Bio-inspired Design Research Articles

Bio-Inspired Secondary Levitation Structure Design for High-Temperature Superconducting Maglev Train

Bio-Inspired Secondary Levitation Structure Design for High-Temperature Superconducting Maglev Train

Design of a Bionic Spider Robot with a Two-Degrees-of-Freedom Leg Structure and Body Frame

Spiders have unique biological characteristics and excellent maneuverability, making them an ideal model for bionic robot design. However, traditional bionic spider robot designs usually have multiple degrees of freedom and confront many challenges. These challenges include complex control requirements, higher energy consumption, larger size and weight, higher risk of failure, and higher cost. This study proposes a leg design with two degrees of freedom to reduce its control and manufacturing costs. It can better control leg movement and improve leg force through a multi-link mechanism and a dual-motor system. In addition, the triangular gait and hexagonal body structure align the weight of the body with the support point, thereby enhancing stability. This study offers a comprehensive and organized approach to bio-inspired robot design, providing a valuable reference for future bionic robot development.

Advances in Spiky Antibacterial Materials: From Bioinspired Design to Application

Bacterial infections, particularly those caused by drug‐resistant bacteria, pose a significant threat to human life and health safety. Despite the preparation and application of numerous antibacterial and disinfection materials, addressing their low efficiency and the emergence of drug resistance remains an urgent concern. Inspired by natural spike antibacterial structures such as those found on cicada wings, extensive research has been conducted on biomimetic antibacterial materials with spiky structures. This review provides an overview of the natural spike antibacterial structure and mechanism, introduces surface coatings and micro/nanoparticle materials featuring spike structures inspired by nature, explores microneedle arrays based on spike antibacterial properties, and showcases applications of these innovative antibacterial materials. Finally, potential avenues for optimization and future development directions for antibacterial materials with spike structures are discussed.

Bio-inspired optimisation design strategy of graded hemp core for hybrid carbon/hemp sandwich laminates

Bio-inspired optimisation design strategy of graded hemp core for hybrid carbon/hemp sandwich laminates

One-shot manufacturable soft-robotic pump inspired by embryonic tubular heart.

Soft peristaltic pumps, which use soft ring actuators instead of mechanical pistons or rollers, offer advantages in transporting liquids with non-uniform solids, such as slurry, food, and sewage. Recent advances in 3D printing with flexible thermoplastic polyurethane (TPU) present the potential for single-step fabrication of these pumps, distinguished from handcrafted, multistep traditional silicone casting methods. However, because of the relatively high hardness of TPU, TPU-based soft peristaltic pumps contract insufficiently and thus cannot perform as well as silicone-based ones. Improving the performance is crucial for fully automated, one-step manufactured soft pumps to lead to industrial use. This study aims to enhance TPU-based soft pumps through bioinspired design. Specifically, it proposed a design inspired by embryonic tubular hearts, in contrast to previous studies that mimicked digestive tracts. The new design facilitated long-axis stretching of an elliptical lumen during non-concentric contractile motion, akin to embryonic tubular hearts. The design was optimized for ring actuators and pumps 3D-printed with shore hardness 85 A TPU filament. The ring actuator achieved over 99% lumen closure with the best designs. The soft pumps transported water at flow rates of up to 218 ml min-1and generated a maximum discharge pressure of 355 mm Hg, comparable to the performance of blood pumps used in continuous renal replacement therapy.

The Role of Bio-Inspired Soft Robotic Gloves in Stroke Rehabilitation: A Comprehensive Analytical Review

Stroke is a leading cause of long-term disability, with many survivors experiencing impaired motor function. Traditional rehabilitation methods often face limitations in achieving full functional recovery. In recent years, bio-inspired soft robotic gloves have emerged as a promising solution for enhancing stroke rehabilitation, mimicking the natural movement and adaptability of biological systems. This paper provides a comprehensive analytical review of bio-inspired soft robotic gloves designed for stroke rehabilitation, focusing on their development, fabrication methods and therapeutic applications. The primary objective of this review is to evaluate the role of bio-inspired designs in the creation of soft robotic gloves and assess their effectiveness in facilitating motor recovery post-stroke. A systematic analysis of existing literature is conducted, exploring various fabrication techniques, including soft material integration, actuators and sensors, as well as the application of these gloves in clinical and therapeutic settings. Findings from this review reveal that bio-inspired soft robotic gloves show significant potential in improving patient outcomes by enhancing finger and hand movement through assisted motor control. These devices offer advantages in terms of comfort, flexibility and adaptability, allowing for prolonged and intensive rehabilitation sessions. However, limitations remain, such as the high cost of fabrication, challenges in achieving precise motor control and the lack of large-scale clinical trials to validate long-term efficacy. The research has several implications: (1) Theoretical: advancing the understanding of bio-inspired design principles in soft robotics; (2) Methodological: highlighting fabrication techniques that enhance glove performance and user adaptability. This review offers original value by consolidating and analysing recent developments in bio-inspired soft robotic gloves, contributing to both the academic literature and practical applications in stroke rehabilitation. It emphasizes the necessity of future research to address current limitations, especially in optimizing performance and reducing production costs, while enhancing patient outcomes.

