Bioinspiration & Biomimetics最新文献

Achieving large initial coil pitches and contractile strokes in twisted and coiled polymer artificial muscles often requires complex and multi-step fabrication processes. We present a Self-induced Large-pitch (SLiP) method for producing polymer muscles with large and stable initial coil pitches through a single-step annealing process, which can be tuned by only adjusting the annealing temperature and duration. The resulting muscles demonstrate contractile and tensile strains of 95.1% and 560%, respectively, under different chiral configurations, as well as a maximum specific power of 3.5 kW/kg and a contractile stroke rate of 40%/s. SLiP muscles are used in various biomimetic and soft robotic prototypes, including a biomimetic arm, large-deformation tentacles, a crawling robot, and a biomimetic hand. This method offers a practical route for realizing polymer muscles with giant stroke and preload-free actuation in soft robotics.

Bionic serrated blades with three configurations for a voluteless centrifugal fan are proposed to improve the aerodynamic performance and suppress the noise, including triangular serrated blade (T-BLE), square serrated blade (S-BLE) and semi-circular serrated blade (C-BLE). The improved delayed detached eddy turbulence model and Ffowcs Williams-Hawkings acoustic model are employed to deal with the flow fields and acoustic characteristics. The models are first validated by comparing the experimental results and simulation data in terms of the aerodynamic and noise tests. Then, a comprehensive analysis of flow field characteristics and acoustic performance of a voluteless fan is conducted. Results indicate that the aerodynamic performance of serrated blades decreases due to the reduced air-exhaust area, with the T-BLE showing a 1.6% reduction. The improvement in wake flow pattern, vortex formation and separation for triangular serrations is pronounced. The serration designs significantly suppress primary tonal noise at the 13th blade passing frequency and other broadband noise. The total sound pressure levels of the T-BLE, S-BLE and C-BLE decrease by 6.27 dB, 4.06 dB and 5.14 dB, respectively. The serration structures inhibit noise generation and propagation by weakening periodic unsteady interactions between wake vortices and stationary flow. In general, the T-BLE achieves better noise reduction while maintaining the same aerodynamic performance.

With the growing demand for underground resources, traditional drilling equipment faces significant limitations in soil environments. In recent years, bionic burrowing robots have attracted increasing research attention for their potential advantages in miniaturization, adaptability, and low energy consumption, although their development is still in the early exploratory stage. This study presents a mole-inspired robot designed based on the remarkable burrowing capability of the naked mole-rat (Heterocephalus glaber), which uses its incisors to break soil and limbs to propel itself forward. The incisor mechanism of the robot achieves a single-degree-of-freedom (DOF) occlusion via a gear drive and linkage transmission system. To analyze the relationship between the incisor tip force and the servo output torque, a mechanical model based on the principle of virtual work and virtual displacement is established, and its accuracy is validated through physical experiments. The leg mechanism employs a Chebyshev-parallelogram composite linkage configuration to achieve single-DOF forward-backward leg motion. To ensure optimal kinematic performance, the leg kinematics are analyzed, and the leg link lengths are optimized through foot-end trajectory planning. Finally, a prototype was developed and tested in soils with varying moisture contents. The experimental results verify the proposed design methodology and mechanical model, confirming the feasibility and effectiveness of the mole-inspired incisor-limb coordination strategy for autonomous burrowing.

Lightweight structures require materials with superior mechanical properties, prompting engineers to investigate composite materials. Inspired by nature's ingenuity, especially the nacre found in seashells, and the hierarchical structures observed in bone and teeth, which exhibit remarkable strength, stiffness, and toughness, this study investigates the role of inelasticity on the mechanical properties of bioinspired composite materials. In contrast to purely elastic materials, which exhibit reversible stress-strain behaviour and fail suddenly upon reaching their yield point, our study integrates plasticity and damage models to allow for a more progressive and controlled failure process. In nacre-like composites, where non-uniform stress distributions are widespread, plasticity is an important mechanism for reducing stress concentrations and avoiding catastrophic failure. This approach produces a more gradual and predictable failure mode. Here, a controlled degradation of interfaces distributes the applied stress more uniformly across the composite, increasing its overall strength and toughness. Our study utilizes representative volume element (RVE) and finite element analysis to model and simulate the failure behaviour of nacre-like composites. Using the scalar degradation variable (SDEG), we note that damage initiates at the interfaces perpendicular to the loading direction, followed by increased stress and eventual failure along the interfaces parallel to the loading direction. We quantify the major contribution of inelasticity in interfaces towards strength and toughness. Additionally, we highlight the previously unexplored contribution of vertical interfaces to toughness by considering influential parameters such as cohesive fracture energy (Gc). The findings of this study provide valuable insights for predicting the strength and toughness of bio-inspired composites when the matrix exhibits inelastic deformation. This work offers valuable results which could greatly help in the design and development of advanced lightweight composite materials for structural applications.

