Properties Of Soft Materials Research Articles

Elasticity of whole blood clots measured via Volume Controlled Cavity Expansion

Measuring and understanding the mechanical properties of blood clots can provide insights into disease progression and the effectiveness of potential treatments. However, several limitations hinder the use of standard mechanical testing methods to measure the response of soft biological tissues, like blood clots. These tissues can be difficult to mount, and are inhomogeneous, irregular in shape, scarce, and valuable. To remedy this, we employ in this work Volume Controlled Cavity Expansion (VCCE), a technique that was recently developed, to measure local mechanical properties of soft materials in their natural environment. Through highly controlled volume expansion of a water bubble at the tip of an injection needle, paired with simultaneous measurement of the resisting pressure, we obtain a local signature of whole blood clot mechanical response. Comparing this data with predictive theoretical models, we find that a 1-term Ogden model is sufficient to capture the nonlinear elastic response observed in our experiments and produces shear modulus values that are comparable to values reported in the literature. Moreover, we find that bovine whole blood stored at 4 °C for greater than 2 days exhibits a statistically significant shift in the shear modulus from 2.53 ± 0.44 kPa on day 2 (N = 13) to 1.23 ± 0.18 kPa on day 3 (N = 14). In contrast to previously reported results, our samples did not exhibit viscoelastic rate sensitivity within strain rates ranging from 0.22 – 21.1 s−1. By surveying existing data on whole blood clots for comparison, we show that this technique provides highly repeatable and reliable results, hence we propose the more widespread adoption of VCCE as a path forward to building a better understanding of the mechanics of soft biological materials.

Fishing Net‐Inspired Mutiscale Ionic Organohydrogels with Outstanding Mechanical Robustness for Flexible Electronic Devices

AbstractMechanically robust and electrically conductive organohydrogels/hydrogels are increasingly required in flexible electronic devices, but it remains a challenge to achieve organohydrogels/hydrogels with integrated high performances. Herein, inspired by the geometric deformability and robustness of fishing nets, multiscale ionic organohydrogels with outstanding isotropic mechanical robustness are developed. The organohydrogels are prepared by introducing polyacrylamide (PAM) hydrogel, Zn2+ and a binary solvent of glycerol‐water into a crosslinked fibrous mat which is electrospun from poly(acrylic acid) (PAA) and poly(vinyl alcohol) (PVA). Because of the unique structure, the resultant organohydrogels, being mentioned as PAA‐PVA/PAM/Zn2+ organohydrogels, exhibit outstanding tensile strength (9.45 MPa), high stretchability, excellent anti‐fatigue property, skin‐like mechanical behaviors and ionic conductivity. Importantly, the organohydrogels are promising in flexible electronic devices capable of operating properly over a wide temperature range and under harsh mechanical conditions, such as mechanical‐electrical signal transducing materials in flexible mechanosensors and robust electrolytes in zinc ion hybrid supercapacitors. Not only the multiscale design strategy will provide a clue to improve the mechanical properties of soft materials, but also the organohydrogels offer promising materials for future flexible electronic devices.

Back Cover: ASBase: Aggregates of fluorescent gels assembled by interfacial dynamic bonds

Researches on both microscopic and macroscopic aggregates are significant, whereas, most studies of aggregates have focused on microscopic building blocks. Fluorescent gels, as the important macroscopic building blocks, show extraordinary fluorescence and soft material properties. Herein, Ji and co-workers summarized a series of aggregates of fluorescent gels based on interfacial non-covalent bonds and dynamic covalent bonds (e283).