Novel Bio-inspired Design for the Carcass Layer of Flexible Risers with Increased Strength Under External Pressure

Novel Bio-inspired Design for the Carcass Layer of Flexible Risers with Increased Strength Under External Pressure

Eliminating Charge Transfer at Cathode-Electrolyte Interface for Ultrafast Kinetics in Na-Ion Batteries.

Sodium-ion batteries suffer from kinetic problems stemming from sluggish ion transport across the electrode-electrolyte interface, causing rapid energy decay during fast-charging or low-temperature operation. One exciting prospect to enhance kinetics is constructing neuron-like electrodes that emulate fast signal transmission in a nervous system. It has been considered that these bioinspired designs enhance electron/ion transport of the electrodes through carbon networks. However, whether they can avoid sluggish charge transfer at the electrode-electrolyte interface remains unknown. By connecting the openings of carbon nanotubes with the surface of carbon-coated Na3V2O2(PO4)2F cathode nanoparticles, here we use carbon nanotubes to trap Na+ ions released from the nanoparticles during charge. Therefore, Na+ movement is confined only inside the neuron-like cathode, eliminating ion transport between the electrolyte and cathode, which has been scarcely achieved in conventional batteries. As a result, a 14-fold reduction in interfacial charge transfer resistance is achieved when compared to unmodified cathodes, leading to superior fast-charging performance and excellent cyclability up to 200C, and surprisingly, reversible operation at low temperatures down to -60 °C without electrolyte modification, surpassing other Na3V2O2(PO4)2F-based batteries reported to date. As battery operation has relied on charge transfer at the electrode-electrolyte interface for over 200 years, our approach departs from this traditional ion transport paradigm, paving the way for building better batteries that work under harsh conditions.

Biomimetic design of elastomers with improved mechanical properties by integrating hydrogen bonds with covalent crosslinking bonds

It is an important issue for rubber to realize reinforcement and expand application gallery in material science and engineering. In the present work, we initiated a bioinspired design to introduce sacrificial hydrogen bonds by post-modifying sulfur crosslinked carboxyl nitrile rubber with pendent urazole through triazolinedione “click” chemistry. The post-modification of the crosslinked rubber can not only avoid adverse effect of the grafted urazoles on rubber vulcanization, but also enable to evaluate the effect of sacrificial hydrogen bonds on the rubber based on a consistent covalent network. Under external stress, the hydrogen bonds between the urazoles can function as sacrificial bonds that would rupture prior to covalent bonds, during which enormous energy is dissipated and meanwhile facilitates the rubber chain orientation. In light of the unique energy dissipating mechanism, the modulus, ultimate stress, and toughness of the hydrogen bonds and sulfur bonds dual-crosslinked rubber material are improved simultaneously without sacrificing the stretchability, and these properties can be easily manipulated by varying the grafting ratio of urazoles.

Biomimetic Multi-Interface Design of Raspberry-like Absorbent: Gd-doped FeNi3@Covalent Organic Framework Derivatives for Efficient Electromagnetic Attenuation.

Structural design and interface regulation are useful strategies for achieving strong electromagnetic wave absorption (EMWA) and broad effective absorption bandwidth (EAB). Herein, a monomer-mediated strategy is employed to control the growth of covalent organic framework (COF) wrapping flower-shaped Gd-doped FeNi3 (GFN), and a novel raspberry-like absorbent based on biomimetic design is fabricated by thermal catalysis. Further, a unique dielectric-magnetic synergistic system is constructed by utilizing the COF-derived nitrogen-doped porous carbon (NPC) as the shell and anisotropic GFN as the core. The electromagnetic parameters of the GFN@NPC composites can be tuned by adjusting the proportions of GFN and NPC. Off-axis electron holography results further clarify the interface polarization and microscale magnetic interactions affecting the EMW loss mechanism. As a result, the GFN@NPC samples exhibit broad EMWA performance. The EAB values of all GFN@NPC composites reach up to 6.0 GHz, with the GFN@NPC-2 sample showing a minimum reflection loss (RLmin) of -69.6 dB at 1.68 mm. In addition, GFN@NPC-2 achieves a maximum radar cross-section (RCS) reduction of 29.75 dB·m2. A multi-layer gradient structure is also constructed using metamaterial simulation to achieve an ultra-wide EAB of 12.24 GHz. Overall, this work provides a novel bio-inspired design strategy to develop high-performance EMWA materials.

