced band-edge modes can support lasing with low thresholds. By sweeping the pump area to access different twist angles, we achieved tuning of laser emission angles in a continuous and wide range (>30°) from a single device. Our work provides a highly tunable platform for moiré-induced light-matter interactions, which opens prospects for programmable and intelligent photonic technologies.

Two-dimensional moiré materials are formed by artificially stacking atomically thin monolayers. Correlated and topological quantum phases can be engineered by precise choice of stacking geometry1-3. These designer electronic properties depend crucially on interlayer coupling and atomic registry4,5. An open question is how the atomic registry responds on ultrafast timescales to optical excitation and whether the moiré geometry can be dynamically reconfigured to tune emergent phenomena in real time. Here we show that femtosecond photoexcitation drives a coherent twist-untwist motion of the moiré superlattice in 2° and 57° twisted WSe2/MoSe2 heterobilayers, resolved directly by ultrafast electron diffraction. On above-band-gap photoexcitation, the moiré superlattice diffraction features are enhanced within 1 ps and subsequently suppressed several picoseconds after, deviating markedly from typical photoinduced lattice heating. Kinetic diffraction analysis, supported by simulations of the sample dynamics, indicates a peak-to-trough local twist angle modulation of 0.6°, correlated with a sub-THz frequency moiré phonon. This motion is driven by ultrafast charge transfer that transiently increases interlayer attraction. Our results could lead to ultrafast control of moiré periodic lattice distortions and, by extension, the local moiré potential that shapes excitons, polarons and correlation-driven behaviours.

We consider graphene deposited on monolayers of such transition-metal dichalcogenides like MoSephantom{0}_2, WSephantom{0}_2, MoSphantom{0}_2, and WSphantom{0}_2. Our key objective in this paper is to study the impact of relative twist angle between the monolayers on the proximity-induced spin-orbit interaction and orbital phenomena in graphene. To do this we use an effective model Hamiltonian for low-energy states, taken from the available literature. The linear response theory and Green function formalism are used to calculate analytical formulas for the spin Hall effect and nonequilibrium current-induced spin polarization in the systems. In addition, we also evaluate the valley Hall effect and nonequilibrium valley polarization, and focus especially on their dependence on the twist angle. We show that the valley Hall conductivity can achieve the quantum value equal to pm 2 e^2/h.

Abstract Twisted multilayer graphene, characterized by its moiré patterns arising from inter-layer rotational misalignment, serves as a rich platform for exploring quantum phenomena. While firstprinciples calculations are computationally prohibitive and empirical interatomic potentials often lack accuracy, machine-learning interatomic potentials (MLIPs) present a promising alternative, offering (near-)DFT accuracy at a significantly reduced computational cost. Despite their success in two-dimensional monolayer materials, MLIPs remain under-explored in twisted multilayer graphene systems. In this work, we develop an Atomic Cluster Expansion (ACE) potential for simulating twisted multilayer graphene and test it on a range of simulation tasks. We propose an approach to construct training and test datasets that incorporate all possible twist angles and local stacking, including incommensurate ones. To achieve this, we generate configurations with periodic boundary conditions suitable for DFT calculations, and then introduce an internal twist and shift within those supercell structures. We further refine the dataset through active learning filtering, guided by Bayesian uncertainty quantification. Our model is validated for accuracy and robustness through a wide range of numerical tests.

Twisted magnetic van der Waals materials offer a promising route for multiferroic engineering, yet modeling large-scale moiré superlattices remains challenging. Leveraging a newly developed SpinGNN++ framework that effectively handles spin-lattice coupled systems, we develop a comprehensive interatomic machine learning potential and apply it to twisted bilayer NiI_{2}. Structural relaxation introduces moiré-periodic "bumps" that modulate the interlayer spacing by about 0.55Å and in-plane ionic shifts up to 0.48Å. Concurrently, our machine learning potential, which faithfully captures all key spin interactions, produces reliable magnetic configurations; combined with the more accurate generalized Katsura-Nagaosa-Balatsky mechanism, it delivers precise spin-driven polarization. For twist angles 1.89°≤θ≤2.45°, both mechanisms become prominent, yielding rich polarization textures that combine ionic out-of-plane dipoles with purely electronic in-plane domains. In the rigid (unrelaxed) bilayer, skyrmions are absent; lattice relaxation is thus essential for generating polar-magnetic topologies. In contrast, near θ≈60°, stacking-dependent ferroelectric displacements dominate, giving rise to polar meron-antimeron networks. These results reveal cooperative ionic and spin-driven ferroelectricity in twisted bilayer NiI_{2}, positioning twisted van der Waals magnets as adaptable platforms for tunable multiferroic devices.