Protocells and Prebiotic Systems

The de novo synthesis and self-assembly of molecules to establish the framework of living systems is a key target in the field of systems chemistry. The construction of synthetic cellular systems from scratch is one important such route to achieve this goal. This Special Collection on Protocells and Prebiotic Systems, guest edited by Dora Tang and Avinash J. Patil, showcases some of the most exciting work done in this field today. (D.Tang photograph copyright MPI-CBG). The de novo synthesis of molecules and their self-assembly to establish the framework of living systems is a key goal of systems chemistry. One route to achieving this is by building synthetic cellular systems from scratch which provides a gateway to understand and control emergence that arises from an integration of functional molecules and biological nanostructures at various length scales. Progress in this area can have significant impact for unravelling the origins of life, synthetic biology and future biomedical applications whilst providing fundamental insights into the mechanisms of biological systems. This Special Collection on Protocells and Prebiotic Systems brings together new and exciting work that is taking place in this field and demonstrates the extraordinary breadth of contributions required to make progress in this area: From prebiotic chemistry, to a survey of the molecular parts which can be used to design and build programmable cell-like compartments, engineer catalytic microreactors or create higher ordered architectures, to the emergence of adaptable systems where chemical environments can tune the physicochemical properties of soft materials. Furthermore, the capability to assimilate these properties to mimic fundamental biological processes such as chemical signaling; motility; energy transduction or cell growth and division are ever increasing. Whilst these examples are crucial for establishing minimal living systems, there are exciting prospects to exploit synthetic-cell-like compartments in wide-ranging applications including biomimetic materials; novel stimuli-responsive delivery platforms; biocatalysis; environmental remediation; tissue engineering; regenerative medicine; living materials and in adaptive integration to biological cells. The opinions expressed in this publication are the view of the author(s) and do not necessarily reflect the opinions or views of ChemSystemsChem, the Publisher, Chemistry Europe, or the affiliated editors. Dora Tang is currently a research group leader at the MPI-CBG, Dresden (Germany). Her multidisciplinary lab reimagines and translates the physical phenemona which drive out of equilibrium processes in cells to novel, robust and dynamic synthetic cellular systems. The minimal systems address questions in origin of life and modern biology. (Photograph copyright MPI-CBG). Avinash J. Patil is a faculty and group leader at the Centre for Organized Matter Chemistry, School of Chemistry, University of Bristol (UK). His research interests cover the design and construction of artificial cells, smart microreactors, and functional hybrid nanomaterials by combining various aspects of biology, materials chemistry, and micro/nanofabrication techniques.

Design, testing and control of a smart haptic interface driven by 3D-printed soft pneumatic actuators for virtual reality-based hand rehabilitation

This work presents the main steps of design and testing of a novel haptic interface and adaptive admittance control scheme for optimal regulation of the human–machine interaction in hand rehabilitation mediated by a smart system in virtual–reality environment. The prototype development is the result of an integrated HW/SW design and, moreover, the advantages from additive manufacturing techniques and mechanical properties of soft materials are exploited for the realization steps. Indeed, to make the interface smart, a network of piezo-resistive force sensors is embedded into the user’s command interface and the acquired signals are used for the adaptive regulation of human–machine interaction. Another distinctive feature of the haptic interface, which enables to identify this latter as a smart system, is the interaction control based on the estimation of the user’s intention within a novel scheme of adaptive admittance control. The enhanced training process in rehabilitation assisted by the haptic interface and virtual environment has been experimentally validated during a series of goal-directed tasks. The improvement of the motor performance of the user under the assistance of the adaptive admittance control has been experimentally evaluated. Further results show that the rehabilitation system supports the quantitative assessment of the robustness of the motor learning performance of the hand under the generation of haptic disturbances.

Controlling extrudate volume fraction through poroelastic extrusion of entangled looped fibers

When a suspension of spherical or near-spherical particles passes through a constriction the particle volume fraction either remains the same or decreases. In contrast to these particulate suspensions, here we observe that an entangled fiber suspension increases its volume fraction up to 14-fold after passing through a constriction. We attribute this response to the entanglements among the fibers that allows the network to move faster than the liquid. By changing the fiber geometry, we find that the entanglements originate from interlocking shapes or high fiber flexibility. A quantitative poroelastic model is used to explain the increase in velocity and extrudate volume fraction. These results provide a new strategy to use fiber volume fraction, flexibility, and shape to tune soft material properties, e.g., suspension concentration and porosity, during delivery, as occurs in healthcare, three-dimensional printing, and material repair.

Magnetic property measurement and analysis of high-frequency soft magnetic materials under non-sinusoidal excitation considering temperature effect

Electrical equipment operates under various temperatures and non-sinusoidal excitation, which makes magnetic properties of soft magnetic materials quite different from those under room temperature and sinusoidal excitation. Magnetic properties and loss characteristics of the ferrite (N87) and nanocrystalline alloy (FT-3KL) are measured and analyzed in the range of 25 °C to 125 °C from 5 kHz to 20 kHz under both square and rectangular excitation with different duty ratios. The temperature dependence of these materials under different conditions is systematically compared with normalization method. The comprehensive performance of core materials is discussed in combination with the experimental phenomena and results.

