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Abstract Pressing environmental challenges require focused research on sustainable solutions in the domains of energy, water, food, land, and climate. The pigment eumelanin has recently been positioned as a promising candidate for solving issues in health, sensors, and energy storage. However, the low solubility of eumelanin in aqueous solvents, difficult film processibility, and high cost have hindered the material from wide deployment. Here, we propose melanin extracted from the black soldier fly, Hermetia illucens (Mel-BSF), as a sustainable alternative for the preparation of organic electrodes in energy storage applications. Mel-BSF displays pseudocapacitive behaviour with a high potential window, good electrochemical stability, and higher maximum capacity (91.8 mAh g−1) compared to synthetic eumelanin (17.3 mAh g−1) as the working electrode material in zinc-ion hybrid capacitors using an ionic liquid electrolyte. Structural and surface investigations reveal that additional aliphatic compounds, potentially lipids present after Mel-BSF refinement, significantly increase the film stability and redox centre availability.

Abstract Enhancing fracture toughness and self‐healing within soft elastomers is crucial to prolonging the operational lifetimes of soft devices. Herein, it is revealed that tuning the polymer chain mobilities of carboxylated‐functionalized polyurethane through incorporating plasticizers or thermal treatment can enhance these properties. Self‐healing is promoted as polymer chains gain greater mobility toward the broken interface to reassociate their bonds. Raising the temperature from 80 to 120 °C, the recovered work of fracture is increased from 2.86 to 123.7 MJ m−3. Improved fracture toughness is realized through two effects. First, strong carboxyl hydrogen bonds dissipate large energies when broken. Second, chain mobilities enable the redistribution of localized stress concentrations to allow crack blunting, enlarging the size of dissipation zones. At optimal conditions of plasticizers (3 wt.%) or temperature (40 °C) to promote chain mobilities, fracture toughness improves from 16.3 to 19.9 and 25.6 kJ m−2, respectively. Insights of fracture properties at healed soft interfaces are revealed through double cantilever beam tests. These measurements indicate that fracture mechanics play a critical role in delaying complete failure at partial self‐healing. By imparting optimal polymer chain mobilities within tough and self‐healing elastomers, effective prevention against damage and better recovery are realized.

Abstract Fiber‐based artificial muscles are promising for smart textiles capable of sensing, interacting, and adapting to environmental stimuli. However, the application of current artificial muscle‐based textiles in wearable and engineering fields has largely remained a constraint due to the limited deformation, restrictive stimulation, and uncomfortable. Here, dual‐responsive yarn muscles with high contractile actuation force are fabricated by incorporating a very small fraction (

A new family of two‐dimensional (2D) transition metal carbides, carbonitrides, and nitrides (MXenes) has attracted increasing attention owing to their electrical, chemical, and physical properties. Together with various attractive properties of the MXenes, they also exhibit electrochemical induced deformation (i.e., expansion/contraction) via ion intercalation/de‐intercalation in/from MXene layers. In this respect, MXenes offer the possibility of application as the electrode of electrochemical actuators (ECAs). While the MXene‐based ECAs are still in their infancy stage, researchers have made great effort to achieve high‐performance MXene‐based electrochemical capacitors (ECs). As the name suggests, both ECAs and ECs shared common traits in which their operations are based on electrochemical processes. This review provides the recent progress in the MXene‐based ECAs in parallel with that in the MXene‐based ECs to gain insights from the relatively mature developments in EC applications. Finally, based on the findings from previous studies on both electrochemical applications, perspectives on future MXene‐based ECAs in terms of electrode, electrolyte, and cell configuration are provided.

Abstract Natural structural materials often possess unique combinations of strength and toughness resulting from their complex hierarchical assembly across multiple length scales. However, engineering such well-ordered structures in synthetic materials via a universal and scalable manner still poses a grand challenge. Herein, a simple yet versatile approach is proposed to design hierarchically structured hydrogels by flow-induced alignment of nanofibrils, without high time/energy consumption or cumbersome postprocessing. Highly aligned fibrous configuration and structural densification are successfully achieved in anisotropic hydrogels under ambient conditions, resulting in desired mechanical properties and damage-tolerant architectures, for example, strength of 14 ± 1 MPa, toughness of 154 ± 13 MJ m−3, and fracture energy of 153 ± 8 kJ m−2. Moreover, a hydrogel mesoporous framework can deliver ultra-fast and unidirectional water transport (maximum speed at 65.75 mm s−1), highlighting its potential for water purification. This scalable fabrication explores a promising strategy for developing bioinspired structural hydrogels, facilitating their practical applications in biomedical and engineering fields.

