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Designing and Manufacturing Hard and Soft Mechanical Metamaterials
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Designing and Manufacturing Hard and Soft Mechanical Metamaterials

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Smart Materials".

Deadline for manuscript submissions: closed (20 September 2022) | Viewed by 8817

Special Issue Editor

Dr. Reza Hedayati

E-Mail Website
Guest Editor
Aerospace Structures and Materials (ASM), Delft University of Technology, Postbus 5, 2600 AA Delft, The Netherland
Interests: mechanical properties; mechanical behavior of materials; mechanical testing; mechanics of materials; finite element analysis; acoustics; solid mechanics; finite element modeling; biomechanics; biomaterials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Mechanical metamaterials are rationally designed materials composed of periodically repeating elements that are engineered to present exotic properties that cannot be found in nature. The apparent properties of mechanical metamaterials have a stronger dependency on their microgeometrical features rather than the base material they are made of. Even though several theoretical and conceptual designs have been presented since decades ago, many types of metamaterials have not been realized until very recently, mainly due to limitations in manufacturing and sufficient computing power.

Recent advancements in manufacturing technologies including additive manufacturing, lithography techniques, macro-, micro-, and nanofabrication techniques, and new material developments have enabled manufacturing of many new types of mechanical metamaterials with advanced functionalities and attractive properties never seen before.

This Special Issue explores the latest advances in designing and manufacturing of such functional structures made of metals, polymers, ceramics, etc. Such metamaterials can be either passive (keep their shape during their application) or active (change their shape upon request by the user).

Dr. Reza Hedayati
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Designer materials
  • Mechanical metamaterials
  • Advanced manufacturing
  • Advanced materials
  • Metasurfaces
  • Additive manufacturing
  • Biomaterials
  • Nanotechnology
  • Flexible and stretchable bioelectronic devices
  • Shape memory materials
  • Self-assembling soft structures
  • Origami and Kirigami
  • Soft robotics
  • Micro-to-nano fabrication of soft biomaterials

Published Papers (2 papers)

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Research

29 pages, 12202 KiB  
Article
Femur Auxetic Meta-Implants with Tuned Micromotion Distribution
by Naeim Ghavidelnia, Mahdi Bodaghi and Reza Hedayati
Materials 2021, 14(1), 114; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14010114 - 29 Dec 2020
Cited by 48 | Viewed by 4484
Abstract
Stress shielding and micromotions are the most significant problems occurring at the bone-implants interface due to a mismatch of their mechanical properties. Mechanical 3D metamaterials, with their exceptional behaviour and characteristics, can provide an opportunity to solve the mismatch of mechanical properties between [...] Read more.
Stress shielding and micromotions are the most significant problems occurring at the bone-implants interface due to a mismatch of their mechanical properties. Mechanical 3D metamaterials, with their exceptional behaviour and characteristics, can provide an opportunity to solve the mismatch of mechanical properties between the bone and implant. In this study, a new porous femoral hip meta-implant with graded Poisson’s ratio distribution was introduced and its results were compared to three other femoral hip implants (one solid implant, and two porous meta-implants, one with positive and the other with a negative distribution of Poisson’s ratio) in terms of stress and micromotion distributions. For this aim, first, a well-known auxetic 3D re-entrant structure was studied analytically, and precise closed-form analytical relationships for its elastic modulus and Poisson’s ratio were derived. The results of the analytical solution for mechanical properties of the 3D re-entrant structure presented great improvements in comparison to previous analytical studies on the structure. Moreover, the implementation of the re-entrant structure in the hip implant provided very smooth results for stress and strain distributions in the lattice meta-implants and could solve the stress shielding problem which occurred in the solid implant. The lattice meta-implant based on the graded unit cell distribution presented smoother stress-strain distribution in comparison with the other lattice meta-implants. Moreover, the graded lattice meta-implant gave minimum areas of local stress and local strain concentration at the contact region of the implants with the internal bone surfaces. Among all the cases, the graded meta-implant also gave micromotion levels which are the closest to values reported to be desirable for bone growth (40 µm). Full article
(This article belongs to the Special Issue Designing and Manufacturing Hard and Soft Mechanical Metamaterials)
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11 pages, 3479 KiB  
Article
Pneumatically-Actuated Acoustic Metamaterials Based on Helmholtz Resonators
by Reza Hedayati and Sandhya Lakshmanan
Materials 2020, 13(6), 1456; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13061456 - 23 Mar 2020
Cited by 22 | Viewed by 3513
Abstract
Metamaterials are periodic structures which offer physical properties not found in nature. Particularly, acoustic metamaterials can manipulate sound and elastic waves both spatially and spectrally in unpreceded ways. Acoustic metamaterials can generate arbitrary acoustic bandgaps by scattering sound waves, which is a superior [...] Read more.
Metamaterials are periodic structures which offer physical properties not found in nature. Particularly, acoustic metamaterials can manipulate sound and elastic waves both spatially and spectrally in unpreceded ways. Acoustic metamaterials can generate arbitrary acoustic bandgaps by scattering sound waves, which is a superior property for insulation properties. In this study, one dimension of the resonators (depth of cavity) was altered by means of a pneumatic actuation system. To this end, metamaterial slabs were additively manufactured and connected to a proportional pressure control unit. The noise reduction performance of active acoustic metamaterials in closed- and open-space configurations was measured in different control conditions. The pneumatic actuation system was used to vary the pressure behind pistons inside each cell of the metamaterial, and as a result to vary the cavity depth of each unit cell. Two pressures were considered, P = 0.05 bar, which led to higher depth of the cavities, and P = 0.15 bar, which resulted in lower depth of cavities. The results showed that by changing the pressure from P = 0.05 (high cavity depth) to P = 0.15 (low cavity depth), the acoustic bandgap can be shifted from a frequency band of 150–350 Hz to a frequency band of 300–600 Hz. The pneumatically-actuated acoustical metamaterial gave a peak attenuation of 20 dB (at 500 Hz) in the closed system and 15 dB (at 500 Hz) in the open system. A step forward would be to tune different unit cells of the metamaterial with different pressure levels (and therefore different cavity depths) in order to target a broader range of frequencies. Full article
(This article belongs to the Special Issue Designing and Manufacturing Hard and Soft Mechanical Metamaterials)
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