Soft Composite Materials Research Articles

멀티 스케일 다중 전개형 협업 로봇을 위한 요소 기술 개발

Multi-scale mass-deployable cooperative robots’ is a next generation robotics paradigm where a large number of robots that vary in size cooperate in a hierarchical fashion to collect information in various environments. While this paradigm can exhibit the effective solution for exploration of the wide area consisting of various types of terrain, its technical maturity is still in its infant state and many technical hurdles should be resolved to realize this paradigm. In this paper, we propose to develop new design and manufacturing methodologies for the multi-scale mass-deployable cooperative robots. In doing so, we present various fundamental technologies in four different research fields. (1) Adaptable design methods consist of compliant mechanisms and hierarchical structures which provide robots with a unified way to overcome various and irregular terrains. (2) Soft composite materials realize the compliancy in these structures. (3) Multi-scale integrative manufacturing techniques are convergence of traditional methods for producing various sized robots assembled by such materials. Finally, (4) the control and communication techniques for the massive swarm robot systems enable multiple functionally simple robots to accomplish the complex job by effective job distribution.

Impregnation of weakly charged anionic microhydrogels with cationic polyelectrolytes and their swelling properties monitored by a high resolution interferometric technique. Transformation from a polyelectrolyte to polyampholyte hydrogel

Deposition of polycations on weakly charged anionic hydrogels and the resulting swelling properties were studied to determine the influence of molecular parameters on the properties of the resulting composite soft materials. The deposition process and swelling properties at various ionic strengths were followed in situ by an interferometric technique allowing continuous monitoring of changes in optical length within the hydrogels with 2nm resolution. The distributions of the polycations labeled with fluorescent dye Alexa Fluor 488 were additionally monitored employing confocal microscopy. Polyallylamine hydrochloride (PAH) of three different molecular weights and a high molecular weight chitosan were employed as polycations. The high resolution interferometric data revealed the classical ionic hydrogel increase in swelling with decreasing ionic strength that increases with the charge density of the anionic hydrogel. Impregnating the anionic hydrogels with PAH polycation resulted in composite materials where PAH where distributed throughout the original polyanionic hydrogel, and where the changes in swelling at various ionic strengths resembled a polyampholyte hydrogel. Exposure to a chitosan yielded a polycation distribution with a distinct chitosan enriched shell at the surface of the hydrogel, and less penetration within the core of the anionic hydrogels. These materials displayed a typically ionic hydrogel swelling signature on changes in ionic strength. The results here show that tuning of molecular parameters can be used to control transport properties of polycations into polyanionic hydrogels and one can also prepare composite soft hydrogels with polyampholyte properties using such a route.

Light Sensitive Liquid Crystals for All-Optical Photonic Devices

We report our recent efforts on the fabrication and characterization of light responsive devices realized in soft composite materials. Periodic microstructures obtained by means of a photolithographic technique and a chemical etching process have been used to micro confine a light responsive liquid crystal stabilized through a self-organization processes. The high quality, light responsive, periodic microstructures have been exploited for realizing different all-optical, fast and low power applications. An overview of the realized photonic devices is presented.

Structure of Nanoparticles Embedded in Micellar Polycrystals

We investigate by scattering techniques the structure of water-based soft composite materials comprising a crystal made of Pluronic block-copolymer micelles arranged in a face-centered cubic lattice and a small amount (at most 2% by volume) of silica nanoparticles, of size comparable to that of the micelles. The copolymer is thermosensitive: it is hydrophilic and fully dissolved in water at low temperature (T ~ 0 °C), and self-assembles into micelles at room temperature, where the block-copolymer is amphiphilic. We use contrast matching small-angle neuron scattering experiments to independently probe the structure of the nanoparticles and that of the polymer. We find that the nanoparticles do not perturb the crystalline order. In addition, a structure peak is measured for the silica nanoparticles dispersed in the polycrystalline samples. This implies that the samples are spatially heterogeneous and comprise, without macroscopic phase separation, silica-poor and silica-rich regions. We show that the nanoparticle concentration in the silica-rich regions is about 10-fold the average concentration. These regions are grain boundaries between crystallites, where nanoparticles concentrate, as shown by static light scattering and by light microscopy imaging of the samples. We show that the temperature rate at which the sample is prepared strongly influence the segregation of the nanoparticles in the grain-boundaries.

