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• The RMS voltage response of the energy harvester is increased by up to 1225%;. • We present a new quasi-zero stiffness mechanism for energy harvesters;. • We derive a stable solution to the adverse effect of the offset distance;. • The nonlinear dynamics of the proposed systems are analyzed comprehensively. The self-powered sensing technology based on gravity-rotation-excited vibration energy harvesting (GRE-VEH) enables information acquisition directly from rotatory machines online. However, the centrifugal effect due to the distance between the mass centroid of the energy harvester and the rotating axis (i.e., offset distance) seriously limits its broad engineering applications. To address this issue, we propose methods of using a tensile force provided by pre-deformed springs to counter the constant centrifugal force around the target rotation speed for improving the performance of the energy harvester affected by offset configurations. The GRE-VEH system with a linear spring is first studied by experiments and simulations, where a distributed-parameter model is developed and experimentally validated. The results well validate the proposed mechanism, where the performance of the harvester prototype significantly increases (by up to 1225%). A parametric study is also performed theoretically. The results indicate that the best performance improvement can be obtained by tuning the parameters related to the tensile length, the stiffness, and the damping of the spring. To enable the proposed mechanism in large centrifugal force cases, a pair of negative springs is introduced to the system for constructing a quasi-zero stiffness (QZS) structure together with the linear spring. The new GRE-VEH system is theoretically studied by an updated model, where the system's main characteristics are revealed. The simulation results well indicate the feasibility of the method using the QZS mechanism. This work paves a new way of solving the offset distance problem for the application of the GRE-VEH and also provides new insight into the application of the QZS mechanism. [Display omitted] [ABSTRACT FROM AUTHOR]

• Distributed-parameter model for a doubly-clamped energy harvester affected by the misalignment-induced torsions in vibration environments. • Experimental validation for the developed model and the effects of the bending-torsional coupling vibration on the harvester. • Characterizations of the bending-torsional coupling vibration for the doubly-clamped beam structures. • Investigations on the effects of the key parameters on the torsion-induced jump-down phenomenon. This article presents a theoretical and experimental study on the unique bending-torsional coupling vibration of a doubly-clamped nonlinear piezoelectric energy harvester due to the misalignment of the centroid and the torsional axis in vibration environments. Based on the Euler-Bernoulli beam theory, the extended Hamilton's principle, and the Galerkin discretization, a distributed-parameter model considering the misalignment is developed, and the corresponding governing equations are formulated. The developed model is validated against experimental data and Finite Element Analysis, where good agreements are achieved. Effects of the key parameters on the system's responses, and the characteristics and the causes of the bending-torsional coupling vibration are studied numerically based on the developed model. The results show that the torsion-induced chaotic motion can activate the jump-down phenomenon, largely reducing the electrical output of the harvester. Additionally, the occurrence of the torsion-induced jump-down phenomenon is sensitive to the system's initial state in some cases and can be reduced or even avoided by effectively tuning parameters that have slight effects on the bending resonance, such as the preloaded axial force and the distance between the torsional axis and the centroid. [ABSTRACT FROM AUTHOR]

• A comprehensive electrode coverage design principle is developed. • Equivalent stiffness and damping are introduced to evaluate coupling coefficients. • Strongly coupled harvesters are compatible with a wide range of electrode coverage. Cantilevers are widely used for piezoelectric vibration energy harvesters (PEHs), thanks to the low resonance frequency and large mechanical strain under weak excitations. Electrode coverage optimization is essential for maximizing output power. In this study, bimorph cantilevers with segmented electrodes are developed to investigate the correlation between effective electrode coverage (EEC) and the harvesting behavior of piezoelectric cantilevers. A nonlinear electromechanical model is established using Hamilton's principle, numerically solved with the method of harmonic balance, and further validated by experimental measurements. Equivalent linear stiffness and equivalent mechanical damping ratio are firstly introduced for evaluating the equivalent effective electromechanical coupling coefficients and identifying strong and weak coupling harvesters. Both harvesters fabricated with and without proof mass behave mainly as strongly coupled systems and can obtain the maximum possible power at a very low EEC. Variation of EEC in higher range acquires almost constant maximum power on dramatically changing resistance. A comprehensive EEC design principle for acquiring the maximum output power is obtained for cantilevered PEHs. An optimal EEC obtaining the maximum effective electromechanical coupling coefficient is needed for acquiring the unique maximum power pick for weakly coupled harvesters, whereas a wide range of EEC can be used to maximize output power for harvesters those mainly behave as strongly coupled systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Propose an auxetic nonlinear piezoelectric energy harvester. • Utilize a pure mechanical structure to enhance both efficiency and bandwidth. • Perform finite element analysis to analyse the performance of the harvester. • Experimentally validate the proposed design and model and conduct parametric studies. In this paper, we design and experimentally validate an auxetic nonlinear piezoelectric energy harvester. This harvester adopts a clamp-clamp beam with auxetic structures, which can improve the efficiency and bandwidth of the energy harvesting based on a pure mechanical structure without outer magnets or stoppers. Finite element analysis is performed to analyse the effects of the auxetic structures on the efficiency and nonlinearity of the energy harvester. The lumped parameter model is utilized to predict the performance of the energy harvester, which well matches the experimental results. In the experimental validation, at 0.1 g base acceleration, the power output of the two types of auxetic energy harvesters is 173% and 94% higher than the conventional nonlinear energy harvester. Besides, the bandwidths of the two types of auxetic energy harvesters are broadened by 1556% and 2142% compared with the linear systems. [ABSTRACT FROM AUTHOR]

