Proceedings Volume 10593

Bioinspiration, Biomimetics, and Bioreplication VIII

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Proceedings Volume 10593

Bioinspiration, Biomimetics, and Bioreplication VIII

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Volume Details

Date Published: 11 July 2018
Contents: 13 Sessions, 27 Papers, 5 Presentations
Conference: SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring 2018
Volume Number: 10593

Table of Contents

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Table of Contents

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  • Front Matter: Volume 10593
  • Inaugural Session
  • Flight I
  • Material Structures I
  • Bio-Optics
  • Energy
  • Robotics
  • Adhesion
  • Particulate Matter
  • Flight II
  • Soft Matter
  • Material Structures II
  • Poster Session
Front Matter: Volume 10593
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Front Matter: Volume 10593
This PDF file contains the front matter associated with SPIE Proceedings Volume 10593, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.
Inaugural Session
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Paradigms for biologically inspired design
T. A. Lenau, A.-L. Metze, T. Hesselberg
Biologically inspired design is attracting increasing interest since it offers access to a huge biological repository of well proven design principles that can be used for developing new and innovative products. Biological phenomena can inspire product innovation in as diverse areas as mechanical engineering, medical engineering, nanotechnology, photonics, environmental protection and agriculture. However, a major obstacle for the wider use of biologically inspired design is the knowledge barrier that exist between the application engineers that have insight into how to design suitable products and the biologists with detailed knowledge and experience in understanding how biological organisms function in their environment. The biologically inspired design process can therefore be approached using different design paradigms depending on the dominant opportunities, challenges and knowledge characteristics. Design paradigms are typically characterized as either problem-driven, solution-driven, sustainability driven, bioreplication or a combination of two or more of them. The design paradigms represent different ways of overcoming the knowledge barrier and the present paper presents a review of their characterization and application.
Flight I
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Bioinspired pitch control using a piezoelectric horizontal tail for rudderless UAVs
A bird’s tail plays a crucial role in flight dynamics by making rapid fine-tuned movements for precise attitude stabilization in addition to large scale deformations used in conjunction with the wings to achieve prolonged maneuvers. However, this control surface geometry differs substantially from those of traditional aircraft such as the vertical rudder which has slower actuation times, less versatility relative to control authority, and increased radar signatures. The current work aims to increase maneuverability in rudderless UAVs using Macro Fiber Composites (MFCs) and multi-material 3D printing to achieve a bidirectional camber morphing horizontal tail. The MFCs are customized with a 55° fiber orientation to achieve bending-twisting coupling resulting in complex curvatures. Previous work investigated the actuator’s capabilities to control yaw and act as an air break during sideslip. The current work investigates the actuator’s ability to control pitch and also analyzes its effectiveness as a rudder during changes in angle of attack. The control effectiveness was assessed via wind tunnel experiments of a full bodied bioinspired UAV of 0.34m wing span with active horizontal tail. Alpha sweeps were conducted across a range of wind speeds. While the complex curvature of the actuator is desirable for control of both yaw and pitch, it also causes coupling between these two degrees of freedom. The magnitude of this coupling is also investigated.
Technological demonstration of an adaptive aileron system
Variation of trailing edge camber proved to be one of the easiest and most effective ways to modify aerofoil shape to match different aircraft operational weights, with benefits approaching 3% of fuel savings or, equivalently, range extension. This is particularly the case of commercial planes, where both initial take-off conditions (because of the unpredictable payload or the specific required mission – transfer flight, for instance) and in-flight states (for the kerosene consumption) can undergo significant differences. Several studies (like the European Research Programs SARISTU or JTI-GRA) demonstrated that the most sensible region for installing an adaptive trailing edge system for those aims is towards the wing tip. This is unfortunately a very delicate area where usually ailerons are deployed and where significant mass insertions could affect the aeroelastic response with some risks of instabilities. Furthermore, the volume available are really limited so that the installation of a fully embedded system is challenging.

