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 - 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 - TY - CHAP A1 - Kravanja, Gaia A1 - Belyaeva, Inna A. A1 - Hribar, Luka A1 - Drevenšek‐Olenik, Irena A1 - Shamonin (Chamonine), Mikhail A1 - Jezeršek, Matija T1 - Adaptive Magneto-Responsive Surfaces Fabricated by Laser-Based Microstructuring T2 - Proceedings of the ASME 2022 Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS 2022): September 12-14, 2022, Dearborn, Michigan N2 - Adaptive surface microstructures are used extensively in nature to control various surface properties such as wettability, adhesion, self-cleaning, drag reduction, etc. Regulation of these properties can be achieved with the appropriate employment of a multitude of smart materials, whose characteristics/response can be controlled by noncontact stimuli, e.g., light, heat, or magnetic field. One of the very promising magneto-regulable smart materials are magnetoactive elastomers (MAEs). They are comprised of a compliant polymer matrix with embedded micrometer-sized ferromagnetic particles. The particles interact with each other and a magnetic field. This results in remarkable tunability of the physical properties of MAEs. This paper reports a fast, resilient, and tailored method for direct surface micromachining of MAEs that enables micro-structuring without mechanical contact between the tool and the material, bypassing the usual constraints of conventional fabrication methods. It is shown that it is possible to fabricate a large variety of different microstructure geometries whose precision is limited predominantly by the size of magnetic particles. Lamellar structures with a high aspect ratio (up to 6:1) oriented either perpendicularly to the surface, can be strongly bent by applying magnetic fields in the range of 0–250 mT. KW - adaptive surfaces KW - magnetoactive elastomers KW - magneto-responsive microstructures KW - laser microstructuring Y1 - 2022 SN - 978-0-7918-8627-4 U6 - https://doi.org/10.1115/SMASIS2022-90742 PB - ASME ER - TY - GEN A1 - Kriegl, Raphael A1 - Kravanja, Gaia A1 - Hribar, Luka A1 - Jezeršek, Matija A1 - Drevenšek‐Olenik, Irena A1 - Shamonin (Chamonine), Mikhail T1 - Characterization of Wetting Properties of Magnetoactive Elastomer Surfaces T2 - Proceedings of the ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS) - 2023, September 11–13, 2023 Austin, Texas, USA N2 - Commercially available contact angle (CA) measuring devices usually do not allow for the application of magnetic fields to the sample under test. A setup for measuring the CA of liquids on magnetosensitive surfaces has been developed specifically for investigating the surfaces of magnetoactive elastomers (MAEs). The addition of a programmable linear stage, which moves a permanent magnet, allows for fine control of the magnetic field applied to the MAE without the need for large and power-consuming electromagnets. Paired with a custom control and evaluation software, this measurement setup operates semiautomatically, limiting operator error and increasing precision, speed, as well as repeatability of static and dynamic CA measurements for different magnetoactive materials. The software is equipped with robust droplet fitting algorithms to avoid experimental challenges arising with soft magnetoactive materials, such as the curling of sample edges or diffuse non-reflective surfaces. Several application examples on MAE surfaces, both processed and unprocessed, are presented. KW - magnetoactive elastomers KW - image processing KW - droplet contour fitting KW - contact angle Y1 - 2023 SN - 978-0-7918-8752-3 U6 - https://doi.org/10.1115/SMASIS2023-110998 N1 - Corresponding author: Raphael Kriegl PB - The American Society of Mechanical Engineers CY - New York, USA ER - TY - JOUR A1 - Straus, Izidor A1 - Kokot, Gašper A1 - Kravanja, Gaia A1 - Hribar, Luka A1 - Kriegl, Raphael A1 - Shamonin (Chamonine), Mikhail A1 - Jezeršek, Matija A1 - Drevenšek‐Olenik, Irena T1 - Dynamically tunable lamellar surface structures from magnetoactive elastomers driven by a uniform magnetic field JF - Soft Matter N2 - Stimuli responsive materials are key ingredients for any application that requires dynamically tunable