Jing Zhang

The proposed strategy that combines magnetic and optical fields to achieve independent position control and task execution of multiple microrobotic collectives in 3D space. The magnetic field excites the self-assembly of colloids and maintains the self-assembled microrobotic collectives without disassembly, while the optical field drives selected microrobotic collectives to perform different tasks.

Abstract

Inspired by natural swarms, various methods are developed to create artificial magnetic microrobotic collectives. However, these magnetic collectives typically receive identical control inputs from a common external magnetic field, limiting their ability to operate independently. And they often rely on interfaces or boundaries for controlled movement, posing challenges for independent, three-dimensional(3D) navigation of multiple magnetic collectives. To address this challenge, self-assembled microrobotic collectives are proposed that can be selectively actuated in a combination of external magnetic and optical fields. By harnessing both actuation methods, the constraints of single actuation approaches are overcome. The magnetic field excites the self-assembly of colloids and maintains the self-assembled microrobotic collectives without disassembly, while the optical field drives selected microrobotic collectives to perform different tasks. The proposed magnetic-photo microrobotic collectives can achieve independent position and path control in the two-dimensional (2D) plane and 3D space. With this selective control strategy, the microrobotic collectives can cooperate in convection and mixing the dye in a confined space. The results present a systematic approach for realizing selective control of multiple microrobotic collectives, which can address multitasking requirements in complex environments.

A one-step sample preparation strategy by leveraging label-free impedance flow cytometry (IFC) based microfluidics to solve the problem of simultaneous sorting and desalting of single-cells is proposed. With this strategy, one only needs to flow mixed cell samples into the microfluidic chip, and then get the target cell samples from the outlet for direct single-cell MS analysis.

Abstract

Single-cell mass spectrometry (MS) is significant in biochemical analysis and holds great potential in biomedical applications. Efficient sample preparation like sorting (i.e., separating target cells from the mixed population) and desalting (i.e., moving the cells off non-volatile salt solution) is urgently required in single-cell MS. However, traditional sample preparation methods suffer from complicated operation with various apparatus, or insufficient performance. Herein, a one-step sample preparation strategy by leveraging label-free impedance flow cytometry (IFC) based microfluidics is proposed. Specifically, the IFC framework to characterize and sort single-cells is adopted. Simultaneously with sorting, the target cell is transferred from the local high-salinity buffer to the MS-compatible solution. In this way, one-step sorting and desalting are achieved and the collected cells can be directly fed for MS analysis. A high sorting efficiency (>99%), cancer cell purity (≈87%), and desalting efficiency (>99%), and the whole workflow of impedance-based separation and MS analysis of normal cells (MCF-10A) and cancer cells (MDA-MB-468) are verified. As a standalone sample preparation module, the microfluidic chip is compatible with a variety of MS analysis methods, and envisioned to provide a new paradigm in efficient MS sample preparation, and further in multi-modal (i.e., electrical and metabolic) characterization of single-cells.

A new microfluidic method for antibody screening that allows for deterministic encapsulation of two cells and for frequent washes with minimal losses in the droplet. This new method is powered by droplet-digital microfluidics, which combines droplet-in-flow techniques with digital microfluidic for the generation and the manipulation of droplets.

Abstract

Monoclonal antibody (mAb) discovery plays a prominent role in diagnostic and therapeutic applications. Droplet microfluidics has become a standard technology for high-throughput screening of antibody-producing cells due to high droplet single-cell confinement frequency and rapid analysis and sorting of the cells of interest with their secreted mAbs. In this work, a new method is described for on-demand co-encapsulation of cells that eliminates the difficulties associated with washing in between consecutive steps inside the droplets and enables the washing and addition of fresh media. The new platform identifies hybridoma cells that are expressing antibodies of interest using antibody-characterization assays to find the best-performing or rare-cell antibody candidates.