Moving from the experience taken in many former projects as the cited ones, the authors faced the problem of installing a fully integrated adaptive trailing edge system within the existing structural skeleton of a reference aileron and defined a design strategy to take into account the aeroelastic modifications due to the installation of such a device. Besides, the architecture preserved the original function of that control surface so that it could work as a standard aileron (classical rigid tab movement) with the augmented function of a deformable, quasi-static shape. In this sense, the proposed system exhibited a double functionality: a conventional rigid aileron with augmented shape modification capability plus a continuous, slow change of the trailing edge, occurring during flight for compensating aircraft weight variation.

The research was carried out within the Italian-Canadian program MDO-505 and led to the realisation of a multifunctional aileron with two operational motor systems (one for the classical aileron working and the other for the morphing enforcement), completely integrated so that no external element was visible or affected the aerodynamics of the wing. The manufacture of this device was possible thanks to the development of a suitable design process that allowed taking into account both the structural and the aeroelastic response of the integrated architecture. This system was part of an adaptive wing section that was completed with the realisations made by the ETS of Montreal, the Quebecoise Consortium for Aerospace Research and Innovation (CRIAQ) and the IAR-NRC, supported by Bombardier and Thales Canada. The joint demonstrator was tested in the wind tunnel at the NRC facilities in Ottawa and gave confirmation of the aerodynamic, aeroelastic and structural predictions.

The paper that is herein presented deals therefore with the design process and the manufacture of an adaptive trailing edge, installed within the existing aileron system of a wing segment, to undergo wind tunnel tests. The resulting device considers the definition of the kinematic structural system, the development of the integrated actuator system, their integration and the assessment of their static and dynamic structural response, and the verification of a safe aeroelastic behavior. Numerical and experimental results are presented, achieved in lab and wind tunnel environments.
Optimisation design process of a morphing winglet
Marco Lo Cascio, Alberto Milazzo, Gianluca Amendola, et al.
Aeronautic and aerospace engineering is recently moving in the direction of developing morphing wing devices, with the aim of making adaptable the aerodynamic shapes to different operational conditions. Those devices may be classified according to two different conceptual architectures: kinematic or compliant systems. Both of them embed within their body all the active components (actuators and sensors), necessary to their operations. In the first case, the geometry variation is achieved through an augmented classical mechanism, while in the second case the form modification is due to a special arrangement of the inner structure creating a distributed elastic hinges arrangement. Whatever is the choice, novel design schemes are introduced. Then, it is almost trivial to conclude that standard methods and techniques cannot be applied easily to these innovative layouts. In other words, because new architectures are produced, the former construction paradigms cannot be maintained as they are but shall be somehow transformed and assimilated by the design engineers’ community. In the meantime, the realization process should go on and morphing elements shall be realized, irrespectively of the full maturity of the associated concepts. Therefore, if optimization methods are important for the better exploitation of usual constructions, they become absolutely necessary for the technological demonstration of the capability of such breakthrough systems. In fact, standing their aim of improving the effectiveness of the aircraft flight and reducing then its overall weight, mass impact plays a fundamental role. Promised benefits could completely vanish if the added should overcome the saved weight!

In the study herein presented, the design process of a morphing winglet is reported. The research is collocated within the Clean Sky 2 Regional Aircraft IADP, a large European programme targeting the development of novel technologies for the next generation regional aircraft. The ultimate scope concerns the definition of an adaptive system for alleviating the gust loads and possibly modifying the wing load distribution in the sense of minimizing the attachment momentum (the parameter that governs the wing sizing). The proposed kinematic system is characterized by movable surfaces, each with its own domain authority, sustained by a winglet skeleton and completely integrated with a devoted actuation system. Preliminary aeroelastic investigations did already establish the robustness of the referred structural layout. This paper summarizes the activities relating to the optimization of the envisaged morphing system architecture. Moving from a standard configuration, a process is carried out to identify the lighter adaptive layout that can bear the external and internal loads without experiencing excessive stress levels for its safe operation. The most severe loads are taken into account for this process, as provided by the industrial partner, showing the reliability of the proposed solution on-board of a standard commercial aircraft. The optimization process produces interesting, sometime surprising, results that promise to reduce the weight impact of the structural skeleton for more than 40% with exclusive reference to the regions undergoing the optimization process. Such figure reduces to 15% if the complete structure is taken into account, and 12% if the skin contribution is included. The innovative outcomes are discussed in detail. Results are verified with a dedicated study that proves the consistency of the procedure and the trustworthiness of the computations.
