Periodic Reporting for period 2 - BOHEME (Bio-Inspired Hierarchical MetaMaterials)
Reporting period: 2021-07-01 to 2022-12-31
BOHEME’s ambitious goal is to design and realise a new class of bioinspired mechanical metamaterials for novel applicative tools in diverse technological fields. Metamaterials exhibit exotic vibrational properties currently unavailable in Nature, and numerous important applications are emerging. However, universally valid design criteria are currently lacking, and their effectiveness is presently restricted to limited frequency ranges. BOHEME starts from an innovative assumption, increasingly supported by experimental evidence, that the working principle behind metamaterials is already exploited in Nature, and that through evolution, this has given rise to optimised designs for impact damping and other wave manipulation purposes.
From the perspective of basic science, the project aims to explore biological structural materials for evidence of this, to investigate novel optimised bio inspired designs (e.g. porous hierarchical structures spanning various length scales,cochlea-inspired spirals that select sound frequencies, spider web-inspired frames that attenuate vibrations) using state-of-the-art analytical and numerical approaches, to design and manufacture vibrationally effective structures, and to experimentally verify their performance over wide frequency ranges.
From the point of view of applications, BOHEME will address technological sectors over various wavelength scales, from low-frequency vibration control (such as vibrations generated by trains), to noise abatement (e.g. in MRI scanners), to nondestructive testing using “acoustic lenses”, to resonating floater arrays to protect against coastal erosion from ocean waves. Industrial partners will provide know-how for proof of principle experiments and possible prototypes. The project is ambitious and inherently multidisciplinary, involving research in biology, mathematics, physics, materials science, structural and ocean engineering, drawing from scientific excellence of the partners. It involves theoretical, numerical and experimental aspects, and is a high-impact endeavour, from which basic science, EU industry and society can benefit.
From the perspective of basic science, the project aims to explore biological structural materials for evidence of this, to investigate novel optimised bio inspired designs (e.g. porous hierarchical structures spanning various length scales,cochlea-inspired spirals that select sound frequencies, spider web-inspired frames that attenuate vibrations) using state-of-the-art analytical and numerical approaches, to design and manufacture vibrationally effective structures, and to experimentally verify their performance over wide frequency ranges.
From the point of view of applications, BOHEME will address technological sectors over various wavelength scales, from low-frequency vibration control (such as vibrations generated by trains), to noise abatement (e.g. in MRI scanners), to nondestructive testing using “acoustic lenses”, to resonating floater arrays to protect against coastal erosion from ocean waves. Industrial partners will provide know-how for proof of principle experiments and possible prototypes. The project is ambitious and inherently multidisciplinary, involving research in biology, mathematics, physics, materials science, structural and ocean engineering, drawing from scientific excellence of the partners. It involves theoretical, numerical and experimental aspects, and is a high-impact endeavour, from which basic science, EU industry and society can benefit.
In the first 36 months, the project has developed theoretical and numerical tools and performed the analysis of selected natural systems, to inspire the design of innovative metamaterial architectures based, and begin to implement them in the selected application areas. A large database of natural systems with interesting dynamic behaviour has been acquired from the literature, and experimental characterization tests have been performed on several of them. Some important systems such as spider webs, suture joints, shells, bones, or the cochlea have been structurally and mechanically characterised for further analysis, using CT scans, AFM and nanoindentation, and ultrasonic experiments, to be compared with FEM predictions. This analysis has led to the choice basic hierarchical metamaterial designs, with specific properties to be replicated and optimized in the creation of bioinspired architectures. Several promising designs were selected for further evaluation. Six main categories are currently under consideration: 1) hierarchical frame (including spider-web like); 2) hierarchical porous (diatom-cell like); 3) Hierarchical and non-hierarchical composite (with sutures); 4) Spiral-like (chiral, cochlea-like); 5) Fractal, self-similar branching. 6) Dynamically tunable structures. Extensive numerical and experimental studies have been performed on these geometries.
Simultaneously, mathematical and numerical tools have been developed to allow faster and more accurate simulations to aid designs. These include spectral methods for waveguide modes and infinite media, multiple scattering techniques and asymptotic methods, homogeneization procedures and advanced meshing approaches.
These methods have been applied to design and simulate innovative architectures, drawing inspiration from biological systems, with optimized structures and enhanced functionalities. For example, we have conceived tunable metamaterials using light stimuli, which can be used as mechanical filters and switches; designed hierarchical porous structures with extreme auxetic behaviour and tunable topological wave guiding behaviour; exploited spider-web architectures to devise hierarchical frame structures with multiple band gap ranges; imitated the structure of trabecular bone to obtain lightweight and strong metamaterials offering superior vibration attenuation capacities; experimentally validated rainbow-based metamaterials with an application in energy harvesting.
Results have led to about 80 publications in international journals, including Nature Communications and Advanced Functional Materials, and disseminated in various seminars and presentations. A patent application has already been submitted by one of the industrial partners on a related application.
Simultaneously, mathematical and numerical tools have been developed to allow faster and more accurate simulations to aid designs. These include spectral methods for waveguide modes and infinite media, multiple scattering techniques and asymptotic methods, homogeneization procedures and advanced meshing approaches.
These methods have been applied to design and simulate innovative architectures, drawing inspiration from biological systems, with optimized structures and enhanced functionalities. For example, we have conceived tunable metamaterials using light stimuli, which can be used as mechanical filters and switches; designed hierarchical porous structures with extreme auxetic behaviour and tunable topological wave guiding behaviour; exploited spider-web architectures to devise hierarchical frame structures with multiple band gap ranges; imitated the structure of trabecular bone to obtain lightweight and strong metamaterials offering superior vibration attenuation capacities; experimentally validated rainbow-based metamaterials with an application in energy harvesting.
Results have led to about 80 publications in international journals, including Nature Communications and Advanced Functional Materials, and disseminated in various seminars and presentations. A patent application has already been submitted by one of the industrial partners on a related application.
Progress beyond the state of the art in BOHEME should be the generation of optimised metamaterials that are effective in multiple frequency ranges, include multifunctionality (e.g. useful static as well as dynamic properties), additional functionality such as tunability, and are based on systematic bioinspired design criteria, which can be exploited in applications at multiple size scales. Expected impacts involve low-frequency vibration control (including from transport infrastructure like trains), noise abatement (focusing on the caser of MRI scanners), nondestructive testing, coastal protection from ocean waves. Exploitation of the project results should be delivered by the two participating SMEs, which can bring commercial advantages to related EU industrial sectors, contributing also to the EU sustainable development goals 9 (Innovation and Infrastructure) and 11 (Sustainable cities and communities).