A Soft,Fast and Versatile Electrohydraulic Gripper with Capacitive Object Size Detection

Soft robotic grippers achieve increased versatility and reduced complexity through intelligence embodied in their flexible and conformal structures. The most widely used soft grippers are pneumatically driven; they are simple and effective but require bulky air compressors that limit their application space and external sensors or computationally expensive vision systems for pick verification. In this study, a multi-material architecture for self-sensing electrohydraulic bending actuators is presented that enables a new class of highly versatile and reconfigurable soft grippers that are electrically driven and feature capacitive pick verification and object size detection. These electrohydraulic grippers are fast (step input results in finger closure in 50 ms), draw low power (6.5 mW per finger to hold grasp), and can pick a wide variety of objects with simple binary electrical control. Integrated high-voltage driving electronics are presented that greatly increase the application space of the grippers and make them readily compatible with commercially available robotic arms.     

Robotic Locomotion and Piezo1 Activity Controlled with Novel Liquid Marble-based Soft Actuators

A novel soft actuator is designed, fabricated, and optimized for applied use in soft robotics and biomedical applications. The soft actuator is powered by the expansion and contraction of a graphene-containing and encased liquid marble using the photothermal effect. Unfortunately, conventional liquid marbles are found to be too fragile and prone to cracking and failure for such applications. After experimentation, it is possible to remedy this problem by synthesizing liquid marbles encased with polymeric shells–polymerized in situ–for added mechanical strength and robustness. These marbles are shown to have intrinsic photothermal activity. They are then situated in bimorph-type soft actuators where one side of the actuator has a dramatically different Young's modulus than the other, leading to directional actuation which is successfully demonstrated in multistep walking soft robots. The soft actuators are shown to successfully activate the mechanosensitive Piezo protein in a transfected human cell line with high effectiveness and no toxicity. Overall, the liquid marble-powered soft actuators described here represent a new soft actuation methodology and a novel tool for mechanobiological studies, such as stem cell fate and organoid differentiation.     

Nanocellulose-Based Functional Materials: From Chiral Photonics to Soft Actuator and Energy Storage

Nanocellulose is currently in the limelight of extensive research from fundamental science to technological applications owing to its renewable and carbon-neutral nature, superior biocompatibility, tailorable surface chemistry, and unprecedented optical and mechanical properties. Herein, an up-to-date account of the recent advancements in nanocellulose-derived functional materials and their emerging applications in areas of chiral photonics, soft actuators, energy storage, and biomedical science is provided. The fundamental design and synthesis strategies for nanocellulose-based functional materials are discussed. Their unique properties, underlying mechanisms, and potential applications are highlighted. Finally, this review provides a brief conclusion and elucidates both the challenges and opportunities of the intriguing nanocellulose-based technologies rooted in materials and chemistry science. This review is expected to provide new insights for nanocellulose-based chiral photonics, soft robotics, advanced energy, and novel biomedical technologies, and promote the rapid development of these highly interdisciplinary fields, including nanotechnology, nanoscience, biology, physics, synthetic chemistry, materials science, and device engineering.     

Bio‐Inspired All‐Organic Soft Actuator Based on a π–π Stacked 3D Ionic Network Membrane and Ultra‐Fast Solution Processing

Next generation electronic products, such as wearable electronics, flexible displays, and smart mobile phones, will require the use of unprecedented electroactive soft actuators for haptic and stimuli‐responsive devices and space‐saving bio‐mimetic actuation. Here, a bio‐inspired all‐organic soft actuator with a π–π stacked and 3D ionic networked membrane based on naphthalene‐tetracarboxylic dianhydride (Ntda) and sulfonated polyimide block copolymers (SPI) is presented, utilizing an ultra‐fast solution process. The π–π stacked and self‐assembled 3D ionic networked membrane with continuous and interconnected ion transport nanochannels is synthesized by introducing simple and strong atomic level regio‐specific interactions of hydrophilic and hydrophobic SPI co‐blocks with cations and anions in the ionic liquid. Furthermore, a facile and ultrafast all‐solution process involving solvent blending, dry casting, and solvent dropping is developed to produce electro‐active soft actuators with highly conductive polyethylenedioxythiophene (PEDOT):polystyrenesulfonate (PSS) electrodes. Ionic conductivity and ion exchange capacity of the π–π stacked Ntda‐SPI membrane can be increased up to 3.1 times and 3.4 times of conventional SPI, respectively, resulting in a 3.2 times larger bending actuation. The developed bio‐inspired soft actuator is a good candidate for satisfying the tight requirements of next generation soft electronic devices due to its key benefits such as low operating voltage and comparatively large strains, as well as quick response and facile processability.     

