In the last 30 days

• Open/close Design and construction principles in nature and architecture

  Jan Knippers and Thomas Speck 2012 Bioinspir. Biomim. 7 015002 Tag this article

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  This paper will focus on how the emerging scientific discipline of biomimetics can bring new insights into the field of architecture. An analysis of both architectural and biological methodologies will show important aspects connecting these two. The foundation of this paper is a case study of convertible structures based on elastic plant movements.

• Open/close A bio-robotic platform for integrating internal and external mechanics during muscle-powered swimming

  Christopher T Richards and Christofer J Clemente 2012 Bioinspir. Biomim. 7 016010 Tag this article

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  To explore the interplay between muscle function and propulsor shape in swimming animals, we built a robotic foot to mimic the morphology and hind limb kinematics of Xenopus laevis frogs. Four foot shapes ranging from low aspect ratio (AR = 0.74) to high (AR = 5) were compared to test whether low-AR feet produce higher propulsive drag force resulting in faster swimming. Using feedback loops, two complementary control modes were used to rotate the foot: force was transmitted to the foot either from (1) a living plantaris longus (PL) muscle stimulated in vitro or (2) an in silico mathematical model of the PL. To mimic forward swimming, foot translation was calculated in real time from fluid force measured at the foot. Therefore, bio-robot swimming emerged from muscle–fluid interactions via the feedback loop. Among in vitro-robotic trials, muscle impulse ranged from 0.12 ± 0.002 to 0.18 ± 0.007 N s and swimming velocities from 0.41 ± 0.01 to 0.43 ± 0.00 m s ⁻¹, similar to in vivo values from prior studies. Trends in in silico-robotic data mirrored in vitro-robotic observations. Increasing AR caused a small (∼10%) increase in peak bio-robot swimming velocity. In contrast, muscle force–velocity effects were strongly dependent on foot shape. Between low- and high-AR feet, muscle impulse increased ∼50%, while peak shortening velocity decreased ∼50% resulting in a ∼20% increase in net work. However, muscle-propulsion efficiency (body center of mass work/muscle work) remained independent of AR. Thus, we demonstrate how our experimental technique is useful for quantifying the complex interplay among limb morphology, muscle mechanics and hydrodynamics.

• Open/close Studying nanostructured nipple arrays of moth eye facets helps to design better thin film solar cells

  Rahul Dewan et al 2012 Bioinspir. Biomim. 7 016003 Tag this article

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  Nipples on the surface of moth eye facets exhibit almost perfect broadband anti-reflection properties. We have studied the facet surface micro-protuberances, known as corneal nipples, of the chestnut leafminer moth Cameraria ohridella by atomic force microscopy, and simulated the optics of the nipple arrays by three-dimensional electromagnetic simulation. The influence of the dimensions and shapes of the nipples on the optics was studied. In particular, the shape of the nipples has a major influence on the anti-reflection properties. Furthermore, we transferred the structure of the almost perfect broadband anti-reflection coatings to amorphous silicon thin film solar cells. The coating that imitates the moth-eye array allows for an increase of the short circuit current and conversion efficiency of more than 40%.

• Open/close A mechanical analysis of woodpecker drumming and its application to shock-absorbing systems

  Sang-Hee Yoon and Sungmin Park 2011 Bioinspir. Biomim. 6 016003 Tag this article

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  A woodpecker is known to drum the hard woody surface of a tree at a rate of 18 to 22 times per second with a deceleration of 1200 g, yet with no sign of blackout or brain damage. As a model in nature, a woodpecker is studied to find clues to develop a shock-absorbing system for micromachined devices. Its advanced shock-absorbing mechanism, which cannot be explained merely by allometric scaling, is analyzed in terms of endoskeletal structures. In this analysis, the head structures (beak, hyoid, spongy bone, and skull bone with cerebrospinal fluid) of the golden-fronted woodpecker, Melanerpes aurifrons, are explored with x-ray computed tomography images, and their shock-absorbing mechanism is analyzed with a mechanical vibration model and an empirical method. Based on these analyses, a new shock-absorbing system is designed to protect commercial micromachined devices from unwanted high- g and high-frequency mechanical excitations. The new shock-absorbing system consists of close-packed microglasses within two metal enclosures and a viscoelastic layer fastened by steel bolts, which are biologically inspired from a spongy bone contained within a skull bone encompassed with the hyoid of a woodpecker. In the experimental characterizations using a 60 mm smoothbore air-gun, this bio-inspired shock-absorbing system shows a failure rate of 0.7% for the commercial micromachined devices at 60 000 g, whereas a conventional hard-resin method yields a failure rate of 26.4%, thus verifying remarkable improvement in the g-force tolerance of the commercial micromachined devices.