Abstract Human affects such as emotions, moods, feelings are increasingly being considered as key parameter to enhance the interaction of human with diverse machines and systems. However, their intrinsically abstract and ambiguous nature make it challenging to accurately extract and exploit the emotional information. Here, we develop a multi-modal human emotion recognition system which can efficiently utilize comprehensive emotional information by combining verbal and non-verbal expression data. This system is composed of personalized skin-integrated facial interface (PSiFI) system that is self-powered, facile, stretchable, transparent, featuring a first bidirectional triboelectric strain and vibration sensor enabling us to sense and combine the verbal and non-verbal expression data for the first time. It is fully integrated with a data processing circuit for wireless data transfer allowing real-time emotion recognition to be performed. With the help of machine learning, various human emotion recognition tasks are done accurately in real time even while wearing mask and demonstrated digital concierge application in VR environment.

Abstract The widespread adoption of renewable and sustainable elastomers in stretchable electronics has been impeded by challenges in their fabrication and lacklustre performance. Here, we realize a printed sustainable stretchable conductor with superior electrical performance by synthesizing sustainable and recyclable vegetable oil polyurethane (VegPU) elastomeric binder and developing a solution sintering method for their composites with Ag flakes. The binder impedes the propagation of cracks through its porous network, while the solution sintering reaction reduces the resistance increment upon stretching, resulting in high stretchability (350%), superior conductivity (12833 S cm−1), and low hysteresis (0.333) after 100% cyclic stretching. The sustainable conductor was used to print durable and stretchable impedance sensors for non-obstructive detection of fruit maturity in food sensing technology. The combination of sustainable materials and strategies for realizing high-performance stretchable conductors provides a roadmap for the development of sustainable stretchable electronics.

Electroadhesion in soft robotics provides controllable interfacial attraction for robotic functionalities but materials selection is limited. Here, Gao et. al. present an iontronic adhesive to design a soft iontronic gripper with self-healability, tunable adhesion at reduced voltages and rapid release.

Tough and healable elastomers are promising materials to realize resilient soft robots but mechanical enhancements often lead to higher stiffness that deteriorates actuation strains. Here, the authors introduce liquid metal nanoparticles into carboxyl polyurethane elastomer to sensitize a dielectric elastomer actuator with responsiveness to electric fields and NIR light.

Designing efficient biological inspired devices and circuits remains a challenge. Here, the authors develop ionic diodes based on gel polymer electrolytes enabling ion rectification through different diffusion and migration of mobile ions for logic gates, nanogenerator and synaptic devices.

Highlights A stable laminated Al2O3/HfO2 insulator is developed by atomic layer deposition at a relatively lower temperature of 150 °C. The flexible thin-film transistors (TFTs) with bottom-gate top-contacted configuration are fabricated on a flexible substrate with the Al2O3/HfO2 insulator. The flexible TFTs present the carrier mobilities of 9.7 cm2 V−1 s−1, ON/OFF ratio of ~ 1.3 × 106, subthreshold voltage of 0.1 V, saturated current up to 0.83 mA, and subthreshold swing of 0.256 V dec−1. Abstract Flexible thin-film transistors (TFTs) have attracted wide interest in the development of flexible and wearable displays or sensors. However, the conventional high processing temperatures hinder the preparation of stable and reliable dielectric materials on flexible substrates. Here, we develop a stable laminated Al2O3/HfO2 insulator by atomic layer deposition at a relatively lower temperature of 150 °C. A sputtered amorphous indium-gallium-zinc oxide (IGZO) with the stoichiometry of In0.37Ga0.20Zn0.18O0.25 is used as the active channel material. The flexible TFTs with bottom-gate top-contacted configuration are further fabricated on a flexible polyimide substrate with the Al2O3/HfO2 nanolaminates. Benefited from the unique structural and compositional configuration in the nanolaminates consisting of amorphous Al2O3, crystallized HfO2, and the aluminate Al–Hf–O phase, the as-prepared TFTs present the carrier mobilities of 9.7 cm2 V−1 s−1, ON/OFF ratio of ~ 1.3 × 106, subthreshold voltage of 0.1 V, saturated current up to 0.83 mA, and subthreshold swing of 0.256 V dec−1, signifying a high-performance flexible TFT, which simultaneously able to withstand the bending radius of 40 mm. The TFTs with nanolaminate insulator possess satisfactory humidity stability and hysteresis behavior in a relative humidity of 60–70%, a temperature of 25–30 °C environment. The yield of IGZO-based TFTs with the nanolaminate insulator reaches 95%.