or on-demand responses. In this work we report experimental and theoretical investigation of magnetic-field driven modifications of soft-magnetic elastomers whose surface was processed by laser ablation into lamellar microstructures that can be manipulated by a uniform magnetic field. We present a minimal hybrid model that elucidates the associated deflection process of the lamellae and explains the lamellar structure frustration in terms of dipolar magnetic forces arising from the neighbouring lamellae. We experimentally determine the magnitude of the deflection as a function of magnetic flux density and explore the dynamic response of lamellae to fast changes in a magnetic field. A relationship between the deflection of lamellae and modifications of the optical reflectance of the lamellar structures is resolved. KW - Intelligente Materialien Y1 - 2023 U6 - https://doi.org/10.1039/D3SM00012E VL - Vol. 19 SP - 3357 EP - 3365 PB - Royal Society of Chemistry ER - TY - JOUR A1 - Straus, Izidor A1 - Kravanja, Gaia A1 - Hribar, Luka A1 - Kriegl, Raphael A1 - Jezeršek, Matija A1 - Shamonin (Chamonine), Mikhail A1 - Drevenšek‐Olenik, Irena A1 - Kokot, Gašper T1 - Surface Modification of Magnetoactive Elastomers by Laser Micromachining JF - Materials N2 - It has been recently demonstrated that laser micromachining of magnetoactive elastomers is a very convenient method for fabricating dynamic surface microstructures with magnetically tunable properties, such as wettability and surface reflectivity. In this study, we investigate the impact of the micromachining process on the fabricated material’s structural properties and its chemical composition. By employing scanning electron microscopy, we investigate changes in size distribution and spatial arrangement of carbonyl iron microparticles dispersed in the polydimethylsiloxane (PDMS) matrix as a function of laser irradiation. Based on the images obtained by a low vacuum secondary electron detector, we analyze modifications of the surface topography. The results show that most profound modifications occur during the low-exposure (8 J/cm^2) treatment of the surface with the laser beam. Our findings provide important insights for developing theoretical models of functional properties of laser-sculptured microstructures from magnetoactive elastomers. KW - magnetoactive elastomer KW - MAE KW - laser micromachining KW - particle distributions KW - SEM Y1 - 2024 U6 - https://doi.org/10.3390/ma17071550 N1 - This research was funded by the Slovenian Research Agency (ARRS): research programs P1-0192, P2-0392, and research project J1-3006. The work of R.K. and M.S. in Regensburg was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), project number 437391117. VL - 2024 IS - 17 / 7 PB - MDPI AG CY - Basel, Switzerland ER - TY - CHAP A1 - Kriegl, Raphael A1 - Jezeršek, Matija A1 - Kravanja, Gaia A1 - Hribar, Luka A1 - Kokot, Gašper A1 - Drevenšek‐Olenik, Irena A1 - Shamonin (Chamonine), Mikhail T1 - Characterization of Tunable Rebound Properties of Microstructured Magnetoactive Elastomers T2 - ASME 2024 Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS), September 9–11, 2024, Atlanta, Georgia, USA N2 - We present a novel method to control the rebounding behavior of small mm-sized solid balls by employing magnetoactive elastomers (MAEs) with microstructured surfaces. An MAE is a composite material consisting of μm-sized ferromagnetic particles dispersed in a soft elastomer (e.g., polydimethylsiloxane) matrix. In the act of rebounding, the ball hits an MAE surface and bounces back. The MAE samples contained 75 wt.