Soft Materials Research Articles

Nanozymes for Treating Ocular Diseases.

Nanozymes, characterized by their nanoscale size and enzyme-like catalytic activities, exhibit diverse therapeutic potentials, including anti-oxidative, anti-inflammatory, anti-microbial, and anti-angiogenic effects. These properties make them highly valuable in nanomedicine, particularly ocular therapy, bypassing the need for systemic delivery. Nanozymes show significant promise in tackling multi-factored ocular diseases, particularly those influenced by oxidation and inflammation, like dry eye disease, and age-related macular degeneration. Their small size, coupled with their ease of modification and integration into soft materials, facilitates the effective penetration of ocular barriers, thereby enabling targeted or prolonged therapy within the eye. This review is dedicated to exploring ocular diseases that are intricately linked to oxidation and inflammation, shedding light on the role of nanozymes in managing these conditions. Additionally, recent studies elucidating advanced applications of nanozymes in ocular therapeutics, along with their integration with soft materials for disease management, are discussed. Finally, this review outlines directions for future investigations aimed at bridging the gap between nanozyme research and clinical applications. This article is protected by copyright. All rights reserved.

Viscous Mechano‐Electric Response of Ferroelectric Nematic Liquid

AbstractDirect viscous mechano‐electric response is demonstrated for a room‐temperature ferroelectric nematic liquid, which combines large spontaneous electric polarization with 3D fluidity. The mechano‐electric transduction is observed in the frequency range 1 −200 Hz via a simple demonstrator device. The liquid is placed into a deformable container with electrodes and the electric current induced by both periodic and irregular actuation of the container is examined. The experiments reveal a rich interplay of several distinct viscous mechano‐electric phenomena, where both shape deformations and material flow cause changes in the electric polarization structure of a ferroelectric nematic liquid. The results show that the mechano‐electric features of the material promise a considerable applicative perspective spanning from sensitive tactile sensors to energy harvesting devices.

Alkyl chain length affecting the structure and interactions of choline-based amino acid ionic liquids: Insights from a computational study

The influences of the alkyl chain length of amino acid anions on the structure and interactions of choline-based amino acid ([Cho][AA]) ionic liquids were investigated based on density functional theory (DFT) and molecular dynamics (MD) simulations. The most stable configuration of the individual [Cho][AA] ion pair was determined, revealing negligible variations in the binding energy between choline cation ([Cho]+) and different amino acid anions ([AA]−). To further characterize the intermolecular interactions between charged entities, the atoms in molecules theory (AIM) and independent gradient model based on Hirshfeld partition (IGMH) were employed, which highlight the presence of robust hydrogen bonds between [Cho]+ and [AA] −, underscoring their significance in shaping the structure of [Cho][AA] ion pairs. The MD studies exhibited the aggregation of anions in [Cho][AA] ILs, which was attributed to side chain interactions of anions. This aggregation effect becomes more pronounced with the elongation of anionic alkyl chain. Simultaneously, radial distribution functions (RDF) analysis revealed a higher probability of hydrogen bonds occurring between [Cho]+ and [AA]− as the alkyl chain in [AA]− lengthened. Additionally, the hydrogen bond lifetimes roughly display an increasing trend as the alkyl chain of the [AA]− increases, which may be due to the reduced diffusion coefficients of ions. Hopefully, our results would contribute fundamental knowledge regarding the impact of alkyl chain length of anions on the structure and interactions in the choline-based amino acid ionic liquids.

Rotational Dynamics of Water near Osmolytes by Molecular Dynamics Simulations.

