I am a PhD Researcher that focuses on characterising the microstructural behaviour of superalloys.
Follow this pinboard to explore the potential of biomimetic materials
In 10 Seconds? Research within the field of biomimetics is becoming ever more popular. Biomimetic material means a material that has been developed by man to ‘mimic’ the properties found in nature. Sea cucumbers found in the sea were of particular interest to material scientists because they have the ability to transform from a soft/squishy state to becoming stiff.
Don’t believe it? Materials scientists developed a material that could transition from stiff too soft through using water as a stimulus to ‘mimic’ the property found in nature. Check out the link on the pinboard - ‘Biomimetic mechanically adaptive nanocomposites’.
The science behind the transition
The newly developed nanocomposite material is made up like any other composite material i.e. matrix and reinforced fibres (providing the mechanical strength). The matrix in this case is polymer based and the fibres are manufactured from cellulose - which forms strong hydrogen bonds with the surrounding matrix.
The research group manufactured this material so that the strong interactions (bonds) between the matrix and the fibre can be essentially switched on and off by a stimuli, in this case water – the water disrupts the bonds that are in place within the matrix, particularly the bonds between the reinforced fibres and the surface hydroxyl units.
Abstract: Fruit walls as well as nut and seed shells typically perform a multitude of functions. One of the biologically most important functions consists in the direct or indirect protection of the seeds from mechanical damage or other negative environmental influences. This qualifies such biological structures as role models for the development of new materials and components that protect commodities and/or persons from damage caused for example by impacts due to rough handling or crashes. We were able to show how the mechanical properties of metal foam based components can be improved by altering their structure on various hierarchical levels inspired by features and principles important for the impact and/or puncture resistance of the biological role models, rather than by tuning the properties of the bulk material. For this various investigation methods have been established which combine mechanical testing with different imaging methods, as well as with in situ and ex situ mechanical testing methods. Different structural hierarchies especially important for the mechanical deformation and failure behaviour of the biological role models, pomelo fruit (Citrus maxima) and Macadamia integrifolia, were identified. They were abstracted and transferred into corresponding structural principles and thus hierarchically structured bio-inspired metal foams have been designed. A production route for metal based bio-inspired structures by investment casting was successfully established. This allows the production of complex and reliable structures, by implementing and combining different hierarchical structural elements found in the biological concept generators, such as strut design and integration of fibres, as well as by minimising casting defects. To evaluate the structural effects, similar investigation methods and mechanical tests were applied to both the biological role models and the metallic foams. As a result an even deeper quantitative understanding of the form-structure-function relationship of the biological concept generators as well as the bio-inspired metal foams was achieved, on deeper hierarchical levels and overarching different levels.
Pub.: 20 Jul '16, Pinned: 23 Apr '17
Abstract: Insect- and bird-size drones-micro air vehicles (MAV) that can perform autonomous flight in natural and man-made environments are now an active and well-integrated research area. MAVs normally operate at a low speed in a Reynolds number regime of 10(4)-10(5) or lower, in which most flying animals of insects, birds and bats fly, and encounter unconventional challenges in generating sufficient aerodynamic forces to stay airborne and in controlling flight autonomy to achieve complex manoeuvres. Flying insects that power and control flight by flapping wings are capable of sophisticated aerodynamic force production and precise, agile manoeuvring, through an integrated system consisting of wings to generate aerodynamic force, muscles to move the wings and a control system to modulate power output from the muscles. In this article, we give a selective review on the state of the art of biomechanics in bioinspired flight systems in terms of flapping and flexible wing aerodynamics, flight dynamics and stability, passive and active mechanisms in stabilization and control, as well as flapping flight in unsteady environments. We further highlight recent advances in biomimetics of flapping-wing MAVs with a specific focus on insect-inspired wing design and fabrication, as well as sensing systems.This article is part of the themed issue 'Moving in a moving medium: new perspectives on flight'.
Pub.: 17 Aug '16, Pinned: 23 Apr '17
Abstract: The cleanup of accidental oil spills in water is an enormous challenge; conventional oil sorbents absorb large amounts of water in addition to oil and other cleanup methods can cause secondary pollution. In contrast, fresh leaves of the aquatic ferns Salvinia are superhydrophobic and superoleophilic, and can selectively absorb oil while repelling water. These selective wetting properties are optimal for natural oil absorbent applications and bioinspired oil sorbent materials. In this paper we quantify the oil absorption capacity of four Salvinia species with different surface structures, water lettuce (Pistia stratiotes) and Lotus leaves (Nelumbo nucifera), and compare their absorption capacity to artificial oil sorbents. Interestingly, the oil absorption capacities of Salvinia molesta and Pistia stratiotes leaves are comparable to artificial oil sorbents. Therefore, these pantropical invasive plants, often considered pests, qualify as environmentally friendly materials for oil spill cleanup. Furthermore, we investigated the influence of oil density and viscosity on the oil absorption, and examine how the presence and morphology of trichomes affect the amount of oil absorbed by their surfaces. Specifically, the influence of hair length and shape is analyzed by comparing different hair types ranging from single trichomes of Salvinia cucullata to complex eggbeater-shaped trichomes of Salvinia molesta to establish a basis for improving artificial bioinspired oil absorbents.
