Leaf-Like TENGs for Harvesting Gentle Wind Energy at An Air Velocity as Low as 0.2 m s−1

Existing technologies for harvesting electrical energy from gentle wind face an enormous challenge due to the limitations of cut-in and rated wind speed. Here, a leaf-like triboelectric nanogenerator (LL-TENG) is proposed that uses contact electrification caused by the damped forced vibration of topology-optimized structure consisting of flexible leaf, vein bearing plate, and counterweight piece. The effectiveness of the topology-optimized leaf-like structure is studied, which solves the problem of reduced output due to electrostatic adsorption between the leaf surfaces while reducing the cut-in (0.2 m s⁻¹) and rated wind speed (2.5 m s⁻¹). The LL-TENG unit having small dimensions of 40 cm⁻² (mass of 9.7 g) at a gentle wind of 2.5 m s⁻¹ exhibits outstanding electrical performances, which produces an open-circuit voltage of 338 V, a short-circuit current of 7.9 µA and the transferred charge density of 62.5 µC m⁻² with a low resonant frequency of 4 Hz, giving an instantaneous peak power of 2 mW. A distributed power source consists of the five LL-TENGs in parallel is developed by designed self-adaptive structure, for which the peak power output reaches 3.98 mW, and its practicability and durability are successfully demonstrated. This study is a promising distributed power source technology to drive electronics in gentle wind outdoor environments.     

Bioinspired and Hierarchically Textile-Structured Soft Actuators for Healthcare Wearables

Soft pneumatic actuators possess the increasing potential for various healthcare applications, such as smart wearable devices, safe human-robot interaction, and flexible manipulators. However, it is difficult to translate the existing technologies to commercial applications due to their inefficient volumetric power, sophisticated control with high operation pressure, slow production, and high cost. To overcome these issues, herein, a caterpillar-inspired actuator using hierarchical textile architectures based on simple fabrication and low-cost strategy is designed. Unlike the existing textile-based pneumatic actuators, the designed actuators are constructed by combining boucle fancy yarns with a novel trilayer-knit architecture. The as-prepared actuators concurrently possess fast response (1100° s⁻¹), large bending actuation strain (1080° m⁻¹), high-power density (272 W m⁻³), mechanical robustness, easy-programmable motions, and human-tactile comfort, which outperforms currently reported textile-based pneumatic actuators. Furthermore, due to the geometrical transition of the engineered hierarchical structure, the developed actuators exhibit superior dual-stiffness effect with stress evolution, providing a facile approach to addressing the conflict of flexibility and force output in soft fluidic actuators. This concept as a paradigm provides new insights to develop soft actuators with outstanding design flexibility, adaptability, and multifunctionality using engineered textile-structure, which has great potential for real-world applications in medical rehabilitation, physiotherapy, and soft robotics.     

Spiral-Shape Fast-Moving Soft Robots

Soft robots typically exhibit limited agility due to inherent properties of soft materials. The structural design of soft robots is one of the key elements to improve their mobility. Inspired by the Archimedean spiral geometry in nature, here, a fast-moving spiral-shaped soft robot made of a piezoelectric composite with an amorphous piezoelectric vinylidene fluoride film and a layer of copper tape is presented. The soft robot demonstrates a forward locomotion speed of 76 body length per second under the first-order resonance frequency and a backward locomotion speed of 11.26 body length per second at the third-order resonance frequency. Moreover, the multitasking capabilities of the soft robot in slope climbing, step jumping, load carrying, and steering are demonstrated. The soft robot can escape from a relatively confined space without external control and human intervention. An untethered robot with a battery and a flexible circuit (a payload of 1.665 g and a total weight of 1.815 g) can move at an absolute speed of 20 mm s⁻¹ (1 body length per second). This study opens a new generic design paradigm for next-generation fast-moving soft robots that are applicable for multifunctionality at small scales.     

