Structure Of Soft Materials Research Articles

Phase transitions in complex functional liquid crystals—The entropy effect

Liquid crystal design and synthesis are being driven towards always more complexity. The self-assembly of poly- and shape-amphiphiles allow tailoring the soft material structures with double and even triple nanosegregation of functional building blocks. Alignment of the anisotropic liquid crystal is crucial, in order to generate a full control over the material’s function and performance. This procedure often needs an isotropic phase at accessible temperatures without decomposition. The impact of thermodynamic factors, such as cohesive energy density difference and entropy contributions, is discussed in this perspective paper using selected examples. In the process of molecular design such considerations can help to adjust transition temperatures and subsequently, to achieve aligned, complex liquid crystalline matter. This will allow access to new fields of liquid crystal applications.

3D Printing of Human Ossicle Models for the Biofabrication of Personalized Middle Ear Prostheses

The middle ear bones (‘ossicles’) may become severely damaged due to accidents or to diseases. In these situations, the most common current treatments include replacing them with cadaver-derived ossicles, using a metal (usually titanium) prosthesis, or introducing bridges made of biocompatible ceramics. Neither of these solutions is ideal, due to the difficulty in finding or producing shape-matching replacements. However, the advent of additive manufacturing applications to biomedical problems has created the possibility of 3D-printing anatomically correct, shape- and size-personalized ossicle prostheses. To demonstrate this concept, we generated and printed several models of ossicles, as solid, porous, or soft material structures. These models were first printed with a plottable calcium phosphate/hydroxyapatite paste by extrusion on a solid support or embedded in a Carbopol hydrogel bath, followed by temperature-induced hardening. We then also printed an ossicle model with this ceramic in a porous format, followed by loading and crosslinking an alginate hydrogel within the pores, which was validated by microCT imaging. Finally, ossicle models were printed using alginate as well as a cell-containing nanocellulose-based bioink, within the supporting hydrogel bath. In selected cases, the devised workflow and the printouts were tested for repeatability. In conclusion, we demonstrate that moving beyond simplistic geometric bridges to anatomically realistic constructs is possible by 3D printing with various biocompatible materials and hydrogels, thus opening the way towards the in vitro generation of personalized middle ear prostheses for implantation.

Single Step Assembly of Janus Porous Biomaterial by Sub-Ambient Temperature Electrodeposition.

Janus porous biomaterials are gaining increasing attention and there are considerable efforts to develop simple, rapid, and scalable methods capable of tuning micro- and macro-structures. Here, a single-step electro-fabrication method to create a Janus porous film by the electrodeposition of the amino-polysaccharide chitosan is reported. Specifically, a Janus structure emerges spontaneously when electrodeposition is performed at sub-ambient temperature (0-5 °C). Sub-ambient temperature electrodeposition experiments show that: a Janus microstructure emerges (potentially as the result of a subtle alteration of the intermolecular interactions responsible for self-assembly); important microstructural features (pore size, porosity, and thicknesses) can be tuned by conditions; and this method is readily scalable (vs serial printing) and can yield complex tubular structures with Janus faces. In vitro studies demonstrate anisotropic cell guidance, and in vivo studies using a rat calvarial defect model further confirm the beneficial features of such Janus porous film for guided bone regeneration. In summary, these results further demonstrate that electro-fabrication provides a simple and scalable platform technology for the controlled functional structures of soft matter for applications in regenerative medicine.

Laser processing of microdroplet structure of liquid crystal in 3D

Processing of mesoscale structures of soft matter and liquid is of great importance in both science and engineering. In this work, we introduce the concept of laser-assisted micromachining to this field and inject a certain number of microdroplets into a preselected location on the surface of a liquid crystal drop through laser irradiation. The impact of laser energy on the triggered injection is discussed. The sequentially injected microdroplets are spontaneously captured by the defect ring in the host drop and transported along this defect track as micro-cargos. By precisely manipulating the laser beam, the tailored injection of droplets is achieved, and the injected droplets self-assemble into one necklace ring within the host drop. The result provides a bottom-up approach for the in-situ and three-dimensional microfabrication of droplet structure of soft matter using a laser beam, which may be applicable in the development of optical and photonic devices.