Photothermal Bimorph Actuators with In‐Built Cooler for Light Mills,Frequency Switches,and Soft Robots

Photothermal bimorph actuators are widely used for smart devices, which are generally operated in a room temperature environment, therefore a low temperature difference for actuation without deteriorating the performance is preferred. The strategy for the actuator is assembling a broadband‐light absorption layer for volume expansion and an additional water evaporation layer for cooling and volume shrinkage on a passive layer. The response time and temperature‐change‐normalized bending speed under NIR, white, and blue light illumination are at the same level of high performance, fast photothermal actuators based on polymer or polymer composites. The classical beam theory and finite element simulations are also conducted to understand the actuation mechanism of the actuator. A new type of light mill is designed based on a wing‐flapping mechanism and a light‐modulated frequency switch. A fast‐walking robot (with a speed of 26 mm s^?1) and a fast‐and‐strong mechanical gripper with a large weight‐lifting ratio (≈2142), respectively, are also demonstrated.     

Highly Bendable Ionic Soft Actuator Based on Nitrogen‐Enriched 3D Hetero‐Nanostructure Electrode

Electrically responsive ionic soft actuators that can exhibit large bending strain under low electrical input power are promising candidates for future soft electronics and wearable devices. However, some drawbacks such as low blocking force, slow response time, and poor durability should be overcome for practical engineering applications. Herein, this study reports defect‐engineered 3D graphitic carbon nitride (GCN) and nitrogen‐doped graphene (NG) hetero‐nanostructure that were developed by one‐pot hydrothermal method in order to design functionally antagonistic hybrid electrodes for superior ionic soft actuators. While NG facilitates rapid electron transfer in 3D networked nanoarchitectures, the enriched‐nitrogen content in GCN provides good wettability and mechanical resiliency with poly(3,4 ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The 3D hybrid nanostructures generate unimpeded ion channels and sufficient contact area with the electrolyte membrane to provide higher capacitance and mechanical integrity, which are critical prerequisites for high‐performance actuation. The developed soft actuator based on the nitrogen‐enriched 3D hetero‐nanostructure is found to exhibit large bending strain (0.52%), wide frequency response, 5 h durability (93% retention), 2.4 times higher bending displacement, and twofold higher electromechanical efficiency compared to PEDOT:PSS under ±0.5 V input voltage. Such 3D functionally antagonistic hybrid electrodes offer hitherto unavailable opportunities in developing ultralow voltage‐driven ionic actuators for the next‐generation soft electronics.     

Versatile Quasi-Solid Ionic Conductive Elastomer Inspired by Desertification Control Strategy for Soft Iontronics

Ionic conductors, such as hydrogels, ionogels, and eutectogels, have attained considerable research interest in various advanced application scenarios. However, such ionic conductors still suffer from the restriction of inherent liquid compositions, which may leak or evaporate. Herein, inspired by the control strategy of desertification caused by soil erosion, a novel internal-external dual enhancement design strategy, i.e., increasing the interaction between the filler itself and its matrix, is proposed to firmly embed the deep eutectic solvent (DES) into polyurethane (PU) to prevent liquid leakage, such that the prepared ionic conductive elastomers (PU-DESs) are quasi-solid. The PU-DESs exhibit marvelous versatility including high stretchability, tensile strength, toughness, self-healing efficiency, antibacterial ability, ionic conductivity, and excellent freezing tolerance. More intriguingly, benefiting from their quasi-solid feature, PU-DESs are endowed with long-term environmental stability. Thanks to these superb versatile features, PU-DESs are further successfully applied in the wearable sensor and triboelectric nanogenerator (TENG) for monitoring human motions and converting mechanical energy into electrical energy, breaking away from the limitations of previous most soft iontronics such as liquid leakage or evaporation and weak mechanical strength. Hence, this study establishes an effective material design strategy for various soft iontronics demanding environmental stability and durability.     

Rugged Soft Robots using Tough,Stretchable, and Self-Healable Adhesive Elastomers

Soft robots are susceptible to premature failure from physical damages incurred within dynamic environments. To address this, we report an elastomer with high toughness, room temperature self-healing, and strong adhesiveness, allowing both prevention of damages and recovery for soft robotics. By functionalizing polyurethane with hierarchical hydrogen bonds from ureido-4[1H]-pyrimidinone (UPy) and carboxyl groups, high toughness (74.85 MJ m⁻³), tensile strength (9.44 MPa), and strain (2340%) can be achieved. Furthermore, solvent-assisted self-healing at room temperature enables retention of high toughness (41.74 MJ m⁻³), tensile strength (5.57 MPa), and strain (1865%) within only 12 h. The elastomer possesses a high dielectric constant (≈9) that favors its utilization as a self-healing dielectric elastomer actuator (DEA) for soft robotics. Displaying high area strains of ≈31.4% and ≈19.3% after mechanical and electrical self-healing, respectively, the best performing self-healable DEA is achieved. With abundant hydrogen bonds, high adhesive strength without additional curing or heating is also realized. Having both actuation and adhesive properties, a “stick-on” strategy for the assembly of robust soft robots is realized, allowing soft robotic components to be easily reassembled or replaced upon severe damage. This study highlights the potential of soft robots with extreme ruggedness for different operating conditions.     