Highly Conductive MXene/PEDOT:PSS-Integrated Poly(N-Isopropylacrylamide) Hydrogels for Bioinspired Somatosensory Soft Actuators

Sophisticated sensing and actuation capabilities of many living organisms in nature have inspired scientists to develop biomimetic somatosensory soft robots. Herein, the design and fabrication of homogeneous and highly conductive hydrogels for bioinspired somatosensory soft actuators are reported. The conductive hydrogels are synthesized by in situ copolymerization of conductive surface-functionalized MXene/Poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) ink with thermoresponsive poly(N-isopropylacrylamide) hydrogels. The resulting hydrogels are found to exhibit high conductivity (11.76 S m⁻¹), strain sensitivity (GF of 9.93), broad working strain range (≈560% strain), and high stability after over 300 loading–unloading cycles at 100% strain. Importantly, shape-programmable somatosensory hydrogel actuators with rapid response, light-driven remote control, and self-sensing capability are developed by chemically integrating the conductive hydrogels with a structurally colored polymer. As the proof-of-concept illustration, structurally colored hydrogel actuators are applied for devising light-driven programmable shape-morphing of an artificial octopus, an artificial fish, and a soft gripper that can simultaneously monitor their own motions via real-time resistance variation. This work is expected to offer new insights into the design of advanced somatosensory materials with self-sensing and actuation capabilities, and pave an avenue for the development of soft-matter-based self-regulatory intelligence via built-in feedback control that is of paramount significance for intelligent soft robotics and automated machines.     

Nano-Engineered Carbon Fibre-Based Piezoelectric Smart Composites for Energy Harvesting and Self-Powered Sensing

The integration of piezoelectric materials onto carbon fiber (CF) can add energy harvesting and self-power sensing capabilities enabling great potential for “Internet of Things” (IoT) applications in motion tracking, environmental sensing, and personal portable electronics. Herein, a CF-based smart composite is developed by integrating piezoelectric poly(3,4-ethylenedioxythiophene) (PEDOT)/CuSCN-coated ZnO nanorods onto the CF surfaces with no detrimental effect on the mechanical properties of the composite, forming composites using two different polymer matrices: highly flexible polydimethylsiloxane (PDMS) and more rigid epoxy. The PDMS-coated piezoelectric smart composite can serve as an energy harvester and a self-powered sensor for detecting variations in impact acceleration with increasing output voltage from 1.4 to 7.6 V under impact acceleration from 0.1 to 0.4 m s⁻². Using epoxy as the matrix for a CF-reinforced plastic (CFRP) device with sensing and detection functions produces a voltage varying from 0.27 to 3.53 V when impacted at acceleration from 0.1 to 0.4 m s⁻², with a lower output compared to the PDMS-coated device attributed to the greater stiffness of the matrix. Finally, spatially sensitive detection is demonstrated by positioning two piezoelectric structures at different locations, which can identify the location as well as the level of the impacting force from the fabricated device.     

Wood Robot with Magnetic Anisotropy for Programmable Locomotion

The development of environmentally-friendly stimuli-responsive materials is vital to green electronics, sensors, and biomedicine. However, fast responsiveness and precise locomotion control of biomass materials have not been accomplished. Herein, a magnetically responsive wood is reported that can achieve programmable locomotion in the rotating magnetic field. The magnetized wood is fabricated by removing lignin from the cell walls, which produces a porous microstructure, enabling facile and stable combination between NdFeB and wood. With the directional arrangement of magnetic moments after magnetization, the magnetized wood with obviously positive and negative magnetic poles is magnetic stability, and can complete various movements including spatial flipping, bypass obstacles, climb up, and down under the driven by magnetic torques. Meanwhile, the magnetized wood is lightweight (0.26 g cm⁻³), showing a fast walking speed of up to 11.3 mm s⁻¹ under magnetic actuation (10 mT and 0.6 Hz), which is greater than those of petroleum-based polymeric materials. Benefitting from the unique porous structure, the magnetized wood can be used as the drug-carrier to deliver and release nano-cargoes effectively. This approach expands the range of stimuli-responsive materials beyond hydrogel, elastomers, and synthetic polymer, inspiring the creation of next-generation intelligent robots based on biocompatible and sustainable biomass materials.     