Recent advances on food‐based applications of monoglyceride oleogels

AbstractMonoglyceride (MG) oleogels are soft matter structures designed to mimic the functionality of fats while maintaining a lipid profile comparable to that of edible oils. These novel fat materials have been mainly investigated as ingredients to reduce saturated fats and eliminate trans fats in the production of several foods, such as spreadables, bakeries, confectioneries, and meat products among others. Due to the versatility that oleogels offer, other relevant technological functionalities as well as the development of health‐promoting systems have been the subject of extensive research. MG oleogels have been explored as oil migration inhibitors, emulsion stabilizers, lipid oxidation stability enhancers, and even as 3D printing materials. Among the most recent applications are the use of MG oleogels as carriers of bioactive compounds as well as the development of systems able to modulate lipid digestion. This review exclusively focuses on the advances over the last decade in technological and nutritional applications of MG oleogels and MG oleogel‐based systems, outlining the most significant findings and conclusions from the literature, as well as challenges and trends for future studies.

Neutrons in Softmatter

Neutron scattering is a powerful method to investigate hierarchical structure and dynamics of soft matter. In this article, several experimental results of surfactant systems, binary liquid mixtures with antagonistic salt, lipid membrane and hydration water by means of Small-Angle Neutron Scattering, Neutron Spin Echo and Quasi-Elastic Neutron Scattering were introduced.

Numerical modeling of optical modes in topological soft matter

Vector and vortex laser beams are desired in many applications and are usually created by manipulating the laser output or by inserting optical components in the laser cavity. Distinctly, inserting liquid crystals into the laser cavity allows for extensive control over the emitted light due to their high susceptibility to external fields and birefringent nature. In this work we demonstrate diverse optical modes for lasing as enabled and stablised by topological birefringent soft matter structures using numerical modelling. We show diverse structuring of light-with different 3D intensity and polarization profiles-as realised by topological soft matter structures in radial nematic droplet, in 2D nematic cavities of different geometry and including topological defects with different charges and winding numbers, in arbitrary varying birefringence fields with topological defects and in pixelated birefringent profiles. We use custom written FDFD code to calculate emergent electromagnetic eigenmodes. Control over lasing is of a particular interest aiming towards the creation of general intensity, polarization and topologically shaped laser beams.

Power-law frictional landscapes induce anomalous diffusion

Particle motion often exhibits anomalous diffusion arising from spatial inhomogeneity in the complex structures of soft materials. Spatial inhomogeneity induces a power-law frictional landscape for the mean-squared displacement of particles in a force-free environment; expressly, 〈x2(t)〉∼tα (i.e., 0<α≤2). We calculate analytically and numerically this mean-squared displacement. By comparing with a XY system in a logarithmic potential, for which anomalous diffusion transitions occur in regimes from normal diffusion to confinement, we investigated the diffusive dynamics of a realistic system away from its equilibrium state. Spatial nonlocal processes were found to be equivalent to time nonlocal ones (i.e., non-Ohmic memory); specifically, the weaker the effective friction produced, the stronger is the diffusion induced. This overcomes the difficulty encountered when evaluating memory effects in experiments. Aided by the generalized Green–Kubo formula, our model is also compared with diffusion processes obeying the scaling behavior of the velocity correlation function. The present study on anomalous diffusion in inhomogeneous environments is helpful because the phenomenon appears in soft, solid and biological matter.

An overview of structure engineering to tailor the functionality of monoglyceride oleogels.

Monoglyceride (MG)-based oleogelation is an effective strategy to create soft matter structures with the functionality of fats, but with a nutritional profile similar to edible oils. MG oleogels are mainly studied to replace or reduce trans and saturated fats as well as to develop novel products with improved physical and organoleptic properties. The process consists of direct dispersion of MGs into the oil at temperatures above the melting point. This is followed by a cooling period in which the gelator network is formed, entrapping the oil in a crystalline structure. MG composition and concentration, oil type, process temperatures, stirring speed, shear rate during cooling, and storage time play a role in the kinetics of MG crystallization within an MG-oil system, which leads to the formation of lipid materials with different properties. A deep understanding of MG oleogelation processing parameters allows for the tailoring of oleogel properties to meet desirable characteristics as solid fat replacers. This review provides insight regarding manipulating physical process parameters to engineer structures with specific functionality. Furthermore, ultrasound technologies and optimization methodologies are discussed as tools for the production of oleogels with specific properties based on their potential use as well as the development of bi- and multi-gelators oleogels using MGs. Finally, the food applications in which MG oleogels have been tested are summarized in addition to the identified gaps that require further research.