• Segmented arc-shaped piezoelectric energy harvester is proposed. • A new distributed-parameter electromechanical coupling model is developed. • The analytical solutions are validated with FEM and experiments. • Energy harvester characteristics with optimal parameters to generate maximum output voltage of 50 V are fully investigated. Advances in energy harvesting techniques, along with low-power electronic devices open up the possibility of developing self-powered engineering systems. Most existing energy harvesters are constructed with beams such as cantilevers, fully-clamped beams and buckled beams. Here we present an attempt to add a new design dimension to the piezoelectric energy harvesters (PEHs) by exploiting a curved-beam structure. This design will be shown to dramatically improve the contemporary harvester performance. To establish an analytical base for curved PEHs, we take a variable-curvature unimorph as the general modelling object and derive its governing equations based on the Timoshenko beam theory. Using the mode expansion method with the consideration of boundary conditions and continuous conditions, we present analytical solutions of the electrical and mechanical response of the PEH. The model developed is verified via the finite element method and it can accurately estimate the modal response of the curved PEH. Prototypes are fabricated and tested to validate the analytical model and solutions. Furthermore, we comprehensively analyzed the key parameter effects including the length of the straight beam, thickness ratio and Young's modulus on the performance of the PEH. The proposed analytical model provides an analytical guidance for composite arc-shaped PEHs with variable curvature and it also helps in the design and optimization of new PEHs. [ABSTRACT FROM AUTHOR]

Researchers have recently focused on improving the efficiency of piezoelectric energy harvesters by redesigning their substrate beams. Two approaches have been explored, including changing the shape of the cross-section area, i.e., width variation, and changing the thickness of cantilever beams. The width changing approach suffers from the deduction of output power from the piezoelectric elements of the trimmed-off regions, while performance deterioration does not occur in the thickness-variable approach. The benefit of thickness-variable beams on energy harvesting has been analyzed theoretically, but its detailed experimental study is still absent. In this study, we for the first time fabricate a thickness-variable harvester based on the Garolite FR-4 epoxy laminate, and validate the superiority of the variable thickness beam on the harvester performance enhancement. A theoretical model is developed based on the Euler-Bernoulli beam theory and numerically solved via the Rayleigh-Ritz method. We compare the thickness-variable composite beam configuration with a conventional uniform-thickness counterpart and unveil the beneficial effect of evenly-distributed strain on performance enhancement. Experiments indicate that the thickness-variable method increases on the energy harvester efficiency by 78%. [ABSTRACT FROM AUTHOR]

Implantable medical devices (IMDs), like pacemakers regulating heart rhythm or deep brain stimulators treating neurological disorders, revolutionize healthcare. However, limited battery life necessitates frequent surgeries for replacements. Ultrasound power transfer (UPT) emerges as a promising solution for sustainable IMD operation. Current research prioritizes implantable materials, with less emphasis on sound field analysis and maximizing energy transfer during wireless power delivery. This review addresses this gap. A comprehensive analysis of UPT technology, examining cutting-edge system designs, particularly in power supply and efficiency is provided. The review critically examines existing efficiency models, summarizing the key parameters influencing energy transmission in UPT systems. For the first time, an energy flow diagram of a general UPT system is proposed to offer insights into the overall functioning. Additionally, the review explores the development stages of UPT technology, showcasing representative designs and applications. The remaining challenges, future directions, and exciting opportunities associated with UPT are discussed. By highlighting the importance of sustainable IMDs with advanced functions like biosensing and closed-loop drug delivery, as well as UPT's potential, this review aims to inspire further research and advancements in this promising field., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

