Soft robots exhibit promising dexterity and adaptability for manipulation because of their high compliance. However, the existing soft robots with invariant stiffness hardly interact with cluttered environments with varying curvatures. In this study, inspired by the maneuverability of an elephant trunk, we proposed a pneumatic soft robot comprised of soft pneumatic actuators and interference plates. By implementing interference plates in diverse patterns, the localized stiffness of our robot can be pre-programmed. To quantify the availability of localized stiffness regulation, we constructed four typical assembly fashions strengthened by the interference plates, and predicted robot profiles by simulation that was validated via experiments. We demonstrated the application of our soft robot with localized stiffness regulation in a variety of scenarios demanding specific configurations. Our design paradigm not only uncovers the potential methodology for regulating robotic curvature precisely, but may inspire next-generation soft robots integrating specified structural and material characteristics learned from natural intelligence.

Biological fish exhibit remarkable adaptability and exceptional swimming performance through their powerful and flexible bodies. Therefore, designing a continuum flexible body is significantly important for the development of a robotic fish. However, it is still challenging to replicate these functions of a biological body due to the limitations of actuation and material. In this paper, based on a tensegrity structure, we propose a bionic design scheme for a continuum robotic fish body with a property of stiffness variation. Its detailed structures and actuation principles are also presented. A mathematical model was established to analyze the bending characteristics of the tensegrity structure, which demonstrates the feasibility of mimicking the fish-like oscillation propulsion. Additionally, the stiffness variation mechanism is also exhibited experimentally to validate the effectiveness of the designed tensegrity fish body. Finally, a novel bionic robotic fish design scheme is proposed, integrating an electronic module-equipped fish head, a tensegrity body, and a flexible tail with a caudal fin. Subsequently, a prototype was developed. Extensive experiments were conducted to explore how control parameters and stiffness variation influence swimming velocity and turning performance. The obtained results reveal that the oscillation amplitude, frequency, and stiffness variation of the tensegrity robotic fish play crucial roles in swimming motions. With the stiffness variation, the developed tensegrity robotic fish achieves a maximum swimming velocity of 295 mm/s (0.84 body length per second, BL/s). Moreover, the bionic tensegrity robotic fish also performs a steering motion with a minimum turning radius of 230 mm (0.68 BL) and an angular velocity of 46.6°/s. The conducted studies will shed light on the novel design of a continuum robotic fish equipped with stiffness variation mechanisms.

Continuum robots always exhibit strong adaptability for exploring unstructured environments and high safety for achieving human-machine interactions. To further enhance their agility, it is imperative that these robots integrate both bending and elongation motion patterns. However, employing a unified actuation strategy will inevitably lead to motion coupling between these patterns, which poses a significant challenge in predicting and regulating morphing profiles. In this letter, inspired by the motion regulation observed in muscle fibers of elephant trunks, we proposed a hybrid-driven modular continuum robot. This robotic configuration enables the modulation of motion patterns through various approaches, thus achieving independent control of bending and elongation motions. Here, each backbone of the module not only produces an elongation rate of 62.76 ± 0.01% but also morphs into a bending profile with an angle of 35.53 ± 1.18°. Then, through theoretical and experimental investigations on a one-segment continuum robot composed of three modules, we illustrated that segregating the actuation approaches for bending and elongation motion patterns effectively mitigates motion coupling, enhancing the motion accuracy of continuum robots. In addition, we also demonstrated the versatility of a two-segment continuum robot, which morphs into diverse profiles for grasping, moving, and releasing items by combining different motion patterns.

Multimodal grasping has emerged as a promising strategy to enhance the grasping diversity of grippers in response to the rapid expansion of application scenarios. Among various designs, the pinch-suction hybrid mechanism and the soft-rigid hybrid structure have proved to be two practical strategies to achieve multimodality. However, existing research on these two strategies still lacks simple and effective collaborative mechanisms to fully leverage the advantages of each mode while ensuring mutual non-interference. In this article, we propose a pinch-suction and soft-rigid hybrid multimodal gripper (HMG), integrating four operating modes into a compact structure. Two simple and effective collaborative mechanisms are introduced to coordinate between pinch and suction operation and between soft and rigid components, respectively. Through the collaboration of different modes, the HMG exhibits a competitive grasping diversity across four aspects, including weight (from 0.2 g to 10 kg), fragility (from jelly to aluminum profile), size scale (from 0.46 mm to 0.55 m), and shape (from poorly pinchable to poorly suckable). We further demonstrate its adaptability and robustness in handling irregular-shaped objects, and its proficiency in executing complex real-world manipulation tasks, underwater operations, and closed-loop grasping. Its enhanced grasping diversity is poised to accelerate diverse applications in daily life, industrial settings, and underwater scenarios.

Fish swim with four main gaits—anguilliform, subcarangiform, carangiform, and thunniform—produced by waves along varying portions of the body. However, how muscle activation length influences swimming performance remains poorly understood. We present a reconfigurable robotic fish that replicates all four gaits in a single platform by rapidly tuning its body stiffness. Vacuum-driven layer jamming muscles in four tensegrity joints enable quick (≤1 s) stiffness modulation (stiffness ratio of 46.6) and gait switching. In thunniform gait, the robot reaches 1.24 body lengths per second, whereas in anguilliform gait, it achieves agile maneuvering with a turning radius of 0.26 body lengths. Fluid simulations show that the thunniform gait generates stronger vortices and 142% more thrust compared with anguilliform motion at 5 Hz, explaining its high-speed performance. The robot dynamically adapts gaits during locomotion—using thunniform for fast traversal and anguilliform for obstacle negotiation—demonstrating environmental adaptability. This work advances understanding of aquatic multimodal locomotion.

Grasping and manipulating objects represents crucial functionalities for modern robotic grippers. Nonetheless, an enduring challenge persists in engineering a gripper capable of achieving adaptive, rapid, and stable grasping behavior simultaneously. Here, we proposed a bistable mechanism derived from compliant tensegrity structures that performs a rapid shape change within 200 ms, based on which a Trident robotic gripper is developed without the need for additional actuation sources. This universal and unactuated paradigm showcases robust grasping abilities with adaptability and rapidity analogous to natural flytrap leaves. The tunable bistable properties, achieved by varying geometrical parameters, endow the gripper with extensive design flexibility. The morphing configuration of the gripper retains residual energy after transitioning between stable states, ensuring stable grasping without requiring a continuous energy supply. The benefits of the gripper empower the creation of a robotic system capable of handling objects with diverse profiles across various fields and an unactuated mechanism proficient in gently grasping and swiftly moving insects.