Incorporating Single-Copper Sites and Host Defense Peptides into a Nanoreactor for Antibacterial Therapy by Bioinspired Design

A sustainable solution to the dramatic spread of antibiotic resistance threatening public health security is the development of antibiotic-free antimicrobial substances. Inspired by natural host defense mechanisms involving amino-terminal copper−nickel binding motif (ATCUN) antimicrobial peptides (AMPs), we have designed and prepared an artificial complex (Cu@G-AMPs) incorporating single-atom Cu catalysts for antibacterial therapy. The substrate of the complex, formed from guanine doped with abundant heteroatoms, anchored single Cu atoms with a coordination number of 2 and an average bond length of 1.91Å. Interestingly, Cu@G-AMPs, exhibiting Fenton-like catalytic activity, caused the inactivation of methicillin-resistant Staphylococcus aureus (MRSA) by generating and delivering reactive oxygen species (ROS) cargo. Mechanistically, the intrinsic stress response system of MRSA underwent an irreversible collapse when Cu@G-AMPs initiated its offensive program associated with non-specific targets. Furthermore, Cu@G-AMPs, which inherited the immunomodulatory properties of AMPs, sequentially carried out the functions of pulling edge closure, stabilizing granulation tissue, promoting collagen fiber proliferation, alleviating inflammation, and promoting neovascularization in wound areas infected by MRSA. Our results show that Cu@G-AMPs will provide a new perspective on untangling the complex regulatory networks that resistant bacteria have cultivated to deactivate commercial antibiotics.

Sawtooth-shaped microsaws for enhanced transdermal drug delivery: Improved drug loading and piercing efficiency

This study presents a novel approach to transdermal drug delivery with the introduction of sawtooth-shaped MicroSaws (MSs), a bioinspired microneedle design that significantly enhances drug loading and piercing efficiency. Unlike traditional microneedles (MNs), MSs, with dimensions of 0.2 mm width, 0.4 mm length, and 0.65 mm height, are engineered using epoxy acrylate (EA) via digital light processing (DLP) 3D printing and coated with polyethylene glycol diacrylate (PEGDA) to ensure biocompatibility. Experimental results demonstrate that MSs outperform conventional MNs in both mechanical piercing tests and drug release studies, showcasing a 30 % increase in drug loading capacity and a 25 % improvement in pierceability. The unique sawtooth design not only facilitates deeper penetration but also creates microchannels that enhance drug diffusion across the stratum corneum. This innovation in microneedle technology holds significant promise for improving patient compliance and therapeutic outcomes in transdermal drug delivery systems.

A Spring Model for Pullout Behavior of Curved, Flexible Structures Embedded in Soil

ABSTRACTThe shape and flexibility of embedded structures, such as tree roots, piles, and anchors, have important impacts on the pullout behavior. However, the rate and manner of mobilization of soil resistances along such structures has not been rigorously explored across a wide range of shapes and structural properties. A spring model for computing compatible displacements of the structure and soil for curved, flexible structures is defined, validated against commonly used methods for computing pile pullout behavior, and then parametrically explored to demonstrate how resistances are mobilized along the length of such structures. The present model allows description of combined axial and transverse loading of these nonlinear structures. The simulation results for the case of normally consolidated clay show that the curvature of a structure causes the distribution of bearing resistance to extend further along the structure than for linear cases. The requirement of equilibrium of the structure produces a coupling between the mobilized bearing and tensile resistance in terms of rate of development and magnitude. Thus, the choices of structure shape impact the magnitude and distribution of mobilized resistance of embedded flexible structures. Implications for anchorage of tree root structures and principles of bioinspired design of anchorage systems are discussed.

A Biodegradable, Porous Flier Inspired by a Parachute-Like Tragopogon Fruit for Environmental Preservation.

