Biomechanical strategies underlying the durability of a wing-to-wing coupling mechanism

Mechanical and elemental characterization of ant mandibles: consequences for bite mechanics

Mandible morphology has an essential role in biting performance, but the mandible cuticle can have regional differences in its mechanical properties. The effects of such a heterogeneous distribution of cuticle material properties in the mandible responses to biting loading are still poorly explored in chewing insects. Here, we tested the mechanical properties of mandibles of the ant species Formica cunicularia by nanoindentation and investigated the effects of the cuticular variation in Young's modulus (E) under bite loading with finite-element analysis (FEA). The masticatory margin of the mandible, which interacts with the food, was the hardest and stiffest region. To unravel the origins of the mechanical property gradients, we characterized the elemental composition by energy-dispersive X-ray spectroscopy. The masticatory margin possessed high proportions of Cu and Zn. When incorporated into the FEA, variation in E effectively changed mandible stress patterns, leading to a relatively higher concentration of stresses in the stiffer mandibular regions and leaving the softer mandible blade with relatively lower stress. Our results demonstrated the relevance of cuticle E heterogeneity in mandibles under bite loading, suggesting that the accumulation of transition metals such as Cu and Zn has a relevant correlation with the mechanical characteristics in F. cunicularia mandibles.

Complexity biomechanics: a case study of dragonfly wing design from constituting composite material to higher structural levels

Presenting a novel framework for sustainable and regenerative design and development is a fundamental future need. Here we argue that a new framework, referred to as complexity biomechanics, which can be used for holistic analysis and understanding of natural mechanical systems, is key to fulfilling this need. We also present a roadmap for the design and development of intelligent and complex engineering materials, mechanisms, structures, systems, and processes capable of automatic adaptation and self-organization in response to ever-changing environments. We apply complexity biomechanics to elucidate how the different structural components of a complex biological system as dragonfly wings, from ultrastructure of the cuticle, the constituting bio-composite material of the wing, to higher structural levels, collaboratively contribute to the functionality of the entire wing system. This framework not only proposes a paradigm shift in understanding and drawing inspiration from natural systems but also holds potential applications in various domains, including materials science and engineering, biomechanics, biomimetics, bionics, and engineering biology.

An image based application in Matlab for automated modelling and morphological analysis of insect wings

Despite extensive research on the biomechanics of insect wings over the past years, direct mechanical measurements on sensitive wing specimens remain very challenging. This is especially true for examining delicate museum specimens. This has made the finite element method popular in studies of wing biomechanics. Considering the complexities of insect wings, developing a wing model is usually error-prone and time-consuming. Hence, numerical studies in this area have often accompanied oversimplified models. Here we address this challenge by developing a new tool for fast, precise modelling of insect wings. This application, called WingGram, uses computer vision to detect the boundaries of wings and wing cells from a 2D image. The app can be used to develop wing models that include complex venations, corrugations and camber. WingGram can extract geometric features of the wings, including dimensions of the wing domain and subdomains and the location of vein junctions. Allowing researchers to simply model wings with a variety of forms, shapes and sizes, our application can facilitate studies of insect wing morphology and biomechanics. Being an open-access resource, WingGram has a unique application to expand how scientists, educators, and industry professionals analyse insect wings and similar shell structures in other fields, such as aerospace.

The combination of structure and material distribution ensures functionality of the honeybee wing-coupling mechanism

Fore- and hindwings of honeybees are coupled and synchronized to flap by means of a forewing posterior recurved margin (PRM) and hindwing hamuli which constitute a hook-furrow coupling. Morphological analysis shows that the PRM is composed of a thickened and sclerotized membrane with the Archimedean spiral configuration and hamuli are a set of tiny, sclerotized hooks with flexible bases. By developing a theoretical PRM model, the influence of cuticle sclerotization and membrane-thickening on a deforming pattern and maximal coupling force was comparatively simulated, indicating that the real PRM is capable of bearing the highest coupling force and the membrane thickening makes more contribution than cuticle sclerotization on augmenting the maximal coupling force that the PRM can resist. In addition, four combined strategies, i.e. the hook shape, Archimedean spiral, rich resilin concentration, and cuticle sclerotization in different parts of the whole system were proposed, and deemed to endow the honeybee wing-coupling with remarkable stability and durability to eliminate a potential structural failure of the coupling over millions of wing flapping cycles across the honeybee lifespan. This study assists us in the comprehensive understanding of the functionality of the hook-furrow wing-coupling and shows us new avenues for biomimetics of mobile coupling mechanisms in modern engineering.

