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Human‐like and creature‐like systems are one of the most representative imaginary blueprints of future robots. To fulfill this blueprint, the development of high‐performance actuators across different length scales is indispensable. Owing to their mechanical compliance and conformability to curvy surfaces of living organisms, flexible actuators have emerged as an essential direction of next‐generation actuators. This review focuses on thin‐film‐shaped flexible actuators (TFFAs), a rising family of flexible actuators, aiming to provide an overview of the state‐of‐art status in this exciting direction. The designs, manufacturing, and mechanisms of various TFFAs are summarized, according to their key composing materials/mechanisms, including, for example, nanomaterials, liquid crystal elastomers, shape memory polymers/alloys, hydrogels, biohybrids, and other mechanisms/materials. The representative applications of TFFAs are introduced, ranging from biomedical uses, robots for environment explorations, to haptic interfaces and reconfigurable electronics. Finally, the grand challenges and open opportunities are discussed in detail. Owing to the outstanding mechanical compliance and conformability to curvy surfaces, thin‐film‐shaped flexible actuators (TFFAs) have emerged as a promising branch of next‐generation actuators. This review summarizes the designs, manufacturing, mechanisms, and applications of representative TFFAs, aiming to provide an overview of the state‐of‐art status in this young and exciting field.

The structuring of the metal‐organic framework material ZIF‐8 as films and membranes through the vapor‐phase conversion of ZnO fractal nanoparticle networks is reported. The extrinsic porosity of the resulting materials can be tuned from 4% to 66%, and the film thickness can be controlled from 80 nm to 0.23 mm, for areas >100 cm2. Freestanding and pure metal‐organic frameworks (MOF) membranes prepared this way are showcased as separators that minimize capacity fading in model Li‐S batteries. A flexible strategy for three‐dimensional structuring of hierarchical metal‐organic frameworks monoliths is presented, which provides unique advantages, including: structural homogeneity, tunable extrinsic porosity, high scalability, and designable geometrical features. The superior control over metal‐organic frameworks’ morphologies and dimensions of the proposed conversion route enables the design and fabrication of a large family of hierarchical metal‐organic frameworks architectures.

The advancement in material science and fabrication techniques has led to the booming of tissue engineering in recent years, covering tissue culture, repair, regeneration, and the rest. Among the aforementioned, considering the indispensable roles of central/peripheral nerve and soft connective tissues playing in life‐sustaining activities, their regenerations have attracted intense research attention, especially using polymeric scaffolds, an easy‐to‐access, cost efficient, biocompatible and diverse family of engineering materials. Herein, commonly used natural and synthetic polymeric materials for tissue scaffolds are outlined. Specially, polymer‐based hybrids, being able to provide both structural support and bio‐microenvironments, are discussed. Additionally, representative manufacturing approaches for polymeric scaffolds, including freeze‐drying, electrospinning, 3D printing, soft lithography among others are highlighted. Notably, combined techniques (e.g., electrospinning, 3D printing, etc.) allowing tailorable structural configurations of composite polymeric scaffolds are also reviewed. Furthermore, recent achievements in central/peripheral nerve and soft connective tissues regenerations using polymeric scaffolds are discussed in detail. In the end, conclusions and outlooks are provided to draw a roadmap for future research. Polymeric tissue scaffolds stand as promising alternatives for allografts and autografts, owing to their tunable mechanical properties, low cost, broad set of accessible materials, and various fabrication techniques. This review summarizes material selections, fabrication methods, and representative applications of polymeric tissue scaffolds, with a special focus on their crucial role in the regeneration of central/peripheral nerve and soft connective tissues.