• Open/close Conceptual design of flapping-wing micro air vehicles

  J P Whitney and R J Wood 2012 Bioinspir. Biomim. 7 036001 Tag this article

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  Traditional micro air vehicles (MAVs) are miniature versions of full-scale aircraft from which their design principles closely follow. The first step in aircraft design is the development of a conceptual design, where basic specifications and vehicle size are established. Conceptual design methods do not rely on specific knowledge of the propulsion system, vehicle layout and subsystems; these details are addressed later in the design process. Non-traditional MAV designs based on birds or insects are less common and without well-established conceptual design methods. This paper presents a conceptual design process for hovering flapping-wing vehicles. An energy-based accounting of propulsion and aerodynamics is combined with a one degree-of-freedom dynamic flapping model. Important results include simple analytical expressions for flight endurance and range, predictions for maximum feasible wing size and body mass, and critical design space restrictions resulting from finite wing inertia. A new figure-of-merit for wing structural-inertial efficiency is proposed and used to quantify the performance of real and artificial insect wings. The impact of these results on future flapping-wing MAV designs is discussed in detail.

• Open/close Leg-adjustment strategies for stable running in three dimensions

  Frank Peuker et al 2012 Bioinspir. Biomim. 7 036002 Tag this article

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  The dynamics of the center of mass (CoM) in the sagittal plane in humans and animals during running is well described by the spring-loaded inverted pendulum (SLIP). With appropriate parameters, SLIP running patterns are stable, and these models can recover from perturbations without the need for corrective strategies, such as the application of additional forces. Rather, it is sufficient to adjust the leg to a fixed angle relative to the ground. In this work, we consider the extension of the SLIP to three dimensions (3D SLIP) and investigate feed-forward strategies for leg adjustment during the flight phase. As in the SLIP model, the leg is placed at a fixed angle. We extend the scope of possible reference axes from only fixed horizontal and vertical axes to include the CoM velocity vector as a movement-related reference, resulting in six leg-adjustment strategies. Only leg-adjustment strategies that include the CoM velocity vector produced stable running and large parameter domains of stability. The ability of the model to recover from perturbations along the direction of motion (directional stability) depended on the strategy for lateral leg adjustment. Specifically, asymptotic and neutral directional stability was observed for strategies based on the global reference axis and the velocity vector, respectively. Additional features of velocity-based leg adjustment are running at arbitrary low speed (kinetic energy) and the emergence of large domains of stable 3D running that are smoothly transferred to 2D SLIP stability and even to 1D SLIP hopping. One of the additional leg-adjustment strategies represented a large convex region of parameters where stable and robust hopping and running patterns exist. Therefore, this strategy is a promising candidate for implementation into engineering applications, such as robots, for instance. In a preliminary comparison, the model predictions were in good agreement with the experimental data, suggesting that the 3D SLIP is an appropriate model to describe human running in three dimensions. The prediction of stable running based on movement-related leg-adjustment strategies indicates that both humans and robots may not require external targets directing the movement to run in three dimensions based on compliant leg function. This new movement-based reference enables the control of 3D running because leg adjustment is less sensitive and gait stability is separated from directional stability.

• Open/close Has biomimetics arrived in architecture?

  Petra Gruber and George Jeronimidis 2012 Bioinspir. Biomim. 7 010201 Tag this article

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  Architecture and construction are highly interdisciplinary fields, integrating many professions and many disciplines on different levels of scale and complexity. Studies of natural systems have at all times been inspirational for design. Investigating the overlaps between biology and architecture we find that a biological paradigm inspires the current frontier of research and innovation in many sectors. Using biology's categories to analyse the field we discover many 'signs of life' in architecture projects, and many researchers are actively involved with ways to implement more and more aspects of life into buildings without calling themselves biomimeticists. Meanwhile the architectural landscape has adopted biomimetics, bionics, biologically inspired design or biomimicry as valid strategies. However, it still lacks a showcase of innovative products or real breakthrough in the form of a 'really biomimetic building'. This implies the interpretation of biomimetics as an architectural style, defining the entirety of a building, best reflected in the overall form.