Gradient Porous Elastic Hydrogels with Shape‐Memory Property and Anisotropic Responses for Programmable Locomotion

Programmable locomotion of responsive hydrogels has gained increasing attention for potential applications in soft robotics, microfluidic components, actuators, and artificial muscle. Modulation of hydrogel pore structures is essential for tailoring their mechanical strength, response speeds, and motion behaviors. Conventional methods forming hydrogels with homogeneous or stepwise‐distributed pore structures are limited by the required compromise to simultaneously optimize these aspects. Here, a heterobifunctional crosslinker enabled hydrothermal process is introduced to synthesize responsive hydrogels with well‐defined gradient pore construction. According to gradient porosity controls, the hydrogels simultaneously exhibit rapid responses to external stimuli, high elasticity/compressibility, and programmable locomotion capability. By incorporating polypyrrole nanoparticles as photothermal transducers, photo/thermal responsive composite hydrogels are formed to enable programmable control of locomotion such as bending, curving, twisting, and octopus‐like swimming under near‐infrared laser stimulation. The tunable pore structures, mechanical properties, and locomotion of this new class of materials make these gradient porous hydrogels potentially suitable for a variety of applications.     

An Autonomous Soft Actuator with Light‐Driven Self‐Sustained Wavelike Oscillation for Phototactic Self‐Locomotion and Power Generation

Mimicking the intelligence of biological organisms in artificial systems to design smart actuators that act autonomously in response to constant environmental stimuli is crucial to the construction of intelligent biomimetic robots and devices, but remains a great challenge. Here, a light‐driven autonomous carbon‐nanotube‐based bimorph actuator is developed through an elaborate structural design. This curled droplet‐shaped actuator can be simply driven by constant white light irradiation, self‐propelled by a light‐mechanical negative feedback loop created by light‐driven actuation, time delay in the photothermal response along the actuator, and good elasticity from the curled structure, performing a continuously self‐oscillating motion in a wavelike fashion, which mimics the human sit‐up motion. Moreover, this autonomous self‐oscillating motion can be further tuned by controlling the intensity and direction of the incident light. The autonomous actuator with continuous wavelike oscillating motion shows immense potential in light‐driven biomimetic soft robots and optical‐energy‐harvesting devices. Furthermore, a self‐locomotive artificial snake with phototaxis is constructed, which autonomously and continuously crawls toward the light source in a wave‐propagating manner under constant light irradiation. This snake can be placed on a substrate made of triboelectric materials to realize continuous electric output when exposed to constant light illumination.     

A Highly Sensitive,Reversible, and Bidirectional Humidity Actuator by Calcium Carbonate Ionic Oligomers Incorporated Poly(Vinylidene Fluoride)

Sensitivity and multi-directional motivation are major two factors for developing optimized humidity-response materials, which are promising for sensing, energy production, etc. Organic functional groups are commonly used as the water sensitive units through hydrogen bond interactions with water molecules in actuators. The multi-coordination ability of inorganic ions implies that the inorganic ionic compounds are potentially superior water sensitive units. However, the particle forms of inorganic ionic compounds produced by classical nucleation limit the number of exposed ions to interact with water. Recent progress on the inorganic ionic oligomers has broken through the limitation of classical nucleation, and realized the molecular-scaled incorporation of inorganic ionic compounds into an organic matrix. Here, the incorporation of hydrophilic calcium carbonate ionic oligomers into hydrophobic poly(vinylidene fluoride) (PVDF) is demonstrated. The ultra-small calcium carbonate oligomers within a PVDF film endow it with an ultra-sensitive, reversible, and bidirectional response. The motivation ability is superior to other bidirectional humidity-actuators at present, which realizes self-motivation on an ice surface, converting the chemical potential energy of the humidity gradient from ice to kinetic energy.     

