Bioinspiration & Biomimetics最新文献

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 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 DRL 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.

Bird forelimbs exhibit complex flight kinematics, including wing morphing and flapping motions with angle asymmetry. However, data on angle-asymmetric flapping in birds are scarce, and well-established theories and methods remain limited. Motivated by this challenge, we present a biofeature reconstruction method of the Morphlight theory that integrates high-speed videography with millimeter resolution 3D scanning to better approximate these kinematic features. Frame-by-frame analysis ofAquila nipalensiswingbeat sequences quantified joint rotations with angle-asymmetric, after which a three-rod Tang model and corresponding flapping equation of the Morphlight theory were formulated to predict the rotational angles of the wing joints. The bird's wings were then scanned to obtain key aerofoil profiles, which were used to construct a bionic airfoil incorporating the secondary remiges. Guided by the measured kinematics, we designed the drive mechanism and implemented a sliding crank-rocker mechanism to realize angle-asymmetric motion during the upstroke and downstroke. The resulting morphing flight vehicleMorphSteppeachieves high biofidelity in both wing geometry and angle-asymmetric flapping kinematics. Both flapping tests without inflow and outdoor flapping experiments were conducted to evaluate the aerodynamic performance and controllability of the morphing flight vehicle. The proposed Morphlight theory inspired by raptor, provides a generalizable framework for high biofidelity design of bird morphing flight vehicle that couples biological morphology with angle-asymmetric flapping kinematics.

Biomimicry offers sustainable, efficient, and adaptable solutions inspired by natural systems. The skeleton of Euplectella aspergillum (EA) represents a highly optimized biological structure. It is composed of silica-based elements known as spicules, which interlock to form a lattice-like framework that provides strength and flexibility. In this study, the structural and functional properties of EA spicules were investigated. The macrostructure revealed a well-organized, multi-component framework consisting of a filter cap, spiral crest, skeletal wall, and anchor base-features that contribute to hydrodynamic efficiency and mechanical stability. The hierarchical architecture was characterized using scanning electron microscopy, atomic force microscopy (AFM), nanoindentation, thermogravimetric analysis, differential scanning calorimetry, and x-ray diffraction (XRD). At the microscale, spicules exhibited a laminated architecture of silica and organic layers, which redirect crack propagation and dissipate energy, enhancing fracture resistance. Nanoindentation and AFM revealed mechanical properties across the spicule cross-section, with an average hardness of 4.436 ± 0.202 GPa, reduced modulus of 39.596 ± 0.374 GPa, and stiffness of 21.200 ± 0.517µN nm^-1. Sink-in behavior indicated the elastic and brittle nature of both silica and organic regions. Localized pile-up near organic interfaces highlighted plastic deformation constraints due to mechanical heterogeneity. Thermal analysis identified approximately 9.83% organic content and confirmed high thermal stability of the silica matrix. A crystallization event occurring at approximately 1090 °C corresponded to the transformation of amorphous silica intoβ-cristobalite, as confirmed by XRD. These findings provide insights into the structural and mechanical properties of EA skeleton, supporting the design of high-performance ceramic materials with enhanced mechanical properties for bioengineering applications.

There is a growing interest in unmanned aerial vehicles (UAVs) being able to perch onto objects, which expands their scope of applications. Many perching strategies are inspired by natural organisms, including birds, insects, and helical morphologies such as tendrils and tails. Inspired by these helical structures, a bistable hybrid gripper is developed that enables a quadcopter to perch on branches and perform aerial grasping. The gripper integrates a bistable steel shell (BSS) as the stiff element, analogous to skeletal support, with a soft 3D-printed helical exoskeleton, analogous to muscular compliance, to achieve both structural strength and adaptability. This hybrid design not only enables conformal wrapping and high load capacity but also allows the UAV to grasp without continuous energy input due to its bistable mechanism. Static models are established to predict the pneumatic transition pressure between the two states, and the results are validated experimentally. Furthermore, the holding and grasping forces, along with robustness against tilt and rotation offsets, are systematically characterized, confirming adaptability to branches with varying diameters and orientations. Experimental demonstrations confirm that UAVs equipped with the gripper can reliably perch on tree branches and perform aerial grasping in realistic field environments.

Adaptive handling of thick or composition-changing fluids is difficult for conventional pumps. In animals, the intestine addresses this challenge by switching between segmental mixing and peristaltic transport according to the physical state of the contents. We translate this principle into a silicone soft pump composed of four pneumatic chambers, each driven by its own phase oscillator. Two tunable factors govern the collective behaviour: (i) the coupling strength, which attempts to maintain neighbouring oscillators in a travelling-wave relationship, and (ii) the local sensor feedback, which forces each oscillator to correct the deformation error of its own chamber. Numerical bifurcation analysis and time-domain simulations show that when the two strengths are balanced within an intermediate range, the controller first generates an antiphase pattern that homogenises a viscous mixture, and then spontaneously shifts to a quarter-cycle travelling wave that drives the now-fluid contents downstream. We built a physical prototype and experimentally confirmed autonomous mode switching between two glycerol-based fluids of contrasting viscosity. These results demonstrate that a minimal, bioinspired, distributed controller can endow soft devices with adaptive, multifunctional pumping capability, thereby opening new routes to food-processing, biomedical, and chemical-handling systems that operate under uncertain conditions.

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.

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 and finite element analysis to model and simulate the failure behaviour of nacre-like composites. Using the scalar degradation variable, 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 simulations of in-line fish pairs, we systematically varied median fin presence on leaders and followers to isolate neighbor-induced performance changes. 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 beyondS= 1.4 l. At higher Reynolds numbers, 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.

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.

Sample Exploring the ocean environment holds profound significance in areas such as resource exploration and ecological protection. Underwater robots struggle with extreme water pressure and often cause noise and damage to the underwater ecosystem, whilebio-inspired soft robots draw inspiration from aquatic creatures to address these challenges. These bio-inspired approaches enable robots to withstand high water pressure, minimize drag, operate with efficient manipulation and sensing systems, and interact with the environment in an eco-friendly manner. Consequently, bio-inspired soft robots have emerged as a promising field for ocean exploration. This paper reviews recent advancements in underwater bio-inspired soft robots, analyses their design considerations when facing different desired functions, bio-inspirations, ambient pressure, temperature, light, and biodiversity , and finally explores the progression from bio-inspired principles to practical applications in the field and suggests potential directions for developing the next generation of underwater soft robots.