Investigation on Magnetorheological Effect of Novel Self-healing Magnetorheological Elastomers

Magnetorheological elastomers(MREs)hold significant promise in various fields such as automotive engineering,and civil engineering,where they serve as intelligent materials.Depending on the application of an external magnetic field,these materials exhibit varying magnetorheological and viscoelastic properties,including shear stress,yield stress,dynamic moduli,and damping.In this work,a new type of MRE,termed self-healing MREs(SH-MREs),has been developed by adding a novel self-healing agent into existing MREs.The dynamic modulus and loss factor of SH-MREs with different compositions have been characterized under various conditions of frequency,temperature,and strain.The results show that as the strain value increases,the loss factor also increases.Moreover,the loss factor initially increases and then decreases with increasing magnetic field strength.Although higher concentrations of ferromagnetic particles increase the loss factor,they enhance the operational range due to their better responsiveness to magnetic fields.SH-MREs demonstrate improved damping capabilities,attributed to the formation of coordination bonds between ferromagnetic particles and the self-healing agent.The stable structure increases the viscosity of MREs.The results of the regression model suggest a direct proportionality between sensitivity to the magnetic field and the ferromagnetic particle concentration.

Interfacial friction effects on sealing performances of elastomer packer

Elastomer sealing performance is of critical importance for downhole tools application including the use of fracturing(Frac)plugs during multi-stage hydraulic fracking.In practice sealing performances of such plugs are normally evaluated through pressure tests,and in numerical simulation studies,maximum contact stress,average contact stress and contact length data are used to determine sealing quality between a packer and casing.In previous studies,the impact of friction forces on sealing performance is often overlooked.This work aims to fill this knowledge gap in determining the influence of friction forces on elastomer packer sealing performances.We first determined the most appropriate constitutive hyperelastic model for the elastomers used in frac plug.Then we compared analytical calculation results with Finite Element Analysis simulation using a simplified tubular geometry and showed the significant influences on interfacial friction on elastomer packer stress distribution,deformation,and contact stress after setting.With the demonstration of validity of FEA method,we conducted systematic numerical simulation studies to show how the interfacial friction coefficients can affect the maximum contact stress,average contact stress,contact stress distribution,and maximum mises stress for an actual packer used in plug products.In addition,we also demonstrated how the groove in a packer can affect packer deformation and evolvement during setting with the consideration of interfacial stress.This study underscores the critical role that friction forces play in Frac plug performance and provides a new dimension for optimizing packer design by controlling interfacial interactions at the packer contact surfaces.

Bioremediation Potential of the Macroalga Ulva lactuca (Chlorophyta) for Ammonium Removal in Elastomer Industry Wastewater

During the production of nitrile rubber, significant amounts of nitrogen in the form of ammonium are generated in the wastewater. The discharge of this high-nitrogen wastewater can lead to serious environmental issues, including eutrophication, disruption of aquatic ecosystems, and groundwater contamination. To mitigate these impacts, this research explored the bioremediation capabilities of the macroalgae Ulva lactuca (Chlorophyta) for removing nitrogen from nitrile rubber production wastewater. The study employed single-phase and Michaelis-Menten decay models based on ammonium consumption, using various dilutions of wastewater to identify the optimal concentration for treatment. The physiological state of the macroalgae was monitored by measuring the photosynthetic capacity and specific growth rate during the experiments. In the presence of U. lactuca, ammonium concentrations decreased in all treatment groups, confirming that the ammonium kinetics conformed to both applied models. Our results show that U. lactuca effectively reduces ammonium concentrations, with an approximate removal rate of 0.020 µM·g−1·min−1 across different wastewater concentrations (70%, 80%, 90%, and 100%). Notably, the treatments with 70%, 80%, and 90% wastewater strength achieved about 67% reduction in ammonium, demonstrating the alga’s capacity to treat high-nitrogen wastewater. The photosynthetic performance of U. lactuca initially declined in control conditions but stabilized across all treatments, highlighting its adaptability. The kinetic analysis using the Michaelis-Menten model indicated a Vmax of 1342 μM·g−1·DMh−1, suggesting a robust capacity for ammonium uptake when fully saturated. Our study underscores the potential of Ulva lactuca as a cost-effective and efficient agent for wastewater bioremediation, particularly in settings with high nitrogen loads.

Stability analysis of a liquid crystal elastomer self-oscillator under a linear temperature field

Self-oscillating systems abound in the natural world and offer substantial potential for applications in controllers,micro-motors,medical equipments,and so on.Currently,numerical methods have been widely utilized for obtaining the characteristics of self-oscillation including amplitude and frequency.However,numerical methods are burdened by intricate computations and limited precision,hindering comprehensive investigations into self-oscillating systems.In this paper,the stability of a liquid crystal elastomer fiber self-oscillating system under a linear temperature field is studied,and analytical solutions for the amplitude and frequency are determined.Initially,we establish the governing equations of self-oscillation,elucidate two motion regimes,and reveal the underlying mechanism.Subsequently,we conduct a stability analysis and employ a multi-scale method to obtain the analytical solutions for the amplitude and frequency.The results show agreement between the multi-scale and numerical methods.This research contributes to the examination of diverse self-oscillating systems and advances the theoretical analysis of self-oscillating systems rooted in active materials.

