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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. Three-dimensional architecture engineering allows for higher performance ceramics with more diverse applications. Here, the authors report a simple and efficient manufacturing process for cellular ceramics in programmed cell-based 3D configurations. [ABSTRACT FROM AUTHOR]

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 (>2×105 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.“The interface mismatch of soft substrates and rigid silicon-based microelectronics frequently causes failures of integrated circuits. Here, the authors develop a stretchable solder based on liquid metal-polymer composites which enables seamless integration of electronic components with soft substrates, showcasing high conductivity and stretchability”. [ABSTRACT FROM AUTHOR]

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 109 μm3 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. In this work, authors demonstrate a fast and versatile microprinting technique to produce high-performance and customizable piezoelectric elements by employing a conductive spiny disc to electrostatically trigger instability to the liquid-air interface of the ink. [ABSTRACT FROM AUTHOR]

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. Piezoelectric biomaterials are limited by the challenges in domain orientation alignment and a weak piezoelectric effect. Here, Zhang et. al. present an active self-assembly strategy via nanoconfinement and in-situ poling, to obtain large-scale, high performance piezoelectric β-glycine nanocrystalline films. [ABSTRACT FROM AUTHOR]

Improving the intrinsic film quality of metal halide perovskites is very critical to increase the power conversion efficiency and long-term stability of perovskite solar cells. Here we report a multifunctional, non-volatile additive that can be used to modulate the kinetics of perovskite film growth through a hydrogen-bond-bridged intermediate phase. The additive enables the formation of large perovskite grains and coherent grain growth from bottom to the surface of the film. The enhanced film morphology results in significantly reduced non-radiative recombinations, thus boosting the power conversion efficiency of inverted (p–i–n) solar cells to 24.8% (24.5% certified) with a low energy loss of 0.36 eV. The unencapsulated devices exhibit improved thermal stability with a T98 lifetime beyond 1,000 h under continuous heating at 65 ± 5 °C in a nitrogen-filled glovebox. This effective approach can also be applied to wide-bandgap perovskites and large-area devices to show reduced voltage loss and high efficiency. A multifunctional additive modulates the kinetics of perovskite film growth, enabling inverted perovskite solar cells with 24.8% power conversion efficiency and enhanced thermal stability. [ABSTRACT FROM AUTHOR]

Highlights: Freestanding lead-free piezoceramic thin films can be derived via water peeling. The d33 value of the freestanding BCZT thin film reaches 209 pm V−1. The freestanding piezoceramic films obtain versatile application scenarios such as energy harvest and virus detection. 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, Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3 (BCZT), shows a high piezoelectric coefficient d33 = 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. [ABSTRACT FROM AUTHOR]

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. The decay of electrostatic charges largely reduces the protective efficacy of electret masks. Here, the authors report a triboelectrification-based self-charging electrostatic face mask with high airborne particle capture efficiency and prolonged stability. [ABSTRACT FROM AUTHOR]

Highlights: The growth of high-quality single-crystalline Te nanobelts is reported by introducing atomically flat hexagonal boron nitride (h-BN) nanoflakes into the chemical vapor deposition system as the growth substrate. The field-effect transistor based on Te grown on h-BN exhibits an ultrahigh hole mobility up to 1370 cm2 V−1 s−1 at room temperature. 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 cm2 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. [ABSTRACT FROM AUTHOR]

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 (d33 = 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. Fabricating geometrically complex piezoceramics in compact sintered bodies has been difficult to achieve. Here the authors demonstrate a gravity-driven sintering strategy where high-temperature viscous behavior of piezoceramic allows for forming of complex shaped sintered bodies. [ABSTRACT FROM AUTHOR]

This paper presents a modeling and dynamic analysis of a rotational high-efficiency compressive-mode piezoelectric energy harvester (HC-PEH) with partially thickened bow-shaped beams. Based on the Euler–Bernoulli beam theory and the extended Hamilton's principle, the governing equations of the rotational HC-PEH system are formulated. The nonlinear electromechanical coupling partial differential equations of the system are transformed into ordinary differential equations in the truncated modal coordinates. The developed distributed-parameter model is validated against experimental data, and a good agreement is achieved. The stability and the nonlinear dynamic behavior of the rotational HC-PEH system in conditions of different offset distances and preloaded axial forces are investigated by numerical simulation results. A parametric study of the parameters directly related to the system design is also performed to provide fundamental guidance for understanding the electrical output performance and modulating the voltage–rotation speed responses of the harvester. The result shows that the design parameters of the bow-shaped beam and the PZT plate have apparent effects on the electrical output of the harvester system. [ABSTRACT FROM AUTHOR]

