Jing Zhang

Biomedical microrobots could overcome current challenges in targeted therapies

A family of hexagonal in-plane chemical ordering (Mo_2/3 R _1/3)₂AlB₂ (R = Tb, Dy, Ho, Er, Tm, and Lu) i-MAB phases and their 2D derivatives MBenes are synthesized. The i-MAB phases with R = Tb to Tm are considered to be non-linear ferromagnetic. The pristine MBene@R exhibits poor supercapacitor performance, which, however, can be greatly enhanced by nitridation.

Abstract

A family of hexagonal in-plane chemical ordering (Mo_2/3 R _1/3)₂AlB₂ (R = Tb, Dy, Ho, Er, Tm, and Lu) i-MAB phases are synthesized with R-3m hexagonal structure. The i-MAB phases with R = Tb to Tm are considered to have a nonlinear ferromagnetic-like coupling magnetic ground state with gradually weakened magnetocrystalline anisotropy due to variant R-R distances and 4f electrons. Their 2D derivatives (2D-MBene) with rare-earth (R) atom vacancies are obtained by chemical etching. The delamination solvent, surface functional terminations, and chemical bond of 2D-MBene can be modified by one-step nitridation in environment-friendly nitrogen instead of ammonia. A phase conversion is caused by nitridation at 973 K from 2D-MBene to Mo₂N, leading to the optimized specific capacitance of 229 F g⁻¹. Besides exploring more rare-earth-containing laminated boride systems, this work also demonstrates the promising application of their 2D derivatives with R vacancies in supercapacitors.

Poly(bisdodecylthioquaterthiophene)-FeCl₃ (7.5% in weight) is used as the sensing layer of a flexible and wearable gas sensor which has alarm capability while exposed to the dimethyl methylphosphonate atmospheres at different hazard levels. By optimizing the Young's modulus, conductivity and flexibility, this sensor could be operated under 1 mV driving voltage and 28 nW power consumption.

Abstract

Conjugated polymer has the potential to be applied on flexible devices as an active layer, but further investigation is still hindered by poor conductivity and mechanical stability. Here, this work demonstrates a dopant-enhanced conductive polymer thin film and its application in dimethyl methylphosphonate (DMMP) sensor. Among five comparable polymers this work employs, poly(bisdodecylthioquaterthiophene) (PQTS12) achieves the highest doping efficiency after doped by FeCl₃, with the conductivity increasing by about five orders of magnitude. The changes in Young's modulus are also considered to optimize the conductivity and flexibility of this thin film, and finally the decay of conductivity is only 9.2% after 3000 times of mechanical bending. This work applies this thin film as the active layer of the DMMP gas sensor, which could be operated under 1 mV driving voltage and 28 nW power consumption, with a sustainable durability against bending and compression. In addition, this sensor is provided with alarm capability while exposed to the DMMP atmospheres at different hazard levels. This work expects that this general approach could offer solutions for the fabrication of low-power and flexible gas sensors, and provide guidance for next-generation wearable devices with broader applications.

Nature Electronics, Published online: 06 December 2023; doi:10.1038/s41928-023-01078-9

Processes to recapture and reuse organic electronic materials—including conductors, semiconductors and dielectrics—using non-toxic solvents allow flexible, wearable electronic devices to be recycled sustainably.

Nature Photonics, Published online: 05 December 2023; doi:10.1038/s41566-023-01361-3

Publisher Correction: Determining the optimal communication channels of arbitrary optical systems using integrated photonic processors

Nature, Published online: 04 December 2023; doi:10.1038/d41586-023-03854-1

The company announces its latest huge chip — but will now focus on developing smaller chips with a fresh approach to ‘error correction’.

Nature Electronics, Published online: 05 December 2023; doi:10.1038/s41928-023-01075-y

Membranes made of metal-coated silicon nitride can be used to assemble van der Waals heterostructures without a polymer support layer, thus improving cleanliness and allowing assembly at more extreme temperature and vacuum conditions.

