Functional morphology and structural characteristics of wings of the ladybird beetle,Coccinella septempunctata(L.)

Study on the factors affecting the mechanical properties of antler under quasi-static compression

In the natural environment, antlers have a significant mechanical structure that protects the deer head from injury. In this paper, the mechanical properties of antlers were evaluated through quasi-static compression tests and microstructural observation of samples from antlers, and the relationship between the sampling position, load direction, and microstructure and their mechanical properties were investigated. Compression experiments confirmed that the tines had the strongest mechanical properties, followed by the main beams and finally the brow tines. The mechanical properties of the test specimens subjected to axial compression were higher than those of lateral compression. The axial load test of the longitudinal sample of the tine of the antler has the best mechanical properties. Its specific energy absorption is 51.33 J/g, the peak crushing force is 1.26 kN, and the mean crushing force is 1.47 kN. There are many tubular structures in the transverse sections of antlers, and the distribution of fibers in the vertical direction is laminar with alternating rows forming a helical structure. Tubular structures were found to be prevalent in some of the better biomechanical structures by comparison. Numerical modeling simulations to describe the effect of tubular structures on the mechanical properties of antlers. The simulation results show that the increase in the size of the tubular structure improves its energy absorption within the variation of a 20% increase in the size of the long and short axis. These findings provide a theoretical and experimental basis for the design of energy-absorbing structures. RESEARCH HIGHLIGHTS: In this paper, transverse and longitudinal samples were taken from the main beam, tine, and brow tine of antlers, and axial and lateral compression were carried out, respectively. In this paper, quasi-static compression experiments were carried out on antler samples to study the effects of sampling position, loading direction, and microstructure on antler mechanical properties. By means of microstructure observation and numerical modeling, it is determined that the size of the antler Havel tube has an effect on its mechanical properties.

Microscopic vibrational circular dichroism on the forewings of a European hornet: heterogenous sequences of protein domains with different secondary structures

We developed a microscopic scanning for vibrational circular dichroism (VCD) spectroscopy in which a quantum cascade laser is equipped with a highly focused infrared light source to attain a spatial resolution of 100 μm. This system was applied to the forewing of a European hornet to reveal how the protein domains are organised. Two-dimensional patterns were obtained from the VCD signals with steps of 100 μm. We scanned the 1500-1740 cm-1 wavenumber range, which covers amide I and II absorptions. Zone sequenced α-helical and β-sheet domains within an area of 200 μm2 in membranes close to where two veins cross. The sign of the VCD signal at 1650 cm-1 changed from positive to negative when probed along the zone axis, intermediated by the absence of VCD activity. The significance of this zone is discussed from the viewpoint of the mechanical properties required for flying motion. These features are unattainable using conventional FTIR (Fourier transform infrared) or FT-VCD methods with a spatial resolution of ∼10 mm2.

Investigating the Mechanical Performance of Bionic Wings Based on the Flapping Kinematics of Beetle Hindwings

The beetle, of the order Coleoptera, possesses outstanding flight capabilities. After completing flight, they can fold their hindwings under the elytra and swiftly unfold them again when they take off. This sophisticated hindwing structure is a result of biological evolution, showcasing the strong environmental adaptability of this species. The beetle's hindwings can provide biomimetic inspiration for the design of flapping-wing micro air vehicles (FWMAVs). In this study, the Asian ladybird (Harmonia axyridis Pallas) was chosen as the bionic research object. Various kinematic parameters of its flapping flight were analyzed, including the flight characteristics of the hindwings, wing tip motion trajectories, and aerodynamic characteristics. Based on these results, a flapping kinematic model of the Asian ladybird was established. Then, three bionic deployable wing models were designed and their structural mechanical properties were analyzed. The results show that the structure of wing vein bars determined the mechanical properties of the bionic wing. This study can provide a theoretical basis and technical reference for further bionic wing design.

Structure and mechanical properties of ladybird elytra as biological sandwich panels

The armour of the ladybird, elytra, protect the body from injury and are well-adapted to flight. However, experimental methods to decipher their mechanical performances had been challenging due to the small size, making it unclear how the elytra balance mass and strength. Here, we provide insights to the relationship between the microstructure and multifunctional properties of the elytra by means of structural characterization, mechanical analysis and finite element simulations. Micromorphology analysis on the elytron revealed the thickness ratio of the upper lamination, middle layer and lower lamination is approximately 51:139:7. The upper lamination had multiple cross fibre layers and the thickness of each fibre layer is not the same. In addition, the tensile strength, elastic modulus, fracture strain, bending stiffness and hardness of elytra were obtained through in-situ tensile and nanoindentation-bending under the influence of multiple loading conditions, which also serve as references for finite element models. The finite element model revealed that structural factors such as thickness of each layer, angle of fibre layer and trabeculae are key to affecting the mechanical properties, but the effect is different. When the thickness of upper, middle and lower layers is the same, the tensile strength provided by unit mass of the model is 52.78% lower than that provided by elytra. These findings broaden the relationship between the structural and mechanical properties of the ladybird elytra, and are expected to inspire the development of sandwich structures in biomedical engineering.