Fabrication of Highly Stretchable and Wearable Elastomer Structure with Liquid Metal Encapsulated in Auxetic Channel

Recently, soft material structures, in which liquids and droplets are introduced into solids in various shapes, have been attracting attention. These structures can be used in the fields of soft electronics, soft robotics, and wearable devices, etc. In this study, we focus on the auxetic structures, which are patterned structures with negative Poisson's ratio. Herein, we fabricated an auxetic channel structure in elastomer using 3D printer and aimed to develop a novel wearable device with liquid metal inflow. This room-temperature liquid metal has been widely used in flexible and stretchable sensors, focusing on embedding liquid metal in microchannels, liquid metal microdroplets formation, captive sensors, and liquid metal nanoparticles, etc.

Laser micro/nanomachining technology for soft matter

Laser micro/nanomachining technology for soft matter achieves the purpose of fabricating the spherical structures of soft matter by combing laser-assisted mechanical injection and controllable self-assembly, which has significant advantages in comparison with conventional methods like droplet microfluidics. In this study, the effects of laser parameters such as laser energy, beam size, and irradiation position on the injection are investigated. It is found that there also exists one upper limit of the laser energy, and if the laser irradiation is too strong, it can introduce a convection flow of liquid crystal rather than trigger off the injection of guest microdroplets. Thus, the laser injection can be achieved in a specific energy range of the laser irradiation. By manipulating the laser beam with a smaller size, the guest water microdroplets can be injected at the preselected location on the surface of a host liquid crystal droplet. In addition, the influences of material parameters such as the surfactant concentration, the material type and phase state of liquid crystal on the laser-assisted mechanical injection, and the size of the injected guest droplet are investigated. It is found that the liquid crystal droplet with higher surfactant concentration requires less energy from the laser irradiation to generate enough mechanical force to trigger off the injection. Because under the same temperature increment, the liquid crystal droplet with higher ion concentration enjoys a stronger surface tension gradient. By comparing several different types of liquid crystals, it is found the injection of guest droplets into a host with a higher elastic constant liquid crystal can be more difficult. The influences of the material type of liquid crystal and the concentration of surfactant on the critical size of guest microdroplets are summarized. Finally, the defect lines of liquid crystal are introduced as the self-assembly template, through which microdroplets of liquid crystal with the sophisticated spherical structure are fabricated. The self-assembly kinetic behaviors of guest droplets in the defect line are analyzed. The laser micro/nanomachining technology of soft matter can be applied to the extreme processing and application development of 3D spherical structures in the fields of optoelectronics, photonics, and biomedicine.

Soft Matter Characterization From Ultrasonic Microrheology and Fractional Calculus

Understanding soft matter mechanical behavior is of great interest as multiphasic combinations of their composition induce new properties which can be exploited for innovative applications. However, the final features optimization requires a tight multiscale control of the structure, even during the elaboration early stages. This paper presents a multifrequency technique to investigate this evolution at mesoscopic scale and its bonds with other scales. A TMS resonator is used as a discrete spectral ultrasonic microrheometer from 5MHz to 50MHz. Then, soft matter can be described as an elastic structure, due to macromolecular interactions, immersed in an effective viscous fluid. An original model of the measured mechanical impedance is proposed and enables the simultaneous monitoring of the effective viscosity and the internal structure. It is based on fractional calculus. In addition to complex shear modulus, the evolution of a fractional parameter, ranging from zero for solids to one for Newtonian fluids, can be studied. The model and the experimental set-up are validated with various complex materials: Newtonian glycerol mixtures, cosmetic emulsions, and silica gels. Effective viscosity accuracy is demonstrated (less than 5% of error for Newtonian fluids). Structural values of complex fluids range from 0.6 (gels) to 1 (liquids). The extracted structural parameter can be linked to the fractal dimension. Hence, this technique is relevant to describe soft matter structure. Moreover, the structural parameter on-line monitoring can be useful to optimize the elaboration process of new products. Indeed, a microscopic characteristic time can be extracted and correlated to the macroscopic gelation time.

