Special Issue "Soft Materials"

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

Deadline for manuscript submissions: 31 October 2021.

Special Issue Editor

Prof. Dr. Stephan Rudykh
E-Mail Website
Guest Editor
Department of Mechanical Engineering, University of Wisconsin—Madison, Madison, WI 53706, USA
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Soft materials is an increasingly active field of research driving science and technology into new exciting directions. Large deformations coupled with various multiphysics phenomena and instabilities at different length scales open an immensely rich research arena. This offers unique opportunities to develop multifunctional materials and devices with novel properties, through the targeted design of material composition and microstructural geometry. Moreover, soft materials represent essential components in biological tissues, a topic of extreme interest for bio-medical applications.

This Special Issue will focus on recent experimental, computational, theoretical and manufacturing advances in the broad field of Soft Materials.

Prof. Dr. Stephan Rudykh
Guest Editor

Manuscript Submission Information

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Keywords

  • Electroactive and magnetoactive elastomers (EAP, DE, MRE, MAE, IPMC)
  • Hydrogels and other soft wet materials
  • Liquid crystal elastomers
  • Shape-memory and light-sensitive polymers
  • Instabilities in soft materials
  • Fracture, and adhesion in soft materials
  • Soft biological and bio-inspired materials
  • Multiphysics phenomena in soft materials
  • Wave propagation and dynamics of soft materials
  • 3D/4D printing and fabrication of soft materials
  • Soft Robotics or Machines
  • Mechanical Metamaterials

Published Papers (4 papers)

