Viscoelastic State Research Articles

Tentative exploration of the 3D printing performance of the mixed inks with egg white proteins and mycoprotein fibrous to improve the quality of mycoprotein alternatives

Mycoprotein (MYC) has unique mycelial properties that make it suitable for mimicking meat fibers. However, the irregular structure of mycelium creates challenges in achieving fiber alignment in meat alternatives. This study explored 3D printing technology to align MYC fibers by formulating inks with various proportions of egg white proteins (EWP) (4 %, 5 %, 6 %, 7 %) and assessing their printing performance. Results showed that extrusion-based 3D printing enabled MYC fiber alignment. The addition of EWP resulted in a nonlinear viscoelastic state in the mixed ink, and increased intra-ring strains to restrict the mobility of the moisture, likely due to hydrogen bonding between mycelial and EWP. Post-printing, the MYC-EWP matrix formed a more ordered mycelial structure. After heating, the 6 % EWP formulation exhibited improved water retention, hardness, chewiness, and other textural properties, making it comparable to beef. This study highlights the potential of 3D printing technology to enhance fiber formation in MYC-based meat alternatives.

Deciphering the molecular mechanism underlying morphology transition in two-component DNA-protein cophase separation.

Nucleic acid and protein co-condensates exhibit diverse morphologies crucial for fundamental cellular processes. Despite many previous studies that advanced our understanding of this topic, several interesting biophysical questions regarding the underlying molecular mechanisms remain. We investigated DNA and human transcription factor p53 co-condensates-a scenario where neither dsDNA nor the protein demonstrates phase-separation behavior individually. Through a combination of experimental assays and theoretical approaches, we elucidated: (1) the phase diagram of DNA-protein co-condensates at a certain observation time, identifying a phase transition between viscoelastic fluid and viscoelastic solid states, and a morphology transition from droplet-like to "pearl chain"-like co-condensates; (2) the growth dynamics of co-condensates. Droplet-like and "pearl chain"-like co-condensates share a common initial critical microscopic cluster size at the nanometer scale during the early stage of phase separation. These findings provide important insights into the biophysical mechanisms underlying multi-component phase separation within cellular environments.

Influence of Gamma-Phase Aluminum Oxide Nanopowder and Polyester-Glass Recyclate Filler on the Destruction Process of Composite Materials Reinforced by Glass Fiber.

Recycling of composite materials is an important global issue due to the wide use of these materials in many industries. Waste management options are being explored. Mechanical recycling is one of the methods that allows obtaining polyester-glass recyclate in powder form as a result of appropriate crushing and grinding of waste. Due to the fact that the properties of composites can be easily modified by adding various types of fillers and nanofillers, this is one of the ways to improve the properties of such complex composite materials. This article presents the strength parameters of composites with the addition of fillers in the form of polyester-glass recyclate and a nanofiller in the form of gamma-phase aluminum nanopowder. To analyze the obtained results, Kolmogorov-Sinai (K-S) metric entropy was used to determine the transition from the elastic to the viscoelastic state in materials without and with the addition of nanoaluminum, during a static tensile test. The tests included samples with the addition of fillers and nanofillers, as well as a base sample without any additives. The article presents the strength parameters obtained from a testing machine during a static tensile test. Additionally, the acoustic emission method was used during the research. Thanks to which, graphs of the effective value of the electrical signal (RMS) were prepared as a function of time, the parameters were previously identified as extremely useful for analyzing the destruction process of composite materials. The values obtained from the K-S metric entropy method and the acoustic emission method were plotted on sample stretching graphs. The influence of the nanofiller and filler on these parameters was also analyzed. The presented results showed that the aluminum nanoadditive did not increase the strength parameters of the composite with recyclate as a result of the addition of aluminum nanofiller; however, its addition influenced the operational parameters, which is reflected in a 5% increase in the UTS value (from 55% to 60%).

