Special Issue "Programmable Anisotropic Materials and Composites"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: 30 April 2021.

Special Issue Editor

Prof. Dr. Jeong Jae Wie
Website
Guest Editor
Department of Polymer Science and Engineering, Inha UniversityIncheon 22212, South Korea
Interests: soft robotics; shape-reconfigurable devices; stimuli-responsive polymer composites; liquid crystalline polymers; self-assembly of soft matters

Special Issue Information

Dear Colleagues,

Programmable anisotropic materials and composites are attractive because of their directed material properties, including mechanical, thermal, electrical, magnetic, and optical properties. Recently, programmable anisotropic materials have also offered the opportunity to study soft robotics, self-assembly, and shape-reconfigurable materials and devices.

The purpose of this Special Issue is to collect high-quality articles in the field of liquid crystalline materials, magnetic composites, as well as novel anisotropic materials programmed by various external stimuli including electrical fields, temperature gradient, spatial confinement, capillary force, and shear force.

It is my pleasure to invite you to submit a manuscript for this Special Issue. Full papers, communications, and reviews are all welcome.

Prof. Dr. Jeong Jae Wie
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 papers will be 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 2000 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

  • liquid crystalline materials
  • magnetic composites
  • self-assembly
  • programmable materials
  • stimuli-responsive materials
  • anisotropic materials
  • soft robotics
  • shape-reconfigurable materials

Published Papers (7 papers)