Material Structures I
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Toward multicontrollable metasurfaces
Multicontrollability is just beginning to emerge as an engineering paradigm. It is necessary for fault-tolerant operation because multiple agents become available to perform a specific function. This built-in redundancy promotes seamless operation in variable conditions. Inspired by biological multicontrollability, multicontrollable metasurfaces have been conceptualized for terahertz applications. Comprising electrically small elements called MetaAtoms made of diverse pixels each of which is variously controlled, a metasurface could be either homogeneous or graded on the wavelength scale. As an example, terahertz transmission of a normally incident plane wave through a metasurface with subwavelength MetaAtoms containing diverse pixels of magnetostatically controllable material (InAs) and thermally controllable material (CdTe) was analyzed. The co-polarized transmission coefficients were found to exhibit stopbands that shift by switching on/off the magnetostatic field and/or increasing/decreasing the temperature.
Bio-Optics
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Bioinspired invertebrate pest detection on standing crops
Javaan Singh Chahl, Huajian Liu
Invertebrate pests are difficult to control and the losses caused by them is huge. In six major Australian grain crops, the estimated annual loss from invertebrate pests is $359.8 million [1, 2]. Pests include molluscs, insects and nematodes all at different stages of their life cycle. Traditionally, light traps and hand nets were used to sample the pests that are capable of flight, and human experts and recent machine vision systems were used to classify the samples. This approach is labour intensive and only captures insect pests at one late stage of their life cycle, which may be too late for integrated pest management (IPM). IPM uses the combination of all possible pest control methods to reduce the amount of insecticide must be used, providing advantages to both the environment and the consumers[3]. IPM would be much easier if there were a technological capability to detect pests on the crop in all stages of the lifecycle of both crops and pests. Many pests have defence mechanisms that involve camouflage of colour and shape. Predators of pests, which includes insects, arachnids and birds have evolved techniques for detecting prey. Besides that, some insects, such as butterflies, are very good at finding healthy leaves. Inspired by the vision of predators of invertebrate pests and leaffeeding insects, we have developed a multispectral 3D vision system that can detect common invertebrate pests on green leaves. The main contribution of this study is that we proposed a high-dimensional colour space named hyper-huesaturation- intensity (HHSI), which is less affected by unstable illumination and could enlarge inter-class distance for material classification.
Replication of large-area Morpho-color material using flexible mold
Akira Saito, Kosei Ishibashi, Junpei Ohga, et al.
The specific metallic blue of Morpho butterfly is structural color having high reflectivity produced by an interference effect. However, a single color in too wide angular range (> ± 40° from the normal) contradicts the optical interference. After we have proven the principle of the mystery by reproducing the specific nanostructures of their scales, we found the artificial Morpho-color to serve wide applications, because it can provide a brilliant single color in wide angular range with high reflectivity without chemical pigment, which is resistant to fading caused by chemical change for long time. We have developed various techniques for applications of the specific color, such as mass-production processes, simulation and control of its optical properties, and substrate-free color materials. One of the remaining key issues is to produce the large-area flexible film, because the flexible film was limited to small area, and large-area Morpho-color material have long been accompanied with the solid substrate, which has limited the variety of applications. By combining these processes to fabricate the small flexible film and solid large-area Morpho-color material, we developed a simple process to mass-fabricate the large-area flexible Morpho-color material. The method was quite simple, whereas this process needed to develop a flexible mold for nano-imprint, because the large-area nano-imprint gives serious stress and damage to the solid mold. Finally, by developing a process to produce a large-area flexible mold, we have successfully replicated the flexible large-area Morpho-color film, which can be realized by immersion into hot water. The fabricated large-area Morpho-color film was flexible, resistant against stress and strain, and found to maintain the original optical properties of Morpho-color. This process will expand the applications of the Morpho-color, which enables the coloring without limit of shape and area.