The forewing of a black cicada Cryptotympana atrata (Hemiptera, Homoptera: Cicadidae): Microscopic structures and mechanical properties

Insects in nature flap their wings to generate lift force and driving torque to adjust their attitude and control stability. An insect wing is a biomaterial composed of flexible membranes and tough veins. In this paper, we study the microscopic structures and mechanical properties of the forewing of the black cicada, Cryptotympana atrata. The thickness of the wing membranes and the diameter of veins varied from the wing root to the tip. The thickness of the wing membranes ranged from 6.0 to 29.9 μm, and the diameter of the wing veins decreased in a gradient from the wing root to the tip, demonstrating that the forewing of the black cicada is a nonuniform biomaterial. The elastic modulus of the membrane near the wing root ranged from 4.45 to 5.03 GPa, which is comparable to that of some industrial membranes. The microstructure of the wing vein exhibited a hollow tubular structure with flocculent structure inside. The "fresh" sample stored more water than the "dry" sample, resulting in a significant difference in the elastic modulus between the fresh and dried veins. The different membrane thicknesses and elastic moduli of the wing veins near the root and tip resulted in varied degrees of deformation on both sides of the flexion line of the forewing during twisting. The measurements of the forewing of the cicada may serve as a guide for selecting airfoil materials for the bionic flapping-wing aircraft and promote the design and manufacture of more durable bionic wings in the future.

A review: Learning from the flight of beetles

Some Coleoptera (popularly referred to as beetles) can fly at a low Reynolds number with their deployable hind wings, which directly enables a low body weight-a good bioinspiration strategy for miniaturization of micro-air vehicles (MAVs). The hind wing is a significant part of the body and has a folding/unfolding mechanism whose unique function benefits from different structures and materials. This review summarizes the actions, factors, and mechanisms of beetle flight and bioinspired MAVs with deployable wings. The elytron controlled by muscles is the protected part for the folded hind wing and influences flight performance. The resilin, the storage material for elasticity, is located in the folding parts. The hind wings' folding/unfolding mechanism and flight performance can be influenced by vein structures of hollow, solid and wrinkled veins, the hemolymph that flows in hollow veins and its hydraulic mechanism, and various mechanical properties of veins. The action of beetle flight includes flapping flight, hovering, gliding, and landing. The hind wing is passively deformed through force and hemolymph, and the attack angle of the hind wing and the nanomechanics of the veins, muscles and mass body determine the flight performance. Based these factors, bioinspired MAVs with a new deployable wing structure and new materials will be designed to be much more effective and miniaturized. The new fuels and energy supply are significant aspects of MAVs.

A matter of size? Material, structural and mechanical strategies for size adaptation in the elytra of Cetoniinae beetles

Nature's masterfully synthesized biological materials take on greater relevance when viewed through the perspective of evolutionary abundance. The fact that beetles (order Coleoptera) account for a quarter of all extant lifeforms on Earth, makes them prime exponents of evolutionary success. In fact, their forewings are acknowledged as key traits to their radiative-adaptive success, which makes the beetle elytra a model structure for next-generation bioinspired synthetic materials. In this work, the multiscale morphological and mechanical characteristics of a variety of beetle species from the Cetoniinae subfamily are investigated with the aim of unraveling the underlying principles behind Nature's adaptation of the elytral bauplan to differences in body weight spanning three orders of magnitude. Commensurate with the integral implications of size variation in organisms, a combined material, morphological, and mechanical characterization framework, across spatial scales, was pursued. The investigation revealed the simultaneous presence of size-invariant strategies (chemical compositions, layered-fibrous architectures, graded motifs) as well as size-dependent features (scaling of elytral layers and characteristic dimensions of building blocks), synergistically combined to achieve similar levels of biomechanical functionality (stiffness, energy absorption, strength, deformation and toughening mechanisms) in response to developmental and selection constraints. The integral approach here presented seeks to shed light on Nature's solution to the problem of size variation, which underpins the diversity of beetles and the living world.