Bringing Quantum Mechanics to Coarse-Grained Soft Materials Modeling

Fundamental knowledge gaps are endemic in our understanding of how emergent properties of soft materials are linked to the quantum mechanical (QM) world. The limitations of current QM modeling paradigms inhibit the understanding and design of classes of soft materials for which QM phenomenology is critical. At its root, these limitations derive from the seemingly innocuous premise of requiring all atomic positions to solve the molecular Schrödinger equation, which necessitates supercomputing resources to incorporate even simple QM phenomenology into small (∼nm) systems of soft materials. Here, we review emerging efforts to overcome these challenges through the development of electronic prediction models that operate at the coarse-grained resolution. We motivate the origins of this new computational paradigm, denoted electronic coarse-graining (ECG), discuss its relationship to existing molecular modeling frameworks, and describe recent successes of ECG and related models for soft materials. Importantly, we highlight the classes of soft materials where ECG models can be potentially transformative.

The microwave absorption properties of soft magnetic materials in frequency up to 40 GHz

With the continuous development of communication technology, the microwave frequency used has been extended to 24∼30 GHz or even higher. Thus, for the research on microwave absorption materials, the commonly used 2∼18 GHz frequency range might no longer be enough. More studies of microwave absorption properties in a higher frequency band are necessary. In this work, we report the microwave absorption properties of several soft magnetic composites in frequency up to 40 GHz. Magnetic materials such as iron, Y2Fe16Si, Ce2Fe17N3−δ, and La2Fe4Co10B micron powders which display excellent microwave absorption properties in 2∼18 GHz, are investigated. Within 2∼40 GHz, the reflection loss (RL) of iron/paraffin, Y2Fe16Si/paraffin, Ce2Fe17N3−δ/paraffin and La2Fe4Co10B/paraffin composites could reach −46.2 dB, −71.4 dB, −49.1 dB, and −40.1 dB, respectively. Moreover, their effective absorption bandwidth (RL < −10 dB) could reach 16.9 GHz, 8.53 GHz, 10.08 GHz, and 8.03 GHz, respectively. Though the measurements are extended to 40 GHz, the absorption properties of these composites become weak when the frequency rises to around 40 GHz, which is restricted by the cutoff frequencies of the materials. The measured data shows that these soft magnetic composites are good candidates for high-frequency microwave absorption materials, while exploring magnetic materials with further higher cutoff frequencies may result in better performance.

Ultrastable emulsions constructed by self-assembly of two protein-polyphenol- anionic polysaccharide ternary complexes-stablized high internal phase emulsions

Compared to conventional high internal phase emulsions (HIPEs), ultrastable HIPEs have recently attracted much attention due to much better stability and protection for bioactive compounds. Here, novel food-grade ultrastable HIPEs were successfully constructed. By simply mixing two individual unstable HIPEs (instability in 3 months in open atmosphere) stabilized by ternary complexes of protein (i.e., lactoferrin), two polyphenols (i.e., (−)-epigallocatechin-3-gallate and curcumin) and two anionic polysaccharides (i.e., κ-carrageenan and low methoxylated pectin), respectively, ultrastable mixed-HIPEs (very stable for 1 year or more in open atmosphere) were achieved unexpectedly. The two individual HIPEs underwent liquid-to-gel and viscous-to-elastic transitions during mixing, exhibiting strong structural synergism. The stabilization was ascribed to the electrostatic repulsive interactions and the formed interpenetrating polymer networks hydrogels in continuous phases; their contribution varied according to the binding sequences of protein, polyphenol, and polysaccharide (for ternary complexes) and the combination modes of individual HIPEs (for mixed-HIPEs). The excellent soft material properties of ternary complexes can provide guarantee for the stsability of emulsion droplets, avoiding their rupture caused by strong squeezing in mixed-HIPEs. This finding greatly expands the type of food grade ultrastable HIPEs. Overall, the novel food-grade ultrastable mixed-HIPEs will offer fascinating opportunities for their future applications in food, medical, cosmetic, and tissue engineering products.

Gap-directed chemical lift-off lithographic nanoarchitectonics for arbitrary sub-micrometer patterning.

We introduce a unique soft lithographic operation that exploits stamp roof collapse-induced gaps to selectively remove an alkanethiol self-assembled monolayer (SAM) on Au to generate surface patterns that are orders of magnitude smaller than structures on the original elastomer stamp. The smallest achieved feature dimension is 5 nm using a micrometer-scale structured stamp in a chemical lift-off lithography (CLL) process. Molecular patterns retained in the gaps between stamp features and their circumscribed or inscribed circles follow mathematical predictions, and their sizes can be tuned by altering the stamp structure dimensions, including height, pitch, and shape. These generated surface molecular patterns can function as biorecognition arrays or be transferred to the underneath Au layer for metallic structure creation. By combining CLL process with this gap phenomenon, soft material properties that are previously thought as demerits can be used to achieve sub-10 nm features in a straightforward sketch.