Biomorphic Actuation Driven Via On-Chip Buckling of Photoresponsive Hydrogel Films

Remotely controllable photoresponsive hydrogel actuators are promising for applications in multiple fields. However, simple deformation mechanisms, which rely on the general swelling/deswelling, limit their performance and application. Herein, we report a displacement amplification mechanism based on the buckling deformation of photoresponsive hydrogel film. The on-chip buckled architecture of the hydrogel enables actuation between a flat 2D shape and tubular 3D buckled shape with remarkable performances, including high deformation ratio (height ratio: ≈360%), tunable cycle motion frequency (0.1—1 Hz) and high cyclic stability. Moreover, localized buckling deformation, such as tube opening and closing, can be controlled in response to photostimulation. Inspired by these biomorphic shapes and motions, an intestine-mimetic device and demonstrate segmentation with substance crushing and peristalsis motion with substance propelling were further fabricated. This study will provide a useful design principle for hydrogel actuators and shed light on diverse applications in soft robotics, dynamic microfluidics and organs-on-chips.     

3D-Printed Photoresponsive Liquid Crystal Elastomer Composites for Free-Form Actuation

Direct ink writing of liquid crystal elastomers (LCEs) offers a new opportunity to program geometries for a wide variety of shape transformation modes toward applications such as soft robotics. So far, most 3D-printed LCEs are thermally actuated. Herein, a 3D-printable photoresponsive gold nanorod (AuNR)/LCE composite ink is developed, allowing for photothermal actuation of the 3D-printed structures with AuNR as low as 0.1 wt.%. It is shown that the printed filament has a superior photothermal response with 27% actuation strain upon irradiation to near-infrared (NIR) light (808 nm) at 1.4 W cm⁻² (corresponding to 160 °C) under optimal printing conditions. The 3D-printed composite structures can be globally or locally actuated into different shapes by controlling the area exposed to the NIR laser. Taking advantage of the customized structures enabled by 3D printing and the ability to control locally exposed light, a light-responsive soft robot is demonstrated that can climb on a ratchet surface with a maximum speed of 0.284 mm s⁻¹ (on a flat surface) and 0.216 mm s⁻¹ (on a 30° titled surface), respectively, corresponding to 0.428 and 0.324 body length per min, respectively, with a large body mass (0.23 g) and thickness (1 mm).     

Air Permeable Vibrotactile Actuators for Wearable Wireless Haptics

Vibrotactile actuators can evoke mechanical stimulations on human skins to induce haptic feedbacks for various human machine interaction applications. However, efforts toward their practical usages encounter several engineering challenges, including wearable comfortability and output abilities. Here, air permeable actuators are developed and embedded in common fabrics for vibrotactile actuation, achieving excellent air permeability of 108 L m⁻² s⁻¹, low preload requirement of 10 mN, high output sensitivity of 0.2 mN/V, and good mechanical durability by surviving 11 million testing cycles. As demonstration examples, a wireless haptic feedback glove is shown to distinguish 32 different English characters and symbols with an overall accuracy of 97.8%, and large size actuators (10 × 10 cm²) are also proved for providing haptic feedback for parts of human body. As such, the proposed system opens a new class of wearable vibrotactile actuators for potential applications in wide fields of metaverse, teleoperation, smart textiles, and robotics.     

Controllable thin-film morphology and structure for 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8BTBT) based organic field-effect transistors

Organic field-effect transistors (OFETs) based on organic semiconductor material 2,7-dioctyl[1]benzothieno[3,2-b] benzothiophene (C8BTBT) as the active layer were fabricated by using organic molecular beam deposition (OMBD) and solution-processed methods, in which the C8BTBT thin-film morphology could be well controlled. In OMBD method, C8BTBT thin-film morphology could be controlled by the thickness of organic semiconductor layer and the deposition rate, of which the high-quality C8BTBT thin film was obtained at a thickness of about 20 nm and at a deposition rate of 1.2 nm/min, resulting in an obvious mobility improvement from 2.8 × 10⁻³ cm² V⁻¹ s⁻¹ to 1.20 cm² V⁻¹ s⁻¹. While in the solution-processing, C8BTBT thin-film morphology and thickness are related to the spin-coating speed and the substrate position in spin coater, i.e., in-centre and off-centre position. The off-centre spin-coating with an optimized speed produced large-size domain C8BTBT thin film and accordingly resulted in a mobility of 1.47 cm² V⁻¹ s⁻¹. Furthermore, an additive polystyrene (PS) was added into C8BTBT solution could further improve the thin-film morphology with more metal-stable phase as well as improve the interface contact with the substrate SiO₂, resulting in the highest mobility up to 3.56 cm² V⁻¹ s⁻¹. The research suggested that C8BTBT-based OFETs with the mobility over 1.20 cm² V⁻¹ s⁻¹ could be fabricated by using both OMBD and solution-processed methods through the thin-film morphology and structure optimization, which shows the potential applications in high-performance flexible and printed electronics.     

