TY - JOUR A1 - Belyaeva, Inna A. A1 - Kramarenko, Elena Yu A1 - Shamonin (Chamonine), Mikhail T1 - Magnetodielectric effect in magnetoactive elastomers: Transient response and hysteresis JF - POLYMER N2 - Magnetodielectric properties of magnetoactive elastomers comprising micrometer-sized iron particles dispersed in compliant elastomer matrices are experimentally studied in stepwise time-varying dc magnetic fields. It is found that imposition of magnetic field significantly increases both the effective lossless permittivity of these composite materials as well as their effective conductivity. These magnetodielectric effects are more pronounced for larger concentrations of soft-magnetic filler particles and softer elastomer matrices. The largest observed relative change of the effective dielectric constant in the maximum magnetic field of 0.57 T is of the order of 1000%. The largest observed absolute change of the loss tangent is approximately 0.8. The transient response of the magnetodielectric effect to a step magnetic-field excitation can be rather complex. It changes from a simple monotonic growth with time for small magnetic-field steps (<0.1 T) to a non-monotonic behavior with a significant rapidly appearing overshoot for large magnetic-field steps (>0.3 T). The settling time to the magnetic-field step excitation can reach roughly 1000 s and it depends on the applied magnetic field and sample composition. There is also significant hysteresis of the magnetodielectric effect on the externally applied magnetic field. These findings are attributed to the rearrangement of ferromagnetic filler particles in external magnetic fields. The results will be useful for understanding and predicting the transient behavior of magnetoactive elastomers in applications where the control magnetic field is time dependent. (C) 2017 Elsevier Ltd. All rights reserved. KW - BEHAVIOR KW - composites KW - DIELECTRIC-PROPERTIES KW - hysteresis KW - MAGNETIC-FIELD KW - magnetoactive elastomer KW - magnetodielectric effect KW - Magnetorhelogical elastomer KW - MELT STATE KW - MICROSTRUCTURE KW - POLYMER DEGRADATION KW - PROGRESS KW - Smart material KW - THERMOOXIDATIVE DEGRADATION KW - TIME-RESOLVED RHEOLOGY KW - Transient response Y1 - 2017 U6 - https://doi.org/10.1016/j.polymer.2017.08.056 VL - 127 SP - 119 EP - 128 PB - ELSEVIER ER - TY - JOUR A1 - Sorokin, Vladislav V. A1 - Belyaeva, Inna A. A1 - Shamonin (Chamonine), Mikhail A1 - Kramarenko, Elena Yu T1 - Magnetorheological response of highly filled magnetoactive elastomers from perspective of mechanical energy density: Fractal aggregates above the nanometer scale? JF - Physical Review E N2 - The dynamic shear modulus of magnetoactive elastomers containing 70 and 80 mass % of carbonyl iron microparticles is measured as a function of strain amplitude via dynamic torsion oscillations in various magnetic fields. The results are presented in terms of the mechanical energy density and considered in the framework of the conventional Kraus model. The form exponent of the Kraus model is further related to a physical model of Huber et al. [Huber et al., J. Phys.: Condens. Matter 8, 409 (1996)] that uses a realistic representation for the cluster network possessing fractal structure. Two mechanical loading regimes are identified. At small strain amplitudes the exponent beta of the Kraus model changes in an externally applied magnetic field due to rearrangement of ferromagnetic-filler particles, while at large strain amplitudes, the exponent beta seems to be independent of the magnetic field. The critical mechanical energy characterizing the transition between these two regimes grows with the increasing magnetic field. Similarities between agglomeration and deagglomeration of magnetic filler under simultaneously applied magnetic field and mechanical shear and the concept of jamming transition are discussed. It is proposed that the magnetic field should be considered as an additional parameter to the jamming phase diagram of rubbers filled with magnetic particles. KW - BEHAVIOR KW - composites KW - hysteresis KW - MAGNETIC-FIELD KW - MODEL KW - RHEOLOGY KW - RUBBER KW - SENSITIVE ELASTOMERS KW - VISCOELASTIC PROPERTIES Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevE.95.062501 VL - 95 IS - 6 PB - Amer Physical Soc ER - TY - JOUR A1 - Belyaeva, Inna A. A1 - Klepp, Jürgen A1 - Lemmel, Hartmut A1 - Shamonin (Chamonine), Mikhail T1 - Feasibility