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Research

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Open AccessFeature PaperArticle
Fractionation of Lignin for Selective Shape Memory Effects at Elevated Temperatures
Materials 2020, 13(8), 1940; https://doi.org/10.3390/ma13081940 - 20 Apr 2020
Abstract
We report a facile approach to control the shape memory effects and thermomechanical characteristics of a lignin-based multiphase polymer. Solvent fractionation of a syringylpropane-rich technical organosolv lignin resulted in selective lignin structures having excellent thermal stability coupled with high stiffness and melt-flow resistance. [...] Read more.
We report a facile approach to control the shape memory effects and thermomechanical characteristics of a lignin-based multiphase polymer. Solvent fractionation of a syringylpropane-rich technical organosolv lignin resulted in selective lignin structures having excellent thermal stability coupled with high stiffness and melt-flow resistance. The fractionated lignins were reacted with rubber in melt-phase to form partially networked elastomer enabling selective programmability of the material shape either at 70 °C, a temperature that is high enough for rubbery matrix materials, or at an extremely high temperature, 150 °C. Utilizing appropriate functionalities in fractionated lignins, tunable shape fixity with high strain and stress recovery, particularly high-stress tolerance were maintained. Detailed studies of lignin structures and chemistries were correlated to molecular rigidity, morphology, and stress relaxation, as well as shape memory effects of the materials. The fractionation of lignin enabled enrichment of specific lignin properties for efficient shape memory effects that broaden the materials’ application window. Electron microscopy, melt-rheology, dynamic mechanical analysis and ultra-small angle neutron scattering were conducted to establish morphology of acrylonitrile butadiene rubber (NBR)-lignin elastomers from solvent fractionated lignins. Full article
(This article belongs to the Special Issue Programmable Anisotropic Materials and Composites)
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Open AccessArticle
Measurement of the Thermophysical Properties of Anisotropic Insulation Materials with Consideration of the Effect of Thermal Contact Resistance
Materials 2020, 13(6), 1353; https://doi.org/10.3390/ma13061353 - 17 Mar 2020
Abstract
A novel method involving the effect of thermal contact resistance (TCR) was proposed using a plane heat source smaller than the measured samples for improving measurement accuracy of the simultaneous determination of in-plane and cross-plane thermal conductivities and the volumetric heat capacity of [...] Read more.
A novel method involving the effect of thermal contact resistance (TCR) was proposed using a plane heat source smaller than the measured samples for improving measurement accuracy of the simultaneous determination of in-plane and cross-plane thermal conductivities and the volumetric heat capacity of anisotropic materials. The heat transfer during the measurement process was mathematically modeled in a 3D Cartesian coordinate system. The temperature distribution inside the sample was analytically derived by applying Laplace transform and the variables separation method. A multiparameter estimation algorithm was developed on the basis of the sensitivity analysis of the parameters to simultaneously estimate the measured parameters. The correctness of the algorithm was verified by performing simulation experiments. The thermophysical parameters of insulating materials were experimentally measured using the proposed method at different temperatures and pressures. Fiber glass and ceramic insulation materials were tested at room temperature. The measured results showed that the relative error was 1.6% less than the standard value and proved the accuracy of the proposed method. The TCRs measured at different pressures were compared with those obtained using the steady-state method, and the maximum deviation was 8.5%. The thermal conductivity obtained with the contact thermal resistance was smaller than that without the thermal resistance. The measurement results for the anisotropic silica aerogels at different temperatures and pressures revealed that the thermal conductivity and thermal contact conductance increased as temperature and pressure increased. Full article
(This article belongs to the Special Issue Programmable Anisotropic Materials and Composites)
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Open AccessArticle
Effects of Helix Geometry on Magnetic Guiding of Helical Polymer Composites on a Gastric Cancer Model: A Feasibility Study
Materials 2020, 13(4), 1014; https://doi.org/10.3390/ma13041014 - 24 Feb 2020
Abstract
This study investigates the effects of soft-robot geometry on magnetic guiding to develop an efficient helical mediator on a three-dimensional (3D) gastric cancer model. Four different magnetically active helical soft robots are synthesized by the inclusion of 5-μm iron particles in polydimethylsiloxane matrices. [...] Read more.
This study investigates the effects of soft-robot geometry on magnetic guiding to develop an efficient helical mediator on a three-dimensional (3D) gastric cancer model. Four different magnetically active helical soft robots are synthesized by the inclusion of 5-μm iron particles in polydimethylsiloxane matrices. The soft robots are named based on the diameter and length (D2-L15, D5-L20, D5-L25, and D5-L35) with samples having varied helical pitch and weight values. Then, the four samples are tested on a flat surface as well as a stomach model with various 3D wrinkles. We analyze the underlying physics of intermittent magnetomotility for the helix on a flat surface. In addition, we extract representative failure cases of magnetomotility on the stomach model. The D5-L25 sample was the most suitable among the four samples for a helical soft robot that can be moved to a target lesion by the magnetic-flux density of the stomach model. The effects of diameter, length, pitch, and weight of a helical soft robot on magnetomotility are discussed in order for the robot to reach the target lesion successfully via magnetomotility. Full article
(This article belongs to the Special Issue Programmable Anisotropic Materials and Composites)
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Open AccessFeature PaperArticle
Effect of Cell Thickness on the Electro-optic Response of Polymer Stabilized Cholesteric Liquid Crystals with Negative Dielectric Anisotropy
Materials 2020, 13(3), 746; https://doi.org/10.3390/ma13030746 - 06 Feb 2020
Abstract
It has previously been shown that for polymer-stabilized cholesteric liquid crystals (PSCLCs) with negative dielectric anisotropy, the position and bandwidth of the selective reflection notch can be controlled by a direct-current (DC) electric field. The field-induced deformation of the polymer network that stabilizes [...] Read more.
It has previously been shown that for polymer-stabilized cholesteric liquid crystals (PSCLCs) with negative dielectric anisotropy, the position and bandwidth of the selective reflection notch can be controlled by a direct-current (DC) electric field. The field-induced deformation of the polymer network that stabilizes the devices is mediated by ionic charges trapped in or near the polymer. A unique and reversible electro-optic response is reported here for relatively thin films (≤5 μm). Increasing the DC field strength redshifts the reflection notch to longer wavelength until the reflection disappears at high DC fields. The extent of the tuning range is dependent on the cell thickness. The transition from the reflective to the clear state is due to the electrically controlled, chirped pitch across the small cell gap and not to the field-induced reorientation of the liquid crystal molecules themselves. The transition is reversible. By adjusting the DC field strength, various reflection wavelengths can be addressed from either a different reflective (colored) state at 0 V or a transparent state at a high DC field. Relatively fast responses (~50 ms rise times and ~200 ms fall times) are observed for these thin PSCLCs. Full article
(This article belongs to the Special Issue Programmable Anisotropic Materials and Composites)
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Open AccessFeature PaperArticle
Lithography-Free Route to Hierarchical Structuring of High-χ Block Copolymers on a Gradient Patterned Surface
Materials 2020, 13(2), 304; https://doi.org/10.3390/ma13020304 - 09 Jan 2020
Abstract
A chemically defined patterned surface was created via a combined process of controlled evaporative self-assembly of concentric polymer stripes and the selective surface modification of polymer brush. The former process involved physical adsorption of poly (methyl methacrylate) (PMMA) segments into silicon oxide surface, [...] Read more.
A chemically defined patterned surface was created via a combined process of controlled evaporative self-assembly of concentric polymer stripes and the selective surface modification of polymer brush. The former process involved physical adsorption of poly (methyl methacrylate) (PMMA) segments into silicon oxide surface, thus forming ultrathin PMMA stripes, whereas the latter process was based on the brush treatment of silicon native oxide surface using a hydroxyl-terminated polystyrene (PS-OH). The resulting alternating PMMA- and PS-rich stripes provided energetically favorable regions for self-assembly of high χ polystyrene-block-polydimethylsiloxane (PS-b-PDMS) in a simple and facile manner, dispensing the need for conventional lithography techniques. Subsequently, deep reactive ion etching and oxygen plasma treatment enabled the transition of the PDMS blocks into oxidized groove-shaped nanostructures. Full article
(This article belongs to the Special Issue Programmable Anisotropic Materials and Composites)
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Open AccessArticle
Properties of Dislocation Drag from Phonon Wind at Ambient Conditions
Materials 2019, 12(6), 948; https://doi.org/10.3390/ma12060948 - 21 Mar 2019
Cited by 6
Abstract
It is well known that, under plastic deformation, dislocations are not only created but also move through the crystal, and their mobility is impeded by their interaction with the crystal structure. At high stress and temperature, this “drag” is dominated by phonon wind, [...] Read more.
It is well known that, under plastic deformation, dislocations are not only created but also move through the crystal, and their mobility is impeded by their interaction with the crystal structure. At high stress and temperature, this “drag” is dominated by phonon wind, i.e., phonons scattering off dislocations. Employing the semi-isotropic approach discussed in detail in a previous paper (J. Phys. Chem. Solids 2019, 124, 24–35), we discuss here the approximate functional dependence of dislocation drag B on dislocation velocity in various regimes between a few percent of transverse sound speed c T and c T (where c T is the effective average transverse sound speed of the polycrystal). In doing so, we find an effective functional form for dislocation drag B ( v ) for different slip systems and dislocation characters at fixed (room) temperature and low pressure. Full article
(This article belongs to the Special Issue Programmable Anisotropic Materials and Composites)
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Review