% of iron. This composite material is known to respond to an applied magnetic field with increased stiffness (due to the magnetorheological effect) and plasticity. To adjust the rebound properties, the top layer of the MAE material was additionally modified by micromachining lamellar structures with different dimensions on the 100 μm scale via laser ablation. Due to the resulting high aspect ratio, these surface structures were sensitive to the magnetic field direction. The lamellas could stand up straight or lay down flat. The rebound behavior was evaluated by using a custom build apparatus that facilitates dropping of the balls in a precise and repeatable manner. A ball was dropped from different heights. The ball trajectory was captured with a high-speed camera to investigate the rebound properties. The recorded video was processed using a custom software written in Python. The experimental procedure and data processing algorithms are presented in detail. The results for the samples with different geometrical dimensions are provided as examples. It is made evident that the magnetic field influences the rebound properties of small non-magnetic balls impinging microstructured MAE surfaces. The change in surface topography is an effective way to control the ball rebound. The fabrication flexibility in geometrical dimensions of surface microstructures opens a convenient way to tune the desired response to magnetic fields. The presented idea may find applications in impact mitigation or small-scale sorting machinery, e.g. for recycling. Y1 - 2024 SN - 978-0-7918-8832-2 U6 - https://doi.org/10.1115/SMASIS2024-139154 PB - American Society of Mechanical Engineers CY - New York, USA ER - TY - JOUR A1 - Kriegl, Raphael A1 - Kravanja, Gaia A1 - Hribar, Luka A1 - Čoga, Lucija A1 - Drevenšek‐Olenik, Irena A1 - Jezeršek, Matija A1 - Kalin, Mitjan A1 - Shamonin (Chamonine), Mikhail T1 - Microstructured Magnetoactive Elastomers for Switchable Wettability JF - Polymers N2 - We demonstrate the control of wettability of non-structured and microstructured magnetoactive elastomers (MAEs) by magnetic field. The synthesized composite materials have a concentration of carbonyl iron particles of 75 wt.% (≈27 vol.%) and three different stiffnesses of the elastomer matrix. A new method of fabrication of MAE coatings on plastic substrates is presented, which allows one to enhance the response of the apparent contact angle to the magnetic field by exposing the particle-enriched side of MAEs to water. A magnetic field is not applied during crosslinking. The highest variation of the contact angle from (113 ± 1)° in zero field up to (156 ± 2)° at about 400 mT is achieved in the MAE sample with the softest matrix. Several lamellar and pillared MAE structures are fabricated by laser micromachining. The lateral dimension of surface structures is about 50 µm and the depth varies between 3 µm and 60 µm. A systematic investigation of the effects of parameters of laser processing (laser power and the number of passages of the laser beam) on the wetting behavior of these structures in the absence and presence of a magnetic field is performed. In particular, strong anisotropy of the wetting behavior of lamellar structures is observed. The results are qualitatively discussed in the framework of the Wenzel and Cassie-Baxter models. Finally, directions of further research on magnetically controlled wettability of microstructured MAE surfaces are outlined. The obtained results may be useful for the development of magnetically controlled smart surfaces for droplet-based microfluidics. Y1 - 2022 U6 - https://doi.org/10.3390/polym14183883 N1 - Corresponding authors: Raphael Kriegl und Mikhail Shamonin VL - 14 IS - 18 SP - 1 EP - 21 PB - MDPI ER - TY - JOUR A1 - Kriegl, Raphael A1 - Jezeršek, Matija A1 - Kravanja, Gaia A1 - Hribar, Luka A1 - Mukhi, Soham A1 - Kokot, Gašper A1 - Drevenšek‐Olenik, Irena A1 - Shamonin (Chamonine), Mikhail T1 - Tunable rebound of millimeter-sized rigid balls by magnetic actuation of elastomer-based surface microstructures JF - Smart Materials and Structures N2 - A novel method for controlling the rebound behavior of small balls made of Al2O3 with a radius of 2.381 mm is presented. It uses different types of micro-structured surfaces of soft magnetoactive elastomers. These surfaces were fabricated via laser micromachining and include fully ablated surfaces as well as micrometer-sized lamellas with a fixed width of 90 µm, height of 250 µm and three different gap sizes (15, 60 and 105 µm). The lamellas can change their orientation from edge-on to face-on configuration according to the direction of the external magnetic field from a permanent magnet. The orientation of the external magnetic field significantly influences the rebound behavior of the balls, from a coefficient of restitution e of to < 0.1. The highest