In this era of artificial intelligence and Internet of Things, emerging new computing paradigms such as in-sensor and in-memory computing call for both structurally simple and multifunctional memory devices. Although emerging two-dimensional (2D) memory devices provide promising solutions, the most reported devices either suffer from single functionalities or structural complexity. Here, this work reports a reconfigurable memory device (RMD) based on MoS 2 /CuInP 2 S 6 heterostructure, which integrates the defect engineering-enabled interlayer defects and the ferroelectric polarization in CuInP 2 S 6 , to realize a simplified structure device for all-in-one sensing, memory and computing. The plasma treatment-induced defect engineering of the CuInP 2 S 6 nanosheet effectively increases the interlayer defect density, which significantly enhances the charge-trapping ability in synergy with ferroelectric properties. The reported device not only can serve as a non-volatile electronic memory device, but also can be reconfigured into optoelectronic memory mode or synaptic mode after controlling the ferroelectric polarization states in CuInP 2 S 6 . When operated in optoelectronic memory mode, the all-in-one RMD could diagnose ophthalmic disease by segmenting vasculature within biological retinas. On the other hand, operating as an optoelectronic synapse, this work showcases in-sensor reservoir computing for gesture recognition with high energy efficiency., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

The intriguing biomineralization process in nature endows the mineralized biological materials with intricate microarchitected structures in a facile and orderly way, which provides an inspiration for processing ceramics. Here, we propose a simple and efficient manufacturing process to fabricate cellular ceramics in programmed cell-based 3D configurations, inspired by the biomineralization process of the diatom frustule. Our approach separates the ingredient synthesis from architecture building, enabling the programmable manufacturing of cellular ceramics with various cell sizes, geometries, densities, metastructures, and constituent elements. Our approach exploits surface tension to capture precursor solutions in the architected cellular lattices, allowing us to control the liquid geometry and manufacture cellular ceramics with high precision. We investigate the geometry parameters for the architected lattices assembled by unit cells and unit columns, both theoretically and experimentally, to guide the 3D fluid interface creation in arranged configurations. We manufacture a series of globally cellular and locally compact piezoceramics, obtaining an enhanced piezoelectric constant and a designed piezoelectric anisotropy. This bioinspired, surface tension-assisted approach has the potential to revolutionize the design and processing of multifarious ceramic materials for structural and functional applications in energy, electronics and biomedicine., (© 2024. The Author(s).)

Artificial peroxisomes (AP) with enzyme-mimetic catalytic activity and recruitment ability have drawn a great deal of attention in fabricating protocell systems for scavenging reactive oxygen species (ROS), modulating the inflammatory microenvironment, and reprogramming macrophages, which is of great potential in treating inflammatory diseases such as rheumatoid arthritis (RA). Herein, a macrophage membrane-cloaked Cu-coordinated polyphthalocyanine-based AP (CuAP) is prepared with a macrocyclic conjugated polymerized network and embedded Cu-single atomic active center, which mimics the catalytic activity and coordination environment of natural superoxide dismutase and catalase, possesses the inflammatory recruitment ability of macrophages, and performs photoacoustic imaging (PAI)-guided treatment. The results of both in vitro cellular and in vivo animal experiments demonstrated that the CuAP under ultrasound and microbubbles could efficiently scavenge excess ROS in cells and tissues, modulate microenvironmental inflammatory cytokines such as interleukin-1β, tumor necrosis factor-α, and arginase-1, and reprogram macrophages by polarization of M1 (proinflammatory phenotype) to M2 (anti-inflammatory phenotype). We believe this study offers a proof of concept for engineering multifaceted AP and a promising approach for a PAI-guided treatment platform for RA.