Median fins, including the dorsal and anal fins, influence fish propulsion by lowering body drag and increasing caudal fin thrust through active movement. While their role in solitary swimming is established, their impact on hydrodynamics within schooling environments remains unclear. Using high-fidelity computational fluid dynamics (CFD) simulations of in-line fish pairs, we systematically varied median fin presence on leaders and followers to isolate neighbor-induced performance changes from the total drag reduction. When comparing the full-finned configuration to the finless configuration at a leader-follower streamwise spacing (S) of 1.1 body lengths (l), the follower's drag was reduced by 9.5%. A significant contribution of the total drag reduction, about 70%, was neighbor-induced, arising from wake-body interactions with the wake of a leader that had median fins, while the rest was attributed to adding the follower's own median fins. This neighbor-induced benefit arises from stronger leader-generated vortex structures that interact with the follower's body, lowering both shear and pressure drag. The neighbor-induced benefits persist across a range of spacings, diminishing only beyond S = 1.4 l where self-induced benefits become more dominant. At higher Reynolds numbers (Re), the neighbor-induced drag reduction also dominates the total drag reduction of the follower. These findings reveal that median fins can serve as hydrodynamic tools for enhancing group swimming performance through neighbor-induced effects, extending their recognized functional role beyond self-induced improvements in solitary swimming.

In biomimetic underwater systems, high-efficiency and low-power propulsion remains a core challenge. Mimicking the characteristics of fish caudal fins and exploring highly biomimetic muscle-driven approaches is regarded as one of the key strategies to address this issue.This study combines the immersed boundary-lattice Boltzmann (IB-LB) method with deep reinforcement learning (DRL) to investigate the interactive effects of caudal fin structural stiffness and active muscle control on propulsive performance and energy consumption.By constructing a virtual fish model with a closed-loop ``perception--decision--action'' feature, the agent can autonomously learn to output tail torque based on environmental feedback, thereby regulating the deflection behavior of the caudal fin. The research evaluates the differences in dynamic responses between rigid and flexible caudal fin configurations under both passive states and active control intervention. The results indicate that rigid caudal fins exhibit significant phase lag and increased energy consumption without control; however, driven by DRL strategies, they can achieve phase compensation and a substantial improvement in propulsive performance. In contrast, flexible caudal fins, relying on stronger passive adaptability, can achieve superior propulsive efficiency in the uncontrolled state, while their speed and energy consumption can be further optimized with the introduction of active regulation.To realize dynamic trade-offs between speed and energy consumption, this study develops a task-sensitive multi-objective dynamic reward function, enabling the agent to switch between ``high-speed propulsion'' and ``high-efficiency energy-saving'' strategies according to requirements. This research not only reveals the synergistic relationship between structural compliance and active control but also demonstrates the potential of deep reinforcement learning in exploring optimal control strategies without prior knowledge. It provides a new research path and theoretical support for the intelligent regulation of bionic fish caudal fins and the design of flexible underwater robots.