The perspective highlights recent advancements in wet and dry transfer techniques for two-dimensional (2D) materials and devices, and reviews multi-scale cleanliness assessment methodologies and passive/active cleaning strategies. The interfacial wetting role played in these methods is emphasized, suggesting that a thorough understanding could lead to the development of effective cleaning strategies to fully harness the potential of 2D materials in the fields of electronics and optoelectronics.

Abstract

Two-dimensional (2D) materials have tremendous potential to revolutionize the field of electronics and photonics. Unlocking such potential, however, is hampered by the presence of contaminants that usually impede the performance of 2D materials in devices. This perspective provides an overview of recent efforts to develop clean 2D materials and devices. It begins by discussing conventional and recently developed wet and dry transfer techniques and their effectiveness in maintaining material “cleanliness”. Multi-scale methodologies for assessing the cleanliness of 2D material surfaces and interfaces are then reviewed. Finally, recent advances in passive and active cleaning strategies are presented, including the unique self-cleaning mechanism, thermal annealing, and mechanical treatment that rely on self-cleaning in essence. The crucial role of interface wetting in these methods is emphasized, and it is hoped that this understanding can inspire further extension and innovation of efficient transfer and cleaning of 2D materials for practical applications.

Nature Nanotechnology, Published online: 04 December 2023; doi:10.1038/s41565-023-01544-7

High-energy interlayer excitons in van der Waals semiconducting transition metal dichalcogenides lie far above the bandgap and emit in the ultraviolet range.

Nature Materials, Published online: 30 November 2023; doi:10.1038/s41563-023-01736-5

Piezoelectrics have longitudinal and transverse piezoelectric coefficients that are opposite in sign. Here, by tuning the interface inversion asymmetry in heterostructures, auxetic systems with positive longitudinal and transverse coefficients are realized, with expansion or contraction along all directions in an electric field.

Nature Chemistry, Published online: 30 November 2023; doi:10.1038/s41557-023-01364-1

The synthesis of two-dimensional (2D) organic lateral heterostructures with desirable properties from organic single crystals remains challenging. Now, 2D organic lateral heterostructures have been produced by using a liquid-phase growth approach and vapour-phase growth method, enabling the structural inversion of organic lateral heterostructures via a two-step strategy.

Nature, Published online: 30 November 2023; doi:10.1038/d41586-023-03777-x

The ‘anthrobots’ were able to repair a scratch in a layer of neurons in the lab.

Nature Electronics, Published online: 04 December 2023; doi:10.1038/s41928-023-01087-8

Through layer-by-layer mechanical peeling, the channel region of a multilayer black phosphorus transistor can be reduced to a monolayer thickness without degrading its lattice and while retaining a multilayer contact region.

Storage systems are essential in electronics, while flexible memory remains challenging. Inspired by brain mechanisms, a class of new memories based on reversible oxidation and reduction of liquid metals is achieved. The resulting memory exhibits outstanding stretchability, bendability, twistability, and integrability. Further realized storage system not only confirms the feasibility of this storage principle but also features multiple advantages.

Abstract

Storage systems are vital components of electronic devices, while significant challenges persist in achieving flexible memory due to the limitations of existing storage methodologies. Inspired by the polarization and depolarization mechanisms in the human brain, here a novel class of storage principles is proposed and achieve a fully flexible memory through introducing the oxidation and deoxidation behaviors of liquid metals. Specifically, reversible electrochemical oxidation is utilized to modulate the overall conductivity of the target liquid metals, creating a substantial 11-order resistance difference for binary data storage. To obtain the best storage performance, systematic optimizations of multiple parameters are conducted. Conceptual experiments demonstrate the memory's stability under extreme deformations (100% stretching, 180° bending, 360° twisting). Further tests reveal that the memory performs better when its unit size gets smaller, warranting superior integrability. Finally, a complete storage system achieves remarkable performance metrics, including rapid storage speed (>33 Hz), long data retention capacity (>43200 s), and stable repeatable operation (>3500 cycles). This groundbreaking method not only overcomes the inherent rigidity limitations of existing electronic storage units but also opens new possibilities for innovating neuromorphic devices, offering fundamental and practical avenues for future applications in soft robotics, wearable electronics, and bio-inspired artificial intelligence systems.