Pub.: 17 Aug '16, Pinned: 23 Apr '17
Abstract: Passive mechanosensing is an energy-efficient and effective recourse for autonomous underwater vehicles (AUVs) for perceiving their surroundings. The passive sensory organs of aquatic animals have provided inspiration to biomimetic researchers for developing underwater passive sensing systems for AUVs. This work is inspired by the 'integumentary sensory organs' (ISOs) which are dispersed on the skin of crocodiles and are equipped with slowly adapting (SA) and rapidly adapting (RA) receptors. ISOs assist crocodiles in locating the origin of a disturbance, both on the water surface and under water, thereby enabling them to hunt prey even in a dark environment and turbid waters. In this study, we construct SA dome receptors embedded with microelectromechanical systems (MEMS) piezoresistive sensors to measure the steady-state pressures imparted by flows and RA dome receptors embedded with MEMS piezoelectric sensors to detect oscillatory pressures in water. Experimental results manifest the ability of SA and RA dome receptors to sense the direction of steady-state flows and oscillatory disturbances, respectively. As a proof of concept, the SA domes are tested on the hull of a kayak under various pressure variations owing to different types of movements of the hull. Our results indicate that the dome receptors are capable of discerning the angle of attack and speed of the flow.
Pub.: 23 Aug '16, Pinned: 23 Apr '17
Abstract: Nature has shaped effective biological sensory systems to receive complex stimuli generated by organisms moving through water. Similar abilities have not yet been fully developed in artificial systems for underwater detection and monitoring, but such technology would enable valuable applications for military, commercial, and scientific use. We set out to design a fluid motion sensor array inspired by the searching performance of seals, which use their whiskers to find and follow underwater wakes. This sensor prototype, called the Wake Information Detection and Tracking System (WIDTS), features multiple whisker-like elements that respond to hydrodynamic disturbances encountered while moving through water. To develop and test this system, we trained a captive harbor seal (Phoca vitulina) to wear a blindfold while tracking a remote-controlled, propeller-driven submarine. After mastering the tracking task, the seal learned to carry the WIDTS adjacent to its own vibrissal array during active pursuit of the target. Data from the WIDTS sensors describe changes in the deflection angles of the whisker elements as they pass through the hydrodynamic trail left by the submarine. Video performance data show that these detections coincide temporally with WIDTS-wake intersections. Deployment of the sensors on an actively searching seal allowed for the direct comparison of our instrument to the ability of the biological sensory system in a proof-of-concept demonstration. The creation of the WIDTS provides a foundation for instrument development in the field of biomimetic fluid sensor technology.
Pub.: 01 Sep '16, Pinned: 23 Apr '17
Abstract: The aim of this study is the biomimetic optimisation of branched fibre-reinforced composites based on the detailed analysis of biological concept generators. The methods include analyses of the functional morphology and biomechanics of arborescent monocotyledons and columnar cacti as well as measurements and modelling of mechanical properties of biomimetic fibre-reinforced composites. The key results show evidence of notch stress reduction by optimised stem-branch-attachment morphology in monocotyledons and columnar cacti. It could be shown that some of these highly interesting properties can be transferred into biomimetic fibre-reinforced composites.
Pub.: 08 Sep '16, Pinned: 23 Apr '17
Abstract: The increasing demand for material and energy efficient products requires new strategies for designing and developing these products. For this, biomimetics is a promising approach adopting the strategies of living organisms to cope with their environmental conditions as inspiration for solving engineering problems. The evolutionary optimized biological models are often characterized by functional integration, a low environmental impact and high level of sustainability.In this paper we describe the general approach of such a biomimetic workflow on the example of topology optimization based on the model of natural ramifications. We compare the load adaptations in cactus ramifications to the load-adaptive growth, which can be found in tree branchings.Compared to trees, the branches of columnar cacti taper towards the branch base with a pronounced constriction at the attachment point. In addition, the cactus wood features distinct indentations on the upper and lower side of the branch base which can be regarded as relief notches helping to modify the stress distribution in these regions with unfavorable fiber course.These results of our research point to a cactus specific load adaptation strategy that might be helpful for the design of fiber reinforced composite structures with restricted design space.
Pub.: 17 Nov '16, Pinned: 23 Apr '17
Abstract: Locomotion of water beetles have been widely studied in biology owing to their remarkable swimming skills. Inspired by the oar-like legs of water beetles, designing a robot that swims under the principle of drag-powered propulsion can lead to highly agile mobility. But its motion can easily be discontinuous and jerky due to backward motions (i.e., retraction) of the legs. Here we proposed novel hair-like appendages and considered their coordination to achieve steady and efficient swimming on the water surface. First of all, several design schemes and a fabrication method of the hair-like appendages, which can passively adjust their projected area while obtaining enough thrust, were proposed. As do water beetles in nature, the coordination between the two pairs of legs were also investigated to achieve steady swimming without backward movement by varying the beating frequency and phase of the legs. To verify the functionality of the hair-like appendages and their coordination, six different types of appendages were fabricated, and two robots (one with single pair of legs and the other with two pairs of legs) were built. Locomotion of the robots were extensively compared through experiments, and it was found that a steady swimming was achieved by properly coordinating the two pairs of legs without sacrificing their speed. Also, owing to the less velocity fluctuation during the swimming, it was shown that using the two pairs of legs was energy efficient than the robot with singe pair of legs.
Pub.: 12 Apr '17, Pinned: 23 Apr '17
Abstract: Cellular composites are of significant interest to the materials research community as they often possess multifunctional physical properties. To meet the application requirements, various design and fabrication methods are adopted to produce highly porous composites. In this work, the one-step and two-step approaches for efficient design and prediction of cellular structure's performance were presented for developing ultra-lightweight and high-strength cellular composites reinforced by discontinuous fibers. The topology designs of a 2D honeycomb hexagon model, a 2D cuttlefish model, and a 3D octahedron model, inspired by biomimetics, were presented. Computer modeling based on finite element analysis was conducted on the periodic representative volume elements identified from the cellular structural models to characterize the designed cellular composites' performance and properties. Additive manufacturing technique (3D printing) was used for prototyping the design, and experimental tests were carried out for validating the design methodology.
Pub.: 20 Mar '17, Pinned: 23 Apr '17
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