Through constructing 2D nanosheet arrays and moisture-induced primary battery system, a high-performance and flexible hydroelectric generator is developed with a sustained open-circuit voltage of 0.65 V, and an excellent short-circuitcurrent of 0.51 mA. Moreover, these prepared flexible hydroelectric generators can be used in the wearable self-powered field.

Abstract

Flexible hydroelectric generators (HEGs) are promising self-powered devices that spontaneously derive electrical power from moisture. However, achieving the desired compatibility between a continuous operating voltage and superior current density remains a significant challenge. Herein, a textile-based van der Waals heterostructure is rationally designed between conductive 1T phase tungsten disulfide@carbonized silk (1T-WS₂@CSilk) and carbon black@cotton (CB@Cotton) fabrics with an asymmetric distribution of oxygen-containing functional groups, which enhances the proton concentration gradients toward high-performance wearable HEGs. The vertically staggered 1T-WS₂ nanosheet arrays on the CSilk fabric provide abundant hydrophilic nanochannels for rapid carrier transport. Furthermore, the moisture-induced primary battery formed between the active aluminum (Al) electrode and the conductive textiles introduces the desired electric field to facilitate charge separation and compensate for the decreased streaming potential. These devices exhibit a power density of 21.6 µW cm⁻², an open-circuit voltage (V _oc) of 0.65 V sustained for over 10 000 s, and a current density of 0.17 mA cm⁻². This performance makes them capable of supplying power to commercial electronics and human respiratory monitoring. This study presents a promising strategy for the refined design of wearable electronics.

The barriers of organisms to water loss are provided by extracellular lipids, but the mechanisms that sculpt these rather rigid lipid layers are not fully understood. In human skin, covalently bound ultra-long ceramides on the surface of corneocytes, the corneocyte lipid envelope, fluidize and rearrange neighboring extracellular matrix lipids, ensuring their malleability into a functional protective barrier against the environment.

Abstract

When the ancestors of men moved from aquatic habitats to the drylands, their evolutionary strategy to restrict water loss is to seal the skin surface with lipids. It is unknown how these rigid ceramide-dominated lipids with densely packed chains squeeze through narrow extracellular spaces and how they assemble into their complex multilamellar architecture. Here it is shown that the human corneocyte lipid envelope, a monolayer of ultralong covalently bound lipids on the cell surface protein, templates the functional barrier assembly by partly fluidizing and rearranging the free extracellular lipids in its vicinity during the sculpting of a functional skin lipid barrier. The lipid envelope also maintains the fluidity of the extracellular lipids during mechanical stress. This local lipid fluidization does not compromise the permeability barrier. The results provide new testable hypotheses about epidermal homeostasis and the pathophysiology underlying diseases with impaired lipid binding to corneocytes, such as congenital ichthyosis. In a broader sense, this lipoprotein-mediated fluidization of rigid (sphingo)lipid patches may also be relevant to lipid rafts and cellular signaling events and inspire new functional materials.

In this review, the research progress of electronic devices based on 2DM-SAM heterojunction is emphatically summarized, including vertical tunneling devices, horizontal conducting devices, and hybrid superlattice devices. The structure, mechanism, functional characteristics, performance regulation, and other aspects of different types of devices are discussed in detail. Finally, the future development directions and application fields of 2DM-SAM heterojunction devices are discussed.

Abstract

2D materials (2DMs), known for their atomically ultrathin structure, exhibit remarkable electrical and optical properties. Similarly, molecular self-assembled monolayers (SAMs) with comparable atomic thickness show an abundance of designable structures and properties. The strategy of constructing electronic devices through unique heterostructures formed by van der Waals assembly between 2DMs and molecular SAMs not only enables device miniaturization, but also allows for convenient adjustment of their structures and functions. In this review, the fundamental structures and fabrication methods of three different types of electronic devices dominated by 2DM-SAM heterojunctions with varying architectures are timely elaborated. Based on these heterojunctions, their fundamental functionalities and characteristics, as well as the regulation of their performance by external stimuli, are further discussed.