A bioinspired broadband reflector in the VIS-NIR wavelength range
Dielectric reflectors which can be found in the shells of some gold beetles (e.g. Anopognathus parvulus and Aspidomorpha tecta) consist of a stack of alternating layers of two high- and low-refractive index materials. Inspired by these structures, here we describe irregularly staggered reflectors which can be designed to feature high reflectance in a broad wavelength band that includes entirely the visible (VIS) and partially the nearinfrared (NIR) regions ([400, 1400] nm). Given the materials and the number of layers, we use a dedicated genetic algorithm to find out the reflector configuration (i.e., the sequence of the thicknesses of the layers) maximizing the reflectance in the considered wavelength band. Some results are reported showing the characteristics of such reflectors.
Energy
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Photosynthesis as a guide to small scale production of energy from CO2
Photosynthesis as a guide to taking up CO2 and nutrient rich water in sunlight and give off O2 and water vapor is the topic of this research. Using photosynthesis as a guide, it has been researched on ways to take up CO2 and water and obtain fresh water, O2 and energy at a small scale.
Bioinspired pseudo-ductile composite laminates with hierarchical energy absorption mechanism
F. Rizzo, F. Pinto, M. Meo
The large diffusion of Carbon Fibre Reinforced Polymers (CFRP) over the last three decades in multiple industrial sectors is due to their excellent in-plane mechanical properties and their exceptional strength-to-weight-ratio. As the use of CFRP moved from non-structural parts to primary structures however, the intrinsic layered nature of these materials and their consequent weak resistance to out-of-plane solicitations has changed the safety approach used for traditional ductile materials, shifting the design paradigm towards more severe safety margins. This zero-damage manufacturing strategy, necessary to prevent catastrophic failures, led to overdesigned composite parts, preventing the full exploitation of their unique characteristics and limiting their use in harsh environments. Based on this premise, the possibility to manufacture composite laminates able to respond with a pseudo-ductile behaviour when subjected to an out-of-plane load is of crucial importance as it would eliminate the need of overdesigned parts and extend the range of applications available to composite structures. This project is aimed to the design, manufacturing and characterisation of a bioinspired CFRP laminate in which the pseudo-ductility arises from an ordered pattern of discontinuities which are created over the surface of the different layers before the curing reaction. The presence of this carved pattern creates a hierarchical interplay of high-strength carbon fibre segments and elastic soft matrix-rich areas which resembles the interaction between the β-sheets crystalline domains and amorphous helical and β-spiral structures typical of spider silk and other biological structures (e.g. cellulose, hair) which enables a combination of high mechanical strength and elasticity. The effect of different geometrical parameters of the carved pattern such as critical length, shape and dimensions, on the mechanical properties of the laminate have been analysed via Finite Element Analyses in order to identify the optimal configuration of the discontinuities, finding the best trade-off between in-plane and out-of-plane mechanical properties. Samples with different carved patterns were then manufactured and their properties were assessed by subjecting them to three-point-bending test. The internal distribution of damaged areas was assessed via different Non Destructive Techniques and was compared with the behaviour of traditional CFRP. Results showed that the presence of the artificial discontinuities is able to induce pseudoductile behaviour into the CFRP, improving the energy absorption mechanism during out-of-plane solicitations without severely affecting the in-plane properties.
Investigation of leaf shape and edge design for faster evaporation in biomimetic heat dissipation systems
Petra Gruber, Ariana I. K. S. Rupp
In previous projects theromodynamics of plants was identified as an interesting field delivering concept generators for technical, especially architectural application. So leaf morphology is determined by a variety of factors, and also significant for plant water and energy balance. However, how leaf design affects evapotranspiration and, consequently, leaf thermal performance and energy budget, has not been investigated in detail. Many leaf-inspired models in the literature overlook leaf hydraulics, capillarity, wetting phenomena in porous materials and the thermal properties of cellulose. To further the knowledge in this field, we have started to research on the relation between wetting, thermal dynamics and shape. We recorded with a thermal camera free convection of wetted models made of laser-cut paper tissue, soaked in water and drying naturally. Families of shapes were abstracted from leaves of deciduous trees: white oak, for their crenations and lobes; maple, for their relatively large teeth; elm, for their smaller hierarchically-ordered serrations. In this abstracted experimental setup, we observed distinct evaporation rates for models with normalized surface area but different boundary perimeters. Outward teeth prompt dewetting nucleation in shapes only differing geometrically, shedding some light on surface designs for heat dissipation versus designs for moist microclimate retention. The biomimetic approach taken will deliver a better understanding of the biological role of leaf structure and support the enhancement of fluid-assisted heat transfer systems, for which further three-dimensional exploration and scale studies are conceptualized.