The behavior of water molecules around organic molecules has attracted considerable attention as a crucial factor influencing the properties and functions of soft matter and biomolecules. Recently, it has been suggested that the change in protein stability upon the addition of small organic molecules (osmolytes) is dominated by the change in the water dynamics caused by the osmolyte, where the dynamics of not only the directly interacting water molecules but also the long-range hydration layer affect the protein stability. However, the relation between the long-range structure of hydration water in various solutions and the water dynamics remains unclear at the molecular level. We performed density-functional tight-binding molecular dynamics simulations to elucidate the varying rotational dynamics of water molecules in 15 osmolyte solutions. A positive correlation was observed between the rotational relaxation time and our proposed normalized parameter obtained by dividing the number of hydrogen bonds between water molecules by the number of nearest-neighbor water molecules. For the 15 osmolyte solutions, an increase or a decrease in the value of the normalized parameter for the second hydration shell tended to result in water molecules with slow and fast rotational dynamics, respectively, thus illustrating the importance of the second hydration shell for the rotational dynamics of water molecules. Our simulation results are anticipated to advance the current understanding of water dynamics around organic molecules and the long-range structure of water molecules.

Current advances and gaps in knowledge on personalizing masks for non-invasive respiratory support: a scoping review.

Non-invasive respiratory support delivered through a face mask has become a cornerstone treatment for adults and children with acute or chronic respiratory failure. However, an imperfect mask fit using commercially available interfaces is frequently encountered, which may result in patient discomfort and treatment inefficiency or failure. To overcome this challenge, over the last decade increasing attention has been given to the development of personalized face masks, which are custom made to address the specific facial dimensions of an individual patient. With this scoping review we aim to provide a comprehensive overview of the current advances and gaps in knowledge regarding the personalization of ventilation masks. We performed a systematic search of the literature, and identified and summarized a total of 23 studies. Most studies included were involved in the development of nasal masks. Studies targeting adult respiratory care mainly focused on chronic (home) ventilation and included some clinical testing in a relevant subject population. In contrast, pediatric studies focused mostly on respiratory support in the acute setting, while testing was limited to bench or case studies only. Most studies were positive regarding the performance (i.e. comfort, level of air leak and mask pressure applied to the skin) of personalized masks in bench testing or in human, healthy or patient, subjects. Advances in the field of 3D scanning and soft material printing were identified, but important gaps in knowledge remain. In particular, more insight into cushion materials, headgear design, clinical feasibility and cost-effectiveness is needed, before definite recommendations can be made regarding implementation of large scale clinical programs that personalize non-invasive respiratory support masks for adults and children.

Direct measurement of repulsive and attractive pair potentials using pairs of optical traps

We present a technique for measuring the interactions between pairs of colloidal particles in two optical traps. This method is particularly suitable for measuring strongly attractive potentials, an otherwise challenging task. The interaction energy is calculated from the distribution of inter-particle separations by accounting for the contribution from the optical traps with arbitrary trap profiles. The method is simple to implement and applicable to different types of pair potentials and optical trapping geometries. We apply the method to measure dipolar pair interactions in experiments with paramagnetic colloids in external magnetic fields. We obtain consistent and accurate results in all regimes, from strongly attractive to repulsive potentials. By means of computer simulations, we demonstrate that the proposed method can be successfully applied to systems with complex pair interactions characterized by multiple attractive and repulsive regimes, which are ubiquitous in soft and biological matter.

Functional Soft Materials with Resistance to Liquid Leakage for Thermal Energy Storage

AbstractFunctional soft materials have great potential commercial applications in thermal energy storage, which are required to have a long life, good flexibility, and resistance to liquid leakage. Herein, a composite hydrogel with thermal storage properties is prepared through coupling molecular self‐assembly and in situ polymerization. Hydrophobic stearic acid (SA), as a thermal storage phase change material (PCM), is dispersed in polyacrylamide (PAM) hydrogel network in the form of oil–water emulsion (O/W). The PAM polymer network with good flexibility physically limits high‐frequency collision between SA PCM droplets. This unique design avoids demulsification in phase change emulsion so that the as‐prepared hydrogel composite can resist liquid leakage. The PAM hydrogel network plays the role of heterogeneous nucleation, resulting in the super‐cooling of SA emulsion at only 0.3 °C. On the other hand, SA PCM droplets in as‐prepared soft material do not directly contact with liquid water, so melting/crystallization process is independent of water. As a result, the soft material exhibits a thermal storage density of up to 99.3 J g−1. The present study is an important step toward designing soft energy storage materials.