Preparation of a macroporous silica–pyridine multidentate material and its adsorption behavior for some typical elements

AbstractA new macroporous silica‐based‐polymer (SiO2‐P) soft ligand composite material, 2,6‐bis(5,6‐di(iso‐butyl)‐1,2,4‐triazine‐3‐yl)pyridine (BDIBTP/SiO2‐P), was synthesized by impregnation and immobilization of BDIBTP and 1‐octanol molecules into the pores of the SiO2‐P particles. The impact of some typical alkali metal and alkaline earths Cs(I), Na(I), K(I), Rb(I), Sr(II), and Ba(II) containing in highly active liquid waste (HLW) on the adsorption of Pd(II) onto BDIBTP/SiO2‐P was studied. It was performed by examining the effects of contact time and the HNO3 concentration in the range of 0.3–7.0 M. BDIBTP/SiO2‐P showed strong adsorption ability and high selectivity for Pd(II) over all the tested metals. The chromatographic partitioning of Pd(II) from a simulated HLW solution was conducted by BDIBTP/SiO2‐P packed column. Pd(II) was effectively eluted with 0.2 M thiourea–0.1 M HNO3. The others showed no adverse impact on separation of Pd(II). The results are beneficial to partitioning of minor actinides and Pd(II) together from HLW by BDIBTP/SiO2‐P in the MPS process developed. © 2012 American Institute of Chemical Engineers AIChE J, 2012

General Purpose Soft Template for Photonic Applications: From All-Optical to Electrical Reconfigurability

In this paper we report on the realization and characterization of a polymer template sculptured in photosensitive material on a chemical inert surface, devoted to micro/nano-confinement of a wide range of organic components, with self-arrangement properties at the nanoscale. The high quality morphology of the polymeric micropattern arrays is obtained by combining a nano-precision level optical holographic setup and a multi-step chemico-physical process. The general purpose template represents the basic platform to be filled with different soft composite materials: Due to their self organization capabilities, light responsive Liquid Crystals (LC) and short pitch Cholesteric LC have been investigated.

In Situ Mechanical Analysis of Genetic Modification and Aging on Soft, Bilayered Drosophila Myocardium

Drosophila melanogaster is a genetically malleable organism with a short life span, making it a tractable system in which to study mechanical effects of genetic perturbation and aging on tissues, such as impaired heart function. However, Drosophila heart tube studies can be hampered by its bilayered structure: a ventral muscle layer covers the contractile cardiomyocytes. We have refined an atomic force microscopy-based analysis to measure individual mechanical components of soft composite materials. The technique was verified using bilayered polydimethylsiloxane. Its biological utility was further demonstrated by its ability to resolve stiffness changes due to cardiac-specific RNA interference to reduce cardiomyocyte myofibrillar assembly or due to aging in Drosophila myocardial layers. Female yellow-white (yw) flies experience decreased diastolic diameter with age (>20%) while cardiomyocytes stiffened more than two-fold with age (1.8± 0.1 vs. 3.8 ± 0.3 kPa in 1 and 5 week old flies, respectively) at cell-cell junctions. Cardiac-specific RNA-interference against myosin heavy chain severely impaired contraction and reduced stiffness after 1 week (1.0± 0.1 vs. 1.8 ± 0.1 kPa) without altering ventral muscle stiffness. This method provides a platform to assess the mechanics of soft biological composite systems and for the first time permits direct measurement of how genetic perturbations, aging, and disease can impact cardiac function in situ.

A Study on the Cutting Phenomenon and Temperature Dependence of Soft Composite Material including Rubber

A Study on the Cutting Phenomenon and Temperature Dependence of Soft Composite Material including Rubber

In Situ Mechanical Analysis of Myofibrillar Perturbation and Aging on Soft, Bilayered Drosophila Myocardium

Drosophila melanogaster is a genetically malleable organism with a short life span, making it a tractable system in which to study mechanical effects of genetic perturbation and aging on tissues, e.g., impaired heart function. However, Drosophila heart-tube studies can be hampered by its bilayered structure: a ventral muscle layer covers the contractile cardiomyocytes. Here we propose an atomic force microscopy-based analysis that uses a linearized-Hertz method to measure individual mechanical components of soft composite materials. The technique was verified using bilayered polydimethylsiloxane. We further demonstrated its biological utility via its ability to resolve stiffness changes due to RNA interference to reduce myofibrillar content or due to aging in Drosophila myocardial layers. This protocol provides a platform to assess the mechanics of soft biological composite systems and, to our knowledge, for the first time, permits direct measurement of how genetic perturbations, aging, and disease can impact cardiac function in situ.