In silico optimization of actuation performance in dielectric elastomercomposites via integrated finite element modeling and deep learning

Dielectric elastomers(DEs)require balanced electric actuation performance and mechanical integrity under applied voltages.Incorporating high dielectric particles as fillers provides extensive design space to optimize concentration,morphology,and distribution for improved actuation performance and material modulus.This study presents an integrated framework combining finite element modeling(FEM)and deep learning to optimize the microstructure of DE composites.FEM first calculates actuation performance and the effective modulus across varied filler combinations,with these data used to train a convolutional neural network(CNN).Integrating the CNN into a multi-objective genetic algorithm generates designs with enhanced actuation performance and material modulus compared to the conventional optimization approach based on FEM approach within the same time.This framework harnesses artificial intelligence to navigate vast design possibilities,enabling optimized microstructures for high-performance DE composites.

Preparation and Properties of Spray Polyurea Elastomer for Aquaculture Foam Floating Balls

[Objectives] This study was conducted to develop a polyurea elastomer which can be sprayed on the surface of expanded polystyrene (EPS) floating balls, so as to improve the surface strength and service life of the floating balls. [Methods] The effects of the types and amounts of isocyanate, chain extenders and polyether polyols on the gelation rate, adhesion and wear resistance of polyurea elastomer were investigated, and it was finally determined the preparation process of polyurea elastomer using liquid isophorone diisocyanate (IPDI) and amino-terminated polyether (D2000) as the main raw materials, dimethylthiotoluene diamine (E300) as the chain extender and silica as the wear resistance modifier through two-step solution polymerization of prepolymerization and chain extension. [Results] The physical properties and chemical resistance tests of spray polyurea elastomer showed that it had good physical properties and acid and alkali resistance, and could meet the requirements of spraying and protection of EPS floating ball surface in marine environment. [Conclusions] Polyurea elastomer coating can improve the aging resistance, wear resistance and acid and alkali resistance of EPS floating balls, and prevent them from being fragile and floating randomly to form marine floating garbage which results in "white pollution".

Numerical Analysis on Magnetic-induced Shear Modulus of Magnetorheological Elastomers Based on Multi-chain Model

Based on the magnetic interaction energy, using derivative of the magnetic energy density, a model is proposed to compute the magnetic-induced shear modulus of magnetorheological elastomers. Taking into account the influences of particles in the same chain and the particles in all adjacent chains, the traditional magnetic dipole model of the magnetorheological elastomers is modified. The influence of the ratio of the distance etween adjacent chains to the distance between adjacent particles in a chain on the magnetic induced shear odulus is quantitatively studied. When the ratio is large, the multi-chain model is compatible with the single chain model, but when the ratio is small, the difference of the two models is significant and can not be neglected. Making certain the size of the columns and the distance between adjacent columns, after constructing the computational model of BCT structures, the mechanical property of the magnetorheological elastomers composed of columnar structures is analyzed. Results show that, conventional point dipole model has overrated the magnetic-induced shear modulus of the magnetorheological elastomers. From the point of increasing the magnetic-induced shear modulus, when the particle volume fraction is small, the chain-like structure exhibits better result than the columnar structure, but when the particle volume fraction is large,the columnar structure will be better.

Preparation and electrostriction of BaTiO_3/polyurethane nanocomposite elastomers

BaTiO3/polyurethane （BaTiO3/PU） nanocomposite elastomers were prepared from barium titanate nanoparticles, polyester polyol, 2, 4-toluene diisocyanate, 1,4-butanediol and 1, 1, 1-trimethanol propane by the one-step method. The density, hardness and dielectric constant of BaTiO3/PU nanocomposite elastomers increased with the increase of the content of BaTiO3 nanoparticles in nanocomposites. The electrostrictive properties of BaTiO3/PU nanocomposite elastomers were investigated by the digital speckle correlation method （DSCM）. It was found that through the on-and-off of the electric field, the electrostrictive strains of BaTiO3/PU nanocomposite elastomers revealed corresponding shrinkage and recovery. The electrostrictive coefficient of BaTiO3/PU nanocomposite elastomers was greater than that of the corresponding polyurethane elastomers, and the electrostrictive coefficient of composites decreased with the increase of the content of barium titanate nanoparticles.