Engineering Tough Supramolecular Hydrogels with Structured Micropillars for Tunable Wetting and Adhesion Properties.

Soft-lithography is widely used to fabricate microstructured surfaces on plastics and elastomers for designable physical properties such as wetting and adhesions. However, it remains a big challenge to construct high-aspect-ratio microstructures on the surface of hydrogels due to the difficulty in demolding from the gel with low strength and stiffness. Demonstrated here is the engineering of tough hydrogels by soft-lithography to form well-defined micropillars. The mechanical properties of poly(acrylamide-co-methacrylic acid) hydrogels with dense hydrogen-bond associations severely depend on temperature, with Young's modulus increasing from 8.1MPa at 15°C to 821.8MPa at -30°C, enabling easy demolding at low temperatures. Arrays of micropillars are maintained on the surface of the gel, and can be used at room temperature when the gel restores soft and stretchable. The hydrogel also exhibits good shape-memory property, favoring tailoring the morphology with a switchable tilt angle of micropillars. Consequently, the hydrogel shows tunable wetting and adhesion properties, as manifested by varying contact angles and adhesion strengths. These surface properties can also be tuned by geometry and arrangement of micropillars. This facile strategy by harnessing tunable viscoelasticity of supramolecular hydrogels should be applicable to other soft materials, and broaden their applications in biomedical and engineering fields.

Microstructure and magnetic properties of Nanomet compacted by spark plasma sintering

Nanocrystalline soft magnetic materials with high saturation polarization and low losses have a high potential in motor applications. Thus, toroidal cores were compacted by spark plasma sintering of flakes of the melt-spun Nanomet alloy Fe-Si-B-P-Cu. The thermal properties of the ribbons were analyzed by DSC to determine the crystallization temperatures. The influence of the initial powder and of the compacting parameters such as maximum temperature and dwell time on the density and the magnetic properties in DC and AC were investigated. An optimum temperature range of approximately 50 K was determined for good soft magnetic properties. An effect of the dwell time was not recognized in the observed range. By compacting flakes of different sizes, the maximum permeability can be adjusted in the range of up to 7000. The microstructure was observed by means of XRD and TEM in order to confirm the amorphous and nanocrystalline state, respectively. Using the Lorenz mode of the TEM, it was possible to calculate the magnetic domain wall width for the samples and compare the resulting calculated magnetic properties with the experiments.

Polymerization/Depolymerization-Induced Self-Assembly under Coupled Equilibria of Polymerization with Self-Assembly.

Depolymerization breaks down polymer chains into monomers like unthreading beads, attracting more attention from a sustainability standpoint. When polymerization reaches equilibrium, polymerization and depolymerization can reversibly proceed by decreasing and increasing the temperature. Here, we demonstrate that such dynamic control of a growing polymer chain in a selective solvent can spontaneously modulate the self-assembly of block copolymer micellar nano-objects. Compared to polymerization-induced self-assembly (PISA), where irreversible growth of a solvophobic polymer block from the end of a solvophilic polymer causes micellization, polymerization/depolymerization-induced self-assembly presented in this study allows us to reversibly regulate the packing parameter of the forming block copolymer and thus induce reversible morphological transitions of the nano-objects by temperature swing. Under the coupled equilibria of polymerization with self-assembly, we found that demixing of the growing polymer block in a more selective solvent entropically facilitates depolymerization at a substantially lower temperature. Taking ring-opening polymerization of δ-valerolactone initiated from the hydroxyl-terminated poly(ethylene oxide) as a model system, we show that polymerization/depolymerization/repolymerization leads to reversible morphological transitions, such as rod-sphere-rod and fiber-rod-fiber, during the heating and cooling cycle and accompanied by changes in macroscopic properties such as viscosity, suggesting their potential as dynamic soft materials.