A significant negative capacitance response is directly observed in the thin film of molecular ferroelectric trimethylchloromethyl ammonium trichlorocadmium. When compared to conventional inorganic ferroelectrics, molecular ferroelectrics, in which order–disorder transition of the molecular induces the occurrence of polarization, would have a smaller ferroelectric anisotropy parameter α and a larger domain wall formation energy.

Abstract

On the path of persisting Moore's Law, one of the biggest obstacles is the “Boltzmann tyranny,” which defines the lower limit of power consumption of individual transistors. Negative capacitance (NC) in ferroelectrics could provide a solution and has garnered significant attention in the fields of nanoelectronics, materials science, and solid-state physics. Molecular ferroelectrics, as an integral part of ferroelectrics, have developed rapidly in terms of both performance and functionality, with their inherent advantages such as easy fabrication, mechanical flexibility, low processing temperature, and structural tunability. However, studies on the NC in molecular ferroelectrics are limited. In this study, the focus is centered on the fabricated high-quality thin films of trimethylchloromethyl ammonium trichlorocadmium(II), and a pioneering investigation on their NC responses is conducted. The findings demonstrate that the NC exhibited by molecular ferroelectrics is comparable to that of conventional HfO₂-based ferroelectrics. This underscores the potential of molecular material systems for next-generation electronic devices.

Tunable magnetic bubbles and topological Hall effect (THE) are demonstrated in 2D magnet Fe₅GeTe₂. The density and size of bubbles can be modulated effectively by adjusting the magnetocrystalline anisotropy and dipolar interaction, respectively. Besides, the controlled topological transformation between skyrmion bubbles and trivial bubbles is achieved by varying the sample thickness, accompanied by the change of THE.

Abstract

Recent observations of nontrivial spin textures and topological Hall effect (THE) in 2D van der Waals (vdW) ferromagnets have stimulated high interest in both fundamental physics and prospective spintronic applications. However, effectively manipulating spin textures and their exhibiting THE, which is the prerequisite for topology-based 2D vdW devices, remains challenging. Here, the effective manipulation of the magnetic bubbles and THE is achieved in Fe₅GeTe₂ (FGT) crystals by utilizing Lorentz imaging and electrical transport measurements. The density and size of magnetic bubbles can be modulated effectively as the temperature and lamella thickness change, indicating the role of magnetocrystalline anisotropy and long-range magnetic dipolar interaction is demonstrated, respectively. More importantly, the spin configurations of bubbles along with THE signal vary with sample thickness, demonstrating a topological transition between skyrmion bubbles and trivial bubbles. The key point lies in the presence or absence of Bloch lines in the stripe domain at different thicknesses. This study presents the reliable manipulations of spin textures and THE in FGT, which may provide valuable insights into the design of 2D vdW devices in spintronics.

Machine Vision

In article number 2306241, Xinghua Wang, Zhongming Wei, Juehan Yang, and co-workers present photodetectors based on AsSbO₃ nanosheets that are able to realize highly selective and high-performance detection in the solar-blind ultraviolet band, benefiting from the ultra-wide bandgap. Owing to the remarkable anisotropic crystal structure, AsSbO₃ also shows significant linear dichroism and nonlinear optical properties.

Planar Josephson junctions based on type-II Weyl semimetal MoTe₂ can function as superconducting diodes with the ratification efficiency up to 50.4% due to the asymmetric Josephson effect in perpendicular magnetic fields. The underlying physics is the Edelstein effect that induces a nontrivial phase shift in the current phase relation of the junctions.