Effect of Cyclic Deformation on Magnetorheological Elastomers

Fatigue properties of magnetorheological elastomer （MRE） samples were investigated based on cis-polybutadiene rubber by using a fatigue test machine. Three MRE samples with iron particles mass fraction of 60%, 70%, and 80% were fabricated, and their properties dependence of three strain amplitudes （50%, 75%, and 100%） were measured. The absolute magnetorheological （MR） effect, storage modulus, and loss modulus of MRE samples after fatigue were evaluated by a modified dynamic mechanical analyzer. The results revealed that MR effect, storage modulus, and loss modulus of MREs containing 80% iron particles depended strongly on the strain amplitudes and the number of cycles, while storage mod-ulus and loss modulus of MREs containing 70% iron particles also depended on the strain amplitudes and the number of cycles but not as strongly as sample which contains 80% iron particles, but the properties of MREs containing 60% iron particles after cyclic deforma-tion were almost independent of the fatigued conditions. In order to investigate the fatigue mechanism of MREs, the sample was carried out with a quasi-static tensile testing and its surface morphology during testing was observed in situ by scanning electron microscopy.

Large conversion of energy in dielectric elastomers by electromechanical phase transition

When air is pumped in, a tubular balloon initially inflates slightly and homogeneously. A short section of the balloon then forms a bulge, which coexists with the unbulged section of the balloon. As more air is pumped in, the bulged section elongates at the expense of the unbulged section, until the entire balloon is bulged. The phenomenon is analogous to the liquid-to-vapor phase transition. Here we study the bulging transition in a dielectric elastomer tube as air is pumped into the balloon and a voltage is applied through the thickness of the membrane. We formulate the condition for coexistent budged and unbulged sections, and identify allowable states set by electrical breakdown and mechanical rupture. We find that the bulging transition dramatically amplifies electromechanical energy conversion. Energy converted in an electromechanical cycle consisting of unbulged and bulged states is thousands of times that in an electromechanical cycle consisting of only unbulged states.

Damping of magnetorheological elastomers

The damping property of magnetorheological elastomers(MREs) is characterized by a modified dynamic mechanical-magnetic coupled analyzer.The influence of external magnetic flux density,damping of matrix,content of iron particles,dynamic strain and driving frequency on the MREs' damping was investigated experimentally.The results indicate that the MREs' damping property depends on the interfacial slip between the inner particles and the matrix.Different from the general composite materials,the interfacial slip in MRE is affected by the external applied magnetic field.

Ionic Elastomers for Electric Actuators and Sensors

In the past decades,ion conductive polymers and elastomers have drawn worldwide attention for their advanced functions in batteries,electroactive soft robotics,and sensors.Stretchable ionic elastomers with dispersed soft ionic moieties such as ionic liquids have gained remarkable attention as soft sensors,in applications such as the wearable devices that are often called electric skins.A considerable amount of research has been done on ionic-elastomer-based strain,pressure,and shear sensors;however,to the best of our knowledge,this research has not yet been reviewed.In this review,we summarize the materials and performance properties of engineered ionic elastomer actuators and sensors.First,we review three classes of ionic elastomer actuators—namely,ionic polymer metal composites,ionic conducting polymers,and ionic polymer/carbon nanocomposites—and provide perspectives for future actuators,such as adaptive four-dimensional(4D)printed systems and ionic liquid crystal elastomers(iLCEs).Next,we review the state of the art of ionic elastomeric strain and pressure sensors.We also discuss future wearable strain sensors for biomechanical applications and sports performance tracking.Finally,we present the preliminary results of iLCE sensors based on flexoelectric signals and their amplification by integrating them with organic electrochemical transistors.

Experimental investigation on vibration characteristics of sandwich beams with magnetorheological elastomers cores

A sandwich beam specimen was fabricated by treating with MR elastomers between two thin aluminum face-plates.Experiment was carried out to investigate the vibration responses of the sandwich beam with respect to the intensity of the magnetic field and excitation frequencies.The results show that the sandwich beams with MR elastomers cores have the capabilities of shifting natural frequencies and the vibration amplitudes decrease with the variation of the intensity of external magnetic field.

Radiation Vulcanization of Magnetorheological Elastomers Based on Silicone Rubber

The fabrication of magnetorheological （MR） elastomers was studied by two vulcanization methods, including heat vulcanization （HV） and radiation vulcanization （RV）, were employed to fabricate MRE samples. The dynamical mechanical properties were characterized by using a dynamic mechanic analyzer. In particular, both the MR effect and its durability were investigated. The experimental results showed that RV samples have large magnetoinduced modulus, large zero-field modulus, and good durability property of MR effect. To explain these results, cubic deformation and plasticizer migration were analyzed. Large magneto-induced modulus of RV sample results from cubic deformation during vulcanization process. And the plasticizer migration results in better durability of MR effect.