Birds utilize feathered wings where individual feathers serve as distinct control surfaces that deform locally under the effect of aerodynamic forces and introduce complex interaction effects. The role of these effects in improving lift generation remains unclear. To investigate this, we analyze a feather-inspired control surface of a flapping foil, composed of three pitching and heaving rigid membranes (referred to as feathers) designed to enhance lift in flapping flight. Two-dimensional numerical simulations are conducted at a Reynolds number of 5000, evaluating the performance of the proposed control surface at three Strouhal numbers (St=0.08,0.12, and 0.2), representative of small bird flight conditions. Our results show that specific combinations of feather lengths maximize the lift-to-power ratio for each Strouhal number. The best-performing cases generate up to twice the mean lift force of a single feather for the same power expenditure. AtSt = 0.12, varying the heave amplitude has minor effects on the peak feather performance. While the upstroke (downstroke) generally produces negative (positive) lift, performance gains are primarily driven by minimizing negative lift during the upstroke. We also quantify the inter-feather interaction effects, which are more pronounced at higher Strouhal numbers. The proposed control surface may be useful in developing efficient micro- and unmanned aerial vehicles.

Environmental perception is a crucial foundation for enhancing the application potential of biomimetic robots. Motivated by the complementary roles of visual and tactile sensing observed in rats, this work proposes a visual-tactile perception for a small-scale bio-inspired robotic rat. The method leverages binocular vision to estimate depth images through an attention-based network and improve perception and localization accuracy by 14.22% based on a dynamic objects removal module. Besides, the whisker sensor is applied to enhance the robot's ability to identify object contours and environmental boundaries in narrow spaces, with obstacle contour and environment boundary reconstruction goodness of fit exceeding 97.00% and 93.87%, respectively. In addition, by integrating the above individual perception methods, we achieve the fusion of vision and tactile sensing for complex environment perception. To the best of our knowledge, this is the first study to implement vision-tactile fusion perception on a miniature biomimetic robot through physical experiments. The experiments demonstrate that our method exhibits promising results on the robotic rat, reducing localization errors in narrow and dim scenes by an average of 29.14% compared to existing state-of-the-art methods.

Generating robust and adaptable legged locomotion with minimal control architecture remains an open challenge in bio-inspired robotics. Existing central pattern generator (CPG) approaches often rely on multi-neuron oscillators, asymmetrical network structures, abstract phase oscillators, or task-specific tuning to produce stable gaits. Here, we address this problem by introducing a minimal sensorimotor control framework based on single-neuron CPGs with proprioceptive feedback. Through stability analysis and physical experiments, we show that fully symmetric coupling between single-neuron units is sufficient to generate self-organized tripod-type gaits, enable reliable gait switching via single-pulse kick control, and sustain locomotion even under leg failure. In the strong-attractoring limit, coordinated locomotion emerges without intrinsic neural oscillations, driven solely by sensory feedback. The same framework, without parameter changes, also produces coordinated quadruped locomotion, illustrating its generality. This demonstrates that complex and robust locomotor patterns can arise from extremely simple decentralized mechanisms. Our results contribute to the search for generative principles underlying locomotion and provide a lightweight, extensible basis for bio-inspired control across diverse robotic platforms.

Soft-body grippers are highly pliable due to the use of flexible materials, which enable safe grasping of objects, but their load-bearing capacity is limited by the mechanical properties of the materials themselves. To address the problem of insufficient stiffness of traditional soft-body grippers, this paper proposes a reconfigurable exoskeleton bionic stiff-flexible gripper inspired by the hydraulic legs of spiders. The gripper is designed with three switchable working modes, and the quick-connect removal mechanism works in concert with the lower fixed jaws to adapt to the grasping needs of objects of different sizes and masses. The joints adopt balloon actuators that mimic the hydraulic leg mechanism of a spider, which can realize adaptive adjustment of the center position and drive the exoskeleton structure to complete the deformation action. Based on the contact-induced extrusion interaction between the balloon and the exoskeleton, a theoretical model of nonlinear actuation is developed. The balloon is simulated using finite element analysis to determine its effective operating range. Furthermore, a rectangular silicone membrane is designed to envelop the exoskeleton surface, enhancing the system's flexibility and ensuring consistent structural support. The experimental evaluation of the comprehensive grasping performance of the gripper shows that the reconfigurable exoskeleton gripper can effectively grasp objects in the size range of 3-230 mm with a maximum weight of 1 kg, which significantly extends the application range and load-bearing capacity of the traditional soft gripper.