Abstract

Superconducting diode effect (SDE) with nonreciprocal supercurrent transport has attracted intense attention recently, not only for its intriguing physics, but also for its great application potential in superconducting circuits. It is revealed in this work that planar Josephson junctions (JJs) based on type-II Weyl semimetal (WSM) MoTe₂ can exhibit a prominent SDE due to the emergence of asymmetric Josephson effect (AJE) in perpendicular magnetic fields. The AJE manifests itself in a very large asymmetry in the critical supercurrents with respect to the current direction. The sign of this asymmetry can also be effectively modulated by the external magnetic field. Considering the special noncentrosymmetric crystal symmetry of MoTe₂, this AJE is understood in terms of the Edelstein effect, which induces a nontrivial phase shift in the current phase relation of the junctions. Besides these, it is further demonstrated that the rectification of supercurrent in such MoTe₂ JJs with the rectification efficiency up to 50.4%, unveiling the great application potential of WSMs in superconducting electronics.

Atomic-scale polar topologies have garnered enormous interest due to their rich emergent physical phenomena and promising applications in next-generation electronics. Herein, ultrasmall polar merons beyond the critical size for ferroelectricity are achieved in 2D materials through the defects engineering. The emerged merons further undergoes rich topological phase transition under external stimuli or through vacancy engineering.

Abstract

Atomic-scale polar topological configurations, such as skyrmions and merons, have garnered enormous interest due to their rich emergent physical phenomena and promising applications in next-generation electronics. Despite recent progress in the exploration of 2D ferroelectrics, isolated polar topological structures in 2D lattices have not yet been explored. Here, an original design principle is proposed to remove the point group limit for polar structures while achieving atomic-scale polar topological structures in non-ferroelectric monolayers caused by defects in 2D materials. The first-principles calculations show that an isolated polar meron with a diameter < 3.0 nm is generated in the deficient lead chalcogenide monolayer, and its formation is attributed to the synergic effects of vacancy-induced radial atomic displacements and symmetry reduction in 2D materials. The emergent polar meron can transform to rich topological configurations under external stimuli or by manipulation of the defect concentrations. Furthermore, this strategy of atomic-scale symmetry breaking via point defect engineering can be applied to a wide variety of 2D materials to induce polar topological structures. This work generalizes the polar topology from perovskite oxides to 2D materials, facilitating exciting opportunities to create high-density topological configurations that enable the exploration of meron/skyrmion-based functional nanodevices.

Magnetic liquid metal (MLM) is a mixture of magnetic particles with gallium-based liquid metals which utilizes an unconventional combination of fluidity, high thermal/electrical conductivity, biocompatibility, and magnetism. This work comprehensively reviews recent developments in the MLMs from the materials to methods of preparations, locomotion of MLMs, their applications, and future outlooks.

Abstract

Magnetic liquid metal (MLM) is a mixture of magnetic particles with gallium-based liquid metals which utilizes an unconventional combination of fluidity, high thermal/electrical conductivity, biocompatibility, and magnetism. Recently, from materials to applications, studies on MLMs have drastically increased. Single or multiple MLMs can be precisely positioned or can act as a carrier for handling other objects. MLMs are also used in biomedical applications such as cancer treatment by hyperthermia and precision delivery of cancer drugs on tumors, or antibacterial coating which kills bacteria. In electronics applications, MLMs are used for magnetic field-driven patterning of metallic lines, reconfigurable interconnects, electronic tattoos, and reconfigurable electromagnetic wave shielding. Phase change (solid/liquid) of MLMs adds another unique capability, morphing. A combination of innovations in the micro/nano robots and MLMs has huge potential to bring an unprecedented disruptive technology for a wide variety of applications including self-morphing shape-recovery robots, highly localized cancer treatment, and reconfigurable stealth/camouflage, among others. This article comprehensively reviews recent developments in MLMs from the materials to methods of preparation, locomotion of MLMs, their applications, and future outlooks.

