News


11/10/2016 Workshop on "Advances in Mechanical Metamaterials" organized by Dr. Marco Miniaci and Dr. Anastasiia O. Krushynska has been held at the University of Trento, Italy, in cooperation with Dr. Federico Bosia, Prof. Nicola M. Pugno, and Prof. D. Bigoni.
01/12/2015 Work on metamaterial seismic shields highlighted in " La Stampa/Origami, and an interview published on PlanetErde.de
28/07/2016 Dr. Anastasiia O. Krushynska has received an IACM Fellowship for Early Career Female Researchers and delivered a keynote talk on spider-web inspired mechanical metamaterials at WCCM XII & APCOM VI in Seoul, South Korea.
01/01/2016 Dr. Anastasiia O. Krushynska has started a T2M Postdoctoral Fellowship in Mechanics of Elastic Metamaterials on the topic of "TuNAMM: Tunable nonlinear acoustic metamaterials" under the Marie Sklodowska-Curie grant within the framework of the European Union's 7th Framework programme for research and innovation.
01/12/2015 Dr. Gianluca Costagliola has started a postdoc fellowship on the topic of contact and friction of biological and bioinspired surfaces

Research Interests


1. Bio-inspired materials:



Many biological systems are characterized by hierarchical structures, i.e. they are composed by smaller components, which can be further composed by other structures at smaller length scales. This hierarchical organization, spanning over many levels with different interactions and across many orders of magnitude of length scale, provides peculiar mechanical properties, so that the whole system is more that the simple sum of its single constituents. In Nature, hierarchical structures are found in biological tissues, e.g. spider silk, tendons, and bones, but it also derives from evolutionary adaptation of anatomical parts, as the gecko paws, whose astonishing adhesive properties attracted in recent years increasing interests. The fundamental aim of research on bio-inspired materials is to mimic Nature in order to design artificial materials with new mechanical properties by exploiting mainly structural organization. By means of hierarchy it is possible to tune material properties such as strength, toughness, adhesion, friction. Our research focus on these aspects by means of numerical simulations and simplified models (e.g. fiber bundle model, random fuse model, spring-block model) aiming to highlight the fundamental mechanisms acting in presence of hierarchical structure and to identify the parameters allowing to modify the macroscopic mechanical properties.

Further information:
S. Signetti , F. Bosia , N. M. Pugno, "Computational modeling of the mechanics of hierarchical materials",
" MRS Bulletin 41, 694-699 (2016)


2. Friction of structured surfaces:



The fundamental laws of friction were already understood by Leonardo da Vinci, and later they were formulated in classical mechanics in the Amonton-Coulomb friction law: the static friction force is proportional to the applied normal load and independent of the apparent contact surface, and the kinetic friction is independent of the sliding velocity. Despite the apparent simplicity, this macroscopic emergent behaviour is actually the sum of different microscopic interactions, spanning from inter-atomic potentials and molecular adhesion forces, to asperity roughness and elastic plastic surface deformation. Providing a unified description of the whole phenomenon from atomistic to macroscopic length scale is an open problem in tribology. The situation is much more complicated if the surfaces are characterized by artificial structures, e.g. grooves, cavities or hierarchical patterning, modifying the geometry of the contact points. The aim of our research is to understand how the global friction coefficients are modified by surface patterning and what is the role of the hierarchy.
Further information:
G. Costagliola, F. Bosia, N. M. Pugno,
"Static and dynamic friction of hierarchical surfaces", arXiv:1609.08846, accepted for publication in Phys. Rev. E (2016)


3. Sound-proof metamaterials:



Spider silk is well-known for its outstanding combination of being lightweight and extremely tough and strong compared to many natural and engineering materials. We designed an acoustic metamaterial made of periodically repeating spider-web geometries inspired by the golden silk orb-weaver, also called the Nephila spider. This architecture, combined with the variable elastic properties of radial and circumferential silk, is capable of attenuating and absorbing vibrations in wide frequency ranges, despite being lightweight. The performed parametric study demonstrates that this new design is very efficient at inhibiting low-frequency sound and is more easily tuned to different frequencies than other sound-controlling materials. Combined with the stiffening mechanical properties and the heterogeneity of spider silk, the tunable acoustic properties demonstrated in our work suggest that spider-web-inspired metamaterials could lead to a new class of applications for controlling vibrations. Possibilities include earthquake protection for suspended bridges and buildings, noise reduction, sub-wavelength imaging, and acoustic cloaking. At smaller scales, the same type of structures could be used for wave attenuation in the acoustic range, such as for sound abatement deriving from road or rail infrastructures.