relative change in the coefficient of restitution between zero field and face-on configuration of is observed for lamellas with a gap of 60 µm. Other characteristics of the ball rebound such as the penetration depth into an Magnetoactive elastomer and the maximum deceleration are investigated as well. The proposed method does not require a constant power supply due to the use of permanent magnets. It may find novel applications in the field of impact engineering. Y1 - 2024 U6 - https://doi.org/10.1088/1361-665X/ad41a9 N1 - Zugehöriges Datenset: https://doi.org/10.5281/zenodo.10419411 VL - 33 IS - 6 PB - IOP Publishing ER - TY - JOUR A1 - Straus, Izidor A1 - Kravanja, Gaia A1 - Kriegl, Raphael A1 - Shamonin (Chamonine), Mikhail A1 - Drevenšek-Olenik, Irena A1 - Jezeršek, Matija A1 - Kokot, Gašper T1 - Laser Micromachining for Polymer Surface Topography Designt JF - JoVE journal : engineering N2 - Soft magnetoactive elastomers (MAEs) are smart materials that respond to external magnetic fields by dynamically altering their mechanical properties. They are composed of magnetically responsive microparticles embedded within a soft polymer matrix, exhibiting an effective shear modulus of up to 100 kPa. In recent decades, MAEs' bulk properties have been successfully exploited for applications such as dynamic vibration damping, vibration sensing, and actuation in soft robotics. Recent research has shifted to their surface properties, revealing promising results on tunable surface features such as roughness, adhesion, and wetting. Even the transport of small solid and fluid objects was demonstrated. The associated surface effects can be significantly enhanced through the precise engineering of surface topography. In this article, an efficient laser micromachining technique, with a resolution of 15 µm, is presented, which enables rapid prototyping of MAE surfaces. It allows the creation of various complex shapes and offers functionality beyond the one achievable with traditional molding techniques. Additionally, the approach is versatile and can be applied to any polymer that sufficiently absorbs the laser light. As an example, a lamellar surface micro-pattern fabrication process and its characterization by optical and scanning electron microscopies are shown. Its response to a magnetic field is demonstrated. The technique provides a flexible and fast solution for optimizing polymer surface design across a wide range of applications. Y1 - 2025 U6 - https://doi.org/10.3791/68126 PB - JoVE ER - TY - JOUR A1 - Geldof, Arne A1 - Kopačin, Jan A1 - Straus, Izidor A1 - Kriegl, Raphael A1 - Kravanja, Gaia A1 - Hribar, Luka A1 - Jezeršek, Matija A1 - Shamonin, Mikhail A1 - Kokot, Gašper A1 - Drevenšek‐Olenik, Irena T1 - Transfer of Energy and Momentum Between Magnetoactive Surface Microstructure and a Solid Object JF - Advanced Engineering Materials N2 - Transport systems utilizing magnetic materials are very promising for applications that require contactless operation and compatibility with biological processes. A critical parameter in these systems is the efficiency of energy and momentum transfer between the transporting platform and the objects being transported. We investigate the physical mechanisms driving directional transport of solid objects by microlamellar structures laser-inscribed on the surface of a magnetoactive elastomer (MAE). When subjected to a rotating magnetic field with a magnitude of 175 mT and a time period of 0.4 s, the lamellas reorient within a few milliseconds, reaching angular velocities up to 1100 rad s−1. This rapid motion is crucial for efficient momentum and energy transfer to objects in contact with the lamellas. The analysis of collisions of a single lamella with a lead ball with a 2.2 mm diameter shows that the lamella can transfer around 50 nJ of energy, propelling the ball to a speed of around 35 mm s−1. We show how this value sets the upper limit for the ball's transport speed on microlamellar structures. We also explain the background of three distinct transport regimes (kicking, pushing, and bouncing modes) observed on these magnetically driven “conveyor belts”. Y1 - 2026 U6 - https://doi.org/10.1002/adem.202502369 VL - 28 IS - 6 PB - Wiley ER -