Biomimetic Color Changing Anisotropic Soft Actuators with Integrated Metal Nanowire Percolation Network Transparent Heaters for Soft Robotics

To add more functionalities and overcome the limitation in conventional soft robots, highly anisotropic soft actuators with color shifting function during actuation is demonstrated for the first time. The electrothermally operating soft actuators with installed transparent metal nanowire percolation network heater allow easy programming of their actuation direction and instantaneous visualization of temperature changes through color change. Due to the unique direction dependent coefficient of thermal expansion mismatch, the suggested actuator demonstrates a highly anisotropic and reversible behavior with very large bending curvature (2.5 cm^?1) at considerably low temperature (≈40 °C) compared to the previously reported electrothermal soft actuators. The mild operating heat condition required for the maximum curvature enables the superior long‐term stability during more than 10 000 operating cycles. Also, the optical transparency of the polymer bilayer and metal nanowire percolation network heater allow the incorporation of the thermochromic pigments to fabricate color‐shifting actuators. As a proof‐of‐concept, various color‐shifting biomimetic soft robots such as color‐shifting blooming flower, fluttering butterfly, and color‐shifting twining tendril are demonstrated. The developed color‐shifting anisotropic soft actuator is expected to open new application fields and functionalities overcoming the limitation of current soft robots.     

Electrically and Sunlight‐Driven Actuator with Versatile Biomimetic Motions Based on Rolled Carbon Nanotube Bilayer Composite

Designing multistimuli responsive soft actuators which can mimic advanced and sophisticated biological movements through simple configuration is highly demanded for the biomimetic robotics application. Here, inspired by the human's flick finger behavior which can release large force output, a soft jumping robot mimicking the gymnast's somersault is designed based on the rolled carbon nanotube/polymer bilayer composite actuator. This new type of rolled bilayer actuator with tubular shape is fabricated and shows electrically and sunlight‐induced actuation with remarkable performances including ultralarge deformation from tubular to flat (angel change >200° or curvature >2 cm^?1), fast response (<5 s), and low actuation voltage (≤10 V). Besides jumping, the uniquely reversible rolling–unrolling actuation can lead to other smart soft robots with versatile complex biomimetic motions, including light‐induced tumbler with cyclic wobbling, electrically/light‐induced crawling‐type walking robots and grippers, electrically induced mouth movement, and ambient‐sunlight‐induced blooming of a biomimetic flower. These results open the way for using one simple type of actuator structure for the construction of various soft robots and devices toward practical biomimetic 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.     

Zero-Power Shape Retention in Soft Pneumatic Actuators with Extensional and Bending Multistability

Power-free shape retention enables soft pneumatic robots to reduce energy cost and avoid unexpected collapse due to burst or puncture. Existing strategies for pneumatic actuation cannot attain motion locking for trajectories combining extension and bending, one of the most common modes of operation. Here, a design paradigm is introduced for soft pneumatic actuators to enable zero-power locking for shape retention in both extension and bending. The underpinning mechanism is the integration of a pneumatic transmitter and a multistable guider, which are programmed to interact for balanced load transfer, flexural and extension steering, and progressive snapping leading to state locking. Through theory, simulations, and experiments on proof-of-concept actuators, the existence of four distinct regimes of deformation is unveiled, where the constituents first interact during inflation to attain locking in extension and bending, and then cooperate under vacuum to enable fully reversible functionality. Finally, the design paradigm is demonstrated to realize a soft robotic arm capable to lock at desired curvature states at zero-power, and a gripper that safely operates with puncture resistance to grasp and hold objects of various shapes and consistency. The study promises further development for zero-power soft robots endowed with multiple deformation modes, sequential deployment, and tunable multistability.     

Liquid Crystal Soft Actuators and Robots toward Mixed Reality

Liquid crystals (LCs) are soft but smart materials that can adjust its chemical or physical properties in response to various external stimuli. Using these materials to construct soft actuators and robots, referred as LC actuators and robots, is expected to replace current machinery part, obtaining lighter and smaller equipment with adjustable and complex functions. Especially, combining these LC actuator and robots with existing virtual reality and augmented reality technologies will produce a new world of mixed reality (MR) with the visual, auditory, and somatosensory interaction. In this review, the recent work on responsive LC actuators and robots is introduced, emphasizing on their potentials in haptic use. By discussing their programmable control via suitable stimuli, the LC actuators and robots are summarized for mechanical outputs, environmental mimic, and fine-tuning of surface texture and roughness. It is anticipated that the continuous development on LC actuators and robots will accelerate the MR technology toward practical application.     

Soft Actuators and Robots that Are Resistant to Mechanical Damage

This paper characterizes the ability of soft pneumatic actuators and robots to resist mechanical insults that would irreversibly damage or destroy hard robotic systems—systems fabricated in metals and structural polymers, and actuated mechanically—of comparable sizes. The pneumatic networks that actuate these soft machines are formed by bonding two layers of elastomeric or polymeric materials that have different moduli on application of strain by pneumatic inflation; this difference in strain between an extensible top layer and an inextensible, strain‐limiting, bottom layer causes the pneumatic network to expand anisotropically. While all the soft machines described here are, to some extent, more resistant to damage by compressive forces, blunt impacts, and severe bending than most corresponding hard systems, the composition of the strain‐limiting layers confers on them very different tensile and compressive strengths.