Creating a bionic scaffold via light-curing liquid crystal ink to reveal the role of osteoid-like microenvironment in osteogenesis

Osteoid plays a crucial role in directing cell behavior and osteogenesis through its unique characteristics, including viscoelasticity and liquid crystal (LC) state. Thus, integrating osteoid-like features into 3D printing scaffolds proves to be a promising approach for personalized bone repair. Despite extensive research on viscoelasticity, the role of LC state in bone repair has been largely overlooked due to the scarcity of suitable LC materials. Moreover, the intricate interplay between LC state and viscoelasticity in osteogenesis remains poorly understood. Here, we developed innovative hydrogel scaffolds with osteoid-like LC state and viscoelasticity using digital light processing with a custom LC ink. By utilizing these LC scaffolds as 3D research models, we discovered that LC state mediates high protein clustering to expose accessible RGD motifs to trigger cell-protein interactions and osteogenic differentiation, while viscoelasticity operates via mechanotransduction pathways. Additionally, our investigation revealed a synergistic effect between LC state and viscoelasticity, amplifying cell-protein interactions and osteogenic mechanotransduction processes. Furthermore, the interesting mechanochromic response observed in the LC hydrogel scaffolds suggests their potential application in mechanosensing. Our findings shed light on the mechanisms and synergistic effects of LC state and viscoelasticity in osteoid on osteogenesis, offering valuable insights for the biomimetic design of bone repair scaffolds.

Effect of non-thermal effects in microwave heating on the rheology and chemical properties of petroleum asphalt

This study systematically analyses the rheological properties of typical petroleum asphalt heated by microwaves at different temperatures through viscosity, penetration, dynamic shear, low-temperature bending, and other rheological tests. The results show that the non-thermal effect of microwaves enhances the fluidity of petroleum asphalt in the high-temperature viscous flow state, becomes softer in the medium-temperature viscoelastic state, and becomes hard and brittle in the low-temperature glassy state. The effect of microwaves also causes some specific changes in the properties of bitumen, including softening point and glass transition temperature in the opposite direction, as well as a large difference in the response of bitumen of different viscosities. The chemical changes in microwave-heated bitumen were analyzed using component tests and microscopic observation. It was found that microwave heating homogenized and dispersed the asphaltene aggregates into small particles, with the heavy components significantly reduced and the light components increased.

Tyre wear model: A fusion of rubber viscoelasticity, road roughness, and thermodynamic state

Wear is due to many causes and involves three major consequences: loss of performance, loss of security and environmental pollution. Depending on the context, the focus on the consequence can be moved: in motorsport tyre’s fundamental role is to guarantee high performance as long as it is possible, in road vehicles safety has decisive importance compared to the safety target, in big densely-populated cities the pollution due to tyre particles can be of considerable importance.The main objective of this work is to describe a necessary set of instruments concerning tyre wear mechanism-related phenomena, allowing to better understand and to develop an improved formulation, able to consider the tread compound viscoelastic characteristics, the pavement roughness and the tyre operating conditions. To this purpose the modelling approach considers the viscoelastic behaviour of the compound, changing instant by instant its nominal characteristics as a function of the excitation frequency and the material temperature.To validate the modelling approach proposed and its reliability in completely different scenarios of use, the authors have selected five datasets collected on vehicles belonging to diverse motorsport, passenger and truck categories, unique in terms of vehicle operating conditions both from kinematic-dynamic and thermodynamic points of view.

Thermal volume expansion as seen by Temperature-modulated optical refractometry, Oscillating dilatometry and Thermo-mechanical analysis

This paper revisits the experimental assessment of the thermal volume expansion behaviour via the novel technique of Temperature-modulated optical refractometry (TMOR) and compares it to two classical dilatometry techniques: Oscillating dilatometry (OD) and Thermo-mechanical analysis (TMA). This is done at the example of a model liquid (n-tetradecane, C14H30) and a homogeneous and isotropic, cross-linked epoxy thermoset in the viscoelastic state. It is shown that the thermal volume expansion coefficients of C14H30 obtained via TMOR and OD agree exceptionally well with each other and indeed reflect thermodynamic constants, if certain experimental boundary conditions are met. In the case of TMA analyses of the epoxy thermoset, the measured data was found to be biased rather easily, especially due to the tracking force that induces additional shape changes beyond thermal expansion. The controlled combination of TMOR and TMA allows differentiating between a “true” thermal volume expansion behaviour and additional shape changing effects.