Improving piezoelectric strain and voltage constant generally compromises piezoelectric performance and mechanical softness. Here, the authors report a bond weakening strategy for organic-inorganic hybrid piezoelectrics and mitigated these issues.

Abstract Solid‐state black electrochromic devices (ECDs) are promising for smart window applications, particularly when privacy protection and low leakage are required. Herein, a Ni–Cu salts/poly(vinyl alcohol) based organohydrogel electrolyte is developed with superior visible‐light transparency (83.8%), ionic conductivity (0.11 mS cm−1), and mechanical properties (tensile strength: 11.1 kPa, breaking strain: 242.6%). Due to the high viscosity of the organohydrogel electrolyte, a homogeneous Ni–Cu alloy film with a surface roughness of around 11.2 nm can be electrodeposited under −3 V for 5 min, and the resulting black color can be retained for over 350 min with a transmittance increase of only 5% at the voltage‐off state. The solid‐state rigid ECD exhibits an outstanding optical contrast between the transparent and colored states (visible light transmittance: 70.8% vs 0.085%), excellent cycling stability with over 90% retention of optical contrast after 2000 cycles. Finally, a flexible ECD is fabricated with the organohydrogel electrolyte and annealed indium tin oxide (ITO)‐coated polyethylene naphthalate (PEN) films as flexible and durable electrodes. It exhibits good mechanical flexibility with transmittance modulation degradation of 10% after 800 bending cycles and switching stability for 400 cycles with up to 43% optical contrast.

Abstract High‐performance multilayer dielectric elastomer actuators (DEAs) are well‐positioned to overcome the insufficient output force and energy density as artificial muscles. However, due to the fabrication process, the multilayer DEAs with nonmodifiable structures often suffer from the limitation of short lifespans and scalable preparation. Herein, reusable multilayer DEAs with the detachable and reconfigurable structure are fabricated. This is achieved by realizing scalable compliant electrodes using the continuous spatial confining forced network assembly (CSNA) method and combining the vacuum lamination (VL) approach to have good attachability and detachability with the VHB dielectric elastomer. The flexible roller‐based CSNA method is used to prepare the large area compliant electrodes composed of α, ω‐dihydroxy polydimethylsiloxane and electrically conductive nanoparticles. The fabricated electrodes can continuously work over 10 000 cycles at 40% strained stretching and maintain smooth surfaces to construct multilayer DEAs. Moreover, owing to the detachable configuration of the DEAs, the electrodes can also be recovered and reused for building new actuators. The lower limb assistive device is demonstrated by detachable multilayer spring roll DEAs, achieving approximately 3.1 degrees of flexion and extension movement of knee models under a voltage of 7 kV. The detachable and reconfigurable multilayer DEAs shed new light on the applications of wearable assistive devices.

Electrically activated soft actuators with large deformability are important for soft robotics but enhancing durability and efficiency of electrochemical actuators is challenging. Here the authors demonstrate that the actuation performance of an ionic two-dimensional covalent-organic framework based electrochemical actuator is improved through the ordered pore structure of opening up efficient ion transport routes

Abstract Charging wearable energy storage devices with bioenergy from human‐body motions, biofluids, and body heat holds great potential to construct self‐powered body‐worn electronics, especially considering the ceaseless nature of human metabolic activities. To bridge the gap between human‐body bioenergy and storage of energy, wearable triboelectric/piezoelectric nanogenerators (TENGs/PENGs), biofuel cells (BFCs), thermoelectric generators (TEGs) have been designed to harvest energy from body‐motions, biofluids, and body heat, respectively. Researchers have explored various strategies using bioenergy harvesters to charge wearable supercapacitors and batteries to relieve or even fully eliminate the recharging process from external power stations, thus, making wearable electronics more sustainable, autonomous, and user friendly. In this article, we review the advances in the design of sustainable energy storage devices charged by human‐body energy harvesters. The progress in multifunctional wearable energy storage devices that cater to the easy integration with human‐body energy harvesters will be summarized. Then, the focus is laid on the integrating strategies (single‐cell strategy and separated‐cell strategy), device design, materials selection, and characteristics of different self‐charging human‐body energy harvesting‐storage systems. Finally, the challenges that impede the wide application of human‐body energy harvesters charged supercapacitors/batteries and prospects will be discussed both from materials and structural design aspects.