Rationally Designed Anti-Glare Panel Arrays as Highway Wind Energy Harvester

The anti-glare panels along highways can block the dazzling lights of opposing vehicles at night, playing an important role in the highway safety. Inspired by the highway anti-glare panels, wind energy harvesting triboelectric nanogenerator (AG-TENG) arrays to properly capture energy from highway moving vehicles is developed. A single AG-TENG installation module can achieve a high power density of 0.2 Wm⁻² at a wind speed of 3 m s⁻¹. This wind speed is too low to drive conventional wind energy harvesting equipment. The performance of the AG-TENG shows no degradation after 80 h of continuous operation (1 440 000 times). Thus, with the rational consideration and features, the system can generate enough power to drive internet of things (IoT) devices and environmental sensors, as well as offer wireless alarming and radio frequency identification vehicle monitoring. This study provides a promising strategy to properly harvest wind energy on highways using existing infrastructures under the condition of even no natural wind, showing broad application prospects in distributed environmental monitoring, intelligent highways, and the IoT.     

Strong,Compressible, and Ultrafast Self-Recovery Organogel with In Situ Electrical Conductivity Improvement

Coordination complexes are widely used to tune the mechanical behaviors of polymer materials, including tensile strength, stretchability, self-healing, and toughness. However, integrating multivalent functions into one material system via solely coordination complexes is challenging, even using combinations of metal ions and polymer ligands. Herein, a single-step process is described using silver-based coordination complexes as cross-linkers to enable high compressibility (>85%). The resultant organogel displays a high compressive strength (>1 MPa) with a low energy loss coefficient (<0.1 at 50% strain). Remarkably, it demonstrates an instant self-recovery at room temperature with a speed >1200 mm s⁻¹, potentially being utilized for designing high-frequency-responsive soft materials (>100 Hz). Importantly, in situ silver nanoparticles are formed, effectively endowing the organogel with high conductivity (550 S cm⁻¹). Given the synthetic simplification to achieve multi-valued properties in a single material system using metal-based coordination complexes, such organogels hold significant potential for wearable electronics, tissue-device interfaces, and soft robot applications.     

A Fully Self-Healing and Highly Stretchable Liquid-Free Ionic Conductive Elastomer for Soft Ionotronics

Soft ionic conductors hold great potential for soft ionotronics, such as ionic skin, human–machine interface and soft luminescent device. However, most hydrogel and ionogel-based soft ionic conductors suffer from freezing, evaporation and liquid leakage problems, which limit their use in complex environments. Herein, a class of liquid-free ionic conductive elastomers (ICEs) is reported as an alternative soft ionic conductor in soft ionotronics. These liquid-free ICEs offer a combination of desirable properties, including extraordinary stretchability (up to 1913%), toughness (up to 1.08 MJ cm⁻³), Young's modulus (up to 0.67 MPa), rapid fully self-healing capability at room temperature, and good conductivity (up to 1.01 × 10⁻⁵ S cm⁻¹). The application of these ICEs is demonstrated by creating a wearable sensor that can detect and discriminate minimal deformations and human body movements, such as finger or elbow joint flexion, walking, running, etc. In addition, self-healing soft ionotronic devices are demonstrated to confront mechanical breakdown, such as an ionic skin and an alternating-current electroluminescent device that can reuse from damage. It is believed that these liquid-free ICEs hold great promises for applications in wearable devices and soft ionotronics.     

