@article{JezeršekKrieglKravanjaetal., author = {Jezeršek, Matija and Kriegl, Raphael and Kravanja, Gaia and Hribar, Luka and Drevenšek-Olenik, Irena and Unold, Heiko and Shamonin (Chamonine), Mikhail}, title = {Control of Droplet Impact through Magnetic Actuation of Surface Microstructures}, series = {Advanced Materials Interfaces}, volume = {10}, journal = {Advanced Materials Interfaces}, number = {11}, publisher = {Wiley}, doi = {10.1002/admi.202202471}, abstract = {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.}, language = {en} } @article{KrieglKovalevShamoninChamonineetal., author = {Kriegl, Raphael and Kovalev, Alexander and Shamonin (Chamonine), Mikhail and Gorb, Stanislav}, title = {Tunable contact angle hysteresis on compliant magnetoactive elastomers}, series = {Extreme Mechanics Letters}, volume = {63}, journal = {Extreme Mechanics Letters}, publisher = {Elsevier}, issn = {2352-4316}, doi = {10.1016/j.eml.2023.102049}, abstract = {It is shown that the advancing (ACA) and receding (RCA) contact angles of water on extremely soft (shear modulus of the order of 10 kPa) magnetoactive elastomer (MAE) films significantly depend on the applied magnetic field. The difference between these angles, known as the contact angle hysteresis, is examined. The roles of the filler concentration and material softness are elaborated. The highest change in the contact angle hysteresis (CAH) from 34° in the absence of magnetic field to 76° in a magnetic field of 0.4 T is achieved for the softest sample with the lowest mass fraction of iron particles (70 wt\%). The dependence of the CAH on magnetization history ("magnetic hysteresis") is observed. This magnetic hysteresis is clearly pronounced for the ACA and has little effect on the RCA. Magnetic field-induced changes of the surface roughness exhibit qualitatively the same hysteresis behavior with regard to the external magnetic field as the ACA. The results are promising for the development of smart surfaces for applications where the dynamic wetting has to be controlled.}, language = {en} } @article{GlavanBelyaevaDrevenšekOleniketal., author = {Glavan, Gašper and Belyaeva, Inna A. and Drevenšek-Olenik, Irena and Shamonin (Chamonine), Mikhail}, title = {Experimental study of longitudinal, transverse and volume strains of magnetoactive elastomeric cylinders in uniform magnetic fields}, series = {Journal of Magnetism and Magnetic Materials}, volume = {579}, journal = {Journal of Magnetism and Magnetic Materials}, publisher = {Elsevier}, issn = {0304-8853}, doi = {10.1016/j.jmmm.2023.170826}, abstract = {Magnetoactive elastomers (MAEs) are promising materials for realization of magnetic field-controlled soft actuators. Herein, a systematic investigation of magnetic field-induced macroscopic deformations of soft MAE cylinders with a diameter of 15 mm in uniform quasi-static magnetic fields directed parallel to the cylinder's axis is reported. The measurements were based on image processing. Thirty-six MAE samples differing in the weight fraction of the iron filler (70 wt\%, 75 wt\% and 80 wt\%), alignment of filling particles, and the aspect ratio (0.2, 0.4, 0.6, 0.8, 1.0 and 1.2) were fabricated. MAE cylinders exhibited high relative change in height (up to 35\% in the field of 485 kA/m) and lateral contraction. The dependence of the maximum extensional strain on the aspect ratio was obtained and compared with theoretical considerations. A concave dent was formed on the free circular base in magnetic fields. This concavity was characterized experimentally. A significant volumetric strain of the order of magnitude of 10\% was calculated in MAEs for the first time. In consequently repeated magnetization cycles, the remanent extensional strain significantly increased after each cycle. The results are qualitatively discussed in the framework of the modern views on the magnetically induced macroscopic deformations of MAEs. The directions of further research are outlined.}, language = {en} } @misc{KrieglKravanjaHribaretal., author = {Kriegl, Raphael and Kravanja, Gaia and Hribar, Luka and Jezeršek, Matija and Drevenšek-Olenik, Irena and Shamonin (Chamonine), Mikhail}, title = {Characterization of Wetting Properties of Magnetoactive Elastomer Surfaces}, series = {Proceedings of the ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS) - 2023, September 11-13, 2023 Austin, Texas, USA}, journal = {Proceedings of the ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS) - 2023, September 11-13, 2023 Austin, Texas, USA}, publisher = {The American Society of Mechanical Engineers}, address = {New York, USA}, isbn = {978-0-7918-8752-3}, doi = {10.1115/SMASIS2023-110998}, abstract = {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.}, language = {en} } @article{KravanjaKrieglHribaretal., author = {Kravanja, Gaia and Kriegl, Raphael and Hribar, Luka and Glavan, Gašper and Drevenšek-Olenik, Irena and Shamonin (Chamonine), Mikhail and Jezeršek, Matija}, title = {Magnetically Actuated Surface Microstructures for Efficient Transport and Tunable Separation of Droplets and Solids}, series = {Advanced Engineering Materials}, volume = {25}, journal = {Advanced Engineering Materials}, number = {22}, publisher = {Wiley-VCH}, issn = {1527-2648}, doi = {10.1002/adem.202301000}, pages = {1 -- 11}, abstract = {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.}, language = {en} } @article{StrausKokotKravanjaetal., author = {Straus, Izidor and Kokot, Gašper and Kravanja, Gaia and Hribar, Luka and Kriegl, Raphael and Shamonin (Chamonine), Mikhail and Jezeršek, Matija and Drevenšek-Olenik, Irena}, title = {Dynamically tunable lamellar surface structures from magnetoactive elastomers driven by a uniform magnetic field}, series = {Soft Matter}, volume = {Vol. 19}, journal = {Soft Matter}, publisher = {Royal Society of Chemistry}, doi = {10.1039/D3SM00012E}, pages = {3357 -- 3365}, abstract = {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.}, language = {en} }