Electrochromic smart windows are promising for green buildings due to energy efficiency, long optical memory effect, and tunable optical transmission. However, their wide application in buildings is impeded by challenges in scalability, cost‐effectiveness, and limited optical contrast. Quantitative field study of energy savings enabled by electrochromic smart windows in buildings is also lacking. Herein, with the established inkjet printing procedures, electrochromic smart windows (900 cm2) are fabricated. With large optical contrast (≈60%), fast switching kinetics (tc = 43 s, tb = 70 s), and long optical memory retention (transmittance

Soft electrical actuators driven by low voltages are promising for interactive human–machine interfaces (iHMI) applications including executing orders to complete various tasks and communicating with humans. The attractive features of low‐voltage soft electrical actuators include their good safety, low power consumption, small system size, and nonrigid or deformable characteristics. This review covers three typical classes of electrical actuators, namely, electrochemical, electrothermal, and other electrical (dielectric, electrostatic, ferroelectric, and plasticized gel) actuators according to their mechanism and working potential range. For each kind of actuators, the advantages, working principle, device configuration/design, materials selection, recent progress, and potential applications for iHMI are summarized, with the strategies for enhancing the actuation performance under low voltages being highlighted. Finally, the challenges for those soft actuators and possible solutions are discussed.

Abstract Organic materials are always viewed as promising electrochromic (EC) materials due to their synthetic versatility, color tunability, ready processability, and derivability from sustainable feedstocks. Most organic materials, however, are prone to undesirable redox side reactions in the presence of oxygen and water. As such, redox–active organic layers are often used in tandem with organic electrolytes to preserve their electrochemical stability. With the growing interest in electronics that are environmentally sustainable and biologically safe, developing aqueous‐compatible organic materials is gaining growing interest. Herein, a rationally designed iron terpyridyl coordination polymer (CP) is prepared by controlled electropolymerization for realization of aqueous compatible EC and energy storage applications. Detailed analysis is established, showing that the CP grows in a 1D fashion and exhibits a predominant capacitive behavior which is reflected from its rapid charge–transfer kinetics. Taking this as an advantage, an integrated hybrid electrochromic zinc battery device is demonstrated with high color contrast, fast response time, and good endurance.

Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere.

Abstract Sodium-ion capacitors (SICs) have received increasing interest for grid stationary energy storage application due to their affordability, high power, and energy densities. The major challenge for SICs is to overcome the kinetics imbalance between faradaic anode and non-faradaic cathode. To boost the Na+ reaction kinetics, the present work demonstrated a high-rate MnS-based anode by embedding the MnS nanocrystals into the N, S-co-doped carbon matrix (MnS@NSC). Benefiting from the fast pseudocapacitive Na+ storage behavior, the resulting composite exhibits extraordinary rate capability (205.6 mAh g−1 at 10 A g−1) and outstanding cycling stability without notable degradation after 2000 cycles. A prototype SIC was demonstrated using MnS@NSC anode and N-doped porous carbon (NC) cathode; the obtained hybrid SIC device can display a high energy density of 139.8 Wh kg−1 and high power density of 11,500 W kg−1, as well as excellent cyclability with 84.5% capacitance retention after 3000 cycles. The superior electrochemical performance is contributed to downsizing of MnS and encapsulation of conductive N, S-co-doped carbon matrix, which not only promote the Na+ and electrons transport, but also buffer the volume variations and maintain the structure integrity during Na+ insertion/extraction, enabling its comparable fast reaction kinetics and cyclability with NC cathode.

