@inproceedings{KravanjaBelyaevaHribaretal., author = {Kravanja, Gaia and Belyaeva, Inna A. and Hribar, Luka and Drevenšek-Olenik, Irena and Shamonin (Chamonine), Mikhail and Jezeršek, Matija}, title = {Adaptive Magneto-Responsive Surfaces Fabricated by Laser-Based Microstructuring}, series = {Proceedings of the ASME 2022 Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS 2022): September 12-14, 2022, Dearborn, Michigan}, booktitle = {Proceedings of the ASME 2022 Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS 2022): September 12-14, 2022, Dearborn, Michigan}, publisher = {ASME}, isbn = {978-0-7918-8627-4}, doi = {10.1115/SMASIS2022-90742}, pages = {6}, abstract = {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.}, language = {en} } @article{KrieglKravanjaHribaretal., author = {Kriegl, Raphael and Kravanja, Gaia and Hribar, Luka and Čoga, Lucija and Drevenšek-Olenik, Irena and Jezeršek, Matija and Kalin, Mitjan and Shamonin (Chamonine), Mikhail}, title = {Microstructured Magnetoactive Elastomers for Switchable Wettability}, series = {Polymers}, volume = {14}, journal = {Polymers}, number = {18}, publisher = {MDPI}, doi = {10.3390/polym14183883}, pages = {1 -- 21}, abstract = {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.}, language = {en} }