Further information:
M. Miniaci, A.O. Krushynska, A.B. Movchan, F. Bosia, N.M. Pugno,
" Spider-web inspired acoustic metamaterials", Applied Physics Letters, 109 (7): 071905, 2016


4. Metamaterials for seismic wave abatement:



Earthquakes are the most catastrophic natural events affecting mankind. Every year there occurs a large number of earthquakes around the world accounting for almost 60% of all disaster-related mortality. Nowadays, traditional seismic isolation systems are based on vibration isolation strategies. In general, these systems are difficult to implement retrospectively, especially in historical buildings, and mostly they are applied locally. As an alternative, we propose to use large-scale metamaterials inhibiting the propagation of incoming waves through interference effects, to protect wider areas without direct modifications to existing structures. Marco Miniaci came to the idea of using large-scale phononic structures seismic wave mitigation during his PhD project at the University of Bologna. Later, he proceeded to work on this topic together with Anastasiia Krushynska, who investigated the viscoelastic effects of surrounding soils on attenuation performance of the metamaterial structures. Together with the added parametric studies, full-field wave displacement and stress maps, as well as risk mitigation analysis, these results have been summarized in the publications below.

Further information:
M. Miniaci, A.O. Krushynska, F. Bosia, N.M. Pugno,
"Large scale mechanical metamaterials as seismic shields", New Journal of Physics, 18: 083041, 2016


5. Hierarchical metamaterials:



Hierarchical structures with constituents over multiple length scales are found in various natural materials like bones, shells, spider silk and others, all of which display enhanced quasistatic mechanical properties, such as high specific strength, stiffness and toughness. At the same time, the role of hierarchy on the dynamic behaviour of metamaterials remains largely unexplored. Our study assesses the effect of bio-inspired hierarchical organization as well as of viscoelasticity on the wave attenuation properties of continuous mechanical metamaterials. We consider single-phase metamaterials formed by self-similar unit cells with different hierarchical levels and types of hierarchy. Results highlight a number of advantages through the introduction of structural hierarchy. Band gaps relative to the corresponding non-hierarchical structures are mostly preserved, while additional "hierarchically-induced" band gaps appear, with novel properties with respect to known local resonance or Bragg scattering mechanisms. Additionally, some hierarchical configurations allow the tuning of the band gap frequencies of regular metamaterial to lower frequencies, with a simultaneous significant reduction of the global structural weight. We show that even small viscoelastic effects, not treated in the current literature, are essential in determining this behaviour. The approach we propose allows the addition of hierarchical elements to existing metamaterial configurations, with the corresponding improvement of the wave damping properties, thus providing indications for the design of structures for practical applications.

Further information:
M. Miniaci, A.O. Krushynska, F. Bosia, N.M. Pugno,
"Bio-inspired hierarchical dissipative metamaterials", arXiv:1606.03596v1,2016


Collaborating Institution:


Funding








BIHSNAM : "Bioinspired Hierarchical Super Nanomaterials"
Duration: 2012-2016
Funding: ERC Starting Grant n.281967
Principal Investigator: Nicola Pugno (University of Trento)
Additional participant: Federico Bosia
Total Budget: 1,000,400 Euro
Local Budget: 150,000 Euro

TuNAMM : "Tunable Nonlinear Acoustic Metamaterials"
Duration: 2016-2017
Funding: Marie Sklodowska-Curie grant N. 609402-2020 researchers: Train to Move (T2M)
Principal Investigator: Anastasiia Krushynska (University of Torino)
Additional participant: Federico Bosia
Total Budget: 53,500 Euro
NEUROFIBRES: "Biofunctionalised Electroconducting Microfibres for the Treatment of Spinal Cord Injury"
Duration: 2017-2020
Funding: FET Proactive n.732344
Principal Investigator: Jorge E. Collazos-Castro (Servicio de Salud de Castilla La Mancha, Spain)
Third party: Federico Bosia
Total Budget: 5,094,120 Euro
Local Budget: 80,000 Euro

COST Action CA15216
Title: "European Network of Bioadhesion Expertise"
Duration: 2016-2020
Funding: EU Framework Programme Horizon 2020
Supporting institution: COST
Coordinator: Dr Stanislav GORB, University of Kiel(Germany)
COST Action CA15125 DENORMS
Title: "Design for Noise Reducing Materials and Structures"
Duration: 2016-2020
Funding: EU Framework Programme Horizon 2020
Supporting institution: COST
Coordinator: Mr Jean-Philippe Groby, CNRS (France)

Recent publications


F. Bosia, E. Lepore, N. T. Alvarez, P. Miller, V. Shanov, N. M. Pugno,
"Knotted synthetic polymer or carbon nanotube microfibres with enhanced toughness, up to 1400 J/g",
Carbon 102, 116-125 (2016)

G. Costagliola, F. Bosia, N. M. Pugno,
"Static and dynamic friction of hierarchical surfaces",
arXiv:1609.08846, accepted for publication in Phys. Rev. E (2016)

M. Miniaci, A.O. Krushynska, A.B. Movchan, F. Bosia, N.M. Pugno,
"Spider-web inspired acoustic metamaterials",
Applied Physics Letters, 109 (7): 071905, 2016

M. Miniaci, A.O. Krushynska, F. Bosia, N.M. Pugno,
"Large scale mechanical metamaterials as seismic shields",
New Journal of Physics, 18: 083041, 2016

A.O. Krushynska, M. Miniaci, F. Bosia, N.M. Pugno,
"Coupling local resonance with Bragg band gaps in single-phase mechanical metamaterials",
Extreme Mechanics Letters, in press (2016)