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Open AccessReview
Contactless Manipulation of Soft Robots
Materials 2019, 12(19), 3065; https://doi.org/10.3390/ma12193065 - 20 Sep 2019
Cited by 3
Abstract
In recent years, jointless soft robots have demonstrated various curvilinear motions unlike conventional robotic systems requiring complex mechanical joints and electrical design principles. The materials employed to construct soft robots are mainly programmable anisotropic polymeric materials to achieve contactless manipulation of miniaturized and [...] Read more.
In recent years, jointless soft robots have demonstrated various curvilinear motions unlike conventional robotic systems requiring complex mechanical joints and electrical design principles. The materials employed to construct soft robots are mainly programmable anisotropic polymeric materials to achieve contactless manipulation of miniaturized and lightweight soft robots through their anisotropic strain responsivity to external stimuli. Although reviews on soft actuators are extensive, those on untethered soft robots are scant. In this study, we focus on the recent progress in the manipulation of untethered soft robots upon receiving external stimuli such as magnetic fields, light, humidity, and organic solvents. For each external stimulus, we provide an overview of the working principles along with the characteristics of programmable anisotropic materials and polymeric composites used in soft robotic systems. In addition, potential applications for untethered soft robots are discussed based on the physicochemical properties of programmable anisotropic materials for the given external stimuli. Full article
(This article belongs to the Special Issue Programmable Anisotropic Materials and Composites)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

1. Title: Virus-like Particles as Self-Assembly, Anisotropic, Shape-reconfigurable Materials
Authors: Mariana Andrade-Medina and Mauricio Carrillo-Tripp
Abstract: A virus is a biological complex formed by an infecting genome inside an outer protein shell called capsid. In many cases, it is possible to form empty capsids in vitro. Such particles, referred to as virus-like particles or VLPs, are monodispersed and retain the nanoscale size and shape of the original virus particle. VLPs have remarkable geometric and physicochemical features. Under the right conditions, they reversibly self-assemble. Changes in pH or salt concentration can reconfigure their shape. Furthermore, VLPs show anisotropic behaviors even though they have symmetrical structures. Here, we will examine a range of applications and implications of VLP-based nanomaterials, focusing on exciting new advancements in their rational design.