of Probing the Filler Restructuring in Magnetoactive Elastomers by Ultra-Small-Angle Neutron Scattering JF - Applied Sciences N2 - Ultra-small-angle neutron scattering (USANS) experiments are reported on isotropic magnetoactive elastomer (MAE) samples with different concentrations of micrometer-sized iron particles in the presence of an in-plane magnetic field up to 350 mT. The effect of the magnetic field on the scattering curves is observed in the scattering vector range between 2.5 x 10(-5) and 1.85 x 10(-4) angstrom(-1). It is found that the neutron scattering depends on the magnetization history (hysteresis). The relation of the observed changes to the magnetic-field-induced restructuring of the filler particles is discussed. The perspectives of employing USANS for investigations of the internal microstructure and its changes in magnetic field are considered. KW - Anisotropy KW - Ferrofluids KW - hysteresis KW - magnetoactive elastomer KW - magnetorheological elastomer KW - Matrix KW - MIicrostructure KW - restructuring of the filler KW - ultra-small-angle neutron scattering Y1 - 2021 U6 - https://doi.org/10.3390/app11104470 VL - 11 IS - 10 SP - 1 EP - 9 PB - MDPI CY - Basel ER - TY - JOUR A1 - Glavan, Gašper A1 - Belyaeva, Inna A. A1 - Shamonin (Chamonine), Mikhail T1 - On the Piezomagnetism of Magnetoactive Elastomeric Cylinders in Uniform Magnetic Fields: Height Modulation in the Vicinity of an Operating Point by Time-Harmonic Fields JF - Polymers N2 - Soft magnetoactive elastomers (MAEs) are currently considered to be promising materials for actuators in soft robotics. Magnetically controlled actuators often operate in the vicinity of a bias point. Their dynamic properties can be characterized by the piezomagnetic strain coefficient, which is a ratio of the time-harmonic strain amplitude to the corresponding magnetic field strength. Herein, the dynamic strain response of a family of MAE cylinders to the time-harmonic (frequency of 0.1-2.5 Hz) magnetic fields of varying amplitude (12.5 kA/m-62.5 kA/m), superimposed on different bias magnetic fields (25-127 kA/m), is systematically investigated for the first time. Strain measurements are based on optical imaging with sub-pixel resolution. It is found that the dynamic strain response of MAEs is considerably different from that in conventional magnetostrictive polymer composites (MPCs), and it cannot be described by the effective piezomagnetic constant from the quasi-static measurements. The obtained maximum values of the piezomagnetic strain coefficient (∼102 nm/A) are one to two orders of magnitude higher than in conventional MPCs, but there is a significant phase lag (35-60°) in the magnetostrictive response with respect to an alternating magnetic field. The experimental dependencies of the characteristics of the alternating strain on the amplitude of the alternating field, bias field, oscillation frequency, and aspect ratio of cylinders are given for several representative examples. It is hypothesized that the main cause of observed peculiarities is the non-linear viscoelasticity of these composite materials. Y1 - 2024 U6 - https://doi.org/10.3390/polym16192706 N1 - Corresponding author der OTH Regensburg: Gašper Glavan VL - 16 IS - 19 ER - TY - JOUR A1 - Jezeršek, Matija A1 - Kriegl, Raphael A1 - Kravanja, Gaia A1 - Hribar, Luka A1 - Drevenšek‐Olenik, Irena A1 - Unold, Heiko A1 - Shamonin (Chamonine), Mikhail T1 - Control of Droplet Impact through Magnetic Actuation of Surface Microstructures JF - Advanced Materials Interfaces N2 - An effective method for on-demand control over the impact dynamics of droplets on a magnetoresponsive surface is reported. The surface is comprised of micrometer-sized lamellas from a magnetoactive elastomer on a copper substrate. The surface itself is fabricated using laser micromachining. The orientation of the lamellae is switched from edge-on (orthogonal to the surface) to face-on (parallel to the surface) by changing the direction of a moderate (<250 mT) magnetic field. This simple actuation technique can significantly change the critical velocities of droplet rebound, deposition, and splashing. Rebound and deposition regimes can be switched up to Weber number We < 13 ± 3, while deposition and splashing can be switched in the range of 32 < We < 52. Because a permanent magnet is used, no permanent power supply is required for maintaining the particular regime of droplet