Textile has been known for thousands of years for its ease of use, comfort, and wear resistance, which resulted in a wide range of applications in garments and industry. More recently, textile emerges as a promising substrate for self-powered wearable power sources that are desired in wearable electronics. Important progress has been attained in the exploitation of wearable triboelectric nanogenerators (TENGs) in shapes of fiber, yarn, and textile. Along with the effective integration of other devices such as supercapacitor, lithium battery, and solar cell, their feasibility for realizing self-charging wearable systems has been proven. In this review, according to the manufacturing process of traditional textiles starting from fibers, twisting into yarns, and weaving into textiles, we summarize the progress on wearable TENGs in shapes of fiber, yarn, and textile. We explicitly discuss the design strategies, configurations, working mechanism, performances, and compare the merits of each type of TENGs. Finally, we present the perspectives, existing challenges and possible routes for future design and development of triboelectric textiles.

Abstract The ability to rationally tune and add new end-groups in polymers can lead to transformative advances in emerging self-healing materials. Self-healing networks manipulated by supramolecular strategies such as hydrogen bonding and metal coordination have received significant attention in recent years because of their ability to extend materials lifetime, improve safety and ensure sustainability. This review describes the recent advancements in supramolecular polymers self-healing networks based on hydrogen bonding, metal-containing polymers and their nanocomposites. Collectively, the aim of this review is to provide a panoramic overview of the conceptual framework for the interesting nexus between hydrogen bonding and metal–ligand interactions for enabling supramolecular self-healing soft materials networks and nanocomposites. In addition, insights on the current challenges and future perspectives of this field to propel the development of self-healing materials will be provided.

Development of wearable devices relies on advance in power sources with complementary mechanical properties. Here the authors use a conductive, stretchable and healable composite to achieve sustained performance in a triboelectric nanogenerator under extreme deformation and after severe mechanical damage.

Abstract In the dawn of energy crisis and rising challenges in powering distributed low energy portable devices, nanogenerators, a class of mechanical energy harvesters is gaining increasing interest in fundamental research and commercial applications. Nanogenerators harvest energy by transducing mechanical energy into electric energy, the performance is highly related to the mechanical and electrical properties of the materials and devices. A typical nanogenerator consists of a substrate, a functional triboelectric active layer, electrode, and separator, which overall built‐up a three dimensional (3D) structure. 3D printing with its ability to form complex 3D structures possess coveted advantages in the development of nanogenerators. In this review, we introduce the importance of 3D structures for nanogenerators and explicitly discuss the different 3D printing methods and the ink formulation to tackle the challenges in 3D structured nanogenerators. Additionally, the principle and application of 4D printing in nanogenerator fabrication are critically highlighted.

Abstract The rational design of previously unidentified materials that could realize excellent electrochemical‐controlled optical and charge storage properties simultaneously, are especially desirable and useful for fabricating smart multifunctional devices. Here, a facile synthesis of a 1D π–d conjugated coordination polymer (Ni‐BTA) is reported, consisting of metal (Ni)‐containing nodes and organic linkers (1,2,4,5‐benzenetetramine), which could be easily grown on various substrates via a scalable chemical bath deposition method. The resulting Ni‐BTA film exhibits superior performances for both electrochromic and energy storage functions, such as large optical modulation (61.3%), high coloration efficiency (223.6 cm2 C−1), and high gravimetric capacity (168.1 mAh g−1). In particular, the Ni‐BTA film can maintain its electrochemical recharge‐ability and electrochromic properties even after 10 000 electrochemical cycles demonstrating excellent durability. Moreover, a smart energy storage indicator is demonstrated in which the energy storage states can be visually recognized in real time. The excellent electrochromic and charge storage performances of Ni‐BTA films present a great promise for Ni‐BTA nanowires to be used as practical electrode materials in various applications such as electrochromic devices, energy storage cells, and multifunctional smart windows.

Next‐generation soft electronics are expected to be intrinsically stretchable, skin conformable, and fully integrated with diverse receptive modules to facilitate bidirectional human–machine interactions. Receptive touch sensors, in particular, should provide stable touch sensing outputs without being affected by external force‐induced strains. Herein, the design and fabrication of an iontronic touch sensing matrix, based on the fringe‐field capacitive mechanism, are introduced for robust touch mapping under large deformation. Enabled by our well‐formulated ink, ionic gel electrodes are directly inkjet printed onto elastomeric substrate to impart superior transparency and elasticity, and hybridized with a customized electronic circuitry through electrical double layers (EDLs) for the multiplexing and transduction of capacitive signals. Notably, the coplanar “interlocking‐diamond” electrode layout in a stretchable modality is adopted for the first time, which helps to boost touch sensitivity and suppress strain‐induced artifacts under static/dynamic deformations. For practical applications, the iontronic matrix demonstrates the capabilities of proximity sensing, multitouch detection, and gesture communication in real time, leading to a robust touch sensing interface that captures high‐fidelity signals during complex human–machine interactions.