Realization of Photoresponsive Diffractive Beam Splitters

We report on the realization of a light beam splitting effect based on a light sensitive diffractive structure. The periodic structure is realized in soft composite materials doped with an high performance light sensitive Liquid Crystal. The capability of the structure as tunable beam splitter, is monitored by combining its zero and first diffracted orders in a MC-Zehnder geometry interferometer. The fringe visibility of the interference pattern can be finely controlled by means of an external pump source. Low driving power and short response time are the main features of this light controlled beam splitter.

Pressure Dependence of the Frequency Permeability Spectra of Soft Ferrite Composite Materials: A Method of Measuring the Natural Ferromagnetic Resonance Frequency

Experimental studies on the complex susceptibility of soft magnetic composite materials (magnetostrictive Ni-Zn and Ni-Zn-Co spinels) in their region of ferrimagnetic resonance (FMR) show that the FMR is an increasing function of the applied pressure. It is shown that powders could advantageously replace their sintered materials counterpart to measure without any ambiguity the natural ferrimagnetic resonance (NFMR) frequencies of bulk materials. It is also shown that such soft ferrite composites can be realized in order to shift FMR to higher values, and to obtain low magnetic losses up to 900 MHz. High frequencies applications can be envisaged.

Microchannel Embedded Elastomeric Layers for Impact Damping

Damping against moderate to high impact is important for variety of engineering and technological applications. While, conventionally, damping has been achieved by using soft, elastic, and viscoelastic composite materials of different kinds, here we show that thin elastic layers embedded with fluid-filled micro-channels can have several advantages not found in the conventional ones. These layers are either smooth, homogeneous, or are embedded with micro-channels of different diameters, either open to atmosphere or are filled with oil of desired viscosity. We sandwich these layers between a rigid substrate and a flexible aluminum foil and subject them to moderate impacting load by colliding with rigid spheres of steel of different diameter. These experiments show that the kinetic energy dissipates more for layers of smaller thickness and for the ones embedded with the fluid filled micro-channels. Furthermore, the dissipation increases with viscosity of the oil inside the channels until a critical viscosity is reached beyond which it decreases. These results suggest that the damping occurs via frictional dissipation at interfaces and the viscous dissipation of liquid inside the channels.

Mesogenic versus non-mesogenic azo dye confined in a soft-matter template for realization of optically switchable diffraction gratings

We report on fabrication and characterization of two different kinds of optically controlled diffraction gratings realized in soft composite materials. The periodic microstructures have been obtained by combining a photolithographic technique and a chemical etching process. The samples have been infiltrated with two classes of photosensitive materials, and then characterized. The first material is a common azo-dye dissolved in a liquid crystal (LC), while the second one is an azobenzene LC (azo-LC). The response and relaxation times, lifetimes and spectral absorption range of the LC mixtures confined in the microstructures were measured. Detailed comparison of investigated characteristics reveals a better overall performance of the azo-LC based sample.

702 軟質複合材料の切削加工に関する研究(OSIH機械加工の高速・高精度化)

702 軟質複合材料の切削加工に関する研究(OSIH機械加工の高速・高精度化)

Three dimensional optical manipulation and structural imaging of soft materials by use of laser tweezers and multimodal nonlinear microscopy

We develop an integrated system of holographic optical trapping and multimodal nonlinear microscopy and perform simultaneous three-dimensional optical manipulation and non-invasive structural imaging of composite soft-matter systems. We combine different nonlinear microscopy techniques such as coherent anti-Stokes Raman scattering, multi-photon excitation fluorescence and multi-harmonic generation, and use them for visualization of long-range molecular order in soft materials by means of their polarized excitation and detection. The combined system enables us to accomplish manipulation in composite soft materials such as colloidal inclusions in liquid crystals as well as imaging of each separate constituents of the composite material in different nonlinear optical modalities. We also demonstrate optical generation and control of topological defects and simultaneous reconstruction of their three-dimensional long-range molecular orientational patterns from the nonlinear optical images.