Revealing High-Rate and High Volumetric Pseudo-Intercalation Charge Storage from Boron-Vacancy Doped MXenes

The design of pseudocapacitive electrodes that exhibit high-rate and high volumetric capacitances is a big challenge, since it requires subtle modulation of ion-intercalation structures that are able to achieve high electrochemical activity, fast ion transport, and facilitated electron transfer, simultaneously. Herein, controllable and selective etching of B atoms from B-doped Ti₃AlC₂ precursors is reported, which generates boron-vacancy doped MXene (B-V-MXene) nanosheets with finely-regulated, ion-intercalation structures. Electrochemical studies and density-functional-theory calculations demonstrate that Ti around vacancies possess higher surface-redox activity with protons than those on pristine MXenes for the improvement of capacitances. In addition, interlayer spacing can be optimized on B-V-MXenes in promoting proton intercalation. More importantly, the dopant B atoms can increase the electron density on Ti, facilitating the adsorption of the intercalated protons; and further, B 2p-Ti 3d hybridized band sits closer to the Fermi energy than that of C 2p bands, which bridges the energy gap for electron transfer in the pseudo-capacitive reaction. With synergy of all these effects, the novel B-V-MXene compact electrodes can deliver the previously unmatched high volumetric capacitances of 807 F cm⁻³ at 1,000 mV s⁻¹ and 1,815 F cm⁻³ at 5 mV s⁻¹, with excellent cycle stability over 10,000 cycles.     

Alternating Magnetic Field-Enhanced Triboelectric Nanogenerator for Low-Speed Flow Energy Harvesting

Low-speed flow energy, such as breezes and rivers, which are abundant in smart agriculture and smart cities, faces significant challenges in efficient harvesting as an untapped sustainable energy source. This study proposes an alternating magnetic field-enhanced triboelectric nanogenerator (AMF-TENG) for low-speed flow energy harvesting, and demonstrates its feasibility through experimental results. AMF-TENG's minimum cut-in speed is 1 m s⁻¹, thereby greatly expanding its wind energy harvesting range. When the wind speed is 1–5 m s⁻¹, the open-circuit voltage (V_OC) is 20.9–179.3 V. The peak power is 0.68 mW at 5 m s⁻¹. In a durability test of 100 K cycles, the V_OC decreases from 188.4 to 174.2 V but remain at 92.5% of the initial value. furthermore, the AMF-TENG can harvest low-speed flow energy from the natural environment to power temperature and humidity sensors and wireless light intensity sensor in smart agriculture. This study provides a promising method for low-speed flow energy harvesting in distributed applications.     

Robust Ferrimagnetism and Switchable Magnetic Anisotropy in High-Entropy Ferrite Film

Ferrimagnetic insulator materials are the enabling technology for the development of next-generation magnetic devices with low power consumption, high operation speed, and high miniaturization capability. To achieve a high-density memory device, a combined realization of robust saturation magnetization (M_s), controllable magnetic anisotropy, and high resistivity (ρ) are highly demanded. Despite significant efforts that have been made recently, simultaneously achieving significant enhancements in these properties in a soft magnetic insulator material still remains a great challenge, severely limiting their practical application. Herein, a high-entropy strategy in an ultra-thin spinel ferrite (CrMnFeCoNi)₃O₄ film is reported that exhibits concurrently a superior saturation magnetization (M_S = 1198 emu cm⁻³), low coercivity (H_C = 90 Oe), and excellent resistivity (ρ = 1233 Ω cm), as well as switchable magnetic anisotropy. The comprehensive lattice probing and microstructure analysis studies reveal that such desirable ferromagnetic properties originate from the high-quality structurally ordered but compositionally disordered single-crystal epitaxial structure. The switchable magnetic anisotropy demonstrated in the high-entropy ferrite film can be attributed to the new antiferromagnetic rock-salt phase. This work unveils the critical benefits of the high-entropy strategy for magnetic oxide thin films, which opens up new opportunities for the development of high-performance magnetic materials.     