Strategies to Diversification of the Mechanical Properties of Organic Crystals

AbstractStructurally ordered soft materials that respond to complementary stimuli are susceptible to control over their spatial and temporal morphostructural configurations by intersectional or combined effects such as gating, feedback, shape‐memory, or programming. In the absence of general and robust design and prediction strategies for their mechanical properties, at present, combined chemical and crystal engineering approaches could provide useful guidelines to identify effectors that determine both the magnitude and time of their response. Here, we capitalize on the purported ability of soft intermolecular interactions to instigate mechanical compliance by using halogenation to elicit both mechanical and photochemical activity of organic crystals. Starting from (E)‐1,4‐diphenylbut‐2‐ene‐1,4‐dione, whose crystals are brittle and photoinert, we use double and quadruple halogenation to introduce halogen‐bonded planes that become interfaces for molecular gliding, rendering the material mechanically and photochemically plastic. Fluorination diversifies the mechanical effects further, and crystals of the tetrafluoro derivative are not only elastic but also motile, displaying the rare photosalient effect.

Physicochemical control of solvation and molecular assembly of charged amphiphilic oligomers at air-aqueous interfaces

Hypothesis: Understanding the rules that control the assembly of nanostructured soft materials at interfaces is central to many applications. We hypothesize that electrolytes can be used to alter the hydration shell of amphiphilic oligomers at the air-aqueous interface of Langmuir films, thereby providing a means to control the formation of emergent nanostructures.Experiments: Three representative salts – (NaF, NaCl, NaSCN) were studied for mediating the self-assembly of oligodimethylsiloxane methylimidazolium (ODMS-MIM+) amphiphiles in Langmuir films. The effects of the different salts on the nanostructure assembly of these films were probed using vibrational sum frequency generation (SFG) spectroscopy and Langmuir trough techniques. Experimental data were supported by atomistic molecular dynamic simulations.Findings: Langmuir trough surface pressure – area isotherms suggested a surprising effect on oligomer assembly, whereby the presence of anions affects the stability of the interfacial layer irrespective of their surface propensities. In contrast, SFG results implied a strong anion effect that parallels the surface activity of anions. These seemingly contradictory trends are explained by anion driven tail dehydration resulting in increasingly heterogeneous systems with entangled ODMS tails and appreciable anion penetration into the complex interfacial layer comprised of headgroups, tails, and interfacial water molecules. These findings provide physical and chemical insight for tuning a wide range of interfacial assemblies.

Probing Isolated Water Molecules in Aqueous Acetonitrile Solutions Using Oxygen K-Edge X-ray Absorption Spectroscopy.

Oxygen K-edge X-ray absorption spectroscopy (XAS) of an aqueous acetonitrile solution exhibited a sharp peak at approximately 537 eV, which was similar to that of water vapor and was not observed in liquid water. The inner-shell spectra of isolated water molecules and water clusters of different sizes surrounded by acetonitrile molecules were obtained by extracting these water structures from the liquid structures of aqueous acetonitrile solutions, as calculated using molecular dynamics simulations. The sharp peak profiles of the O K-edge XAS spectra were derived not from water clusters but from isolated water molecules surrounded by acetonitrile molecules. The present study proposes that isolated water molecules are easily formed in aqueous acetonitrile solutions and that the electronic structures of the isolated water molecules can be analyzed using O K-edge XAS spectra, which separates the contributions of small water clusters.

Turning Ultra-Low Coercivity and Ultra-High Temperature Stability Within 897 K via Continuous Crystal Ordering Fluctuations.

High-performance soft magnetic materials are important for energy conservation and emission reduction. One challenge is achieving a combination of reliable temperature stability, high resistivity, high Curie temperature, and high saturation magnetization in a single material, which often comes at the expense of intrinsic coercivity-a typical trade-off in the family of soft magnetic materials with homogeneous microstructures. Herein, a nanostructured FeCoNiSiAl complex concentrated alloy is developed through a hierarchical structure strategy. This alloy exhibits superior soft magnetic properties up to 897K, maintaining an ultra-low intrinsic coercivity (13.6 A m-1 at 297 K) over a wide temperature range, a high resistivity (138.08µΩcm-1 at 297K) and the saturation magnetization with only a 16.7% attenuation at 897 K. These unusual property combinations are attributed to the dual-magnetic-state nature with exchange softening due to continuous crystal ordering fluctuations at the atomic scale. By deliberately controlling the microstructure, the comprehensive performance of the alloy can be tuned and controlled. The research provides valuable guidance for the development of soft magnetic materials for high-temperature applications and expands the potential applications of related functional materials in the field of sustainable energy.