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Research

Open AccessArticle
The Emergence of Sequential Buckling in Reconfigurable Hexagonal Networks Embedded into Soft Matrix
Materials 2021, 14(8), 2038; https://doi.org/10.3390/ma14082038 - 18 Apr 2021
Viewed by 276
Abstract
The extreme and unconventional properties of mechanical metamaterials originate in their sophisticated internal architectures. Traditionally, the architecture of mechanical metamaterials is decided on in the design stage and cannot be altered after fabrication. However, the phenomenon of elastic instability, usually accompanied by a [...] Read more.
The extreme and unconventional properties of mechanical metamaterials originate in their sophisticated internal architectures. Traditionally, the architecture of mechanical metamaterials is decided on in the design stage and cannot be altered after fabrication. However, the phenomenon of elastic instability, usually accompanied by a reconfiguration in periodic lattices, can be harnessed to alter their mechanical properties. Here, we study the behavior of mechanical metamaterials consisting of hexagonal networks embedded into a soft matrix. Using finite element analysis, we reveal that under specific conditions, such metamaterials can undergo sequential buckling at two different strain levels. While the first reconfiguration keeps the periodicity of the metamaterial intact, the secondary buckling is accompanied by the change in the global periodicity and formation of a new periodic unit cell. We reveal that the critical strains for the first and the second buckling depend on the metamaterial geometry and the ratio between elastic moduli. Moreover, we demonstrate that the buckling behavior can be further controlled by the placement of the rigid circular inclusions in the rotation centers of order 6. The observed sequential buckling in bulk metamaterials can provide additional routes to program their mechanical behavior and control the propagation of elastic waves. Full article
(This article belongs to the Special Issue Soft Materials)
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Open AccessArticle
Energy Absorption and Mechanical Performance of Functionally Graded Soft–Hard Lattice Structures
Materials 2021, 14(6), 1366; https://doi.org/10.3390/ma14061366 - 11 Mar 2021
Cited by 1 | Viewed by 932
Abstract
Today, the rational combination of materials and design has enabled the development of bio-inspired lattice structures with unprecedented properties to mimic biological features. The present study aims to investigate the mechanical performance and energy absorption capacity of such sophisticated hybrid soft–hard structures with [...] Read more.
Today, the rational combination of materials and design has enabled the development of bio-inspired lattice structures with unprecedented properties to mimic biological features. The present study aims to investigate the mechanical performance and energy absorption capacity of such sophisticated hybrid soft–hard structures with gradient lattices. The structures are designed based on the diversity of materials and graded size of the unit cells. By changing the unit cell size and arrangement, five different graded lattice structures with various relative densities made of soft and hard materials are numerically investigated. The simulations are implemented using ANSYS finite element modeling (FEM) (2020 R1, 2020, ANSYS Inc., Canonsburg, PA, USA) considering elastic-plastic and the hardening behavior of the materials and geometrical non-linearity. The numerical results are validated against experimental data on three-dimensional (3D)-printed lattices revealing the high accuracy of the FEM. Then, by combination of the dissimilar soft and hard polymeric materials in a homogenous hexagonal lattice structure, two dual-material mechanical lattice statures are designed, and their mechanical performance and energy absorption are studied. The results reveal that not only gradual changes in the unit cell size provide more energy absorption and improve mechanical performance, but also the rational combination of soft and hard materials make the lattice structure with the maximum energy absorption and stiffness, in comparison to those structures with a single material, interesting for multi-functional applications. Full article
(This article belongs to the Special Issue Soft Materials)
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Open AccessArticle
Engineering Gels with Time-Evolving Viscoelasticity
Materials 2020, 13(2), 438; https://doi.org/10.3390/ma13020438 - 16 Jan 2020
Cited by 8 | Viewed by 1213
Abstract
From a mechanical point of view, a native extracellular matrix (ECM) is viscoelastic. It also possesses time-evolving or dynamic behaviour, since pathophysiological processes such as ageing alter their mechanical properties over time. On the other hand, biomaterial research on mechanobiology has focused mainly [...] Read more.
From a mechanical point of view, a native extracellular matrix (ECM) is viscoelastic. It also possesses time-evolving or dynamic behaviour, since pathophysiological processes such as ageing alter their mechanical properties over time. On the other hand, biomaterial research on mechanobiology has focused mainly on the development of substrates with varying stiffness, with a few recent contributions on time- or space-dependent substrate mechanics. This work reports on a new method for engineering dynamic viscoelastic substrates, i.e., substrates in which viscoelastic parameters can change or evolve with time, providing a tool for investigating cell response to the mechanical microenvironment. In particular, a two-step (chemical and enzymatic) crosslinking strategy was implemented to modulate the viscoelastic properties of gelatin hydrogels. First, gels with different glutaraldehyde concentrations were developed to mimic a wide range of soft tissue viscoelastic behaviours. Then their mechanical behaviour was modulated over time using microbial transglutaminase. Typically, enzymatically induced mechanical alterations occurred within the first 24 h of reaction and then the characteristic time constant decreased although the elastic properties were maintained almost constant for up to seven days. Preliminary cell culture tests showed that cells adhered to the gels, and their viability was similar to that of controls. Thus, the strategy proposed in this work is suitable for studying cell response and adaptation to temporal variations of substrate mechanics during culture. Full article
(This article belongs to the Special Issue Soft Materials)
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Open AccessArticle
On the Influence of Inhomogeneous Interphase Layers on Instabilities in Hyperelastic Composites
Materials 2019, 12(5), 763; https://doi.org/10.3390/ma12050763 - 06 Mar 2019
Cited by 8 | Viewed by 1116
Abstract
Polymer-based three-dimensional (3D) printing—such as the UV-assisted layer-by-layer polymerization technique—enables fabrication of deformable microstructured materials with pre-designed properties. However, the properties of such materials require careful characterization. Thus, for example, in the polymerization process, a new interphase zone is formed at the boundary [...] Read more.
Polymer-based three-dimensional (3D) printing—such as the UV-assisted layer-by-layer polymerization technique—enables fabrication of deformable microstructured materials with pre-designed properties. However, the properties of such materials require careful characterization. Thus, for example, in the polymerization process, a new interphase zone is formed at the boundary between two constituents. This article presents a study of the interphasial transition zone effect on the elastic instability phenomenon in hyperelastic layered composites. In this study, three different types of the shear modulus distribution through the thickness of the interphasial layer were considered. Numerical Bloch-Floquet analysis was employed, superimposed on finite deformations to detect the onset of instabilities and the associated critical wavelength. Significant changes in the buckling behavior of the composites were observed because of the existence of the interphasial inhomogeneous layers. Interphase properties influence the onset of instabilities and the buckling patterns. Numerical simulations showed that interlayer inhomogeneity may result in higher stability of composites with respect to classical layup constructions of identical shear stiffness. Moreover, we found that the critical wavelength of the buckling mode can be regulated by the inhomogeneous interphase properties. Finally, a qualitative illustration of the effect is presented for 3D-printed deformable composites with varying thickness of the stiff phase. Full article
(This article belongs to the Special Issue Soft Materials)
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