Nature Electronics, Published online: 27 June 2024; doi:10.1038/s41928-024-01190-4

Two-dimensional (2D) semiconductors could be used to build advanced 3D chips based on monolithic 3D integration. But challenges related to growing single-crystalline materials at low temperatures — as well as enhancing the performance of 2D transistors — need to be addressed first.

Nature Electronics, Published online: 27 June 2024; doi:10.1038/s41928-024-01191-3

Atomic-layer yttrium doping can be used to form ohmic contacts between molybdenum disulfide channel layers and metals, creating high-performance 2D transistors with low contact resistances.

A full-color ultrathin graphite-based electrochromic device is developed using Fabry-Perot (F-P) nanocavities. This device controls the optical reflectivity by adjusting the optical properties of ultrathin graphite through lithium-ion intercalation/de-intercalation and the thickness of the dielectronic SiO₂ layer. These findings pave the way for full-color displays with minimal energy consumption and inspire extensive research in low-power photonics.

Abstract

Ultrathin graphite-based materials have revolutionized optoelectronics through their multispectral and energy-efficient tunability. However, their narrow color range poses a challenge in applications requiring a broad spectrum of colors for effective information delivery or aesthetic enhancement. Here, full-color tunability is achieved in ultrathin graphite-based electrochromic devices using Fabry-Perot (F-P) nanocavities. By adjusting the optical properties (n, k) of ultrathin graphite through lithium-ion intercalation/de-intercalation and the thickness of the dielectronic SiO₂ layer, managed to control the optical reflectivity in the visible spectrum. Moreover, this prototype device consumes only 1.59 mW cm⁻², just one-tenth of the commercial organic light-emitting displays’ energy usage. Furthermore, the pixel size in the Fabry-Perot nanocavity-type electrodes can be reduced to 2 µm, under half that of contemporary displays like Micro-LED. These results pave the way for full-color displays with minimal energy consumption and inspire extensive research in low-power photonics.

This work introduces an innovative inverse design framework for multifunctional on-chip metasurfaces, enabling hypermultiplexed RGB-hologram. By combining wavelengths, distances, and excitation directions multiplexing, a 36-channel metasurface is achieved. The effectiveness of the proposed inverse design method is validated through 3D full-wave simulations. This approach simplifies metasurface design and advances versatile photonic applications.

Abstract

The waveguide-integrated metasurface introduces a novel photonic chip capable of converting guided modes into free-space light. This enables functions such as off-chip beam focusing, steering, and imaging. The challenge lies in achieving hyper-multiplexing across diverse parameters, including guided-wave mode type, direction, polarization, and notably, multiple wavelengths. Here, a comprehensive end-to-end inverse design framework is introduced, rooted in a physical model, for the multifunctional design of on-chip metasurfaces. This framework allows for metasurface optimization through a target-field-driven iteration process. A hypermultiplexed on-chip metasurface capable of generating red-green-blue holograms at multiple target planes is demonstrated, with both independent and cooperative control over guided-wave direction. Significantly, the proposed method streamlines the design process utilizing only the positions of meta-atoms as the design variable. Nine independent holographic channels are demonstrated through a combination of wavelength and distance multiplexing. Moreover, by incorporating the excitation direction into the design, the metasurface produces a total of 36 distinct holograms. The robustness of these results against fabrication discrepancies is validated through 3D full-wave electromagnetic simulations, aligning well with advanced manufacturing techniques. The research presents a universal design framework for the development of multifunctional on-chip metasurfaces, opening up new avenues for a wide range of applications.

Flexible and transparent fully 2D materials based memristors exhibit reliable threshold resistive switching behavior with a high degree of stochasticity. A true random number generator circuit for advanced data encryption can be developed using the Graphene/hexagonal boron nitride/Graphene devices with high cycle-to-cycle variability of switching voltages and state currents as entropy source.