Dissipative particle dynamics for coarse-grained models

We develop a computational method based on Dissipative Particle Dynamics (DPD) that introduces solvent hydrodynamic interactions to coarse-grained models of solutes, such as ions, molecules, or polymers. DPD-solvent (DPDS) is a fully off-lattice method that allows straightforward incorporation of hydrodynamics at desired solvent viscosity, compressibility, and solute diffusivity with any particle-based solute model. Solutes interact with the solvent only through the DPD thermostat, which ensures that the equilibrium properties of the solute system are not affected by the introduction of the DPD solvent, while the thermostat coupling strength sets the desired solute diffusivity. Thus, DPDS can be used as a replacement for traditional molecular dynamics thermostats such as Nosé–Hoover and Langevin. We demonstrate the applicability of DPDS in the case of polymer dynamics and electroosmotic flow through a nanopore. The method should be broadly useful as a means to introduce hydrodynamic interactions to existing coarse-grained models of solutes and soft materials.

Dynamic analyses of a soft tissue-implant interface: Biological responses to immediate versus delayed dental implants.

To qualitatively and quantitatively evaluate the formation and maturation of peri-implant soft tissues around 'immediate' and 'delayed' implants. Miniaturized titanium implants were placed in either maxillary first molar (mxM1) fresh extraction sockets or healed mxM1 sites in mice. Peri-implant soft tissues were evaluated at multiple timepoints to assess the molecular mechanisms of attachment and the efficacy of the soft tissue as a barrier. A healthy junctional epithelium (JE) served as positive control. No differences were observed in the rate of soft-tissue integration of immediate versus delayed implants; however, overall, mucosal integration took at least twice as long as osseointegration in this model. Qualitative assessment of Vimentin expression over the time course of soft-tissue integration indicated an initially disorganized peri-implant connective tissue envelope that gradually matured with time. Quantitative analyses showed significantly less total collagen in peri-implant connective tissues compared to connective tissue around teeth around implants. Quantitative analyses also showed a gradual increase in expression of hemidesmosomal attachment proteins in the peri-implant epithelium (PIE), which was accompanied by a significant inflammatory marker reduction. Within the timeframe examined, quantitative analyses showed that connective tissue maturation never reached that observed around teeth. Hemidesmosomal attachment protein expression levels were also significantly reduced compared to those in an intact JE, although quantitative analyses indicated that macrophage density in the peri-implant environment was reduced over time, suggesting an improvement in PIE barrier functions. Perhaps most unexpectedly, maturation of the peri-implant soft tissues was a significantly slower process than osseointegration.

Next-Generation Cardiac Interfacing Technologies Using Nanomaterial-Based Soft Bioelectronics.

Cardiac interfacing devices are essential components for the management of cardiovascular diseases, particularly in terms of electrophysiological monitoring and implementation of therapies. However, conventional cardiac devices are typically composed of rigid and bulky materials and thus pose significant challenges for effective long-term interfacing with the curvilinear surface of a dynamically beating heart. In this regard, the recent development of intrinsically soft bioelectronic devices using nanocomposites, which are fabricated by blending conductive nanofillers in polymeric and elastomeric matrices, has shown great promise. The intrinsically soft bioelectronics not only endure the dynamic beating motion of the heart and maintain stable performance but also enable conformal, reliable, and large-area interfacing with the target cardiac tissue, allowing for high-quality electrophysiological mapping, feedback electrical stimulations, and even mechanical assistance. Here, we explore next-generation cardiac interfacing strategies based on soft bioelectronic devices that utilize elastic conductive nanocomposites. We first discuss the conventional cardiac devices used to manage cardiovascular diseases and explain their undesired limitations. Then, we introduce intrinsically soft polymeric materials and mechanical restraint devices utilizing soft polymeric materials. After the discussion of the fabrication and functionalization of conductive nanomaterials, the introduction of intrinsically soft bioelectronics using nanocomposites and their application to cardiac monitoring and feedback therapy follow. Finally, comments on the future prospects of soft bioelectronics for cardiac interfacing technologies are discussed.