New devices inspired by flying seeds, or more technically by fruits with dispersal units, could have a significant impact for environmental monitoring and aerial seeding. Among the various types of dispersal units (e.g., winged, gliding), parachuted or plumed units offer the lowest vertical descent speed (i.e., 0.3-0.7 ms-1), making them an appealing solution for wind-driven distribution over large areas. Here, a biodegradable and porous parachute flier based on cellulose acetate, inspired by a Tragopogon pratensis fruit is presented. A micrometric-thick pappus is 3D printed and integrated with a porous colorimetric indicator or a porous beak, with micrometric pores, fabricated through injection molding and leaching techniques. Thanks to the bioinspired design and the lightweight porous structure, the artificial Tragopogon mimics the aerodynamics and descent speed of the natural species. Its feasibility is demonstrated in aerial seeding by integrating the beak with a mustard seed (as a model), and in environmental monitoring by coupling it with colorimetric indicators for rain pH and nitrate levels in soils. The proposed flier represents a significant advancement as it is the first parachute-like biodegradable solution, seamlessly integrated into natural ecosystems, thus contributing to moving a step forward in artificial solutions with zero impact.

90-degree peeling of elastic thin films from elastic soft substrates: Theoretical solutions and experimental verification

Peeling of thin films has been widely used in adhesion measurement, film transfer and bio-inspired design. Most previous studies focused on the peeling of thin films from rigid substrates, but soft substrates are common in practical applications. Herein, we propose a two-dimensional model based on the bilinear cohesive law to characterize the 90-degree peeling of elastic thin films from elastic soft substrates, and obtain theoretical solutions expressed in terms of the Chebyshev series. The theoretical solutions match well with the finite element method results, including the load-displacement curves and the bulging deformation of soft substrates. We find that with decreasing substrate modulus, the maximum peeling force (Pmax) decreases but the steady-state peeling force remains unchanged. With the present solutions, the interfacial strength and fracture energy can be extracted simultaneously from the 90-degree peeling experiments of thin film/soft substrate systems, and then the experimentally measured Pmax for different film thicknesses can be well predicted. Furthermore, we obtain a new power scaling law of Pmax, where the scaling exponent depends on substrate elasticity. These results can help us measure the interfacial properties of thin film/soft substrate systems via peel tests, and regulate their peeling behaviors by interface design.

Natural Selection on Hydroxyapatite Fiber Orientations for Resisting Damage of Enamel

Teeth have excellent mechanical properties, with high wear resistance and excellent fracture resistance. This is due to their well-organized multilevel hierarchical structure. While a number of studies in the last decades have revealed the relationship between tooth structure and mechanical properties, there is still no general agreement on how different orientations of hydroxyapatite (HAp) fibers affect the mechanical properties of enamel. With a scanning electron microscope and nanoindenter, the orientations of HAp fibers and their properties were investigated. HAp fibers have two different orientations: parallel and perpendicular to the surface. Fibers oriented parallel to the surface exhibited higher hardness, elastic modulus and wear resistance. Under applied force, fibers oriented perpendicular to the surface suffered deeper shearing in the protein along the long axis, resulting in lower mechanical properties. Teeth resist damaging fractures by combining hard and soft structures. This study may lead to new insights into how nature selects for tooth structure and provide a theoretical basis for the bioinspired design.

A rapid-response soft end effector inspired by the hummingbird beak.

Biology is a wellspring of inspiration in engineering design. This paper delves into the application of elastic instabilities-commonly used in biological systems to facilitate swift movement-as a power-amplification mechanism for soft robots. Specifically, inspired by the nonlinear mechanics of the hummingbird beak-and shedding further light on it-we design, build and test a novel, rapid-response, soft end effector. The hummingbird beak embodies the capacity for swift movement, achieving closure in less than [Formula: see text]. Previous work demonstrated that rapid movement is achieved through snap-through deformations, induced by muscular actuation of the beak's root. Using nonlinear finite element simulations coupled with continuation algorithms, we unveil a representative portion of the equilibrium manifold of the beak-inspired structure. The exploration involves the application of a sequence of rotations as exerted by the hummingbird muscles. Specific emphasis is placed on pinpointing and tailoring the position along the manifold of the saddle-node bifurcation at which the onset of elastic instability triggers dynamic snap-through. We show the critical importance of the intermediate rotation input in the sequence, as it results in the accumulation of elastic energy that is then explosively released as kinetic energy upon snap-through. Informed by our numerical studies, we conduct experimental testing on a prototype end effector fabricated using a compliant material (thermoplastic polyurethane). The experimental results support the trends observed in the numerical simulations and demonstrate the effectiveness of the bio-inspired design. Specifically, we measure the energy transferred by the soft end effector to a pendulum, varying the input levels in the sequence of prescribed rotations. Additionally, we demonstrate a potential robotic application in scenarios demanding explosive action. From a mechanics perspective, our work sheds light on how pre-stress fields can enable swift movement in soft robotic systems with the potential to facilitate high input-to-output energy efficiency.