Unified one-dimensional finite element for the analysis of hyperelastic soft materials and structures

Based on the Carrera unified formulation (CUF) and first-invariant hyperelasticity, this work proposes a displacement-based high order one-dimensional (1 D) finite element model for the geometrical and physical nonlinear analysis of isotropic, slightly compressible soft material structures. Different strain energy functions are considered and they are decomposed in a volumetric and an isochoric part, the former acting as penalization of incompressibility. Given the material Jacobian tensor, the nonlinear governing equations are derived in a unified, total Lagrangian form by expanding the three-dimensional displacement field with arbitrary cross-section polynomials and using the virtual work principle. The exact analytical expressions of the elemental internal force vector and tangent matrix of the unified beam model are also provided. Several problems are addressed, including uniaxial tension, bending of a slender structure, compression of a three-dimensional block, and a thick pinched cylinder. The proposed model is compared with analytical solutions and literature results whenever possible. It is demonstrated that, although 1 D, the present CUF-based finite element can address simple to complex nonlinear hyperelastic phenomena, depending on the theory approximation order.

Development of Novel Soft Materials with Mechanical Anisotropy using 3D Printed Lattice Structures and Application for Soft Robots

Introduction: In recent years, soft robots made of soft, highly elastic materials have been attracting attention as an alternative to conventional robots made of hard rigid bodies such as metal. Soft robots are expected to play an active role in fields where there are many opportunities to interact with humans, such as collaborative work, nursing care, and welfare. Soft robots are often made of polymers such as rubber, gel, and plastic. By controlling the properties of flexible materials, such as large elastic deformation, elastic modulus, and viscoelasticity, it is possible to design and develop functionalities that take advantage of the softness, which has not been possible with conventional robot technology. In this study, we investigated how to control the physical properties of soft matter by compositing the 3D printed lattice structure of soft matter with silicone rubber. Experiments: 3D model data of the lattice, called “igeta structure” (beam and girder structure) was designed using OpenSCAD, script-based 3D CAD software. Five 3D models of lattice structures with different crossing angles were created and they were 3D printed with an FDM 3D printer using Thermoplastic polyurethane (TPU) material. The printed lattice models were placed in a 20mm cubic mold, and silicone rubber (Ecoflex00-30) was poured into the mold and cured. Compression tests in three orthogonal axes (X, Y, and Z) were performed on these five models using an ORIENTEC STA-1150 universal testing machine. Results and discussion: Figure 1 shows the Young’s modulus of igeta structure and silicone composite models calculated from compression tests. Anisotropy of Young’s modulus varied depending on the crossing angles of the lattice structure. In particular, the Young's modulus in the x-axis is remarkably changed. These results confirm that it is possible to change the anisotropy of the elastic material depending on the shape of the lattice structure. Its will be useful for designing soft robots and confirming their functions. Figure 1

Controlling solvent quality by time: Self-avoiding sprints in nonequilibrium polymerization.

A fundamental paradigm in polymer physics is that macromolecular conformations in equilibrium can be described by universal scaling laws, being key for structure, dynamics, and function of soft (biological) matter and in the materials sciences. Here we reveal that during diffusion-influenced, nonequilibrium chain-growth polymerization, scaling laws change qualitatively, in particular, the growing polymers exhibit a surprising self-avoiding walk behavior in poor and θ solvents. Our analysis, based on monomer-resolved, off-lattice reaction-diffusion computer simulations, demonstrates that this phenomenon is a result of (i) nonequilibrium monomer density depletion correlations around the active polymerization site, leading to a locally directed and self-avoiding growth, in conjunction with (ii) chain (Rouse) relaxation times larger than the competing polymerization reaction time. These intrinsic nonequilibrium mechanisms are facilitated by fast and persistent reaction-driven diffusion ("sprints") of the active site, with analogies to pseudochemotactic active Brownian particles. Our findings have implications for time-controlled structure formation in polymer processing, as in, e.g., reactive self-assembly, photocrosslinking, and three-dimensional printing.

