Materials

Research

Jump to: Review

13 pages, 3541 KiB

Open AccessFeature PaperArticle

Development of the Functionalized Nanocomposite Materials for Adsorption/Decontamination of Radioactive Pollutants

by Gyo Eun Gu, Joonwon Bae, Ho Seok Park and Jin-Yong Hong

Materials 2021, 14(11), 2896; https://doi.org/10.3390/ma14112896 - 28 May 2021

Cited by 8 | Viewed by 2133

Abstract

A polymer-based nanofiber membrane with a high specific surface area, high porosity and abundant adsorption sites is demonstrated for selective trapping of radionuclides. The Prussian blue (PB)/poly(methyl methacrylate) (PMMA) nanofiber composites were successfully prepared through a one-step, single-nozzle electrospinning method. Various analytical techniques [...] Read more.

A polymer-based nanofiber membrane with a high specific surface area, high porosity and abundant adsorption sites is demonstrated for selective trapping of radionuclides. The Prussian blue (PB)/poly(methyl methacrylate) (PMMA) nanofiber composites were successfully prepared through a one-step, single-nozzle electrospinning method. Various analytical techniques were used to examine the physical and chemical properties of PB nanoparticles and electrospun nanofibers. It is possible to enhance binding affinity and selectivity to radionuclide targets by incorporation of the PB nanoparticles into the polymer matrix. It is noteworthy that the maximum ¹³³Cs adsorption capacity of hte PB/PMMA nanofiber filter is approximately 28 times higher than that of bulk PB, and the removal efficiency is measured to be 95% at 1 ppm of ¹³³Cs. In addition, adsorption kinetics shows that the PB/PMMA nanofiber has a homogenous surface for adsorption, and all sites on the surface have equal adsorption energies in terms of ion-exchange between cyano groups of the introduced PB nanoparticles and radionuclides. Full article

(This article belongs to the Special Issue Programmable Anisotropic Materials and Composites)

► Show Figures

Figure 1

10 pages, 2430 KiB

Open AccessCommunication

Photo-Mechanical Response Dynamics of Liquid Crystal Elastomer Linear Actuators

by Przemysław Grabowski, Jakub Haberko and Piotr Wasylczyk

Materials 2020, 13(13), 2933; https://doi.org/10.3390/ma13132933 - 30 Jun 2020

Cited by 11 | Viewed by 3631

Abstract

With continuous miniaturization of many technologies, robotics seems to be lagging behind. While the semiconductor technologies operate confidently at the nanometer scale and micro-mechanics of simple structures (MEMS) in micrometers, autonomous devices are struggling to break the centimeter barrier and have hardly colonized [...] Read more.

With continuous miniaturization of many technologies, robotics seems to be lagging behind. While the semiconductor technologies operate confidently at the nanometer scale and micro-mechanics of simple structures (MEMS) in micrometers, autonomous devices are struggling to break the centimeter barrier and have hardly colonized smaller scales. One way towards miniaturization of robots involves remotely powered, light-driven soft mechanisms based on photo-responsive materials, such as liquid crystal elastomers (LCEs). While several simple devices have been demonstrated with contracting, bending, twisting, or other, more complex LCE actuators, only their simple behavior in response to light has been studied. Here we characterize the photo-mechanical response of a linear light-driven LCE actuator by measuring its response to laser beams with varying power, pulse duration, pulse energy, and the energy spatial distribution. Light absorption decrease in the actuator over time is also measured. These results are at the foundation of further development of soft, light-driven miniature mechanisms and micro-robots. Full article

(This article belongs to the Special Issue Programmable Anisotropic Materials and Composites)

► Show Figures

Figure 1

13 pages, 4948 KiB

Open AccessFeature PaperArticle

Fractionation of Lignin for Selective Shape Memory Effects at Elevated Temperatures

by Ngoc A. Nguyen, Christopher C. Bowland, Peter V. Bonnesen, Kenneth C. Littrell, Jong K. Keum and Amit K. Naskar

Materials 2020, 13(8), 1940; https://doi.org/10.3390/ma13081940 - 20 Apr 2020

Cited by 3 | Viewed by 3036

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)

► Show Figures

Figure 1

12 pages, 2215 KiB

Open AccessArticle

Measurement of the Thermophysical Properties of Anisotropic Insulation Materials with Consideration of the Effect of Thermal Contact Resistance

by Dongxu Han, Kai Yue, Liang Cheng, Xuri Yang and Xinxin Zhang

Materials 2020, 13(6), 1353; https://doi.org/10.3390/ma13061353 - 17 Mar 2020

Cited by 8 | Viewed by 2463

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)

► Show Figures

Figure 1

13 pages, 3461 KiB

Open AccessArticle

Effects of Helix Geometry on Magnetic Guiding of Helical Polymer Composites on a Gastric Cancer Model: A Feasibility Study

by Yongju Kim, Jeong Eun Park, Jeong Jae Wie, Su Geun Yang, Don Haeng Lee and Young-Joo Jin

Materials 2020, 13(4), 1014; https://doi.org/10.3390/ma13041014 - 24 Feb 2020

Cited by 6 | Viewed by 3066

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)

► Show Figures

Figure 1

10 pages, 2812 KiB

Open AccessFeature PaperArticle

Effect of Cell Thickness on the Electro-optic Response of Polymer Stabilized Cholesteric Liquid Crystals with Negative Dielectric Anisotropy

by Kyung Min Lee, Ecklin P. Crenshaw, Mariacristina Rumi, Timothy J. White, Timothy J. Bunning and Michael E. McConney

Materials 2020, 13(3), 746; https://doi.org/10.3390/ma13030746 - 6 Feb 2020

Cited by 10 | Viewed by 2720

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)

► Show Figures

Figure 1

12 pages, 3884 KiB

Open AccessFeature PaperArticle

Lithography-Free Route to Hierarchical Structuring of High-χ Block Copolymers on a Gradient Patterned Surface

by Ha Ryeong Cho, Ayoung Choe, Woon Ik Park, Hyunhyub Ko and Myunghwan Byun

Materials 2020, 13(2), 304; https://doi.org/10.3390/ma13020304 - 9 Jan 2020

Viewed by 3020

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)

► Show Figures

Figure 1

14 pages, 460 KiB

Open AccessArticle

Properties of Dislocation Drag from Phonon Wind at Ambient Conditions

by Daniel N. Blaschke

Materials 2019, 12(6), 948; https://doi.org/10.3390/ma12060948 - 21 Mar 2019

Cited by 23 | Viewed by 2561

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)

► Show Figures

Figure 1

Review

Jump to: Research

22 pages, 6338 KiB

Open AccessReview

Contactless Manipulation of Soft Robots

by Jae Gwang Kim, Jeong Eun Park, Sukyoung Won, Jisoo Jeon and Jeong Jae Wie

Materials 2019, 12(19), 3065; https://doi.org/10.3390/ma12193065 - 20 Sep 2019

Cited by 34 | Viewed by 7340

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)

► Show Figures