Insights about the ability of folate based supramolecular gels to act as targeted therapeutic agents.

With the aim to obtain targeted chemotherapeutic agents, imidazolium and ammonium-based folate salts were synthesized. Their photophysical behavior was investigated both in buffer and buffer/DMSO solution as well as in solid phase, performing UV-vis and fluorescence investigations. Properties of the aggregates were also analyzed by dynamic light scattering. Gelation ability of the salts was analyzed in biocompatible solvents, and gel phases obtained were characterized by determining critical gelation concentrations and gel-solution transition temperatures. Insights about gelator interactions in the tridimensional network were also gained performing ATR-FTIR investigation. Properties of soft materials were further analyzed performing rheology measurements, scanning electron microscopy, fluorescence and resonance light scattering investigations. Antiproliferative activity of organic salts was tested towards two breast cancer cell lines, expressing different levels of folate receptor, namely MDA-MB-231 and MCF-7, and a normal epithelial cell line, like h-TER T-RPE-1, by using MTT assay. Dichlodihydrofluorescein acetate test was performed to verify the role of oxidative stress in cell death. Finally, antiproliferative activity was also evaluated in gel phase, to verify if salts were able to retain biological activity also after the entrapment in the gelatinous network. Results collected evidence that folate based organic salts were able to behave as targeted chemotherapeutic agents both in solution and gel phase, showing uptake mechanism and selectivity indexes that depend on both cancer cell line nature and salt structure.

Studying the high-rate deformation of soft materials via laser-induced membrane expansion.

Cavitation is a phenomenon that occurs when the internal pressure of a material exceeds the resistance to deformation provided by the surrounding medium. Several measurements, such as the blister test, bubble inflation, and cavitation rheology, take advantage of this phenomenon to measure the local mechanical properties of soft materials at relatively low deformation rates. Here, we introduce a new measurement called laser-induced membrane expansion (LIME) that measures the shear modulus of a thin membrane at high strain rates (≈106 s-1 to 108 s-1) by using laser ablation to rapidly expand a thin (tens of microns) elastomeric membrane. To demonstrate the capabilities of this measurement, we use LIME to study the mechanical properties of poly(dimethylsiloxane) (PDMS) membranes at several thicknesses (from 10 μm to 60 μm) and crosslink densities. We find that the shear modulus of the PDMS measured by LIME was weakly dependent on the crosslink density, but was strongly strain rate dependent with values ranging from 106 Pa to 108 Pa. This measurement platform presents a new approach to studying the mechanical properties of soft but thin materials over a range of deformation rates.

Fluorescence-readout as a powerful macromolecular characterisation tool.

The last few decades have witnessed significant progress in synthetic macromolecular chemistry, which can provide access to diverse macromolecules with varying structural complexities, topology and functionalities, bringing us closer to the aim of controlling soft matter material properties with molecular precision. To reach this goal, the development of advanced analytical techniques, allowing for micro-, molecular level and real-time investigation, is essential. Due to their appealing features, including high sensitivity, large contrast, fast and real-time response, as well as non-invasive characteristics, fluorescence-based techniques have emerged as a powerful tool for macromolecular characterisation to provide detailed information and give new and deep insights beyond those offered by commonly applied analytical methods. Herein, we critically examine how fluorescence phenomena, principles and techniques can be effectively exploited to characterise macromolecules and soft matter materials and to further unravel their constitution, by highlighting representative examples of recent advances across major areas of polymer and materials science, ranging from polymer molecular weight and conversion, architecture, conformation to polymer self-assembly to surfaces, gels and 3D printing. Finally, we discuss the opportunities for fluorescence-readout to further advance the development of macromolecules, leading to the design of polymers and soft matter materials with pre-determined and adaptable properties.

Using laser-induced breakdown spectroscopy to characterize the surface mechanical properties of soft materials

The ratio of ionic to atomic lines with surface rigidity implying the feasibility of characterizing soft surface mechanical properties using LIBS.