Jones matrix analysis of dichroic phase retarders realized in soft matter composite materials

Materials showing birefringence and polarization selective absorption (dichroism) affect the polarization state of incoming light in a peculiar way, quite different from the one exhibited by phase retarders like waveplates. In this paper, we report on the characterization of a Polymer LIquid CRYstal Polymer Slices (POLICRYPS) diffraction grating used as a dichroic phase retarder; the dichroic behaviour of the grating is due to the polarization-dependent diffraction efficiency. Experimental data are validated with a theoretical model based on the Jones matrix formalism, while the grating behavior is modeled by means of the dichroic matrix. In this way, the birefringence of the analyzed structure is easily obtained. For comparison purposes, also two systems different from POLICRYPS have been fabricated and tested.

Study on Slicing for Soft Composite Materials by Cutting Method

Soft composite materials are used for a functional film for a thermal interface material. The surface of this functional film must be flatter and thinner, and contacting fillers to have a better thermal conductivity. Cutting would meet these requirements to slice such soft materials. Soft composite materials consisting of acrylic rubber bulk and graphite fillers were prepared and sliced into films (1mm thickness) as thermal interface materials by developed cutting method. Measurements of curl radius and cutting forces were conducted on the orthogonal cutting experiments. It was found that the following three strategies were effective for reducing curl of chip and cutting force : (1) higher operating temperature, (2) slower cutting speed, and (3) larger tool rake angle. This result suggested a useful method for the effective slicing by controlling the cutting conditions.

Copolymer-Induced Stabilizing Effect of Highly Swollen Hexagonal Mesophases

We show that small amounts of copolymer that decorate an oil/water interface can greatly enhance the stability of swollen surfactant hexagonal phases, comprising oil tubes regularly arranged in a water matrix. Both the radius of the tubes and the thickness of the aqueous channel between the tubes can be controlled independently over large ranges. Such soft composite materials offer a potential interest for the synthesis of mesoporous materials.

Colloidal Shape Controlled by Molecular Adsorption at Liquid Crystal Interfaces

The ability to control finely the structure of materials remains a central issue in colloidal science. Due to their elastic properties, liquid crystals (LC) are increasingly used to organize matter at the micrometer scale in soft composites. Textures and shapes of LC droplets are currently controlled by the competition between elasticity and anchoring, hydrodynamic flows, or external fields. Molecules adsorbed specifically at LC interfaces are known to orient LC molecules (anchoring effect), but other induced effects have been poorly explored. Using specifically designed amphitropic surfactants, we demonstrate that large-shape transformations can be achieved in direct LC/water emulsions. In particular, we focus on unusual nematic filaments formed from spherical droplets. These results suggest new approaches to design new soft LC composite materials through the adsorption of molecules at liquid crystal interfaces.

Catalytic activity of a soft composite material: Nanoparticle location–activity relationship

A nanostructure, fiber-shaped morphology of a conjugated polymer (poly-5 amono- ortho-cresol, PAOC) has been synthesized using palladium acetate as the oxidizing agent. A one pot, in situ chemical synthesis approach has been utilized in which palladium acetate was reduced during the polymerization process of 5-amono- o-cresol (AOC) and formed well dispersed palladium nanoparticles in the polymer fibers. The resultant composite material was characterized by means of optical, thermo and micro-analytical techniques. The elemental identity of the nanoparticles was determined by means of electron energy loss spectroscopy (EELS) mapping using analytical transmission electron microscopy (TEM). Subsequently, the sample was used as a catalyst for a model gas-phase hydrogenation reaction. The activation and deactivation behaviour of the catalyst as a function of temperature is discussed in the light of different phase transition points of the polymer as well as the orientation of the palladium nanoparticles. The fact that palladium nanoparticles (∼2 nm) were uniformly distributed throughout the polymer matrix makes the composite material an excellent hybrid structure.