Abstract

Data encryption is an essential building block in modern electronic systems to prevent spying and hacking. Every day more and more objects produce electronic data, and this needs to be encrypted before being transmitted. Hence, designing devices, circuits, and systems for data encryption that can be integrated in all kinds of objects and that consume low amounts of energy is highly necessary. Here, this work reports the fabrication of flexible and transparent electronic circuits consisting of devices that exhibit threshold-type resistive switching with a high degree of stochasticity. The cycle-to-cycle variability of switching voltages and state currents is significant but confined within a well-defined range, which is consistent across multiple devices. This allows to design an efficient protocol for true random number generation. The circuits are fabricated with only synthetic 2D materials, can be fabricated in a scalable manner, and can be integrated in any object.

Mechanical control of bending strain induces the change in the piezoelectricity-induced effective refractive index, which allows the manipulation of the photonic bandgap in P/mAu/M/CPB@Al₂O₃@PAN device, and the subsequent shift of low-loss single-mode lasing serves as signal sources with high recognizability (F _OSR ≈ 600), ultrasensitivity (S_λ ≈ 160 nm RIU⁻¹), and superior mechanical reliability for sensing application of a strain-gauge nanolaser.

Abstract

Interest in flexible photonics has been motivated by the development of artificial smart skins. In particular, coupling of photonics and mechanics can offer opportunities to realize ultrasensitive strain sensor, however, low-cost fabrication of flexible sensing device with desired photonic functionality remains a challenge. Hereby, the study reports an ultrasensitive strain-gauge sensor based on the poly(ethylenenaphthalate (PEN))/monocrystal Au/MgF₂/CsPbBr₃ nanorod/Al₂O₃/polyacrylonitrile (in short P/mAu/M/CPB@Al₂O₃@PAN), which are sensitive to nanoscale structure alterations of PEN substrate via the stress response of the single-mode laser based on the piezoelectric-effect. Wherein a low-threshold single-mode lasing (P _th ≈ 170 nJ cm⁻²) is achieved through coating Al₂O₃ on the CsPbBr₃ nanorod, producing the higher quality factor (Q ≈ 1637) to guarantee a much higher sensitivity in sensing application. Reversible spectral regulating of ≈3 nm in single-mode-lasing wavelength, with a subnanometre scale resolution <0.4 nm and the wavelength sensitivity (S_λ) as high as 160 nm RIU⁻¹, is validated in response to applied strain ranging from −1.31% to 1.31%. This work not only represents essential progress in construction of ultrasensitive and cost-effective flexible photonic sensor, but also lays the foundation for the potential application in smart photonic skins.

A 2D semiconductor/α-In₂Se₃ ferroelectric tunnel junction is demonstrated in this work for advanced memresitive technologies. The 2D semiconducting electrode can depress thermionic emission, enhance Schottky barrier modulation, and be modulated by gate voltage. Therefore, the structure exhibits superior characteristics such as high robustness, temperature independence, gate programmability, giant tunnel electroresistance, and robust negative differential resistance effect.

Abstract

Ferroelectric tunnel junctions (FTJs) have gained substantial attention as emerging electronic devices such as nonvolatile memory and artificial synapse, owing to their low power consumption and nonvolatile properties. In this work, a 2D semiconductor (2DS)/α-In₂Se₃/metal FTJ structure is proposed that combines a semiconductor ferroelectric material and a semiconducting electrode. The incorporation of 2DS not only enhances the barrier height modulation but also provides an effective approach to mitigate the thermionic current leakage. Notably, the proposed MoS₂/α-In₂Se₃/Ti FTJs exhibit both room-temperature negative differential resistance (NDR) effect and high tunnel electroresistance (TER) exceeding 10⁴ simultaneously. Furthermore, the versatility of this structure extends to several 2DS (including MoS₂, PdSe₂, and SnSe₂) and graphene electrodes to rationalize both tunneling and thermionic current transport mechanisms. The proposed 2DS/α-In₂Se₃/metal FTJs present great superiority over existing structures in terms of robustness, temperature independence, high TER, and versatility for various potential application scenarios.