Highly aligned 1D tellurium is epitaxially grown on 2D monolayer transition metal dichalcogenides (TMDs). A one-pot chemical vapor deposition (CVD) technique eliminates the normally required transfer steps, thereby producing mixed-dimensional heterostructures with an ultraclean interface and good contact. The mixed-dimensional p-n Te/MoSe₂ heterojunction photodetector presents self-driven behavior with high responsivity (328 mA W⁻¹), external quantum efficiency (79 %), and specific detectivity (8.2  ×  10⁹ Jones).

Abstract

Mixed-dimensional heterostructures provide additional freedom to construct diverse functional electronic and optoelectronic devices, gaining significant interest. Herein, highly-aligned pseudo-1D tellurium is epitaxially grown on 2D monolayer transition metal dichalcogenides (TMDs), including MoSe₂, MoS₂, and WS₂. A one-pot chemical vapor deposition (CVD) technique eliminates the normally required transfer steps, thereby producing mixed-dimensional heterostructures with an ultraclean interface. The controllable epitaxial growth of Te/TMD heterostructures are verified by Raman, scanning probe microscopy (SPM), and transmission electron microscopy (TEM) observation. The photoluminescence results indicate that the emission from TMDs is quenched in the heterostructure, confirming the efficient transfer of photogenerated carriers from TMDs to Te. Additionally, the mixed-dimensional p-n Te/MoSe₂ heterojunction photodetector presents self-driven behavior with high responsivity (328 mA W⁻¹), external quantum efficiency (79%), and specific detectivity (8.2 ×  10⁹ Jones). The modified facile synthesis strategy and proposed growth mechanism in this study shed light on synthesizing mixed-dimensional heterojunctions. This opens avenues for fabricating functional devices with reduced sizes and high densities, further enabling miniaturization and integration opportunities.

Nature Photonics, Published online: 30 November 2023; doi:10.1038/s41566-023-01342-6

Memristor phase shifters

Nature Materials, Published online: 28 November 2023; doi:10.1038/s41563-023-01714-x

By inserting an epitaxial in-plane buffer layer of Bi5FeTi3O15, an artificial flux closure architecture enables ferroelectric polarization from a single unit cell of BaTiO3 or BiFeO3.

Nature Materials, Published online: 28 November 2023; doi:10.1038/s41563-023-01692-0

A compact, time- and energy-efficient computing architecture — based on ferroelectric-defined reconfigurable two-dimensional photodiode arrays — is shown to be capable of in-memory sensing and computing.

Nature Electronics, Published online: 30 November 2023; doi:10.1038/s41928-023-01073-0

Rhombohedral-stacked molybdenum disulfide with sliding ferroelectric behaviour can be used to create atomically thin ferroelectric transistors for computing-in-memory device applications.

A biomimetic nociceptor with multi-dimensional mechano-sensing ability is demonstrated. Centrosymmetric crystal ZGGO:Cr exhibits strong force-induced electricity and luminescence output, with electrical signals quantitatively evaluating the pain level and the visual luminescence output providing pain site. This biomimetic nociceptor can be integrated with wireless communication module and intelligent analysis module to enable accurate recognition and feedback toward external harmful stimuli.

Abstract

Pain sensation is a crucial aspect of perception in the body. Force-activated nociceptors encode electrochemical signals and yield multilevel information of pain, thus enabling smart feedback. Inspired by the natural template, multi-dimensional mechano-sensing materials provide promising approaches for biomimetic nociceptors in intelligent terminals. However, the reliance on non-centrosymmetric crystals has narrowed the range of these materials. Here centrosymmetric crystal Cr³⁺-doped zinc gallogermanate (ZGGO:Cr) with multi-dimensional mechano-sensing is reported, eliminating the limitation of crystal structure. Under forces, ZGGO:Cr generates electrical signals imitating those of neuronal systems, and produces luminescence for spatial mapping of mechanical stimuli, suggesting a path toward bionic pain perception. On that basis, a wireless biomimetic nociceptor system is developed and a smart pain reflex in a robotic hand and robot-assisted biopsy surgery of rat and dog is achieved.