The Effect of a Ferromagnetic Steel Enclosure on Magnetic Shielding Systems: Analysis, Modeling, and Experimental Validation

The magnetic shielding device, made of high-permeability soft magnetic material, is sensitive to external influences and requires a protective steel enclosure. A steel enclosure, being strongly ferrimagnetic, can alter the surrounding magnetic field distribution, thus impacting the shielding effectiveness. This study proposes a novel analytical approach to quantify this effect, which has not been previously researched. The method develops a simplified finite element simulation model based on the structural symmetry of the steel enclosure. By using this model, this study analyzes the impact of steel structures with varying heights, widths, and remanent magnetization values. The validity of the method is confirmed through experimental tests on steel buildings. The findings offer insights into the optimal placement of magnetic shielding systems and provide theoretical guidance for designing large-scale magnetic shielding devices.

A gelatin-based ionic conductor with a dense/loose alternating network enabled by surface active cellulose

Although conductive and stretchable ionic conductors are increasingly prepared for flexible sensing applications, such as health monitoring, tissue engineering, and electronic skin, achieving a balance between remarkable mechanical properties and high sensing sensitivity remains a significant challenge. In this work, a dense/loose alternating network was meticulously constructed through a pre-assembly process in sodium citrate solution and a subsequent re-assembly in FeCl3 solution. This approach ensured the robustness of the network structure and facilitated ion migration. Within the network, a gelatin network cross-linked via covalently and hydrogen bonds was significantly enhanced by a synergy of micro-enhancement and dynamic bidirectional crosslinking containing hydrogen bonds, imine bonds, and Fe coordinate bonds enabled by surface active cellulose. Benefiting from the dense network, the obtained composite hydrogels delivered a strong tensile strength (496.3 kPa), outstanding elastic modulus (917.6 kPa), and an excellent energy dissipation rate (55.6 %) at 80 % of strain. The loose polymer network can also endow Fe3+/Cl− ions with sensitive mobility, leading to an ultra-high sensing sensitivity (maximum GF: 20.06). These exceptional properties enable the ionic conductor to accurately detect a wide range of motions and pressures without being affected by environmental noise. With attributes such as reusability, biodegradability, strength, and sensitivity, this ionic conductor emerges as a reliable soft material with promising applications in the field of healthcare monitoring, wearable strain sensor sensors, and writing anti-counterfeiting materials.

A high performance triboelectric nanogenerator using assembled sugar naphthalimides for self-powered electronics and sensors

A new class of N-glycosyl naphthalimide ricinoleate (NGNR) amphiphiles were generated using environmentally friendly reaction conditions in good yields. To investigate the potential applications of NGNR amphiphiles within the realm of supramolecular materials, molecular self-assembly experiments were conducted extensively across a diverse range of solvents and oils and observed the gel formation. Molecular-level interactions and assembly patterns were investigated by employing FTIR, SAXRD, UV–vis, and fluorescence spectroscopy, and a plausible assembly mechanism was proposed. The morphology of the supramolecular architecture was identified by scanning electron microscopy. Additionally, rheological studies provided insight into these soft materials' strength and processability. Further, in the process of fabricating a triboelectric nanogenerator (TENG) device, silicone rubber serves as an electron acceptor and assembled NGNR serves as an electron donor. The developed TENG demonstrated a significant improvement in performance over TENG made with amorphous NGNR, with output voltage, current, and power density of 410 V, 100 µA, and 5.1 W/m2, respectively, highlighting the importance of the assembly process. Furthermore, TENG is used to continuously power up small electronic device (calculator), which is useful in building self-powered electronic devices. Lastly, due to its high sensitivity and stability, the TENG was used to detect the humidity of the environment in the food processing, textile, and agriculture sectors. The change in TENG response is notably significant up to 70 % relative humidity (RH). This work showcases the development of self-powered humidity sensors.