Critical-Like Gelation Dynamics in Cellulose Nanocrystal Suspensions.

We use time-resolved mechanical spectroscopy to offer a detailed picture of the gelation dynamics of cellulose nanocrystal (CNC) suspensions following shear cessation in the presence of salt. CNCs are charged, rodlike colloids that self-assemble into various phases, including physical gels serving as soft precursors for biosourced composites. Here, a series of linear viscoelastic spectra acquired across the sol-gel transition of CNC suspensions are rescaled onto two master curves that correspond to a viscoelastic liquid state prior to gelation and to a soft solid state after gelation. These two states are separated by a critical gel point, where all rescaling parameters diverge in an asymmetric fashion yet with exponents that obey hyperscaling relations consistent with previous works on isotropic colloids and polymer gels. Upon varying the salt content, we further show that these critical-like dynamics result in both time-connectivity and time-concentration superposition principles.

Acoustic Emission and K-S Metric Entropy as Methods to Analyze the Influence of Gamma-Aluminum Oxide Nanopowder on the Destruction Process of GFRP Composite Materials

Composites are materials that are widely used in industry, including yachting, railway and aviation. The properties of these materials can be modified by changing the type of reinforcement, the type of matrix, as well as the use of additives in the form of fillers and nanofillers that improve their mechanical or specific parameters. Due to the fact that these materials are often used for important structures, computational models using FEM tools may not be sufficient to determine the actual strength parameters, and what is more, to check them during operation. When designing structures made of composite materials, it is necessary to use high safety factors due to their behavior under several different types of loads, which is still difficult to determine precisely. This situation makes these structures much heavier and characterized by much higher strength properties than those that would actually be needed. In this article, the Kolmogorov-Sinai (K-S) metric entropy was used to determine the transition from the elastic to the viscoelastic state in GFRP (glass fiber reinforced polymer) composite materials without and with the addition of nanoaluminum, during a static tensile test. Additionally, the acoustic emission method was used during the research. This signal was further processed, and graphs were made of the number of events and the amplitude as a function of time. The obtained values were plotted on tensile graphs. The influence of the nano-filler on these parameters was also analyzed. The presented results show that it is possible to determine additional parameters affecting the strength of the structure for any composite materials.

Characterization of nano-silica vegetable grease with diffusing wave spectroscopy DWS and Raman spectroscopy

The diffusing wave spectroscopy (DWS) method made it possible to identify changes in the dynamics of the free movement of particles in the grease under the influence of temperature, which changed the viscoelastic properties of the grease. Changes in the parameters determined by DWS method influenced changes in the chemical structure, which was confirmed by Raman spectroscopy, determining the integral intensity of the unsaturated to saturated bond bands found in the grease. The article presents the results of the influence of temperature on changes in the viscoelastic states of vegetable grease evaluated on the basis of properties determined by DWS (diffusing wave spectroscopy). The following parameters were used to evaluate the viscoelastic states: the intensity correlation function (ICF), the correlation function of mean square displacement (MSD), the elastic modulus G′ and the viscosity modulus G″. A significant effect of temperature on changes in the microstructure of vegetable grease was observed, which was reflected in the viscoelastic parameters. The dynamics of the free movement of molecules in the grease was changed, which affected the elasticity of the system and the displacement of the G′ and G″ modules towards higher frequencies.

Surfactant Modified Bentonite Characterization: Effects and Comparative Analysis

Extensive soils can be found all over the world. The clay mineral montmorillonite is predominantly responsible for soil expansion. Because of their ability to shrink and swell with seasonal changes in moisture content, these expansive soils can cause significant damage to engineering construction. To stabilize the effects of swelling soil various ground improvement techniques, incorporate mineralogical modification of clays. The application of nanotechnology increased in past few years to deal with clay minerals as it possesses the same dimensional properties. To understand the behaviour of Nano modified clay, bentonite was selected as it represents the montmorillonite clay mineral. The characterization of surface-treated bentonite by nanomaterial was carried out. The study of physio-chemical properties and textural properties of surface-modified bentonite clay was carried out. Swelling pressure was evaluated by a consolidometer test. With the advanced nanotechnology instrumentation technique, particle size analysis, zeta potential, wettability, contact angle, infra-red spectroscopy, rheological properties, BET surface area, pH values, XRD, TGA, etc was carried out for treated and untreated soil, to understand the comparative behaviour of surface modification. It was found that by using Nano surfactant, liquid limit and shrinkage limit were reduced considerably. The increase in the quantity of surfactant increases the d-spacing. Thermal stability and particle size increase after surface treatment of bentonite clay. Soil reaches a visco-elastic state and BET surface area decreased after surface modification.