Phenomenological description of semi-soft nematic elastomers

Nematic elastomers are new materials that have many remarkable properties.In this article,we study how nonlinear elasticity of semi-soft nematic elastomers can be described phenomenologically.We start with a theory based on strain tensor only,and then continue to develop a phenomenological description with the liquid crystal order tensor included explicitly.Such a description has the virtue of being able to treat the strain tensor and the liquid crystal order tensor equally and thus making the complicated symmetries of nematic elastomers easier to understand.

Transient thermo-mechanical analysis for bimorph soft robot based on thermally responsive liquid crystal elastomers

Thermally responsive liquid crystal elastomers (LCEs) hold great promise in applications of soft robots and actuators because of the induced size and shape change with temperature. Experiments have successfully demonstrated that the LCE based bimorphs can be effective soft robots once integrated with soft sensors and thermal actuators. Here, we present an analytical transient thermo-mechanical model for a bimorph structure based soft robot, which consists of a strip of LCE and a thermal inert polymer actuated by an ultra-thin stretchable open-mesh shaped heater to mimic the unique locomotion behaviors of an inchworm. The coupled mechanical and thermal analysis based on the thermo-mechanical theory is carried out to underpin the transient bending behavior, and a systematic understanding is therefore achieved. The key analytical results reveal that the thickness and the modulus ratio of the LCE and the inert polymer layer dominate the transient bending deformation. The analytical results will not only render fundamental understanding of the actuation of bimorph structures, but also facilitate the rational design of soft robotics.

Damping of Magnetorheological Elastomers

The damping property of magnetorheological （MR） elastomers is characterized by a modified dynamic mechanical-magnetic coupled analyzer. The influences of the external magnetic flux density, damping of the matrix, content of iron particles, dynamic strain, and driving frequency on the damping properties of MR elastomers were investigated experimentally. The experimental results indicate that the damping properties of MR elastomers greatly depend on the interfacial slipping between the inner particles and the matrix. Different from general composite materials, the interracial slipping in MR elastomers is affected by the external applied magnetic field.

Preparation and properties of cast polyurethane elastomers with molecularly uniform hard segments based on 2,4-toluene diisocyanate and 3,5-dimethyl-thioltoluenediamine

A series of three cast polyurethane elastomers were prepared from 2,4-toluene diisocyanate (TDI) and 3,5-dimethyl-thioltoluenediamine (D MTDA) chain extender, with polyethylene adi-pate (PEA), polyoxytetramethylene glycol (PTMG) and polycaprolactone (PCL) soft seg-ments. The polyol molecular weights em-ployed was 2000g/mol. The polyurethane elastomers were characterized by an elec-tronmechanical universal testing machine, an Akron abrasion loss tester, a LX-A Shore du-rometer, a rebound resilience equipment and a Dynamic- Mechanical analyzer. In addition, fractured surface of the polyurethane elas-tomers was investigated by a field emission scanning electron microscopy (SEM). The test results showed the PCL based elastomer ex-hibits the excellent tear and stress-strain properties that polyester based elastomers offer, while retaining superior compression set and resilience similar to polyether based elas-tomers. The static and dynamic properties of the PCL based elastomer were more suitable for dynamic applications. The SEM micro-graphs of all polyurethane samples indicated the existing of the microphase separation structure. Particles of the dispersed phase formed by the hard phase and crystalline part of the soft phase grows bigger with the in-creasing crystallinity of the soft segments. The hard domains are irregular shapes and with the sizes of a few micrometers.

Influence of Diisocyanate on Polyurethane Elastomers Which Crosslinked by β-Cyclodextrin

A series of polyurethane elastomers (PUEs) were synthesized by using β-cyclodextrin (β-CD) as cross-linker from aliphatic, alicyclic, aromatic diisocyanates, and polyol. The PUEs were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), swelling test, hardness test and tensile test. The influence of diisocyanate on microphase separation and properties of PUEs was evaluated.

Enhancement in Magnetorheological Effect of Magnetorheological Elastomers by Surface Modification of Iron Particles

In order to obtain magnetorheological （MR） elastomers with high magnetorheological effect, a family of anisotropic rubber-based MR elastomers was developed using a new form of chemical modification. Three different kinds of surfactants, i.e. anionic, nonionic and compound surfactants, were employed separately to modify iron particles. The MR effect was evaluated by measuring the dynamic shear modulus of MR elastomer with a magneto-combined dynamic mechanical analyzer. Results show that the relative MR effect can be up to 188% when the iron particles are modified with 15% Span 80. Besides the surface activity of Span 80, however, such high modifying effect is partly due to the plasticizing effect of Span 80. Compared with the single surfactant, the superior surface activity of compound surfactant makes the relative MR effect reach 77% at a low content of 0.4%. Scanning electron microscope observation shows that the modification of compound surfactant results in perfect compatibility between particles and rubber matrix and special self-assembled structure of particles. Such special structure has been proved beneficial to the improvement of the relative MR effect.