Photoelectrochemical water splitting is a promising approach for the carbon‐free production of hydrogen using sunlight. Here, robust and efficient WO3 photoanodes for water oxidation were synthesized by the scalable one‐step flame synthesis of nanoparticle aerosols and direct gas‐phase deposition. Nanostructured WO3 films with tunable thickness and band gap and controllable porosity were fabricated by controlling the aerosol deposition time, concentration, and temperature. Optimal WO3 films demonstrate superior water oxidation performance, reaching a current density of 0.91 mA at 1.24 V vs. reversible hydrogen electrode (RHE) and an incident photon‐to‐current conversion efficiency (IPCE) of ca. 61 % at 360 nm in 0.1 m H2SO4. Notably, it is found that the excellent performance of these WO3 nanostructures arises from the high in situ restructuring temperature (ca. 1000 °C), which increases oxygen vacancies and decreases charge recombination at the WO3/electrolyte interface. These findings provide a scalable approach for the fabrication of efficient photoelectrodes based on WO3 and other metal oxides for light‐driven water splitting. Deposits from flames: Efficient WO3 photoanodes were fabricated by a scalable one‐step method by deposition from flame‐made nanoparticle aerosols (see figure). A short deposition time of 10 s was sufficient for the fabrication of robust WO3 films that do not require post‐calcination treatment and achieve a photocurrent density for water oxidation of 0.91 mA cm−2 at 1.24 V vs. RHE in 0.1 m H2SO4, and incident photon to current conversion efficiency of ca. 61 % at 360 nm.

Development of low‐cost and earth‐abundant metal catalysts, as alternative to noble metals, is a promising approach for direct hydrogen production from solar light with integrated photoelectrochemical devices. Herein, a mild electrochemical method is used to directly synthesize two earth‐abundant catalysts, namely, CoP and CoSe, on planar‐junction p+nn+‐Si solar cells. It is observed that the CoP–Si photocathodes achieve the best performance with ≈12 h of stability, a photocurrent density of up to 38 mA cm−2 at 0 V versus the reversible hydrogen electrode (RHE), and an onset potential of 488 mV versus RHE, and one of the most efficient solar‐driven hydrogen generation from earth‐abundant systems to date. Overall solar water splitting is also demonstrated in a tandem device configuration with a top TiO2 nanorod arrays photoanode achieving more than 5 h continuous hydrogen production. These results demonstrate the feasibility of using low‐cost earth‐abundant materials and the established Si solar cells technology for direct water splitting powered from sunlight. A mild and convenient light‐assisted electrochemical method is used for the deposition of earth‐abundant CoP catalysts on Si photocathode, which demonstrates one of the most efficient solar‐driven hydrogen generation from earth‐abundant systems to date. It demonstrates the potential of earth‐abundant catalysts as substitution of noble metal catalyst for renewable hydrogen production from sunlight.

The climbing microrobots have attracted growing attention due to their promising applications in exploration and monitoring of complex, unstructured environments. Soft climbing microrobots based on muscle-like actuators could offer excellent flexibility, adaptability, and mechanical robustness. Despite the remarkable progress in this area, the development of soft microrobots capable of climbing on flat/curved surfaces and transitioning between two different surfaces remains elusive, especially in open spaces. In this study, we address these challenges by developing voltage-driven soft small-scale actuators with customized 3D configurations and active stiffness adjusting. Combination of programmed strain distributions in liquid crystal elastomers (LCEs) and buckling-driven 3D assembly, guided by mechanics modeling, allows for voltage-driven, complex 3D-to-3D shape morphing (bending angle > 200°) at millimeter scales (from 1 to 10 mm), which is unachievable previously. These soft actuators enable development of morphable electroadhesive footpads that can conform to different curved surfaces and stiffness-variable smart joints that allow different locomotion gaits in a single microrobot. By integrating such morphable footpads and smart joints with a deformable body, we report a multigait, soft microrobot (length from 6 to 90 mm, and mass from 0.2 to 3 g) capable of climbing on surfaces with diverse shapes (e.g., flat plane, cylinder, wavy surface, wedge-shaped groove, and sphere) and transitioning between two distinct surfaces. We demonstrate that the microrobot could navigate from one surface to another, recording two corresponding ceilings when carrying an integrated microcamera. The developed soft microrobot can also flip over a barrier, survive extreme compression, and climb bamboo and leaf.