RHEOLOGICAL PROPERTIES OF SOILS OF DIFFERENT LAND USE IN THE SYKTYVKAR URBAN DISTRICT OF THE KOMI REPUBLIC

The mechanical characteristics of soils of the same genesis and different land use of Syktyvkar are studied: agrod- ernovo-podzolic urban-stratified soil within the city, post-frost park soil, podzolic soil of suburban territory. The analysis of their relationship with the content of organic matter and granulometric composition is carried out. In agrodern-podzolic urban-stratified soil, the strength properties are largely due to the content of large granulometric fractions (> 0.25 mm), and in podzolic soil - the content of organic matter. Rows of soils were built according to the values of rheological parameters. The strength of structural bonds, estimated by the parameter of the initial modulus of elasticity, is greatest in podzolic soil, a wide range of linear viscoelastic state distinguishes the horizons of agroderno-podzolic urban-stratified soil. Both post-frost and podzolic soil have the same average values of the starting point of the viscous flow region.

Applying Super High Resolution Fluorescence Microscope and Advanced Smart Cloud Algorithm in Real-Time Quantitative Processing and Analysis of Electroconvection

In an electrochemical cell at high current densities, electroconvection plays a critical role in determining the morphology of electrodeposited metals. The resultant dendrite formation leads to risky battery performance failure. Over the past decades, though intensive theoretical analysis and experimental effort have been done, the detailed structure and dynamics of electroconvection remain unknown, because experimental observations lacked the resolution to expose the fundamental, hierarchical spatial structure of these flows, while the data processing algorithms were not fully established for large sample size. To address this shortcoming, we built an advanced optical electrochemical cell that fits in situ imaging with a super-resolution fluorescence microscope. By observing and recording real-time motions of electrolytes, electroconvection flows have been interrogated at unprecedented, high temporal and spatial resolution. As a complement to the visualization studies, a cloud-computing analysis algorithm was developed by combining a higher resolution Particle Image Velocimetry algorithm and a machine learning model to enable velocity distribution data over the entire optical field of view at nanoscale or microscale spatial resolution. Consequently, detailed velocity maps are obtained across the optical electrochemical cell, allowing us to quantitatively measure and analyze the initiation and evolution of the hierarchical microstructures inside the electroconvection in a unidirectional electric field. With these powerful tools, we further studied the effect of polymer viscoelasticity on electroconvection and electrodeposition. The addition of an ultrahigh molar mass polyethylene oxide to the electrolytes transforms the materials to a viscoelastic fluid state that changes the electroconvection dependence on time and voltage and induces a smooth electrodeposition on the metal anode by unique polymer rheological properties. Especially, the relaxation of long polymer chains in electrolyte provides a promising manner to prevent dendrite growth. We further analyzed these observations using direct numerical simulations for Newtonian and viscoelastic fluid models, and the quantitative analysis of experimental results indicates good consistency with simulation predictions.

Melt pool size of optical glass irradiated by semiconductor laser

ABSTRACT Using a continuous laser to soften glass locally is a novel way of selective glass forming. Due to gaussian distribution of laser power density, a temperature gradient will be generated on glass treated with localized irradiation by laser, which brings about the coexistence of a glass state and a viscoelastic state. This situation creates a bulge on the surface of the softened area. Based on this phenomenon, we propose a measurement approach and a calculation model for the softening zone width of glass irradiated locally by laser and verify the calculation model through simulations and experiments. The maximum temperature deviation of the proposed temperature field prediction model is 4.7°C, while the minimum deviation is 0.53°C; making the deviation between the calculation model of the softening zone width and the experimental measurement result less than 0.319%.