  Architecture is developed in different layers and has to meet often contradictory requirements that make information transfer difficult. Too many possibilities and levels of information are interconnected to identify simple straightforward questions and answers. In addition, other challenges have to be met for the adoption of principles from biology in architecture and there is still a difficulty in the gathering of information. Finding phenomena that lend themselves as role models is a challenge for architects and designers in spite of various attempts at generating databases and knowledge transfer systems. Whenever designers stumble across an interesting phenomenon, the relevant information is often available only in a generic manner or, even worse, limited to a narrow view angle related to a specific interest. In order to get hold of transferable information, research from another perspective in life sciences is needed, so that interdisciplinary collaboration can provide the platform essential for successful developments, as illustrated in the present collection of papers.

  In spite of all of the participating research groups working with a biomimetic focus, the translations and inspirations discussed in the papers are located mostly on the level of generic abstract principles, sometimes also referred to as 'deep principles'. Examples include composite materials aspects, anisotropy and heterogeneity, when we talk about materials and systems, and morphological differentiation and adaptation when we consider form generation processes.

  Tom Wiscombe designs visionary buildings that explore the potentials of architectural surfaces to be shifted from two-dimensionality to one or three dimensionality by introducing de-lamination, winding, fusing, blending and embedding of building systems. The use of non-mineral materials and suggestion of the logic of healing and weaving are directly taken from biological material processing. Functionally graded materials and the introduction of microparticles and biochemical systems shall further extend the possibilities to create future environments.

  Jan Knippers, Thomas Speck and Achim Menges have initiated a successful interdisciplinary collaboration between architecture, computational design, engineering and biology. They interpret architecture and biological evolution as nondeterministic processes, sharing parallels but fundamental differences at the same time. Those differences are the basis for the investigation of new technologies. The ICD/ITKE Research Pavillion 2010 stands as an example for a homogenous construction using a single textured material, parametric differentiation and shaping of large elastic deformations, using digital simulation, planning and production processes. The development of the so-called Flectofin ^® lamellas for shading of facades is based on the kinematics of the Strelitzia reginae flower, and again exploits an effect usually unwelcomed in engineering—torsional buckling—together with the use of fibre reinforced material. The introduction of such a system into a large scale building facade is presented with the thematic pavilion at EXPO 2012 in Korea, designed and engineered by SOMA Architects, Vienna and Knippers Helbig Advanced Engineering, Stuttgart, New York. These large scale implementations of principles derived from nature show the potential for the application of biomimetics in architectural design.

  Achim Menges' paper is a concise discussion of morphogenetic computational design, presenting form generation in contrast to the traditional form definition and form finding strategies in architectural design. Computational design allows for radically new approaches in the use, processing and generation of information that is translated into architectural form via new technologies. The generative design process is limited by phylogenetic and physical constraints. According to Menges, the challenge of this approach lies in resolving the complexity arising from the interrelation and reciprocal effects of material systems and dynamic environments. Evolutionary design exploration is introduced as a method together with a detailed description of case studies exploring the design of form-performance relations of overall building morphologies and urban block morphologies.

  Taken together, the presented papers show a promising development towards the implementation of biomimetics in the design of future built environments.

  References

  Wiscombe T 2012 Beyond assemblies: systems convergence and multi-materiality Bioinspir. Biomim. 7 015001

  Knippers J and Speck T 2012 Design and construction principles in nature and architecture Bioinspir. Biomim. 7 015002

  Menges A 2012 Biomimetic design processes in architecture: morphogenetic and evolutionary computational design Bioinspir. Biomim. 7 015003

• Open/close Investigation of a bio-inspired lift-enhancing effector on a 2D airfoil

  Joe Johnston and Ashok Gopalarathnam 2012 Bioinspir. Biomim. 7 036003 Tag this article

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  A flap mounted on the upper surface of an airfoil, called a ‘lift-enhancing effector’, has been shown in wind tunnel tests to have a similar function to a bird's covert feathers, which rise off the wing's surface in response to separated flows. The effector, fabricated from a thin Mylar sheet, is allowed to rotate freely about its leading edge. The tests were performed in the NCSU subsonic wind tunnel at a chord Reynolds number of 4 × 10 ⁵. The maximum lift coefficient with the effector was the same as that for the clean airfoil, but was maintained over an angle-of-attack range from 12° to almost 20°, resulting in a very gentle stall behavior. To better understand the aerodynamics and to estimate the deployment angle of the free-moving effector, fixed-angle effectors fabricated out of stiff wood were also tested. A progressive increase in the stall angle of attack with increasing effector angle was observed, with diminishing returns beyond the effector angle of 60°. Drag tests on both the free-moving and fixed effectors showed a marked improvement in drag at high angles of attack. Oil flow visualization on the airfoil with and without the fixed-angle effectors proved that the effector causes the separation point to move aft on the airfoil, as compared to the clean airfoil. This is thought to be the main mechanism by which an effector improves both lift and drag. A comparison of the fixed-effector results with those from the free-effector tests shows that the free effector's deployment angle is between 30° and 45°. When operating at and beyond the clean airfoil's stall angle, the free effector automatically deploys to progressively higher angles with increasing angles of attack. This slows down the rapid upstream movement of the separation point and avoids the severe reduction in the lift coefficient and an increase in the drag coefficient that are seen on the clean airfoil at the onset of stall. Thus, the effector postpones the stall by 4–8° and makes the stall behavior more gentle. The benefits of using the effector could include care-free operations at high angles of attack during perching and maneuvering flight, especially in gusty conditions.