Abstract Reversible electrochemical mirror (REM) electrochromic devices with electrochemical tunability in multiple optical states are exciting alternatives to conventional electrochromic smart windows. Electrochromic devices are studied extensively, yet widespread adoptions have not been achieved due to problems associated with durability, switching speed, limited options on optical states, and cost. In this study, a REM electrochromic device based on CuSn alloy is developed, which offers highly reversible switching between transparent, greyish‐blue, and mirror states via reversible electrodeposition and dissolution. The alloying element, Sn acts as an electrochemical mediator, which facilitates the electrodeposition and dissolution of Cu. The CuSn‐based REM device shows superior cycling stability for 2400 cycles (transmittance mode) and 1000 cycles (reflectance mode). The electrodeposited CuSn alloy film is resistant to surface oxidation in ambient air, with a 2.9% difference in reflectance at 2000 nm after 3 days. In addition, the alloy film exhibits excellent NIR reflectance property with thermal modulation of 18.5 °C at a high temperature of 180 °C. The REM device with zero power consumption maintains its mirror state for at least 100 min, making it a promising candidate for energy‐efficient applications.

In the era of big data, with the development and application of 5G technology, artificial intelligence technology, and wearable electronics, the acquisition, storage, search, sharing, analysis, and even visual presentation require huge amounts of data in storage and processing at any time. This propounds a strong demand for the stretchable and wearable memory devices with ultrafast switching, high density, and high energy efficiency. Herein, an overview of the advanced progresses made on developing stretchable resistive switching random‐access memory (RRAM) is presented, concentrating on the fundamental components, materials selection principles, and configuration design strategies. The basic electrical and mechanical properties of stretchable components to meet the functionality of memory storage are summarized. Novel materials with the intrinsically stretchable features toward the realization of stretchable RRAM are discussed. Ingenious configuration design strategies to obtain stretchable RRAM are evaluated. Finally, the challenges and perspectives for the practical applications of stretchable RRAM are also addressed. Some helpful guidelines are provided in promoting the development on stretchable and wearable RRAM for making deployable and portable artificial intelligence and smart devices.

The emergence of soft energy devices provides new possibilities for various applications, it also creates significant challenges in the selection of structural design and material compatibility. Herein, we demonstrate a stretchable transmissive electrochromic energy storage device by inkjet-printing single layer of WO3 nanoparticles on an elastomeric transparent conductor. Such hybrid electrode is highly conductive and deformable, making it an excellent candidate for the application: large optical modulation of 40%, fast switching speed (

Incorporation of triboelectric nanogenerators into textiles is attractive for self-powered wearable electronics. Here the authors employ black phosphorus with a hydrophobic coating in a durable, washable, and air permeable textile-based device that converts biomechanical motion into electricity.

Nanolaminates are extensively studied due to their unique properties, such as impact resistance, high fracture toughness, high strength, and resistance to radiation damage. Varieties of nanolaminates are being fabricated to achieve high strength and fracture toughness. In this study, one such nanolaminate fabricated through accumulative roll bonding (Cu(16)/Nb(16) ARB nanolaminate, where 16 nm is the layer thickness) was used as a test material. Cu(16)/Nb(16) ARB nanolaminate exhibits crystallographic anisotropy due to the existence of distinct interfaces along the rolling direction (RD) and the transverse direction (TD). Nanoindentation was executed using a Berkovich tip, with the main axis oriented either along TD or RD of the Cu(16)/Nb(16) ARB nanolaminate. Subsequently, height profiles were obtained along the main axis of the Berkovich indent for both TD and RD using scanning probe microscopy (SPM), which was later used to estimate the pile-up along the RD and TD. The RD exhibited more pile-up than the TD due to the anisotropy of the Cu(16)/Nb(16) ARB interface and the material plasticity along the TD and RD. An axisymmetric 2D finite element analysis (FEA) was also performed to compare/validate nanoindentation data, such as load vs. displacement curves and pile-up. The FEA simulated load vs. displacement curves matched relatively well with the experimentally generated load–displacement curves, while qualitative agreement was found between the simulated pile-up data and the experimentally obtained pile-up data. The authors believe that pile-up characterization during indentation is of great importance to documenting anisotropy in nanolaminates.