Tailoring Rate and Temperature-Dependent Fracture of Polyether Networks with Organoaluminum Catalysts

Polyethers are ubiquitous in engineering and biomedical applications because their oxygen-rich backbone allows them to interact with a variety of polar small molecules such as ions, gases, and pharmaceuticals. These materials are also able to sustain large reversible deformations when cross-linked at the molecular scale, leading to an interesting combination of functional and mechanical properties. We synthesized two families of polyether networks by organoaluminum-catalyzed ring-opening copolymerization of ethyl glycidyl ether (EGE) monomer and 1,4-butanediol diglycidyl ether (BDGE) cross-linker and explored the relationship between network architecture and fracture properties. The key result is that living copolymerizations, as enabled by a chelate of triethylaluminum with dimethylaminoethanol, afford access to a critical cross-link density, νx ≈ 3 × 1025 chains/m3, and loss tangent, tan(δ) ≈ 0.09, at which fracture is dominated by chain scission rather than friction. Such control over the fracture resistance of polyether networks unveils the potential of living copolymerizations to design the functional and mechanical properties of soft materials.

Remote Sensing of the Nano-Rheological Properties of Soft Materials Using Magnetic Nanoparticles and Magnetic AC Susceptometry.

We have developed a nano-rheological characterization tool to extract the frequency- and scale-dependent rheological properties of soft materials during oral processing. Taking advantage of AC susceptometry, the dynamic magnetization of magnetic nanoparticles blended in the matrix material is measured. The magnetic AC susceptibility spectra of the particles are affected by the viscosity and mechanical modulus of the matrix material and provide the rheological properties of the matrix. Commercially available iron-oxide magnetic nanoparticles with 80 and 100 nm particle sizes are used as tracers in the frequency range of 1 Hz-10 kHz. The AC susceptibility is measured using two differentially connected coils, and the effects of the sample temperature and distance with respect to the detection coils are investigated. The developed measurement setup shows the feasibility of remote nano-rheological measurements up to 2 cm from the coil system, which can be used to, e.g., monitor the texture of matrix materials during oral processing.

Editorial: Exploring the mechanical properties of soft materials at multiple length scales

Editorial: Exploring the mechanical properties of soft materials at multiple length scales

Evaluation of shear piezoelectric coefficients by a bimorph cantilever technique for extruded and oriented poly(l‐lactide) films

AbstractUniaxially stretched poly(l‐lactide) (US‐PLA) films display shear piezoelectric properties of interests for smart applications. However, the measurement of these properties is quite challenging and a simple technique based on bimorph cantilevers is here used. This technique is validated with commercial piezoelectric poly(vinylidene fluoride) (PVDF) films. A piezoelectric coefficient d31 close to 19 pm/V is then obtained with a precision close to 5% and a good accuracy to expected values. For US‐PLA films made by extrusion—machine‐direction orientation, shear piezoelectric coefficients d14 up to 5.9 pm/V are found. Relevant trends can be captured but a low precision on d14, close to 10%, is highlighted. This behavior is probably related to film thickness heterogeneities arising from the extrusion processing at the laboratory scale. Piezoelectric voltage coefficients (g14) and electromechanical coupling coefficients could be also easily obtained with additional measurements of the dielectric permittivity and mechanical compliance. Outstanding g14 coefficients up to 320 mV.m/N are confirmed for US‐PLA films with a precision close to 20%. The bimorph cantilever technique consequently represents a simple and reliable technique to evaluate piezoelectric properties of soft materials, in particular shear piezoelectric properties of US‐PLA films for future developments and optimizations at the pilot scale.

Observational constraints on soft dark energy and soft dark matter: Challenging ΛCDM cosmology

Soft cosmology is an extension of standard cosmology allowing for a scale-dependent equation-of-state (EoS) parameter in the dark sectors, which is one of the properties of soft materials in condensed-matter physics, that may arise either intrinsically or effectively. We use data from Cosmic Microwave Background (CMB), Baryonic Acoustic Oscillations (BAO), Supernovae Type Ia (SNIa), and Redshift space distortion (RSD) probes, in order to impose observational constraints on soft dark energy and soft dark matter. We examine three simple models, corresponding to the minimum extensions of ΛCDM scenario, namely we consider that at large scales the dark sectors have the EoS's of ΛCDM model (dust dark matter and cosmological constant respectively), while at intermediate scales either dark energy or dark matter or both, may have a different EoS according to constant “softness” parameters sde and sdm. The observational confrontation shows that for almost all datasets the softness parameters deviate from their ΛCDM values, in a prominent way for soft dark energy and mildly for soft dark matter, and thus the data favor soft cosmology. Finally, performing a Bayesian evidence analysis we find that the examined models are certainly preferred over ΛCDM cosmology.