Ionic Liquid Interface

Cell culture at the liquid interface has been attracting attention as an aspect of mechanobiology. In article number 2310105, Takeshi Ueki, Jun Nakanishi, and co-workers propose ionic liquid interface as a novel liquid cell culture platform. Phenotype of cells is determined by the mechanical properties of protein nanolayers which is depended on the chemical structure of the ionic liquid.

It is found that curvature in 2D semiconductors triggers the modified geometric potential with curvature-induced bandgap change, resembling the effective potential of black holes. The atomic-scale observation of bound states in the modified geometric potential shows an analog of the stable orbits near black holes. The modified geometric potential is related to curvature-induced variations in both band gap and spin-orbit interaction.

Abstract

One of the exotic expectations in the 2D curved spacetime is the geometric potential from the curvature of the 2D space, still possessing unsolved fundamental questions through Dirac quantization. The atomically thin 2D materials are promising for the realization of the geometric potential, but the geometric potential in 2D materials is not identified experimentally. Here, the curvature-induced ring-patterned bound states are observed in structurally deformed 2D semiconductors and formulated the modified geometric potential for the curvature effect, which demonstrates the ring-shape bound states with angular momentum. The formulated modified geometric potential is analogous to the effective potential of a rotating charged black hole. Density functional theory and tight-binding calculations are performed, which quantitatively agree well with the results of the modified geometric potential. The modified geometric potential is described by modified Gaussian and mean curvatures, corresponding to the curvature-induced changes in spin-orbit interaction and band gap, respectively. Even for complex structural deformation, the geometric potential solves the complexity, which aligns well with experimental results. The understanding of the modified geometric potential provides us with an intuitive clue for quantum transport and a key factor for new quantum applications such as valleytronics, spintronics, and straintronics in 2D semiconductors.

By integrating a zinc anode-based electrochromic device and an Internet of Things (IoT) system, a novel window system is demonstrated. This window system facilitates the continuous conversion of photovoltaic-generated electricity to power indoor appliances while also allowing dynamic control of visible and near-infrared light. These findings open up new opportunities for the development of electrochromic windows.

Abstract

Integration of solar cells and electrochromic windows offers crucial contributions to green buildings. Solar-charging zinc anode-based electrochromic devices (ZECDs) present opportunities for addressing the solar intermittency issue. However, the limited energy storage capacity of ZECDs results in wasted harnessing of solar energy as well as overcharging. Herein, spectral-selective dual-band ZECDs that continuously transport solar energy to indoor appliances by remotely controlling the repeated bleached-tinted cycles during the daytime, are reported. Hexagonal phase cesium-doped tungsten bronze (h-Cs_0.32WO₃, CWO) nanocrystals are adopted for dual-band ZECDs due to their independent control ability of near-infrared (NIR) and visible (VIS) light transmittance (∆T = 73.0%, 700 nm; ∆T = 83.7%, 1200 nm) and excellent cycling stability (0.8% optical contrast decay at 1200 nm after 10 000 cycles). The prototype device (i.e., CWO//Zn//CWO) delivers extraordinary thermal insulation capability, displaying a 10 °C difference between “bright” and “dark” modes. Furthermore, an Internet of Things (IoT) controller to control the NIR and VIS lights of the CWO//Zn//CWO window wirelessly with a smartphone, empowering the continuous discharging of the solar-charged window during the daytime remotely, is developed. Such windows represent an intriguing potential technology whose future impact on green buildings may be substantial.

Exploring novel techniques for optimizing ceramic catalyst filter (CCF) systems, textured fused silica-based waveguides are integrated with ultraviolet (UV) light-emitting diodes (LEDs) for the photocatalytic reactions, enhancing formaldehyde (HCHO) removal efficiency by 70% compared to the conventional CCF systems. The simulated and experimental evidence validates UV light extraction from textured waveguides into the channels, revolutionizing HCHO removal even at lower UV LED power.