• Open/close Biomimetic robotic Venus flytrap (Dionaea muscipula Ellis) made with ionic polymer metal composites

  Mohsen Shahinpoor 2011 Bioinspir. Biomim. 6 046004 Tag this article

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  The work described in this paper is a novel design of a robotic Venus flytrap (VFT) ( Dionaea muscipula Ellis) by means of ionic polymeric metal composite (IPMC) artificial muscles as distributed nanosensors and nanoactuators. Rapid muscular movements in carnivorous plants, such as VFT, which are triggered by antenna-like sensors (trigger hair), present a golden key to study distributed biomolecular motors. Carnivorous plants, such as VFT, possess built-in intelligence (trigger hairs), as a strategy to capture prey, that can be turned on in a controlled manner. In the case of the VFT, the prey that is lured by the sweet nectar in the VFT pair of jaw-like lobes has to flip and move the trigger hairs, which are colorless, bristle-like and pointed. The dynamically moved trigger hairs then electro-elastically send an electric signal to the internal ions in the lobe to migrate outwardly for the jaw-like lobes to close rapidly to capture the prey. The manner in which the VFT lobes bend inward to capture the prey shows a remarkable similarity with typical IPMCs bending in an electric field. Furthermore, the mechano-electrical sensing characteristics of IPMCs also show a remarkable resemblance to mechano-electrical trigger hairs on the lobes of the VFT. The reader is referred to a number of papers in connection with sensing and actuation of IPMCs in particular. Thus, one can integrate IPMC lobes with a common electrode in the middle of one end of the lobes to act like a spine and use IPMC bristles as trigger finger to sense the intrusion of a fly or insect to send a sensing signal to a solid state relay which then triggers the actuation circuit of the IPMC lobes to rapidly bend toward each other and close. The two lobes, which form the trap, are attached to the midrib common electrode which is conveniently termed the spine. The upper surface of each lobe is dished, and spaced along the free margins of the lobes with some 15–20 prong-like teeth. These are tough and pointed, and are inclined at an inward angle so that when the trap is sprung shut they will interlock. We have been experimenting with the VFT closing of its jaw-like lobes that close in about 0.3 s and have gained a lot of knowledge to report on the ionic and electrical mechanisms involved in the operation of such intelligent distributed biomolecular motors.

• Open/close Hydrodynamic pressure sensing with an artificial lateral line in steady and unsteady flows

  Roberto Venturelli et al 2012 Bioinspir. Biomim. 7 036004 Tag this article

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  With the overall goal being a better understanding of the sensing environment from the local perspective of a situated agent, we studied uniform flows and Kármán vortex streets in a frame of reference relevant to a fish or swimming robot. We visualized each flow regime with digital particle image velocimetry and then took local measurements using a rigid body with laterally distributed parallel pressure sensor arrays. Time and frequency domain methods were used to characterize hydrodynamically relevant scenarios in steady and unsteady flows for control applications. Here we report that a distributed pressure sensing mechanism has the capability to discriminate Kármán vortex streets from uniform flows, and determine the orientation and position of the platform with respect to the incoming flow and the centre axis of the Kármán vortex street. It also enables the computation of hydrodynamic features which may be relevant for a robot while interacting with the flow, such as vortex shedding frequency, vortex travelling speed and downstream distance between vortices. A Kármán vortex street was distinguished in this study from uniform flows by analysing the magnitude of fluctuations present in the sensor measurements and the number of sensors detecting the same dominant frequency. In the Kármán vortex street the turbulence intensity was 30% higher than that in the uniform flow and the sensors collectively sensed the vortex shedding frequency as the dominant frequency. The position and orientation of the sensor platform were determined via a comparative analysis between laterally distributed sensor arrays; the vortex travelling speed was estimated via a cross-correlation analysis among the sensors.