Nanoparticle networks, self-assembled from flame generated hot aerosols consisting of ceramic nanoparticles with well-controlled particle size, are promising materials for many different applications, especially for photodetectors and VOC sensors. Furthermore, the great structural flexibilities of these self-assembled nanoparticle networks including tuneable thickness and hierarchical porosity, precisely-controlled averaged particle size as well as chemical composition make them as potential platforms for templated materials synthesis via chemical conversion. On the other hand, metal-organic framework (MOF), is a growing family of microporous materials consisting of metal cations connected by organic linkers. Their unique properties, including a narrow pore size distribution (intrinsic porosity), designable topology, high accessible surface area, and chemical mutability, make MOFs promising materials for a variety of applications including gas storage, separation, catalysis, biotechnology, optics, microelectronics and energy production/storage. However, there are still several bottlenecks hindering the structural engineering of metal-organic frameworks, especially for pure crystalline MOF materials, including limited attainable thickness, scalability, poor mechanical stability (i.e. brittle nature of MOFs), hard to realize the morphological control (e.g. tuneable extrinsic hierarchical porosity) and geometric designs on pure crystalline MOF components. Thus, a facile synthetic approach for MOF structuring is highly desirable, which could afford the fabrication of three-dimensional MOF materials with possibly unlimited thickness, free-standing feature, the control over extrinsic hierarchy as well as pre-determined designs of MOFs while maintain their crystalline property and intrinsic extreme accessible surfaces. Firstly, we started with the synthesis of pure ZnO nanoparticle networks and the optimization of their particle size. Later, using the ZnO nanoparticle networks with an optimal particle size, a high-performing UV photodetector has been prepared to show a proof of concept application of such structural engineering. After achieving the first structural control over ZnO nanoparticle networks, a multi-dimensional control has been further investigated associated with its potential use for multi-functional devices including transparent conductive oxides and gas sensors. Given the successful structural control over nanoparticle networks, considering the existing bottlenecks in current MOF fabrication, this multi-dimensional structural control has been successfully replicated to MOF preparation via a means of gas phase conversion. Therefore, in this thesis, a systematic study has been presented from the synthesis and applications of nanoparticle networks to those of metal-organic frameworks in the sequence of: (i) the synthesis of three-dimensional nanoparticle networks (i.e. ZnO-based metal oxide nanoparticle networks), (ii) the realization of a precise particle size control over the synthesized nanoparticle networks (e.g. ZnO) and the use of resulted optimal structure for photodetector application, (iii) the realization of chemical composition manipulation over the synthesized nanoparticle networks (e.g. ZnO nanoparticle networks with varied Al doping concentrations) and the use of the resulted structures as proof of concept applications for both porous conductive electrodes and VOC sensor, (iv) the establishment of a synthetic pathway from nanoparticle networks to metal-organic frameworks based on the replication of the structural control over nanoparticle networks towards metal-organic frameworks, and the proof of concept application of the resulted free-standing metal-organic frameworks monolith for effective molecular sieve in batteries, and (v) the use of the established fabrication approach (i.e. from nanoparticle networks to metal-organic frameworks) for monolithic metal-organic framework patterning.

Photoelectrochemical water splitting is a promising approach for the carbon‐free production of hydrogen using sunlight. Here, robust and efficient WO 3 photoanodes for water oxidation were synthesized by the scalable one‐step flame synthesis of nanoparticle aerosols and direct gas‐phase deposition. Nanostructured WO 3 films with tunable thickness and band gap and controllable porosity were fabricated by controlling the aerosol deposition time, concentration, and temperature. Optimal WO 3 films demonstrate superior water oxidation performance, reaching a current density of 0.91 mA at 1.24 V vs. reversible hydrogen electrode (RHE) and an incident photon‐to‐current conversion efficiency (IPCE) of ca. 61 % at 360 nm in 0.1  m H 2 SO 4 . Notably, it is found that the excellent performance of these WO 3 nanostructures arises from the high in situ restructuring temperature (ca. 1000 °C), which increases oxygen vacancies and decreases charge recombination at the WO 3 /electrolyte interface. These findings provide a scalable approach for the fabrication of efficient photoelectrodes based on WO 3 and other metal oxides for light‐driven water splitting.

Aero-engine rotor system is the core component of engine. Aim at difficulties of fault diagnosis of engine rotor system, a method to detect the fault feature is proposed, which is based on recurrence plot (RP) and recurrence quantification analysis(RQA) by research of the characteristics and the mechanism of faults. An experiment is used to detect the fault of rotor system by using this new method. The results showed that the RQA is an effective way to extract features from vibration signal and by the use of quantitative features it is possible to identify and classify different types of rotor. Comparing with classical statistical features, the proposed algorithm has better classification rate. The research will be helpful in the further study of fault diagnosis of rotor system.