Specialized morphology and material properties make a honey bee tongue both extendible and structurally stable

The honey bee, Apis mellifera ligustica, uses the specialized tongue structured by ∼120 segmental units, coated by bushy hairs, to dip varying concentration nectar flexibly at small scales. While dipping, the segmental units elongate by 20%, coordinated with rhythmical erection of hairs, the pattern of which is demonstrated to be capable of both increasing nectar intake rate and saving energy. The compliance in the segmental units allows extension of the tongue, which however, challenges the structural stability while traveling through the viscous fluid. In this combined experimental and theoretical investigation, we apply scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), micro-computed tomography scanning (micro-CT), atomic force microscopy (AFM), and mechanical models to reveal the structural and material specializations in a bee tongue for meeting the functionally contradictive demands. We find that each segmental unit is a complex structure, which is composed of an intersegmental membrane (ISM) and a ring-like hair base (RHB), with spatially distributed discrete changes in material properties. The combination of these two components makes the tongue multifunctional, in which the ISMs characterized by resilin-rich material make the segmental units compliant, while the RHBs with rigid sclerotized material provide stable supporting for hairs. Our study may enlighten deployable mechanisms with correlative functional components, especially the microscopic mechanisms applied in viscous fluid tranport. STATEMENT OF SIGNIFICANCE: The honey bee tongue is a versatile tool that extends to probe into varying-shaped corollas, retracting with 3,000 glossal hairs staying erected to load nectar. The combined requirement of both deformability and structural stability imposes opposing demands on structural stiffness. Here we show that glossal hairs are supported by rigid continuum ring-like hair bases, embedded in the elastic resilient intersegmental membrane, making the whole tongue both flexible and rigid at the same time. Our findings extend our understanding of relationship between morphology, material composition and biomechanics of dynamic biological surfaces, which may inspire design paradigms of multifunctional deployable mechanisms coordinating deformability and structural stability.

Wing Coupling in Bees and Wasps: From the Underlying Science to Bioinspired Engineering

Wing-to-wing coupling mechanisms synchronize motions of insect wings and minimize their aerodynamic interference. Albeit they share the same function, their morphological traits appreciably vary across groups. Here the structure-material-function relationship of wing couplings of nine castes and species of Hymenoptera is investigated. It is shown that the springiness, robustness, and asymmetric behavior augment the functionality of the coupling by reducing stress concentrations and minimizing the impacts of excessive flight forces. A quantitative link is established between morphological variants of the coupling mechanisms and forces to which they are subjected. Inspired by the coupling mechanisms, a rotating-sliding mechanical joint that withstands tension and compression and can also be locked/unlocked is fabricated. This is the first biomimetic research of this type that integrates approaches from biology and engineering.

Coupling wings with movable hooks - resilin in the wing-interlocking structures of honeybees

Hymenoptera are characterised by the presence of one forewing pair and one hindwing pair. The two wings of each body side are coupled to each other during flight making the morphologically four-winged insects functionally two-winged. This coupling is formed by a row of hook-like structures, called hamuli, that are located at the leading edge of the hindwing and interlock with a thickened and recurved margin present at the trailing edge of the forewing. In this study, autofluorescence analyses performed with confocal laser scanning microscopy revealed differences in the exoskeleton material composition of the interlocking structures. While the wing veins and the recurved margin are strongly sclerotised and chitinous, the wing membranes mainly contain the elastomeric protein resilin. The hamuli are composed of sclerotised chitinous material, and each hamulus base is surrounded by and embedded in material that features large proportions of resilin and is located in strongly sclerotised socket-like wing vein structures. This exoskeleton organisation likely allows movements of the hamuli and, in combination with the exoskeleton material gradients visualized in the other interlocking structures, is assumed to guarantee an effective wing coupling and to simultaneously decrease the risk of wear and damage under mechanical loads occurring in flight, coupling and decoupling situations.

WingMesh: A Matlab-Based Application for Finite Element Modeling of Insect Wings

The finite element (FE) method is one of the most widely used numerical techniques for the simulation of the mechanical behavior of engineering and biological objects. Although very efficient, the use of the FE method relies on the development of accurate models of the objects under consideration. The development of detailed FE models of often complex-shaped objects, however, can be a time-consuming and error-prone procedure in practice. Hence, many researchers aim to reach a compromise between the simplicity and accuracy of their developed models. In this study, we adapted Distmesh2D, a popular meshing tool, to develop a powerful application for the modeling of geometrically complex objects, such as insect wings. The use of the burning algorithm (BA) in digital image processing (DIP) enabled our method to automatically detect an arbitrary domain and its subdomains in a given image. This algorithm, in combination with the mesh generator Distmesh2D, was used to develop detailed FE models of both planar and out-of-plane (i.e., three-dimensionally corrugated) domains containing discontinuities and consisting of numerous subdomains. To easily implement the method, we developed an application using the Matlab App Designer. This application, called WingMesh, was particularly designed and applied for rapid numerical modeling of complicated insect wings but is also applicable for modeling purposes in the earth, engineering, mathematical, and physical sciences.