Morphological Group Theory of Soft Matter Structure - A New Mathematics of Natural Image Numbers

The accurate understanding and interpretation of the SARS-CoV-2 electron microscope photos (EMP) is of great significance for the scientific treatment of coronary pneumonia and precise strategy. Here I study the image mathematics and physics description of micro-images of soft matter system by the morphology group theory of material structure, and show that there is a natural image numbers equation, which can be used to describe not only the common feature of soft matter structure, but also to correct classify the states into different classes, so that to study the morphology physics for soft matter science and biology, some important basic concepts of biophysics, such as the central dogma of molecular biology, Gene sequence analysis, heuristic recognition of SARS-CoV-2 can also be newly explained and understood by the equation.

A NIST facility for resonant soft x-ray scattering measuring nano-scale soft matter structure at NSLS-II

We present the design and performance of a polarized resonant soft x-ray scattering (RSoXS) station for soft matter characterization built by the national institute of standards and technology at the national synchrotron light source-II (NSLS-II). The RSoXS station is located within the spectroscopy soft and tender beamline suite at NSLS-II located in Brookhaven national laboratory, New York. Numerous elements of the RSoXS station were designed for optimal performance for measurements on soft matter systems, where it is of critical importance to minimize beam damage and maximize collection efficiency of polarized x-rays. These elements include a novel optical design, sample manipulator and sample environments, as well as detector setups. Finally, we will report the performance of the measurement station, including energy resolution, higher harmonic content and suppression methods, the extent and mitigation of the carbon absorption dip on optics, and the range of polarizations available from the elliptically polarized undulator source.

ViewSq, a Visual Molecular Dynamics (VMD) module for calculating, analyzing, and visualizing X-ray and neutron structure factors from atomistic simulations

viewSq, a Visual Molecular Dynamics (VMD) module for calculating, analyzing, and visualizing X-ray and neutron structure factors from atomistic simulations

Proliferation of mesenchymal stem cells by graphene-attached soft material structure

This paper aims to clarify the effect of a structure of graphene attached on soft material, as against conventional rigid materials, and the thereby-obtained graphene-based micro/nano-scale surface structures on proliferation of human mesenchymal stem cells (MSCs). The cell culture tests are conducted using graphene-attached poly(dimethylsiloxane) (PDMS) substrates having various surface structures and graphene-attached glass substrates as the scaffolds. The fluorescence microscopy observation results demonstrate that the existence of graphene film on PDMS significantly promotes the cellular proliferation and elongation in both cases using two kinds of media, and the rate of cell growth for the graphene-attached PDMS substrates is much larger compared to the graphene-attached glass substrates. The difference in the graphene-based surface structures on PDMS has little influence on the degree of cell growth. It is implied that the number of cells corresponds to the rate of graphene covering the surface of PDMS, suggesting that the cell growth strongly depends on the projected surface area of the graphene film attached on PDMS.

A cosolvent surfactant mechanism affects polymer collapse in miscible good solvents

The coil–globule transition of aqueous polymers is of profound significance in understanding the structure and function of responsive soft matter. In particular, the remarkable effect of amphiphilic cosolvents (e.g., alcohols) that leads to both swelling and collapse of stimuli-responsive polymers has been hotly debated in the literature, often with contradictory mechanisms proposed. Using molecular dynamics simulations, we herein demonstrate that alcohols reduce the free energy cost of creating a repulsive polymer–solvent interface via a surfactant-like mechanism which surprisingly drives polymer collapse at low alcohol concentrations. This hitherto neglected role of interfacial solvation thermodynamics is common to all coil–globule transitions, and rationalizes the experimentally observed effects of higher alcohols and polymer molecular weight on the coil-to-globule transition of thermoresponsive polymers. Polymer–(co)solvent attractive interactions reinforce or compensate this mechanism and it is this interplay which drives polymer swelling or collapse.