impact. The presented technology is highly flexible and enables selective fabrication and actuation of microstructures on complex devices. It has great potential for applications in soft robotics, microfluidics, and advanced thermal management. Y1 - 2023 U6 - https://doi.org/10.1002/admi.202202471 VL - 10 IS - 11 PB - Wiley ER - TY - JOUR A1 - Glavan, Gašper A1 - Kettl, Wolfgang A1 - Brunhuber, Alexander A1 - Shamonin (Chamonine), Mikhail A1 - Drevenšek‐Olenik, Irena T1 - Effect of Material Composition on Tunable Surface Roughness of Magnetoactive Elastomers JF - Polymers N2 - We investigated magnetic-field-induced modifications of the surface roughness of magnetoactive elastomers (MAEs) with four material compositions incorporating two concentrations of ferromagnetic microparticles (70 wt% and 80 wt%) and exhibiting two shear storage moduli of the resulting composite material (about 10 kPa and 30 kPa). The analysis was primarily based on spread optical reflection measurements. The surfaces of all four materials were found to be very smooth in the absence of magnetic field (RMS roughness below 50 nm). A maximal field-induced roughness modification (approximately 1 m/T) was observed for the softer material with the lower filler concentration, and a minimal modification (less than 50 nm/T) was observed for the harder material with the higher filler concentration. All four materials showed a significant decrease in the total optical reflectivity with an increasing magnetic field as well. This effect is attributed to the existence of a distinct surface layer that is depleted of microparticles in the absence of a magnetic field but becomes filled with particles in the presence of the field. We analyzed the temporal response of the reflective properties to the switching on and off of the magnetic field and found switching-on response times of around 0.1 s and switching-off response times in the range of 0.3-0.6 s. These observations provide new insight into the magnetic-field-induced surface restructuring of MAEs and may be useful for the development of magnetically reconfigurable elastomeric optical surfaces. KW - magnetically tunable surface reflectivity KW - magnetically tunable surface roughness KW - magnetorheological elastomer KW - magnetorheological polymers KW - surface properties Y1 - 2019 U6 - https://doi.org/10.3390/polym11040594 N1 - Corresponding author: Gašper Glavan VL - 11 IS - 4 SP - 1 EP - 13 PB - MDPI CY - Basel ER - TY - JOUR A1 - Glavan, Gašper A1 - Salamon, Peter A1 - Belyaeva, Inna A. A1 - Shamonin (Chamonine), Mikhail A1 - Drevenšek‐Olenik, Irena T1 - Tunable surface roughness and wettability of a soft magnetoactive elastomer JF - Journal of applied polymer science N2 - Surface topographical modifications of a soft magnetoactive elastomer (MAE) in response to variable applied magnetic field are investigated. The analysis is performed in situ and is based on optical microscopy, spread optical reflection and optical profilometry measurements. Optical profilometry analysis shows that the responsivity of magnetic field-induced surface roughness with respect to external magnetic field is in the range of 1 mu m/T. A significant hysteresis of surface modifications takes place for increasing and decreasing fields. Investigations of shape of sessile water droplets deposited on the MAE surface reveal that field-induced topographical modifications affect the contact angle of water at the surface. This effect is reversible and the responsivity to magnetic field is in the range of 20 degrees/T. Despite the increased surface roughness, the apparent contact angle decreases with increasing field, which is attributed to the field-induced protrusion of hydrophilic microparticles from the surface layer. KW - CONTACT KW - EVAPORATION KW - FORCE KW - hydrophobic polymers KW - MAGNETIC-MATERIALS KW - magnetism and magnetic properties KW - optical properties KW - STIMULI-RESPONSIVE SURFACES KW - stimuli-sensitive polymers KW - structure-property relationships Y1 - 2018 U6 - https://doi.org/10.1002/app.46221 VL - 135 IS - 18 PB - Wiley ER - TY - JOUR A1 - Kravanja, Gaia A1 - Kriegl, Raphael A1 - Hribar, Luka A1 - Glavan, Gašper A1 - Drevenšek‐Olenik, Irena A1 - Shamonin (Chamonine), Mikhail A1 - Jezeršek, Matija T1 - Magnetically Actuated Surface Microstructures for Efficient Transport and Tunable Separation of Droplets and Solids JF - Advanced Engineering Materials N2 - Efficient