Robotics
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Interactive experiments in a robotics-based platform to simulate zebrafish response to a predator
Rana El Khoury, Roni Barak Ventura, Gabrielle Cord-Cruz, et al.
Biomimetic robotics is emerging as a promising research tool in the study of animal behavior, providing highlycontrollable and customizable stimuli in laboratory experiments and field trials. Here, we introduce a novel robotics-based approach to study predator-prey interactions in fish. Our animal model, zebrafish, is gaining traction as a species of choice for investigations of fear and anxiety in preclinical research. The platform integrates three-dimensional real-time tracking, four-degree-of-freedom robotic manipulation, and data-driven Markov chains to allow for unprecedented, interactive experiments on zebrafish.
Performance analysis of resilient bioinspired structural systems
Reena R. Patel, Guillermo A. Riveros, David S. Thompson, et al.
Lightweight structures are in demand in many application areas since they provide an optimum use of available resources. For example, in the transportation and aviation industries, lightweight structures increase the energy efficiency. However, lightweight structures need to have adequate strength for their safe usage. This work investigates the performance of novel proof-of-concept structural systems developed based on the rostrum (snout) of the paddlefish. Numerical experiments are conducted on the conceptual prototypes of bioinspired, energy- dissipative mechanical system models with different lattice patterns that mimic those found in the rostrum of the paddlefish. The performance of the models is quantified in terms of deformations and maximum principal stresses experienced by the model under a blast load using fixed plate and cantilever beam boundary conditions. The bioinspired models showed identical trends of stress and deformation. However, the heterogeneous bioinspired structures showed a decrease of 30% in deformation and experienced lower stresses as compared to a structure with identical geometry and homogeneous material properties.
Adhesion
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Observation of micro-topography of newt toe pads and investigating on wet adhesive properties of microstructured surface of PDMS
Ling Gong, Xiaojie Wang, Haiwu Yu, et al.
The newts (Cynops orientalis) display unique attachment and climbing abilities in wet conditions. The surface microstructure of newt toe pads plays an important role in friction enhancement that ensures fast motion on wet and smooth surfaces. Followed by observing the micro and nanoscale structural features of foot pads of the newts, four micro-patterned surfaces including round pillars, hexagonal pillars and two composite structures were fabricated on Polydimethylsiloxane (PDMS). The static friction and wet-adhesion properties of the microstructured surface of PDMS were measured on the multi-functional surface meter and adhesion equipment, respectively. Effects of micropattern, normal load, wetting condition on static friction properties, and effects of amount of liquid, approach-retraction cycle on adhesion properties were investigated. Our results can give insights into the climbing behavior of newts when they attach and move on wet and smooth surfaces, and possible applications of dense nanopillar arrays on the man-made foot pads for friction enhancement.
A wall-climbing robot using gecko-inspired dry adhesives and underactuated modular connecting mechanism
Xuan Wu, Rongchuan Wang, Tao Mei, et al.
This paper proposes the design, fabrication, and testing of a wall-climbing robot (WCR) using gecko-inspired dry adhesives. The robot consists of two tank-like modules, which utilize adhesive timing belts for locomotion and adhesion. A single module is firstly optimized in design to maximize the adhesive force. Then, an under-actuated compliant mechanism is designed to connect two modules. The robot mimics not only the gecko's multiscale adhesive structures but also its multiscale bio-adjustment mechanism. Inspired by the gecko's digital behavior, the robot can performs gripping-in and furling out motions to adjust preloading forces for each module on surfaces sloped from 0 to 180 degrees with respect to the level, via the under-actuated compliant mechanism. The robot's prototype is manufactured using 3Dprinting. Dry adhesives with pillar-patterned surface are fabricated. The adhesives then form a layer and cover the exterior surface of the flexible belts. Testing performances show that the robot can achieve stable scaling on the wall and ceiling with adjustable contact force, as well as the terrain-compatibility for surface transitioning.
