Hamed Rajabi

Hamed Rajabi
London South Bank University | LSBU · Department of Mechanical Engineering and Design

Doctor of Science; Doctor of Engineering

About

125
Publications
28,259
Reads
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967
Citations
Citations since 2017
66 Research Items
825 Citations
2017201820192020202120222023050100150200
2017201820192020202120222023050100150200
2017201820192020202120222023050100150200
2017201820192020202120222023050100150200
Introduction
Dr. Hamed Rajabi is a Lecturer at London South Bank University. He leads the Mechanical Intelligence Research Group, where he and his group work on the mechanics of biological materials/structures and their biomimetic applications for technology. His aim is to develop nature-inspired concepts and elaborate them into a technology readiness level that can be directly converted into marketable products.
Additional affiliations
October 2014 - March 2016
Christian-Albrechts-Universität zu Kiel
Position
  • Researcher
October 2014 - April 2018
Christian-Albrechts-Universität zu Kiel
Position
  • Researcher
September 2010 - June 2014
Islamic Azad University of Lahijan
Position
  • Lecturer

Publications

Publications (125)
Article
Full-text available
During flight, vibrations potentially cause aerodynamic instability and noise. Besides muscle control, the intrinsic damping in bird feathers helps to reduce vibrations. The vanes of the feathers play a key role in flight, and they support feathers’ aerodynamic function through their interlocked barbules. However, the exact mechanisms that determin...
Article
Geometry and material are two key factors that determine the functionality of mechanical elements under a specific boundary condition. Optimum combinations of these factors fulfil desired mechanical behaviour. By exploring biological systems, we find widespread spiral-shaped mechanical elements with various combinations of geometries and material p...
Article
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Cable-driven continuum robots with hyper-redundant deformable backbones show great promise in applications, such as inspection in unstructured environments, where traditional rigid robots with discrete links and joints fail to operate. However, the motion of existing continuum robots is still constrained by their homogeneous backbones, and limited...
Article
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The ability to fly is crucial for migratory insects. Consequently, the accumulation of damage on the wings over time can affect survival, especially for species that travel long distances. We examined the frequency of irreversible wing damage in the migratory butterfly Vanessa cardui to explore the effect of wing structure on wing damage frequency,...
Article
Insect wings are deformable airfoils, in which deformations are mostly achieved by complicated interactions between their structural components. Due to the complexity of the wing design and technical challenges associated with testing the delicate wings, we know little about the properties of their components and how they determine wing response to...
Article
Full-text available
Compliant grasping is an important function of continuum robots that interact with humans and/or unpredictable environments. However, the existing robots often have cross‐sections that remain constant along their length. This causes the robots to exhibit poor grasping ability, especially when dealing with objects with diverse curvatures. Here, insp...
Article
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Despite significant scientific advances in the past decades, most structures around us are static and ironically outdated from a technological perspective. Static structures have limited efficiency and durability and typically perform only a single task. Adaptive structures, in contrast, adjust to different conditions, tasks, and functions. They no...
Article
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Compound eyes of insects should be both thin and transparent to allow light to pass through, and at the same time mechanically stable to serve as exoskeleton. These conflicting requirements make the corneal cuticle an interesting example for studying cuticle biomechanics as well as for designing composite materials that seek similar properties. Her...
Article
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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 inse...
Article
Full-text available
Cuticle is one of the most abundant, but least studied, biological composites. As a result, it has contributed very little to the field of biomimetics. An important step to overcome this problem is to study cuticle biomechanics by means of accurate mechanical measurements. However, due to many reasons, mechanical testing on fresh cuticle specimens...
Article
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The avian feather combines mechanical properties of robustness and flexibility while maintaining a low weight. Under periodic and random dynamic loading, the feathers sustain bending forces and vibrations during flight. Excessive vibrations can increase noise, energy consumption, and negatively impact flight stability. However, damping can alter th...