2. Title: Properties of dislocation drag from phonon wind at ambient conditions
Author: Daniel N. Blaschke
Abstract: It is well known that under plastic deformation, dislocations are not only created but also move through the crystal, and their mobility is impeded by their interaction with the crystal structure. At high stress and temperature, this "drag" is dominated by phonon wind, i.e. the scattering off phonons. Employing the semi-isotropic approach discussed in detail in [J. Phys. Chem. Solids 124 (2019) 24], we discuss here the approximate functional dependence on dislocation velocity in various regimes between a few percent of transverse sound speed c_t and c_t (where c_t is the effective average transverse sound speed of the
polycrystal). In doing so, we find an effective functional form for dislocation drag B(v) for different slip systems and dislocation characters at fixed (room) temperature and low pressure.

3. Title: Hierarchically Ordered Nanostructures on a Chemically Defined Surface via Flow-Enabled Self-Assembly
Authors: Ha Ryeong Cho; Woon-Ik Park; Myunghwan Byun
Abstract: By capitalizing on two consecutive self-assembly processes at different length scales, hierarchically ordered structures composed of diblock copolymers on gradient chemically patterned surface were crafted. A chemically modified surface at micrometer scale was first fabricated by flow-enabled self-assembly of polymer lines, followed by the physical detachment of weakly deposited polymer, resulting in physically adsorbed polymer stripes on the Si substrate [1-2]. Subsequently, asymmentric diblock copolymer, poly(styrene-b-dimethylsiloxane) (PS-b-PDMS), was spin-coated and treated with solvent vapor for unfavorable interfacial interaction-driven destabilization of diblock copolymer thin film and simulataneous microphase separation of immiscible blocks, thus giving highly ordered nanocylinders in spatially defined surface at micrometer scale. Selection of PS-b-PDMS as the target diblock copolymer was strongly motivated with easy organic-inorganic trasfromation of nanostructures through plasma treatment [3]. The entire experimental results were carefully analyzed using optical microscopy (OM), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Notably, ultrathin, chemically defined polymer stripes were well-prepared in a simple, unconventional, and remarkably controllable manner at low cost, dispensing with the need for costly and multistep lithography techniques. These hierarchically ordered structures may offer as a promising template for the potential applications such as optics, electronics, optoelectronics with tunable functionalities, and desirable spatial arrangement.

4. Title: Electrical Switching between Reflective and Transparent States in Polymer Stabilized Cholesteric Liquid Crystals
Authors: Kyung Min Lee, Timothy J. White, Timothy J. Bunning, and Michael E. McConney 
Abstract: 

We report on a unique color switching in polymer stabilized cholesteric liquid crystals (PSCLCs) with negative dielectric anisotropy.  The electrical switching is enabled in these thin PSCLC samples through a DC-field induced pitch variation across the liquid crystal cell. At lower DC-fields a relatively small non-linear pitch variation across the thickness of the cell shifts the PSCLC reflection to longer wavelengths. At higher DC voltages a strong non-linearity in the cholesteric liquid crystal pitch and the spectral reflection disappears and becomes transparent.  This transparency is created by the combination of a strongly chirped pitch and relatively small thickness of the cells, which creates a PSCLC with such a strong variation in pitch that there is no spectral reflection pitches associated with any wavelength to lead to reflection.    By adjusting the DC field strength, different colored reflections can be addressed.  The switching behavior of the PSCLC can be potentially used in display applications.

5. Title: Contactless Manipulation of Soft Robots
     Author: Jae Gwang Kim, Jeong Eun Park, Su Kyoung Won, Jisoo Jeon, Jeong Jae Wie

6. Title: Fractionation of lignin for selective shape memory effects of its derivatives at elevated temperatures
   Authors: Ngoc A. Nguyen, Peter V. Bonnesen, Christopher C. Bowland and Amit K. Naskar

7. Title: Development of the functionalized nanocomposite materials for adsorption/decontamination of radioactive pollutants
Authors: Gyo Eun Gu1,2, Ho Seok Park2*, and Jin-Yong Hong1*

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