Adhesive beads
The objective of this project is to develop a new form of cyanoacrylate also known as superglue, namely in the form of adhesive beads. The benefits of this research would lead to a new functional product that includes an active, liquid form of superglue in the center with a hard outer coating that, when needed, could be activated. This could be beneficial in situations when the adhesive needs to act very quickly. For example, the bead could be inserted into the respective area and then activated to start the bonding process. This would eliminate the time that the superglue spends in contact with the moisture in the air, which starts the curing process. The main function is an increase in bonding strength, decrease in time exposed to the air, and use in hard to reach locations.

The superglue has been successfully made into beads by mixing the superglue with acid. Producing a shell coating on the beads by adding a base to the acid-superglue mix at which time the outer surface of the bead cures while the inner portion remains as liquid glue. At a too basic pH the entire bead cures, and at a too acidic pH no shell forms. The technology is uses ph to set up a shell of superglue and try to quench the reaction so the center of the bead remains liquid and reactive.
Particulate Matter
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Enzyme mimetic bio-inorganic nanoparticles (Conference Presentation)
Enzymes play a crucial role in biochemical processes and are essential for many synthetic processes in industry. In spite of their great catalytic performance and high selectivity for material conversion, their chemical and/or thermal stability is a limiting factor for many processes that opt for a high throughput. Increasing the stability of enzymes thus promises considerable increase in productivity of numerous industrial processes. A promising pathway for such stability enhancement is the generation of hybrid bioinorganic nanomaterials that show catalytic properties similar to enzymes, but at the same time benefit from the chemical and thermal stability of the inorganic constituent. In this presentation we will show that a combination of inorganic nanoparticles with a surrounding protein shell can indeed mimic a variety of enzyme-analogue reactions in both activity and inhibition. Moreover, the catalytic activity can even be enhanced if the materials are exposed to environmental conditions under which traditional protein-based enzymes become inactive.
Flight II
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Robustness strategies in bio-inspired flight systems: morphology, dynamics and flight control
H. Liu, T. Nakata, R. Noda, et al.
Insect and bird size drones – micro air vehicles (MAV) that can perform autonomous flight in natural and man-made environment and hence suitable for environmental monitoring, surveillance, and assessment of hostile situations are now an active and well-integrated research area. Biological flapping-flight system design that has been validated through a long period of natural selection offers an alternative paradigm that can be scaled down in size, but normally brings lowspeed aerodynamics and flight control challenges in achieving autonomous flight. Thus mimetics in bioinspired flight systems is expected to be capable of providing with novel mechanisms and breakthrough technologies to dominate the future of MAVs. Flying insects that power and control flight by flapping wings perform excellent flight stability and manoeuvrability while steering and manoeuvring by rapidly and continuously varying their wing kinematics. Flapping wing propulsion, inspired by insects, birds and bats, possesses potential of high lift-generating capability under lowspeed flight conditions and may provide an innovative solution to the dilemma of small autonomous MAVs. In this study, with a specific focus on robustness strategies and intelligence in insect and bird flights in terms of morphology, dynamics and flight control, we present the state of the art of flying biomechanics in terms of flapping wing aerodynamics, flexible wing and wing-hinge dynamics, passive and active mechanisms in stabilization and control, as well as flapping flight in unsteady environments. We further highlight recent advances in biomimetics of insect-inspired flapping MAVs in concern with wing design and fabrication.
Transition flight control simulations of bioinspired FWMAV with extended unsteady vortex-lattice method
This study carries out the transient flight control simulation of a Flapping-Wing Micro Air Vehicle using Extended Unsteady Vortex-Lattice Method. This method uses the panel method and unsteady vortex-lattice (UVLM) method including the leading-edge suction analogy for leading-edge vortices (LEVs) effect and the vortex-core growth model for the effect of eddy viscosity in the vortex wake. This method has advantages in that it requires relatively less computational cost compared to CFD and provides more precise aerodynamic forces and moments than the conventional quasi-steady aerodynamic model. Based on the multibody dynamic analysis with the aerodynamic model, gainscheduling LQR controller is designed for non-linear system to track reference input.