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Energy‐Efficient Robot Locomotion In article number 2100133, Poramate Manoonpong and co‐workers present an integrative approach, combining 3D printing with soft material, finite element modeling, and neural control, to investigate the Fin Ray effect at various crossbeam angles and demonstrate that, among other angles, the Fin Ray model with nonstan...
Article
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Insects are the most diverse animal taxon, both in terms of the number of species and the number of individuals [...]
Article
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Robot foot and gripper structures with compliancy using different mechanical solutions have been developed to enhance proper contact formations and gripping on various substrates. The Fin Ray structure is one of the solutions. Although the Fin Ray effect has been proposed and exploited, no detailed investigation has been conducted on the effect of...
Article
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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 t...
Article
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Bioinspired Engineering In article number 2004383, Hamed Rajabi and co-workers investigate the wing-to-wing coupling of nine castes and species of bees and wasps. They showed that the diverse morphologies of the coupling mechanisms in the examined insects can be linked to forces to which the couplings are subjected. The researchers design and fabri...
Article
Some insects, such as bees, wasps, and bugs, have specialized coupling structures to synchronize the wing motions in flight. Some others, such as ladybirds, are equipped with coupling structures that work only at rest. By locking elytra into each other, such structures provide hindwings with a protective cover to prevent contamination. Here, we sho...
Article
The ant Harpegnathos venator can engage in various labors using a pair of elongated mandibles with the ability to rotate about two orthogonal axes. This biaxial rotation enables the ant to gently handle their small, fragile eggs with enhanced contact area and smaller work space. However, how this biaxial rotation influences the ant's predation abil...
Article
Insect cuticle can reach a wide range of material properties, which is thought to be the result of adaptations to applied mechanical stresses. Biomechanical mechanisms behind these property variations remain largely unknown. To fill this gap, here we performed a comprehensive study by simultaneous investigation of the microstructure, sclerotization...
Article
Full-text available
For flying insects, stability is essential to maintain the orientation and direction of motion in flight. Flight instability is caused by a variety of factors, such as intended abrupt flight manoeuvres and unwanted environmental disturbances. Although wings play a key role in insect flight stability, little is known about their oscillatory behaviou...
Article
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Structures with variable stiffness have received increasing attention in the fields of robotics, aerospace, structural, and biomedical engineering. This is because they not only adapt to applied loads, but can also combine mutually exclusive properties. Here inspired by insect wings, the concept of “triple stiffness” is introduced and applied to en...
Article
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Elongated rostra (snouts) are remarkable features of many female weevils. The female of Curculio glandium uses the snout to excavate channels in acorns to oviposit. Considering the slenderness of the rostrum, the excavation of channels in solid substrates without buckling is a challenging task from both engineering and biological points of view. He...
Article
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We unveiled the penile penetration mechanics of two earwig species, Echinosoma horridum, whose intromittent organ, termed virga, is extraordinarily long, and E. denticulatum, whose virga is conversely short. We characterised configuration, geometry, material and bending stiffness for both virga and spermatheca. The short virga of E. denticulatum ha...
Article
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Mobility and support are two structural properties that are often mutually exclusive. However, combining them could enhance the performance of mechanical components, and offer novel technical applications. Here through the implementation of a bioinspired interlocking mechanism in the design of a supportive, yet mobile, wrist splint, we tackled the...
Article
The biomechanics underlying the predatory strike of dragonfly larvae is not yet understood. Dragonfly larvae are aquatic ambush predators, capturing their prey with a strongly modified extensible mouthpart. The current theory of hydraulic pressure being the driving force of the predatory strike can be refuted by our manipulation experiments and rei...
Article
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Durability and load-bearing are difficult to be combined in engineering systems. Hence, in majority of man-made structures, the two characteristics are typically mutually exclusive. Nature, however, has provided us with design strategies, through which many biological systems have overcome this conflict. Insect wings represent a striking example of...