Three-dimensional wing structure attenuates aerodynamic efficiency in flapping fly wings

The aerial performance of flying insects ultimately depends on how flapping wings interact with the surrounding air. It has previously been suggested that the wing's three-dimensional camber and corrugation help to stiffen the wing against aerodynamic and inertial loading during flapping motion. Their contribution to aerodynamic force production, however, is under debate. Here, we investigated the potential benefit of three-dimensional wing shape in three different-sized species of flies using models of micro-computed tomography-scanned natural wings and models in which we removed either the wing's camber, corrugation, or both properties. Forces and aerodynamic power requirements during root flapping were derived from three-dimensional computational fluid dynamics modelling. Our data show that three-dimensional camber has no benefit for lift production and attenuates Rankine-Froude flight efficiency by up to approximately 12% compared to a flat wing. Moreover, we did not find evidence for lift-enhancing trapped vortices in corrugation valleys at Reynolds numbers between 137 and 1623. We found, however, that in all tested insect species, aerodynamic pressure distribution during flapping is closely aligned to the wing's venation pattern. Altogether, our study strongly supports the assumption that the wing's three-dimensional structure provides mechanical support against external forces rather than improving lift or saving energetic costs associated with active wing flapping.

Bio-inspired broadband absorbers induced by copper nanostructures on natural leaves

In this work, two copper-based biometamaterials were engineered using leaves of water cabbage (Pistia stratiotes) and purple bauhinia (Phanera purpurea) as templates. The copper sputtering was implemented to produce a thin copper film on the surface of leaves. The scanning electron microscopy (SEM) images exhibited the root hair-like nanostructure of water cabbage leaf and single comb-like nanostructure of purple bauhinia leaf. In spite of copper coating, the leaf surfaces of water cabbage and purple bauhinia were black and exhibited excellent light absorption at visible and near infrarrred wavelengths. It was estimated that these two types of leaves could absorb roughly 90% of light. Finite-difference time-domain (FDTD) calculations predicted the low reflectance stemming from the leaf nanostructures and copper coating layer. Because of the low cost of copper as a coating metal and simple procedure, this can be a promising method for quick fabrication of a thin copper film on the leaf nanostructure for application in blackbody or as the light absorbers.

Investigation on Microstructure of Beetle Elytra and Energy Absorption Properties of Bio-Inspired Honeycomb Thin-Walled Structure under Axial Dynamic Crushing

The beetle elytra requires not only to be lightweight to make a beetle fly easily, but also to protect its body and hind-wing from outside damage. The honeycomb sandwich structure in the beetle elytra make it meet the above requirements. In the present work, the microstructures of beetle elytra, including biology layers and thin-walled honeycombs, are observed by scanning electron microscope and discussed. A new bionic honeycomb structure (BHS) with a different hierarchy order of filling cellular structure is established. inspired by elytra internal structure. Then the energy absorbed ability of different bionic models with the different filling cell size are compared by using nonlinear finite element software LS-DYNA (Livermore Software Technology Corp., Livermore, CA, USA). Numerical results show that the absorbed energy of bionic honeycomb structures is increased obviously with the increase of the filling cell size. The findings indicate that the bionic honeycomb structure with second order has an obviously improvement over conventional structures filled with honeycombs and shows great potential for novel clean energy absorption equipment.

Effect of microtrichia on the interlocking mechanism in the Asian ladybeetle, Harmonia axyridis (Coleoptera: Coccinellidae)

The hindwings of beetles are folded under the elytra when they are at rest but are extended during flight, which can provide bioinspiration for the design of deployable micro air vehicles (MAVs). Beetle hindwings must be able to be both securely locked under the elytra and freely extended for flight, depending on the required action. To investigate the locking mechanism, this study used environmental scanning electron microscopy (ESEM) to examine the microstructures of the elytra, hindwings and abdomen of the Asian ladybeetle, Harmonia axyridis (Pallas, 1773). On the ventral side (VS) of the elytra, the microtrichia show a transitional structure from the lateral edge to the medial edge. On the hindwing surface, the folded regions were observed on both the dorsal side (DS) and the VS. On the abdomen, the microtrichia between the abdominal segments show a cyclical change from sparse to dense in each segment in the middle of the abdomen. Furthermore, the different directions of microtrichia that lead to self-locking friction on the surfaces of the hindwing, elytron and abdomen appear to facilitate interlocking. A model for the interlocking of the hindwings of the H. axyridis was established, and its underlying mechanism is discussed.