Comparison of bio-inspired flapping foil propulsion systems with rotary propulsion
Srikanth Dharwada, Aman Agarwal, Prabhu Rajagopal
Conventional rotary thrusters used in underwater Remotely Operated Vehicles (ROV) suffer from disadvantages such as high noise, entangling with floating objects and limited efficiency. Our group has studied bio-inspired propulsion with a single caudal fin which overcomes some of these disadvantages. However, it still faces some problems such as low thrust density (thrust generated per unit volume of the thruster), pitch/yaw and centre of mass (COM) oscillations in the body increasing the energy cost of transport. The solution being proposed is a novel dual flapping foil arrangement actuated using a single motor which tackles the limitations of single flapping foil. Comparison of efficiency, maximum thrust and thrust density has been performed between single and dual flapping foil propulsion. Also, this solution is benchmarked against commercially available rotary thrusters. The results showed that thrust density of bioinspired propulsion was not at par with rotary thrusters. However, the efficiency obtained was comparable.
Soft Matter
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Bio-inspired passive variable recruitment of fluidic artificial muscles
Edward M. Chapman, Matthew Bryant
This paper explores the modeling and analysis of the effect of minimum actuation pressure previously observed in literature. This minimum pressure is similar in kind to the minimum amplitude of the signal for muscle actuation seen in mammalian muscles. This minimum actuation, or “threshold” pressure is used a method of mechanically encoding the control of FAM engagement and the actuation efficiency of a group, or ‘bundle’ of muscles with differing threshold pressures is compared with a single muscle of equivalent force and strain. The results of this analysis indicate the efficacy of using this design and control method; it is advantageous in cases where a range of displacements and forces are necessary.
Actuation of soft materials through ultrasonic atomization
Soft robotics have the potential to improve traditional robotics since soft materials are safer and more compliant to unpredictable surroundings. To date, various methods have been investigated to actuate such soft materials. The main objective of this research is to introduce a new method of soft robotic actuation through ultrasonic atomization. The mechanism of actuation is based on purposefully embedding pockets of liquid in a soft polymer matrix. It is known that, when a layer of liquid is subjected to ultrasonic waves, a capillary wave forms on the surface. When the amplitude of the ultrasonic wave exceeds a critical point, small droplets are ejected from crests of the capillary wave. The small droplets allow the liquid to evaporate at faster rates even when the temperature is below the boiling point, thereby building up vapor pressure and expanding the soft polymer matrix. Here, a soft structure was fabricated that enclosed a small amount of ethanol. Ultrasonic waves generated by a piezoelectric transducer atomized and evaporated ethanol in the expandable structure. During the expansion, temperature, displacement, and stress was measured to characterize the resulting actuation behavior of the system. Separate sets of tests were conducted on a hot plate to compare the effect of atomization versus evaporation. In addition, the voltage of the piezoelectric transducer was controlled to analyze the relationship between voltage and actuation rate. Finally, the durability of the expandable structure was also shown through cyclic actuation and cooling. The results showed the potential of ultrasonic atomization as a new mechanism for soft robotic actuation, where actuation could be produced and controlled in a noncontact manner (i.e., without requiring a tethered connection to deliver air or fluid).
Characterizing nitinol wire bond strength in silicone for artificial skin muscles
Paul Mazza, Michael Milenski, Anthony D. Santamaria, et al.
This study examines the bonding force between Nitinol wire and silicone polymer. The purpose is to understand the feasibility and limitations of using nitinol wire as an actuator in artificial skin. This study improves upon previous work, which studied silicone embedded nitinol and expands its scope by looking deeper into the wire/polymer configuration, and manufacturing process which can lead to air bubbles at the wire/silicone interface. Prior results were less consistent due to the presence of tiny bubbles in samples, which lead to variable maximum pulling forces between tests. This study addresses this issue, and improves the manufacturing process, so that the capacity of the bonding between wires and polymers can be increased.This is accomplished by using an injection molding method preceded by a vacuum stage.When samples are manufactured and tested with the improved method there is a significant improvement in the strength and consistency of results. A maximum pull force improvement of 32% was seen in the vacuum prepared samples. This lays the foundation for developing computer simulations of the artificial skin using experimentally verified data. Future work will continue to address the manufacturing process, material variants, as well as checking the effect of different wire diameters and materials. All this data will go into developing a predictive numerical model using commercial finite element analysis software, which will assist in the creation of more complex shapes of controllable artificial skin. These complex wire/polymer configurations will be used to address current biomedical issues, such as facial paralysis, and assisting burn victims, or in humanoid robotics.