Experimental investigation on aerodynamic noise and flow structures of a vibrissa-shaped cylinder

The noise mitigation effect of bio-inspired geometries has attracted growing attention from both research and industry, such as the vibrissa-shaped cylinder derived from the harbor seal. Experiments were conducted to investigate the far-field noise and the near-field wake of the flow past a vibrissa cylinder, a circular cylinder, and an elliptical cylinder at Re=3.6×104, in the subcritical flow regime. The frequency characteristic of the far-field acoustic pressure and the near-field velocities are analyzed. The mean and fluctuating velocities, dominant flow modes from proper orthogonal decomposition in both vertical and horizontal planes as well as the time-frequency behavior of the dominant flow structures from wavelet transform are also presented to better understand the wake dynamics and the direct relation of these flow structures with the far-field noise. The vibrissa cylinder reduces the overall sound pressure level by 13.2 dB and 8.3 dB compared with the circular and the elliptical cylinders, respectively, with a remarkable attenuation of the tonal peak associated with vortex shedding. From the detailed velocity measurements in multiple wake planes, it is clearly observed that vortex shedding of the vibrissa cylinder is weaker in strength and significantly less coherent in the spanwise direction than the other two cylinder cases, accompanied by more transient changes. The results also reveal the distinct flow behaviors behind the nodal and saddle planes of the vibrissa cylinder, further contributing to this three-dimensional vortex shedding. Consequently, the power spectral density of the tonal peaks associated with the vortex shedding in both near-field velocities and far-field acoustic pressure are attenuated, leading to a lower noise level. Understanding the detailed flow dynamics of the vibrissa cylinder will provide useful insights into more efficient bio-inspired cylinder designs in noise mitigation and wake control.

A bioinspired hierarchical gradient structure to maximize resilience and enhanced cooling performance in polymeric radiative cooling coatings

Despite the extensive advancements in recent years, polymeric daytime radiative cooling (PDRC) coatings face certain challenges, encompassing restricted spectral performance, susceptibility to aging, poor mechanical strength, and so forth. Herein, we proposed a facile biomimetic 500 μm thick PDRC coating, featuring a gradient distribution of pore sizes throughout the cross-section. The proposed functional structure demonstrates spectral characteristics of a near-ideal broadband emitter by attaining over 0.95 emissivity in the main atmospheric window and 0.99 reflectance in the visible spectrum. During the outdoor experiment, it achieved an 8.5 °C subambient temperature drop along with a cooling power of ∼106 W/m2 at the solar irradiance of ∼800 W/m2 and ∼650 W/m2, respectively. Experimental findings highlight that the bioinspired design results in a tensile strength of ∼9 MPa along with a tensile strain of over 200%, which is more than twice that of non-gradient porous PDRC coatings. In addition, it offers tunable surface contact angle and manifests its resilience in anti-ultraviolet and water resistance tests. Furthermore, a building energy model reveals a decrease in cooling load of between 34 and 119 kWh/(m2.year), establishing its real-world application under broader climatic regions.

Bioinspired microstructure design simultaneously enhances strain-rate stiffening and toughening of composites

Keratinous biological materials, such as baleen, pangolin scales, and human hair, have similar constituent materials. However, their strain-rate dependent mechanical properties vary due to differences in their microstructures. Inspired by the microstructures observed in baleen, here we present novel microstructural designs of three types of lamellar-tubular fibers, namely the lamellar-tubular fiber (LTF), mineralized lamellar-tubular fiber (MLTF) and hollow mineralized-lamellar-tubular fiber (HMLTF). We systematically investigated their strain-rate dependent mechanical behaviors with comparison to the conventional cylinder-fiber (CF) reinforced composites. Through the finite element analysis (FEA), we found that the baleen-inspired composites have superior strain-rate stiffening and toughening effects than the conventional fiber reinforced composite. Rate-dependent constitutive models decoupling elastic and inelastic regimes were constructed for these bioinspired composites. Based on the FEA results, three constitutive parameters were obtained to quantitatively characterize the rate-dependent mechanical behaviors of these composites, especially the microstructure-induced difference. Furthermore, our study found that the baleen-inspired tubular microstructure improves stiffness and strain-rate stiffening through raising the stress levels of all phases and improves toughness and strain-rate toughening through enlarging the deformation in the inelastic region. This novel bioinspired design is hopeful to pave ways for the development of advanced composites with simultaneously enhanced strain-rate stiffening and toughening.