Abstract

The cordierite-based ceramic catalyst filter (CCF) has attracted considerable attention as a promising future air purification system due to its ability to filtrate particulate matter (PM), as well as decompose volatile organic compounds (VOCs) through ultraviolet (UV)-activated photocatalytic reactions. Its performance, however, is strictly limited because majority of UV photons are absorbed near the entrance of the high-aspect-ratio air-flow channels, thus, only a limited portion of photocatalysts is activated during the flow of polluted air. In this study, a high-performance CCF is presented featuring textured waveguides (TWs) aligned with an array of UV light-emitting diodes (LEDs) emitting at a peak wavelength of 365 nm, which are inserted into an array of high-aspect-ratio channels. TWs ensure the delivery of UV photons deep inside channels via total internal reflection and scattering, enabling the activation of majority of photocatalysts, resulting in remarkable improvement in VOCs removal efficiency. The proposed CCF system exhibits much higher formaldehyde (HCHO) removal efficiency by 70% compared to conventional CCF systems even subjected to much lower UV light power densities. It is strongly believed that it is possible to further improve the removal efficiency, while maintaining effective PM filtering and ultralow electrical power consumption, by optimization of the geometry of the CCF system with TWs.

The intercalation of large organic molecules decouples the interlayer interaction of VOCl and induces the intralayer ferromagnetic (FM) coupling. Meanwhile, the intercalation also guides the charge injection, promotes the hybridization of 3d orbital electrons, and further strengthens the FM interaction, ultimately achieving the transition from pristine antiferromagnetism to room-temperature ferromagnetism with out-of-plane anisotropy.

Abstract

2D van der Waals (vdW) magnets are gaining attention in fundamental physics and advanced spintronics, due to their unique dimension-dependent magnetism and potential for ultra-compact integration. However, achieving intrinsic ferromagnetism with high Curie temperature (T _C) remains a technical challenge, including preparation and stability issues. Herein, an applicable electrochemical intercalation strategy to decouple interlayer interaction and guide charge doping in antiferromagnet VOCl, thereby inducing robust room-temperature ferromagnetism, is developed. The expanded vdW gap isolates the neighboring layers and shrinks the distance between the V-V bond, favoring the generation of ferromagnetic (FM) coupling with perpendicular magnetic anisotropy. Element-specific X-ray magnetic circular dichroism (XMCD) directly proves the source of the ferromagnetism. Detailed experimental results and density functional theory (DFT) calculations indicate that the charge doping enhances the FM interaction by promoting the orbital hybridization between t _{2 g} and e_g . This work sheds new light on a promising way to achieve room-temperature ferromagnetism in antiferromagnets, thus addressing the critical materials demand for designing spintronic devices.

To advance high-quality imaging units in optoelectronic systems, a phototransistor that shows reconfigurable multifunctional photoresponsive behaviors with superior characteristics is reported. Thanks to the programmable two-dimensional electron gas which can be modulated by drain/gate voltage inputs under different light exposure, a triplex photo-imaging functionality with capable of self-powering, photoconduction, and photo-synaptic operation is achieved, providing guidance toward system-on-chip photoelectric systems.