Piezoceramics with global porosity and local compaction are highly desired to exploit the combination of mechanical and electrical properties. However, achieving such a functional combination is challenging because of the lack of techniques for applying uniform pressure inside porous ceramic green parts. Nature provides many examples of generating strong forces inside the macro and micro channels via the state transformation of water. Inspired by these phenomena, we present a technique of "ice and fire", that is, water freezing (ice pressing) and high-temperature sintering (fire), to produce ideal porous piezoceramics. We introduce a new compaction method called the "ice pressing method", which manipulates liquid phase transition for compaction. This method has several advantages, including uniform pressure distribution, a wide pressure range, high effectiveness, and selective freezing. It can generate an ultrahigh pressure of up to 180 MPa on the piezoceramic green skeletons in minutes while retaining their functional pore structures. By exploiting the Mpemba phenomenon, we further accelerate the compaction procedure by 11%. The first ice-pressed and second fire-consolidated lead zirconate titanate (PZT) ceramics are highly densified and exhibit an outstanding piezoelectric response ( d 33 = 531 pC N -1 ), comparable to conventional pressed bulk counterparts and 10-20 times higher than those of unpressed materials. The novel ice pressing method breaks the limitation of lacking a compaction technique for porous ceramics. The versatile and effective ice pressing method is a green and low-cost route promoting applications in sensors, acoustics, water filtration, catalyst substrates, and energy harvesting.

Nature abounds with examples of superior mobility through the fusion of aerial and ground movement. Drawing inspiration from such multimodal locomotion, we introduce a high-performance hybrid hopping and flying robot. The proposed robot seamlessly integrates a nano quadcopter with a passive telescopic leg, overcoming limitations of previous jumping mechanisms that rely on stance phase leg actuation. Based on the identified dynamics, a thrust-based control method and detachable active aerodynamic surfaces were devised for the robot to perform continuous jumps with and without position feedback. This unique design and actuation strategy enable tuning of jump height and reduced stance phase duration, leading to agile hopping locomotion. The robot recorded an average vertical hopping speed of 2.38 meters per second at a jump height of 1.63 meters. By harnessing multimodal locomotion, the robot is capable of intermittent midflight jumps that result in substantial instantaneous accelerations and rapid changes in flight direction, offering enhanced agility and versatility in complex environments. The passive leg design holds potential for direct integration with conventional rotorcraft, unlocking seamless hybrid hopping and flying locomotion.

Sensor matrices are essential in various fields including robotics, aviation, health care, and industrial machinery. However, conventional sensor matrix systems often face challenges such as limited reconfigurability, complex wiring, and poor robustness. To address these issues, we introduce a one-wire reconfigurable sensor matrix that is capable of conforming to three-dimensional curved surfaces and resistant to cross-talk and fractures. Our frequency-located technology, inspired by the auditory tonotopy, reduces the number of output wires from row × column to a single wire by superimposing the signals of all sensor units with unique frequency identities. The sensor units are connected through a shared redundant network, giving great freedom for reconfiguration and facilitating quick repairs. The one-wire frequency-located technology is demonstrated in two applications-a pressure sensor matrix and a pressure-temperature multimodal sensor matrix. In addition, we also show its potential in monitoring strain distribution in an airplane wing, emphasizing its advantages in simplified wiring and improved robustness.

The rapid-developing soft robots and wearable devices require flexible conductive materials to maintain electric functions over a large range of deformations. Considerable efforts are made to develop stretchable conductive materials; little attention is paid to the frequent failures of integrated circuits caused by the interface mismatch of soft substrates and rigid silicon-based microelectronics. Here, we present a stretchable solder with good weldability that can strongly bond with electronic components, benefiting from the hierarchical assemblies of liquid metal particles, small-molecule modulators, and non-covalently crosslinked polymer matrix. Our self-solder shows high conductivity (>2×10 5   S  m -1 ), extreme stretchability (~1000%, and >600% with chip-integrated), and high toughness (~20 MJ m -3 ). Additionally, the dynamic interactions within our solder's surface and interior enable a range of unique features, including ease of integration, component substitution, and circuit recyclability. With all these features, we demonstrated an application as thermoforming technology for three-dimensional (3D) conformable electronics, showing potential in reducing the complexity of microchip interfacing, as well as scalable fabrication of chip-integrated stretchable circuits and 3D electronics., (© 2023. The Author(s).)

Nanoparticles, films, and patterns are three critical piezoelectric elements with widespread applications in sensing, actuations, catalysis and energy harvesting. High productivity and large-area fabrication of these functional elements is still a significant challenge, let alone the control of their structures and feature sizes on various substrates. Here, we report a fast and versatile electrostatic disc microprinting, enabled by triggering the instability of liquid-air interface of inks. The printing process allows for fabricating lead zirconate titanate free-standing nanoparticles, films, and micro-patterns. The as-fabricated lead zirconate titanate films exhibit a high piezoelectric strain constant of 560 pm V -1 , one to two times higher than the state-of-the-art. The multiplexed tip jetting mode and the large layer-by-layer depositing area can translate into depositing speeds up to 10 9  μm 3  s -1 , one order of magnitude faster than current techniques. Printing diversified functional materials, ranging from suspensions of dielectric ceramic and metal nanoparticles, to insulating polymers, to solutions of biological molecules, demonstrates the great potential of the electrostatic disc microprinting in electronics, biotechnology and beyond., (© 2023. Springer Nature Limited.)