Article
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Sperm removal behaviour (SRB) is known in many animals, and male genital structures are often involved in the SRB, e.g. rubbing female genitalia vigorously. However, it remains unclear how those male genital structures function properly without severe genital damage during SRB. In the present study, we focused on the bushcricket Metaplastes ornatus...
Article
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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 comp...
Article
The exoskeleton of nearly all insects consists of a flexible core and a stiff shell. The transition between these two is often characterized by a gradual change in the stiffness. However, the functional significance of this stiffness gradient is unknown. Here by combining finite-element analysis and multi-objective optimization, we simulated the me...
Preprint
Dragonfly larvae capture their prey with a strongly modified -extensible- mouthpart using a biomechanically unique but not yet understood mechanism. The current opinion of hydraulic pressure being the driving force of the predatory strike can be refuted by our manipulation experiments and reinterpretation of former studies. On this fact, we present...
Article
The evolution of wings has played a key role in the success of insect species, allowing them to diversify to fill many niches. Insect wings are complex multifunctional structures, which not only have to withstand aerodynamic forces but also need to resist excessive stresses caused by accidental collisions. This Commentary provides a summary of the...
Article
Insects thrived soon after they acquired the ability to fly. Beyond the reach of the non-flying competitors, flying insects colonized a wide variety of habitats. Although flight is an efficient way to disperse and escape predators, it is energetically costly. Hence, various strategies are served to enhance flight efficiency as much as possible. A s...
Preprint
Full-text available
Asteraceae, the most successful flowering plant family, is adapted to the vast range of ecological niches. Their adaptability is partially based on their strong ability of reproduction. The initial, yet challenging, step for plant reproduction is to transport pollen to flower-visiting pollinators. Using quantitative experiments and numerical simula...
Article
Insect wings have no flight muscles, except those situated in the thorax. However, they continuously respond to forces acting on them during flight. This ability is achieved by the specialised design of the wings and plays a key role in their aerodynamic performance. Dragonfly (Anisoptera) wings represent an extreme example of this automatic shape...
Article
A striking characteristic of insect cuticle is the wide range of its material property values, with respect to stiffness, strength and toughness. The elastic modulus of cuticle, for instance, ranges over seven orders of magnitude in different structures and different species. Previous studies suggested that this characteristic is influenced by the...
Article
Cuticle plays an important role in the evolutionary success of insects. Many studies on insect cuticle reported a soft, resilin-rich endocuticle. However, a recent study indicated the presence of a sclerotised endocuticle in the weevil, Pachyrhynchus sarcitis kotoensis, which contradicts the former knowledge. To understand the degree of sclerotisat...
Article
Digger wasps of the family Crabronidae (Insecta: Hymenoptera) are generally known to use their sting to paralyze or kill a prey. However, only a few species of digger wasps transport their prey to the nest impaled on the sting. How sting morphology correlates with this peculiar type of prey carriage is still unclear. We examined the sting morpholog...
Article
Stink bugs have wing coupling mechanisms to synchronize flapping of their wings. The wing coupling is performed through a clamp-like structure on the fore wing (i.e., hemelytron) and a rolled margin on the hind wing. Here we used modern imaging techniques to investigate structural characteristics and material composition of the wing coupling of the...
Article
Worker honeybees (Apis mellifera) are morphologically four-winged, but are functionally dipterous insects. During flight, their fore- and hindwings are coupled by means of the forewing posterior rolled margin (PRM) and hindwing hamuli. Morphological analysis shows that the PRM can be connected to the hamuli, so that the fore- and hindwing are firml...
Article
Full-text available
Many insects possess a hyper-elongated intromittent organ with a diameter of only a few micrometers. Using morphological and theoretical approaches, we investigated the biomechanics of sperm transfer through such organs by calculating (1) how far and how fast sperm could fill in the penis by capillary action, (2) how much capillary pressure is gene...
Article
The biological success of insects is attributed to evolution of their wings. Over 400 million years of evolution, insect wings have become one of the most complex and adaptive locomotor structures in the animal kingdom. Although seemingly fragile, they satisfactorily perform their intended function under millions of cycles of repeated stress withou...