Molecular Dynamics Study of Cured ED-20 Epoxy Resin for Predicting the Glass Transition Temperature and Relationship with Structure Features.

A structural model of ED-20 epoxy resin cured by triethylenetetramine was constructed using a molecular dynamics (MD) simulation method. In order to model the epoxy resin hardening, we modified a typical stepwise protocol introducing cross-links between the amino groups and epoxide carbon atoms that allowed us to reproduce experimentally observed glass transition temperature at the value of 360-364 K. The set of MD trajectories of the final molecular-mechanical model can be useful for analysis of alterations in structural and physical properties of the epoxy resin depending on scaleable parameters. The relationships among qualitative alterations in macromolecular structure, the glass transition temperature, and the number of imposed cross-links were elucidated. Analysis of intermolecular interactions between the largest macromolecules and other molecules of a system made it possible to observe the features of the transition from glassy to the viscoelastic state of the studied polymer during the temperature rise.

Mechanism of thermoviscoelasticity driven solid-liquid interface reducing friction for polymer alloy coating

High-temperature ablation is a common failure phenomenon that limits the service life of the transmission parts on heavy-duty machines used in heavy load, high temperature, high shock conditions due to in-sufficient supply of lubricating oil and grease. Traditional self-lubricating coatings prepared by inorganic, organic or organic-inorganic hybrid methods are prone to be oxidated at high temperatures to lose their friction reducing function, so that it is difficult to meet the engineering requirements of high-temperature lubrication. We design viscoelastic polymer coatings by a high-temperature self-lubricating and wear-resistant strategy. Polytetrafluoroethylene (PTFE, Tm = 329 °C) and polyphenylene sulfide (PPS, Tg = 84 °C, Tm = 283 °C) are used to prepare a PTFE/PPS polymer alloy coating. As the temperature increases from 25 to 300 °C, the PTFE/PPS coating softens from glass state to viscoelastic state and viscous flow state, which is owing to the thermodynamic transformation characteristic of the PPS component. Additionally the friction coefficient (µ) decreased from 0.096 to 0.042 with the increasing of temperature from 25 to 300 °C. The mechanism of mechanical deformation and surface morphology evolution for the PTFE/PPS coating under the multi-field coupling action of temperature (T), temperature-centrifugal force (T-Fω), temperature-centrifugal force-shearing force (T-Fω-Fτ) were investigated. The physical model of “thermoviscoelasticity driven solid-liquid interface reducing friction” is proposed to clarify the self-lubricating mechanism determined by the high-temperature viscoelastic properties of polymers. The high-temperature adjusts the viscosity (η) of the coating, increases interface slipping and intensifies shear deformation (τ), reducing the friction coefficient. The result is expected to provide a new idea for designing anti-ablation coatings served in high temperature friction and wear conditions.

Self-healing magnetorheological elastomers based on thermoreversible Diels–Alder networks

Magnetorheological (MR) elastomers are a class of stimuli-responsive materials of which the damping and stiffness can be reversibly tailored by applying magnetic fields. However, concerns such as fatigue damage, insufficient MR efficiencies with low loadings of magnetic particles or highly crosslinked elastomers, and lack of reprocessability remain unaddressed for conventional MR elastomers. To this end, a series of self-healing MR elastomers (SHMRE) were prepared based on thermoreversible Diels–Alder covalent crosslinks. The application of magnetic pulses yielded pre-aligned magnetic particles chains within the curing matrix which strongly influenced the SHMRE rheological properties. The resulting composites do not only exhibit a large MR effect but also efficient self-healing properties at room temperature. We found that the particle loading and the field-induced orientation of the aggregates affect the magnitude of the MR response, the mechanical strength and the healing efficiency. In addition, the MR response is also strongly influenced by the temperature. With a temperature increase from room temperature to 70 °C, a change in the MR response from 90% to 462% is observed while the SHMRE retain a solid viscoelastic state at 50 wt% particles loading. Interestingly, the thermoreversible features of the synthesized networks also allow potential reprocessability of SHMRE when heating these systems above the gel transition temperature (89 °C–90 °C). The final low viscous state makes it possible for the magnetic particles to be potentially restructured as chains by applying a magnetic field, which are retained upon cooling when the solid network state is recovered. The proposed SHMRE systems are shown to be a highly efficient and reprocessable solution to substitute classical MR elastomers in a wider context of generalized MR materials.