Although the crystal phase of two-dimensional (2D) transition metal dichalcogenides (TMDs) has been proven to play an essential role in fabricating high-performance electronic devices in the past decade, its effect on the performance of 2D material-based flash memory devices still remains unclear. Here, we report the exploration of the effect of MoTe 2 in different phases as the charge-trapping layer on the performance of 2D van der Waals (vdW) heterostructure-based flash memory devices, where a metallic 1T'-MoTe 2 or semiconducting 2H-MoTe 2 nanoflake is used as the floating gate. By conducting comprehensive measurements on the two kinds of vdW heterostructure-based devices, the memory device based on MoS 2 /h-BN/1T'-MoTe 2 presents much better performance, including a larger memory window, faster switching speed (100 ns), and higher extinction ratio (10 7 ), than that of the device based on the MoS 2 /h-BN/2H-MoTe 2 heterostructure. Moreover, the device based on the MoS 2 /h-BN/1T'-MoTe 2 heterostructure also shows a long cycle (>1200 cycles) and retention (>3000 s) stability. Our study clearly demonstrates that the crystal phase of 2D TMDs has a significant impact on the performance of nonvolatile flash memory devices based on 2D vdW heterostructures, which paves the way for the fabrication of future high-performance memory devices based on 2D materials.

Piezoelectric biomaterials have attracted great attention owing to the recent recognition of the impact of piezoelectricity on biological systems and their potential applications in implantable sensors, actuators, and energy harvesters. However, their practical use is hindered by the weak piezoelectric effect caused by the random polarization of biomaterials and the challenges of large-scale alignment of domains. Here, we present an active self-assembly strategy to tailor piezoelectric biomaterial thin films. The nanoconfinement-induced homogeneous nucleation overcomes the interfacial dependency and allows the electric field applied in-situ to align crystal grains across the entire film. The β-glycine films exhibit an enhanced piezoelectric strain coefficient of 11.2 pm V -1 and an exceptional piezoelectric voltage coefficient of 252 × 10 -3 Vm N -1 . Of particular significance is that the nanoconfinement effect greatly improves the thermostability before melting (192 °C). This finding offers a generally applicable strategy for constructing high-performance large-sized piezoelectric bio-organic materials for biological and medical microdevices., (© 2023. The Author(s).)

Most electronics such as sensors, actuators and energy harvesters need piezoceramic films to interconvert mechanical and electrical energy. Transferring the ceramic films from their growth substrates for assembling electronic devices commonly requires chemical or physical etching, which comes at the sacrifice of the substrate materials, film cracks, and environmental contamination. Here, we introduce a van der Waals stripping method to fabricate large-area and freestanding piezoceramic thin films in a simple, green, and cost-effective manner. The introduction of the quasi van der Waals epitaxial platinum layer enables the capillary force of water to drive the separation process of the film and substrate interface. The fabricated lead-free film, [Formula: see text] (BCZT), shows a high piezoelectric coefficient d 33  = 209 ± 10 pm V -1 and outstanding flexibility of maximum strain 2%. The freestanding feature enables a wide application scenario, including micro energy harvesting, and covid-19 spike protein detection. We further conduct a life cycle analysis and quantify the low energy consumption and low pollution of the water-based stripping film method., (© 2023. The Author(s).)

Atomically 2D layered ferroelectric semiconductors, in which the polarization switching process occurs within the channel material itself, offer a new material platform that can drive electronic components toward structural simplification and high-density integration. Here, a room-temperature 2D layered ferroelectric semiconductor, bismuth oxychalcogenides (Bi 2 O 2 Se), is investigated with a thickness down to 7.3 nm (≈12 layers) and piezoelectric coefficient (d 33 ) of 4.4 ± 0.1 pm V -1 . The random orientations and electrically dependent polarization of the dipoles in Bi 2 O 2 Se are separately uncovered owing to the structural symmetry-breaking at room temperature. Specifically, the interplay between ferroelectricity and semiconducting characteristics of Bi 2 O 2 Se is explored on device-level operation, revealing the hysteresis behavior and memory window (MW) formation. Leveraging the ferroelectric polarization originating from Bi 2 O 2 Se, the fabricated device exhibits "smart" photoresponse tunability and excellent electronic characteristics, e.g., a high on/off current ratio > 10 4 and a large MW to the sweeping range of 47% at V GS  = ±5 V. These results demonstrate the synergistic combination of ferroelectricity with semiconducting characteristics in Bi 2 O 2 Se, laying the foundation for integrating sensing, logic, and memory functions into a single material system that can overcome the bottlenecks in von Neumann architecture., (© 2023 Wiley-VCH GmbH.)