Biomimetic polyimide-supported cuprous oxide as photocatalytic film with tunable hydrophobicity and enhanced thermal stability (Conference Presentation)
I-Hsiang Tseng, Li-Huan Kang
Flexible and thermally stable polyimide (PI) film containing hierarchical structure was synthesized as the substrate to support cuprous oxide for photocatalytic reduction of carbon dioxide. With the nanocasting technique, the structure on the leaves of Xanthosoma sagittifolium was duplicated on the surface of PI film. Followed by the ion-exchange process and adequate thermal-treatment, cuprous oxide nanoparticles were successfully immobilized on the artificial PI leaves and had the capability to photoreduce carbon dioxide. The biomimetic PI films obtained via two types of ion-exchange processes exhibited significant differences in UV-VIS absorption and in the depth distribution of cuprous oxide. With the selection of biomimetic structure, the hydrophobicity of the photocatalytic film was tunable that the photoreduction products were consequently varied. With the presence of hierarchical structure on the surface, the thermal stability of PI film was also enhanced. Therefore, the flexible photocatalytic film is a promising material for the application in the field requiring high mechanical and thermal stability, such as industrial flue-gas treatments.
Material Structures II
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Versatile strategies for the development of wood-based functional materials
Tobias Keplinger, Marion Frey, Ingo Burgert
Reaching a sustainable society represents one of the key challenges of the 21st century and wood as an abundant and renewable resource has the potential to serve as one of the main materials for this transition. In this regard different concepts for the development of novel wood-based functional materials, fabricated by the in situ formation of different materials systems are shown. Another focus is laid on densified cellulose composites, a novel material concept based on delignification and densification of wood, resulting in a high performance natural fibre reinforced composite material. This approach represents a promising alternative to common glass- and fiber reinforced composites but also to other manufacturing approaches such as 3D printing.
Poster Session
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Using the chemistry of seawater to make functional smart ports
Natural process design, is a biological mimicking system in which natural integrated systems are studied and then implemented for human use. Design with natural process is a drawing from the "experience" of evolution. To make an ocean port relies on using the same chemicals which undergo different forces from nature and use various natural processes such as occur in corrals. It integrates many separate functions such as self formation, sensing, repair, self recycling and improving the environment.
In-situ coating for CO2 conversion at tail pipes and in ambient air in which oxygen is given off: it makes coated concrete stronger
Natural systems balance CO2 gas overloads by sequestering it in limestone; this technology uptakes CO2 in a similar way. Making Portland cement accounts for 8-10% of CO2 emissions worldwide. Thus there is a tremendous opportunity to utilize this excess CO2 in a limestone like product, concrete. This coating technology takes up CO2 to provide a permanent CO2 sequestration site in concrete while releasing O2 and enhancing the strength and life span of concrete to create a significant environmental impact.
Development of a PVDF based artificial basilar membrane
Mohammadsadegh Saadatzi, Mohammad Nasser Saadatzi, Vahid Tavaf, et al.
In spite of many studies concerning the potential of auditory nerve actions, the timing of neural excitation in relation to basilar membrane motion is still not well understood. In this study, therefore, a Piezoelectric Artificial Basilar Membrane (PABM) is fabricated using Denton Explorer evaporator. The proposed dynamical system is made of polyvinylidene fluoride membrane on which 40 chromium electrodes were deposited with thickness close to 104 Å. The PABM sensor was tested with variable engineering parameters that contribute to its frequency selection capabilities. To characterize the frequency selectivity of the PABM, mechanical displacements were measured using a very precise high-resolution data acquisition board. When electrical and acoustic stimuli were applied, the measured resonance frequencies were in the ranges of 600to2000. These results demonstrate that the mechanical frequency selectivity of this PABM is close to the human communication frequency range (300–3000 Hz), which is a vital feature of potential auditory prostheses.