Study of viscoelastic transition in heat-resistant polycrystalline alloy VZhl71 of the Ni - Co - Cr system

Heat-resistant materials used, for example, in aircraft parts, are exposed to high temperatures and are heated under the impact of variable external forces. At a certain point in time, the material that first experienced a small deformation ceases to be simply elastic and graduates into a viscoelastic state. Microyield thus developed in the material, subsequently leads to the creep. We present the results of studying the microyield in a heat-resistant polycrystalline alloy VZhl71 of the Ni - Co - Cr system. A high-temperature background of the internal friction was studied by mechanical spectroscopy. It is shown that the transition of the alloy from an elastic to a viscoelastic state proceeds in two stages and is accompanied by microyield resulted from the dislocation movement. The first and second activation energies of the high-temperatureinternal friction background are determined for the state of the material under consideration. An expression for calculating the transition temperature is derived. The results obtained can be used in the study of the states of heat-resistant, high-temperature and structured materials, as well as amorphous metals and alloys.

Interactive deformable electroluminescent devices enabled by an adaptable hydrogel system with optical/photothermal/mechanical tunability.

Deformable electroluminescent devices (DELDs) with mechanical adaptability are promising for new applications in smart soft electronics. However, current DELDs still present some limitations, including having stimuli-insensitive electroluminescence (EL), untunable mechanical properties, and a lack of versatile stimuli response properties. Herein, a facile approach for fabricating in situ interactive and multi-stimuli responsive DELDs with optical/photothermal/mechanical tunability was proposed. A polyvinyl alcohol (PVA)/polydopamine (PDA)/graphene oxide (GO) adaptable hydrogel exhibiting optical/photothermal/mechanical tunability was used as the top ionic conductor (TIC). The TIC can transform from a viscoelastic state to an elastic state via a special freezing-salting out-rehydration (FSR) process. Meanwhile, it endows the DELDs with a photothermal response and thickness-dependent light shielding properties, allowing them to dynamically demonstrate "on" or "off" or "gradually change" EL response to various mechanical/photothermal stimuli. Thereafter, the DELDs with a viscoelastic TIC can be utilized as pressure-responsive EL devices and laser-engravable EL devices. The DELDs with an elastic TIC can withstand both linear and out-of-plane deformation, enabling the designs of various interactive EL devices/sensors to monitor linear sliders, human finger bending, and pneumatically controllable bulging. This work offers new opportunities for developing next-generation EL-responsive devices with widespread application based on adaptable hydrogel systems.

A viscoelastic Mooney–Rivlin model for adhesive curing and first steps toward its calibration based on photoelasticity measurements

The transition of polymer adhesives from an initially liquid to a fully cured viscoelastic state is accompanied by three phenomenological effects, namely an increase in stiffness and viscosity in conjunction with a decrease in volume (curing shrinkage). Under consideration of these phenomena, some of us (Hossain et al. in Computational Mechanics 46:363-375, 2010) have devised a generic, viscoelastic finite strain framework for the simulation of the curing process of adhesives, which renders a thermodynamically consistent model regardless of the selected free energy density. In the present work, this generic curing framework is modified by means of more precise integration schemes and is applied to a hyperelastic Mooney–Rivlin material based on an additive volumetric-isochoric split of the strain energy density. The benefit of this decomposition is directly related to the distinct material responses of various polymers to volumetric and isochoric deformations [4]. The resulting Mooney–Rivlin curing model provides the foundation for implementing a user-defined material subroutine (UMAT) in Abaqus requiring the Cauchy stress and a non-standard formulation of the tangent operator. To this end, the corresponding transformations are presented. Additionally, a first attempt to determine the evolution of the curing-dependent material parameters through optimization with respect to a photoelasticity measurement is presented. A subset of the material properties, which reflect the emergence of shrinkage stresses inside a ceramic-epoxy composite after its fabrication, is determined via inverse parameter identification. However, due to a lack of experimental data and some rather strong assumptions made on the physics involved, this demonstration can currently be considered only as a proof-of-concept.