Electrostatic adsorption is an important complement to the mechanical filtration for high-efficiency air filtering. However, the electrostatic charge decays with time, especially in humid conditions. In this work, a self-charging air filter is presented to capture airborne particles in an efficient and long-lasting manner without the need of external power sources. Leveraging the triboelectric effect between the electrospun poly(vinylidene fluoride) nanofiber film and nylon fabric, the self-charging air filter-based mask excited by breathing can continuously replenish electrostatic charges. As a result, its effective lifespan is up to 60 hours (including 30 hours of wearing), with a minimum filtration efficiency of 95.8% for 0.3-μm particles. The filtration efficiency and lifespan are significantly higher than those of a commercial surgical mask. Furthermore, we uncover the quantitative relation between filtration efficiency and surface electrostatic potential. This work provides an effective strategy to significantly prolong the electrostatic adsorption efficacy for high-performance air-filtering masks., (© 2022. The Author(s).)

Self-assembled monolayers (SAMs) have been widely employed as an effective way to modify interfaces of electronic/optoelectronic devices. To achieve a good control of the growth and molecular functionality of SAMs, we develop a co-assembled monolayer (co-SAM) for obtaining efficient hole selection and suppressed recombination at the hole-selective interface in inverted perovskite solar cells (PSCs). By engineering the position of methoxy substituents, an aligned energy level and favorable dipole moment can be obtained in our newly synthesized SAM, ((2,7-dimethoxy-9H-carbazol-9-yl) methyl) phosphonic acid (DC-PA). An alkyl ammonium containing SAM is co-assembled to further optimize the surface functionalization and interaction with perovskite layer on top. A champion device with an excellent power conversion efficiency (PCE) of 23.59 % and improved device stability are achieved. This work demonstrates the advantage of using co-SAM in improving performance and stability of PSCs., (© 2022 Wiley-VCH GmbH.)

The lack of stable p-type van der Waals (vdW) semiconductors with high hole mobility severely impedes the step of low-dimensional materials entering the industrial circle. Although p-type black phosphorus (bP) and tellurium (Te) have shown promising hole mobilities, the instability under ambient conditions of bP and relatively low hole mobility of Te remain as daunting issues. Here we report the growth of high-quality Te nanobelts on atomically flat hexagonal boron nitride (h-BN) for high-performance p-type field-effect transistors (FETs). Importantly, the Te-based FET exhibits an ultrahigh hole mobility up to 1370 cm 2  V -1  s -1 at room temperature, that may lay the foundation for the future high-performance p-type 2D FET and metal-oxide-semiconductor (p-MOS) inverter. The vdW h-BN dielectric substrate not only provides an ultra-flat surface without dangling bonds for growth of high-quality Te nanobelts, but also reduces the scattering centers at the interface between the channel material and the dielectric layer, thus resulting in the ultrahigh hole mobility ., (© 2022. The Author(s).)

Highly compact and geometrically complex piezoceramics are required by a variety of electromechanical devices owing to their outstanding piezoelectricity, mechanical stability and extended application scenarios. 3D printing is currently the mainstream technology for fabricating geometrically complex piezoceramic components. However, it is hard to print piezoceramics in a curve shape while also keeping its compactness due to restrictions on the ceramic loading and the viscosity of feedstocks. Here, we report a gravity-driven sintering (GDS) process to directly fabricate curved and compact piezoceramics by exploiting gravitational force and high-temperature viscous behavior of sintering ceramic specimens. The sintered lead zirconate titanate (PZT) ceramics possess curve geometries that can be facilely tuned via the initial mechanical boundary design, and exhibit high piezoelectric properties comparable to those of conventional-sintered compact PZT (d 33  = 595 pC/N). In contrast to 3D printing technology, our GDS process is suitable for scale-up production and low-cost production of piezoceramics with diverse curved surfaces. Our GDS strategy is an universal and facile route to fabricate curved piezoceramics and other functional ceramics with no compromise of their functionalities., (© 2021. The Author(s).)