transportation of droplets (∽10 ¹ ̶̶̶̶ 10 ² µl) and small solid objects (∽10 ¹ ̶ 10 ² mm ³ ) have important applications in many fields, such as microfluidics, lab‐on‐a‐chip devices, drug delivery, etc. A novel multifunctional surface consisting of a periodic array of micro‐lamellae from a soft magnetoactive elastomer (MAE) on a plastic substrate is reported for these purposes. The physical origin of the propulsion is the bending of soft magnetic lamellae in non‐uniform magnetic fields, which is also observed in uniform magnetic fields. The magnetoactive surface is fabricated using a facile and rapid method of laser ablation. The propulsion of items is realized using a four‐pole rotating magnet. This results in a cyclic lamellar fringe motion over the micro‐structured surface and brings an advantage of easy reciprocation of transport by rotation reversal. Two modes of object transportation are identified: “pushing” mode for precise control of droplet and solid positioning and “bouncing” mode for heavier solid objects transportation. A water droplet of 5 μl or a glass sphere with a 2.1 mm diameter can be moved at a maximum speed of 60 mm s ⁻¹ . The multifunctionality of the proposed mechatronic platform is demonstrated on the examples of selective solid‐liquid separation and droplet merging. KW - Keywordslaser micromachinings KW - magnetoactive elastomers KW - magnetoresponsivesurfaces KW - object separations KW - object transportations Y1 - 2023 U6 - https://doi.org/10.1002/adem.202301000 SN - 1527-2648 VL - 25 IS - 22 SP - 1 EP - 11 PB - Wiley-VCH ER - TY - JOUR A1 - Kravanja, Gaia A1 - Belyaeva, Inna A. A1 - Hribar, Luka A1 - Drevenšek‐Olenik, Irena A1 - Shamonin (Chamonine), Mikhail A1 - Jezeršek, Matija T1 - Laser Micromachining of Magnetoactive Elastomers as Enabling Technology for Magnetoresponsive Surfaces JF - Advanced Materials Technologies N2 - A simple method for structuring of the surface of a magnetoactive elastomer (MAE) on the tens of micrometers scale, which capabilities extend beyond conventional mold-based polymer casting, is reported. The method relies on the ablation of the material by absorption of nanosecond infrared pulses from a commercial laser. It is shown that it is possible to fabricate parallel lamellar structures with a high aspect ratio (up to 6:1) as well as structures with complex scanning trajectories. The method is fast (fabrication time for the 7 × 7 mm2 is about 60 s), and the results are highly reproducible. To illustrate the capabilities of the fabrication method, both orthogonal to the MAE surface and tilted lamellar structures are fabricated. These magnetosensitive lamellae can be easily bent by ±45° using an external magnetic field of about 230 mT. It is demonstrated that this bending allows one to control the sliding angle of water droplets in a great range between a sticky (>90°) and a sliding state (<20°). Perspectives on employing this fabrication technology for magnetosensitive smart surfaces in microfluidic devices and soft robotics are discussed. Y1 - 2021 U6 - https://doi.org/10.1002/admt.202101045 VL - 7 IS - 5 SP - 1 EP - 8 PB - Wiley ER - TY - JOUR A1 - Kravanja, Gaia A1 - Belyaeva, Inna A. A1 - Hribar, Luka A1 - Drevenšek‐Olenik, Irena A1 - Jezeršek, Matija A1 - Shamonin (Chamonine), Mikhail T1 - Tunable Drop Splashing on Magnetoactive Elastomers JF - Advanced Materials Interfaces N2 - The significant effect of an external dc magnetic field on the splashing behavior of ethanol drops impacting on the unstructured (flat) surface of soft magnetoactive elastomers (MAEs) is reported. The Weber number corresponding to the transition between the deposition and the splashing regime is reduced by ≈20% in a moderate magnetic field of ≈300 mT. Alongside this effect, a two-fold increase of the initial deceleration of the ejection sheet is observed for the softest sample. The main underlying mechanism for the observed phenomena is believed to be the magnetic-field-induced stiffening of the MAEs. Further possible mechanisms are magnetically induced changes in the surface roughness and magnetic-field-induced plasticity (magnetic shape memory effect). The potential application areas are magnetically regulable wetting and magneto-responsive surfaces for controlling the drop splashing. Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-24504 N1 - Corresponding author: Mikhail Shamonin VL - 8 IS - 11 SP - 1 EP - 7 PB - Wiley ER -