Abstract

High-quality imaging units are indispensable in modern optoelectronic systems for accurate recognition and processing of optical information. To fulfill massive and complex imaging tasks in the digital age, devices with remarkable photoresponsive characteristics and versatile reconfigurable functions on a single-device platform are in demand but remain challenging to fabricate. Herein, an AlGaN/GaN-based double-heterostructure is reported, incorporated with a unique compositionally graded AlGaN structure to generate a channel of polarization-induced two-dimensional electron gas (2DEGs). Owing to the programmable feature of the 2DEGs by the combined gate and drain voltage inputs, with a particular capability of electron separation, collection and storage under different light illumination, the phototransistor shows reconfigurable multifunctional photoresponsive behaviors with superior characteristics. A self-powered mode with a responsivity over 100 A W⁻¹ and a photoconductive mode with a responsivity of ≈10⁸ A W⁻¹ are achieved, with the ultimate demonstration of a 10 × 10 device array for imaging. More intriguingly, the device can be switched to photoelectric synapse mode, emulating synaptic functions to denoise the imaging process while prolonging the image storage ability. The demonstration of three-in-one operational characteristics in a single device offers a new path toward future integrated and multifunctional imaging units.

When isotropic epitaxial Germanium (Ge) is engineered into porous structure, an anisotropic porous Ge (PGe) layer is obtained. Using effective medium approximation theory, the optical constants are derived from ellipsometric data, showing the optical anisotropy (birefringence) and depolarization factors can be controlled by tuning the porosification parameters. This optical anisotropy in PGe allows applications in sensors and birefringence-related optical devices.

Abstract

Porous semiconductors have garnered significant attention owing to their distinctive physical and chemical properties. In this study, optical anisotropy is presented in porous germanium (PGe) on a Si (001) substrate. Both n- and p-type PGe, achieved through bipolar electrochemical etching, exhibit optical anisotropy along the Ge <001> direction, as determined by spectroscopic ellipsometry. Birefringence and depolarization factors are controllable by adjusting the etching parameters and doping concentration of the epitaxial Ge layer. The gradient porosity and pore distribution in PGe can be well captured by the optical models. The findings of optical anisotropy in PGe-on-Si hold promise for applications in optical elements or sensors for gas or biomolecules.

Tb³⁺-doped Ca₃Ga₄O₉ material can exhibit color-tunable photoluminescence and non-pre-irradiation mechanoluminescence. It primarily shows the important application values for multicolor displays, stress imaging, and anti-counterfeiting signature.

Abstract

Materials that can emit light under optical/mechanical stimulation are usually called photoluminescent/mechanoluminescent (PL/ML) materials. PL materials are used in diverse fields for half a century. While, ML materials have burst out in the last two decades, and now are showing great application potential in the fields of anti-counterfeiting, information storage, and stress imaging. It is of great significance to explore new luminescent materials with PL and ML dual response. In this study, Tb³⁺-doped Ca₃Ga₄O₉ phosphors with color-tunable PL and non-pre-irradiation ML properties are reported. Ca₃Ga₄O₉ exhibits a broadband blue emission centering at 425 nm, which originates from the ⁴T₂-⁴A₂ transition of electrons in d orbits of Ga³⁺. Due to the energy transfer from host to Tb³⁺, color-tunable emission from blue to cyan, and ultimately to green can be realized by increasing the concentration of Tb³⁺. Particularly, ML is seen from Ca₃Ga₄O₉:Tb³⁺ under grinding and from the Ca₃Ga₄O₉:Tb³⁺/PDMS film under bending or stretching originated from the triboelectric mechanism. The non-pre-irradiation ML behavior is evidenced by the contrast thermoluminescence (TL) experiments. This study not only provides a new candidate toward multi-purpose luminescent applications, but also demonstrates a good case in which the triboelectric effect can efficiently trigger the non-pre-irradiation ML behavior.

Nature Materials, Published online: 24 June 2024; doi:10.1038/s41563-024-01926-9

Lipid bilayers under the influence of electric fields, similar to those across cell membranes, act as moderators of shear force between solid surfaces, presenting a new route to tuning interfacial properties across thin films.

Nature Communications, Published online: 24 June 2024; doi:10.1038/s41467-024-49735-7

Understanding FRET of metal nanoparticles at the atomic level has long been a challenge. Here, the authors have achieved FRET activity with atomically precise Cu clusters by using a cocrystallisation-induced spatial confinement strategy.