Analysis of the Annealing Budget of Metal Oxide Thin-Film Transistors Prepared by an Aqueous Blade-Coating Process

Metal oxide (MO) semiconductors are widely used in electronic devices due to their high optical transmittance and promising electrical performance. This work describes the advancement toward an eco-friendly, streamlined method for preparing thin-film transistors (TFTs) via a pure water-solution blade-coating process with focus on a low thermal budget. Low temperature and rapid annealing of triple-coated indium oxide thin-film transistors (3C-TFTs) and indium oxide/zinc oxide/indium oxide thin-film transistors (IZI-TFTs) on a 300 nm SiO₂ gate dielectric at 300 °C for only 60 s yields devices with an average field effect mobility of 10.7 and 13.8 cm² V⁻¹ s⁻¹, respectively. The devices show an excellent on/off ratio (>10⁶), and a threshold voltage close to 0 V when measured in air. Flexible MO-TFTs on polyimide substrates with AlO_x dielectrics fabricated by rapid annealing treatment can achieve a remarkable mobility of over 10 cm² V⁻¹ s⁻¹ at low operating voltage. When using a longer post-coating annealing period of 20 min, high-performance 3C-TFTs (over 18 cm² V⁻¹ s⁻¹) and IZI-TFTs (over 38 cm² V⁻¹ s⁻¹) using MO semiconductor layers annealed at 300 °C are achieved.     

Jumping like an insect: Design and dynamic optimization of a jumping mini robot based on bio-mimetic inspiration

This paper presents a bio-inspired design of a jumping mini robot including the theoretical analysis on jumping dynamics based on a simplified biological model, the dynamically optimized saltatorial leg design, the overall design of the jumping robot prototype and, as a part of the bio-mimetic research, and the measuring and comparing of the jumping characteristics between the robot and animal. The artificial saltatorial leg is designed to imitate the characteristics of a real jumping insect, kinematically and dynamically, and proposed to reduce the contact force at tarsus–ground interface during jumping acceleration thus optimizes the jumping motion by minimizing the risk of both leg ruptures and tarsus slippage. Then by means of high speed camera experiment, the jumping characteristics of the theoretical jumping model, the jumping insect leafhopper and the robot are compared so as to show the dynamic similarity and optimization results among them. The final energy integrated jumping robot prototype is able to accomplish a movement of continuous jumping, of which a single jumping reaches 100 mm high and 200 mm long, about twice and four times of its body length respectively.     

Recent Development of Jumping Motions Based on Soft Actuators

Drawing inspiration from the jumping motions of living creatures in nature, jumping robots have emerged as a promising research field over the past few decades due to great application potential in interstellar exploration, military reconnaissance, and life rescue missions. Early reviews mainly focused on jumping robots made of lightweight and rigid materials with mechanical components, concentrating on jumping control and stability. Herein, attention is paid to the jumping mechanisms of soft actuators assembled from various soft smarting materials and powered by different stimulus sources. The challenges and prospects of soft jumping actuators are also discussed. It is hoped that this review will contribute to the further development of soft jumping actuators and broaden their practical applications.     

Mimosa-Inspired High-Sensitive and Multi-Responsive Starch Actuators

Artificial intelligent actuators are extensively explored for emerging applications such as soft robots, human-machine interfaces, and biomedical devices. However, intelligent actuating systems based on synthesized polymers suffer from challenges in renewability, sustainability, and safety, while natural polymer-based actuators show limited capabilities and performances due to the presence of abundant hydrogen-bond lockers. Here this study reports a new hydrogen bond-mediated strategy to develop mimosa-inspired starch actuators (SA). By harnessing the unique features of gelatinization and abundant hydrogen bonds, these SA enable high-sensitivity and multi-responsive actuation in various scenarios. The non-gelatinized SA can be irreversibly programmed into diverse shapes, such as artificial flowers, bowl shapes, and helix structures, using near-infrared light. Furthermore, the gelatinized SA exhibit reversibly multi-responsive actuation when exposed to low humidity (10.2%), low temperature (37 °C), or low-energy light (0.42 W cm⁻²). More importantly, the SA demonstrate robust applications in smart living, including artificial mimosa, intelligent lampshade, and morphing food. By overcoming the hydrogen-bond lockers inherent in natural polymers, SA open new avenues for next-generation recyclable materials and actuators, bringing them closer to practical applications.