Article
Ctenoid scales protect the fish body against predators and other environmental impacts. At the same time, they allow for sufficient degree of flexibility to perform species-specific locomotion. The scales of the flatfish Solea solea were chosen to study the specific mechanical behavior and material properties of the ctenoid scales. Using scanning e...
Data
The sketch of the samples for nanoindentation. (A) The mature cuticle. (B) The teneral cuticle. (C) The lizard tooth.
Data
The stiffness of the elytral cuticle of the mature and teneral weevil, Pachyrhynchus sarcitis kotoensis, and the tooth of the lizard, Japalura swinhonis.
Data
Compression test on a mature Pachyrhynchus sarcitis kotoensis.
Data
Compression test on a teneral Pachyrhynchus sarcitis kotoensis.
Article
Full-text available
Robust body armor is one of many anti-predator strategies used among animal taxa. The exoskeleton of insects can serve as the secondary defense mechanism in combination with the primary defense such as warning color. Aposematic Pachyrhynchus weevils advertise their unprofitability and use their robust exoskeleton for effective defense against lizar...
Article
Full-text available
Nature has evolved structures with high load-carrying capacity and long-term durability. The principles underlying the functionality of such structures, if studied systematically, can inspire the design of more efficient engineering systems. An important step in this process is to characterize the material properties of the structure under investig...
Article
Active tactile exploration behaviour is constrained to a large extent by the morphological and biomechanical properties of the animal's somatosensory system. In the model organism Carausius morosus, the main tactile sensory organs are long, thin, seemingly delicate, but very robust antennae. Previous studies have shown that these antennae are compl...
Article
Adult dragonflies can be divided into two major groups, perchers and fliers, exhibiting notably different flight behaviour. Previous studies have yielded conflicting results regarding the link between the wing macro-morphology and flight style in these two groups. In this study, we present the first systematic investigation of the micro-morphologic...
Article
Full-text available
During their lifespan, the long and narrow tibiae of the stick insect Carausius morosus (Sinéty, 1901) experience substantial compressive loads. The mechanical load on the tibiae increases as the weight of the insect rises. The increase in the body weight is accompanied by a notable increase in the insect's body size and, accordingly, by an increas...
Article
Full-text available
Dragonfly wings resist millions of cycles of dynamic loading in their lifespan. During their operation, the wings are subjected to relatively high mechanical stresses. They further experience accidental collisions which result from the insects' daily activities, such as foraging, mating and fighting with other individuals. All these factors may lea...
Data
Development of the von Mises stress in the model of the gula cuticle of the beetle P. marginata with discontinuous exponential stiffness profile (DC-EXP) by the increase of the applied displacement. The same legend as that used in figure 5 is also valid here.
Article
Full-text available
Insect cuticle is a biological composite with a high degree of complexity in terms of both architecture and material composition. Given the complex morphology of many insect body parts, finite element (FE) models play an important role in the analysis and interpretation of biomechanical measurements, taken by either macroscopic or nanoscopic techni...
Article
Statement of significance: In this study, we investigate the wing nodus, a specialized wing component in dragonflies. Using a combination of modern imaging techniques, we demonstrate the presence of resilin in the nodus, which is expected to facilitate the wing deformability in flight. The specific geometry of the nodus, however, seems to restrain...
Article
Locust wings are able to sustain millions of cycles of mechanical loading during the lifetime of the insect. Previous studies have shown that cross veins play an important role in delaying crack propagation in the wings. Do cross veins thus also influence the fatigue behaviour of the wings? Since many important fatigue parameters are not experiment...
Article
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Dragonflies are fast and manoeuvrable fliers and this ability is reflected in their unique wing morphology. Due to the specific lightweight structure, with the crossing veins joined by rubber-like resilin patches, wings possess strong deformability but can resist high forces and large deformations during aerial collisions. The computational results...