A simple and innovative strategy based on phase separation is developed to prepare multifunctional noncovalent cross-linked ionogels by 3D printing of HPA in BMIMBF4. These ionogels show remarkable stretchability, ultra-low hysteresis, excellent temperature tolerance, extraordinary ionic conductivity, and outstanding durability. Furthermore, the ionogels exhibit unique thermochromic and multiple photoluminescent properties, which can synergistically be applied for thermo-mechano-multimodal ionotronics and anti-counterfeiting.

Abstract

Ionogel has recently emerged as a promising ionotronic material due to its good ionic conductivity and flexibility. However, low stretchability and significant hysteresis under long-term loading limit their mechanical stability and repeatability. Developing ultralow hysteresis ionogels with high stretchability is of great significance. Here, a simple and effective strategy is developed to fabricate highly stretchable and ultralow-hysteresis noncovalent cross-linked ionogels based on phase separation by 3D printing of 2-hydroxypropyl acrylate (HPA) in 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄). Ingeniously, the sea-island structure of the physically cross-linked network constructed by the smaller nanodomains and larger nanodomain clusters significantly minimizes the energy dissipation, endowing these ionogels with remarkable stretchability (>1000%), ultra-low hysteresis (as low as 0.2%), excellent temperature tolerance (−33–317 °C), extraordinary ionic conductivity (up to 1.7 mS cm⁻¹), and outstanding durability (5000 cycles). Moreover, due to the formation of nanophase separation and cross-linking structure, the as-prepared ionogels exhibit unique thermochromic and multiple photoluminescent properties, which can synergistically be applied for anti-counterfeiting and encrypting. Importantly, flexible thermo-mechano-multimodal visual ionotronic sensors for strain and temperature sensing with highly stable and reproducible electrical response over 20 000 cycles are fabricated, showing synergistically optical and electrical output performances.

Nature Communications, Published online: 22 June 2024; doi:10.1038/s41467-024-49518-0

The Mermin-Wagner theorem states that for short-range isotropic interactions, magnetic order in two dimensions is destroyed by magnetic fluctuations at finite temperatures. Observing this situation is challenging due to the finite size of typical laboratory samples. Here, Kiaba et al observe the suppression of magnetic order in oxide superlattices, at the thickness of the superlattice layers are reduced to one monolayer.

This review provides a comprehensive overview of the research progress of various piezoelectric biomaterials for applications in biomedicine and nanotechnology. Furthermore, the remaining challenges and future perspectives on the development of high-performance piezoelectric biomaterials are discussed. This review aims to advance the understanding of structure–property relationship and promote the rational design of innovative piezoelectric biomaterials.

Abstract

Bioelectricity provides electrostimulation to regulate cell/tissue behaviors and functions. In the human body, bioelectricity can be generated in electromechanically responsive tissues and organs, as well as biomolecular building blocks that exhibit piezoelectricity, with a phenomenon known as the piezoelectric effect. Inspired by natural bio-piezoelectric phenomenon, efforts have been devoted to exploiting high-performance synthetic piezoelectric biomaterials, including molecular materials, polymeric materials, ceramic materials, and composite materials. Notably, piezoelectric biomaterials polarize under mechanical strain and generate electrical potentials, which can be used to fabricate electronic devices. Herein, a review article is proposed to summarize the design and research progress of piezoelectric biomaterials and devices toward bionanotechnology. First, the functions of bioelectricity in regulating human electrophysiological activity from cellular to tissue level are introduced. Next, recent advances as well as structure–property relationship of various natural and synthetic piezoelectric biomaterials are provided in detail. In the following part, the applications of piezoelectric biomaterials in tissue engineering, drug delivery, biosensing, energy harvesting, and catalysis are systematically classified and discussed. Finally, the challenges and future prospects of piezoelectric biomaterials are presented. It is believed that this review will provide inspiration for the design and development of innovative piezoelectric biomaterials in the fields of biomedicine and nanotechnology.