Extensive efforts have been made to harvest energy from water in the form of raindrops1–6, river and ocean waves7,8, tides9 and others10–17. However, achieving a high density of electrical power generation is challenging. Traditional hydraulic power generation mainly uses electromagnetic generators that are heavy, bulky, and become inefficient with low water supply. An alternative, the water-droplet/solid-based triboelectric nanogenerator, has so far generated peak power densities of less than one watt per square metre, owing to the limitations imposed by interfacial effects—as seen in characterizations of the charge generation and transfer that occur at solid–liquid1–4 or liquid–liquid5,18 interfaces. Here we develop a device to harvest energy from impinging water droplets by using an architecture that comprises a polytetrafluoroethylene film on an indium tin oxide substrate plus an aluminium electrode. We show that spreading of an impinged water droplet on the device bridges the originally disconnected components into a closed-loop electrical system, transforming the conventional interfacial effect into a bulk effect, and so enhancing the instantaneous power density by several orders of magnitude over equivalent devices that are limited by interfacial effects. A device involving a polytetrafluoroethylene film, an indium tin oxide substrate and an aluminium electrode allows improved electricity generation from water droplets, which bridge the previously disconnected circuit components. [ABSTRACT FROM AUTHOR]

This paper presents a novel buckled compressive-mode piezoelectric energy harvesting device (BC-PEH) to improve the energy harvesting capability. The BC-PEH synthesizes the merits of the force amplification effect of the flexural motion and the broad bandwidth of buckled-beam structures. In this paper, both theoretical and experimental investigations are performed on the BC-PEH, under both harmonic and random excitations. Taking negative stiffness, nonlinear damping and nonlinear piezoelectric coupling into account, we build an analytical model that provides a comprehensive insight into the nonlinear electromechanical coupling system. The influence of parameters on the performance is thoroughly discussed via the harmonic balance method and numerical technique. The analytical results closely render the experimental data and demonstrate a considerable performance enhancement. Compared with state-of-the-art energy harvesters, the BC-PEH prototype not only exhibits its superiority in terms of power density, normalized power density and power normalized by mass and acceleration, but also indicates a 194% broader working bandwidth. [ABSTRACT FROM AUTHOR]

Nonlinear vibrations of longitudinally moving functionally graded material (FGM) plates containing porosities and contacting with liquid are investigated. The FGM plates contain porosities because of technical issues during the FGM preparation. Two types of porosity distribution, namely even and uneven distribution, are taken into account. The liquid is assumed to be incompressible, inviscid and irrotational. The velocity potential along with Bernoulli's equation is employed to describe the dynamic liquid pressure on the plates. Considering geometric nonlinearity described by the von Kármán nonlinear theory, the governing equation of the system is developed by utilizing D'Alembert's principle. Then, the Galerkin method is employed to reduce the governing equation into a set of ordinary differential equations. An approximately analytical analysis on the nonlinear steady-state response is performed by means of the harmonic balance method; the stability of steady-state response is examined by a perturbation analysis. To have an intuitive understanding of parameter effects, this study retains all dimensional parameters in the analytical results. The possibility of appearance of internal resonance is confirmed by linear analysis of the system. For moving porous FGM plates contacting with liquid, a distinctive internal resonance phenomenon can occur between the first two modes, as we shall see. Different from the common internal resonance, the present internal resonance is very sensitive to external force and can be motivated by quite small force. Results are presented to examine the effects of different parameters on the frequency response of the system. [ABSTRACT FROM AUTHOR]

Over the centuries, scientists and engineers have been fascinated by the directional transport of water on the peristome of pitcher plant. Through experimental investigation and theoretical analysis, here we reveal the more complex picture of droplet transport on this peculiar natural surface. First, we demonstrate that in addition to the presence of the asymmetric arch-shaped microcavity with gradient wedge corners and sharp edges, the structural gradient in the first-tier microgroove of the pitcher's peristome also plays an important role in the regulation of the directional droplet transport. Moreover, the directional liquid transport only occurs in a limited condition. Without the intricate control of the interplay between its multiscale structures and multiscale sources of water, as well as the dynamic conditions of water, the preferential directional droplet transport will collapse. The new transport phenomenon and the mechanisms we reveal will provide important insights for the design of asymmetric morphologies for droplet manipulation. The way many natural surfaces transport water has been a fascinating subject for many centuries. The paper presents an experimental and theoretical investigation of droplets transport on the peristome of pitcher plants and shows that this depends on the multiscale structures of both the surface and the water. [ABSTRACT FROM AUTHOR]