Increasing attention has been paid to the next generation of ‘green’ electronic devices based on renewable nanocellulose, owing to its low roughness, good thermal stability and excellent optical properties. Various proof-of-concept transparent nanopaper-based electronic devices have been fabricated; these devices exhibit excellent flexibility, bendability and even foldability. In this review, we summarize the recent progress of transparent nanopaper that uses different types of nanocellulose, including pure nanocellulose paper and composite nanocellulose paper. The latest development of transparent and flexible nanopaper electronic devices are illustrated, such as electrochromic devices, touch sensors, solar cells and transistors. Finally, we discuss the advantages of transparent nanopaper compared to conventional flexible plastic substrate and the existing challenges to be tackled in order to realize this promising potential.

Achieving nanostructures with high surface area is one of the most challenging tasks as this metric usually plays a key role in technological applications, such as energy storage, gas sensing or photocatalysis, fields in which NiO is gaining increasing attention recently. Furthermore, the advent of modern NiO-based devices can take advantage of a deeper knowledge of the doping process in NiO, and the fabrication of p-n heterojunctions. By controlling experimental conditions such as dopant concentration, reaction time, temperature or pH, NiO morphology and doping mechanisms can be modulated. In this work, undoped and Sn doped nanoparticles and NiO/SnO2 nanostructures with high surface areas were obtained as a result of Sn incorporation. We demonstrate that Sn incorporation leads to the formation of nanosticks morphology, not previously observed for undoped NiO, promoting p-n heterostructures. Consequently, a surface area value around 340 m2/g was obtained for NiO nanoparticles with 4.7 at.% of Sn, which is nearly nine times higher than that of undoped NiO. The presence of Sn with different oxidation states and variable Ni3+/Ni2+ ratio as a function of the Sn content were also verified by XPS, suggesting a combination of two charge compensation mechanisms (electronic and ionic) for the substitution of Ni2+ by Sn4+. These results make Sn doped NiO nanostructures a potential candidate for a high number of technological applications, in which implementations can be achieved in the form of NiO–SnO2 p-n heterostructures.

With the rapid development of wearable electronic systems, the need for stretchable nanogenerators becomes increasingly important for autonomous applications such as the Internet-of-Things. Piezoelectric nanogenerators are of interest for their ability to harvest mechanical energy from the environment with its inherent polarization arising from crystal structures or molecular arrangements of the piezoelectric materials. In this work, 3D printing is used to fabricate a stretchable piezoelectric nanogenerator which can serve as a self-powered sensor based on synthesized oxide–polymer composites.

A piezoelectric energy harvester was developed in this paper. It is actuated by the vibration leakage from the nodal position of a high-power ultrasonic cutting transducer. The harvester was excited at a low displacement amplitude (0.73 µmpp). However, its operation frequency is quite high and reaches the ultrasonic range (24.4 kHz). Compared with another low frequency harvester (66 Hz), both theoretical and experimental results proved that the advantages of this high frequency harvester include (i) high current generation capability (up to 20 mApp compared to 1.3 mApp of the 66 Hz transducer) and (ii) low impedance matching resistance (500 Ω in contrast to 50 kΩ of the 66 Hz transducer). This energy harvester can be applied either in sensing, or vibration controlling, or simply energy harvesting in a high-power ultrasonic system.

Soft actuators are gaining significant attention due to their ability to provide realistic tactile sensations in various applications. However, their soft nature makes them vulnerable to damage from external factors, limiting actuation stability and device lifespan. The susceptibility to damage becomes higher with these actuators often in direct contact with their surroundings to generate tactile feedback. Upon onset of damage, the stability or repeatability of the device will be undermined. Eventually, when complete failure occurs, these actuators are disposed of, accumulating waste and driving the consumption of natural resources. This emphasizes the need to enhance the durability of soft tactile actuators for continued operation. This review presents the principles of tactile feedback of actuators, followed by a discussion of the mechanisms, advancements, and challenges faced by soft tactile actuators to realize high actuation performance, categorized by their driving stimuli. Diverse approaches to achieve durability are evaluated, including self-healing, damage resistance, self-cleaning, and temperature stability for soft actuators. In these sections, current challenges and potential material designs are identified, paving the way for developing durable soft tactile actuators. [ABSTRACT FROM AUTHOR]