@article{MonkmanSindersbergerPrem, author = {Monkman, Gareth J. and Sindersberger, Dirk and Prem, Nina}, title = {Magnetically enhanced photoconductive high voltage control}, series = {ISSS Journal of Micro and Smart Systems}, volume = {11}, journal = {ISSS Journal of Micro and Smart Systems}, publisher = {Springer Nature}, doi = {10.1007/s41683-021-00088-z}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-30606}, pages = {317 -- 328}, abstract = {The recent surge of interest in electrostatic actuators, particularly for soft robotic applications, has placed increasing demands on high voltage control technology. In this respect, optoelectronic bidirectional switching and analogue regulation of high voltages is becoming increasingly important. One common problem is the leakage current due to dark resistance of the material or device used. Another is the physical size of such elements. However, their ability to provide galvanic separation makes them a very attractive alternative to conventional (wired) semiconductor elements. This paper gives an overview of available methods and devices before introducing a concept based on the combination of photoresistive and magnetoresistive effects in Gallium Arsenide that are potentially applicable to other semiconductor materials.}, language = {en} } @article{MonkmanStrieglPremetal., author = {Monkman, Gareth J. and Striegl, Birgit and Prem, Nina and Sindersberger, Dirk}, title = {Electrical Properties of Magnetoactive Boron-Organo-Silicon Oxide Polymers}, series = {Macromolecular Chemistry and Physics}, volume = {221}, journal = {Macromolecular Chemistry and Physics}, number = {4}, publisher = {Wiley}, doi = {10.1002/macp.201900342}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-26488}, pages = {1 -- 8}, abstract = {The electrical properties of rheopectic magnetoactive composites comprising boron-organo-silicon oxide dielectric matrices containing carbonyl iron microparticles are presented for the first time. The increase in interfacial magnetocapacitance is seen to greatly exceed that experienced when using conventional elastomeric matrices such as polydimethylsiloxane. In addition to the increase in capacitance, a simultaneous and sharp decrease in the parallel electrical resistance over several orders of magnitude is also observed. The effects are time dependent but repeatable. Potential applications include magnetically controlled frequency dependent devices, magnetic sensor systems, weighting elements for neural networks, etc.}, language = {en} } @article{PremSindersbergerMonkman, author = {Prem, Nina and Sindersberger, Dirk and Monkman, Gareth J.}, title = {Infrared spectral analysis of low concentration magnetoactive polymers}, series = {Journal of Applied Polymer Science}, volume = {137}, journal = {Journal of Applied Polymer Science}, number = {7}, publisher = {Wiley}, organization = {WILEY}, issn = {1097-4628}, doi = {10.1002/app.48366}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-25913}, pages = {1 -- 7}, abstract = {This work concerns an area of magnetoactive polymer (MAP) research seldom considered. Traditionally only MAP with high concentrations of magnetic filler (typically between 10 and 90 wt\%) have been investigated. This article deals with a hitherto neglected aspect of research, namely MAP containing lower magnetic filler concentrations (1 to 3 wt\%). This article utilizes a range of spectroscopic analysis methods (Raman and FTIR) and their applicability to MAP characterization at wavelengths ranging from 2.5 to 25 mu m. Particular attention is paid to low carbonyl iron particle (CIP) concentrations in MAP for which the emergence of capillary doublets at a critical 2 wt\% concentration is revealed. This results in measurable magnetic field-dependent changes in IR absorption at a wavelength of 4.255 mu m together with a detectable CO2 susceptibility. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48366.}, language = {en} } @article{PremSindersbergerStriegletal., author = {Prem, Nina and Sindersberger, Dirk and Striegl, Birgit and B{\"o}hm, Valter and Monkman, Gareth J.}, title = {Shape memory effects using magnetoactive Boron-organo-silicon oxide polymers}, series = {Macromolecular Chemistry and Physics}, volume = {221}, journal = {Macromolecular Chemistry and Physics}, number = {15}, publisher = {Wiley}, doi = {10.1002/macp.202000149}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-23205}, pages = {1 -- 8}, abstract = {Thermomechanical shape memory materials have certain disadvantages when it comes to 3D volumetric reproduction intended for rapid prototyping or robotic prehension. The need to constantly supply energy to counteract elastic retraction forces in order to maintain the required geometry, together with the inability to achieve conformal stability at elevated temperatures, limits the application of thermal shape memory polymers. Form removal also presents problems as most viscoelastic materials do not ensure demolding stability. This work demonstrates how magnetoactive boron-organo-silicon oxide polymers under the influence of an applied magnetic field can be used to achieve energy free sustainable volumetric shape memory effects over extended periods. The rheopectic properties of boron-organo-silicon oxide materials sustain form removal without mold distortion.}, language = {en} } @article{MaierSchlattlGuessetal., author = {Maier, Robert and Schlattl, Andreas and Guess, Thomas and Mottok, J{\"u}rgen}, title = {CausalOps - Towards an industrial lifecycle for causal probabilistic graphical models}, series = {Information and Software Technology}, journal = {Information and Software Technology}, publisher = {Elsevier}, issn = {0950-5849}, doi = {10.1016/j.infsof.2024.107520}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-73350}, abstract = {Context: Causal probabilistic graph-based models have gained widespread utility, enabling the modeling of cause-and-effect relationships across diverse domains. With their rising adoption in new areas, such as safety analysis of complex systems, software engineering, and machine learning, the need for an integrated lifecycle framework akin to DevOps and MLOps has emerged. Currently, such a reference for organizations interested in employing causal engineering is missing. This lack of guidance hinders the incorporation and maturation of causal methods in the context of real-life applications. Objective: This work contextualizes causal model usage across different stages and stakeholders and outlines a holistic view of creating and maintaining them within the process landscape of an organization. Method: A novel lifecycle framework for causal model development and application called CausalOps is proposed. By defining key entities, dependencies, and intermediate artifacts generated during causal engineering, a consistent vocabulary and workflow model to guide organizations in adopting causal methods are established. Results: Based on the early adoption of the discussed methodology to a real-life problem within the automotive domain, an experience report underlining the practicability and challenges of the proposed approach is discussed. Conclusion: It is concluded that besides current technical advancements in various aspects of causal engineering, an overarching lifecycle framework that integrates these methods into organizational practices is missing. Although diverse skills from adjacent disciplines are widely available, guidance on how to transfer these assets into causality-driven practices still need to be addressed in the published literature. CausalOps' aim is to set a baseline for the adoption of causal methods in practical applications within interested organizations and the causality community.}, language = {en} } @article{GrabingerHauserMottok, author = {Grabinger, Lisa and Hauser, Florian and Mottok, J{\"u}rgen}, title = {On the perception of graph layouts}, series = {Journal of Software: Evolution and Process}, journal = {Journal of Software: Evolution and Process}, publisher = {Wiley}, doi = {10.1002/smr.2599}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-62973}, abstract = {In the field of software engineering, graph-based models are used for a variety of applications. Usually, the layout of those graphs is determined at the discretion of the user. This article empirically investigates whether different layouts affect the comprehensibility or popularity of a graph and whether one can predict the perception of certain aspects in the graph using basic graphical laws from psychology (i.e., Gestalt principles). Data on three distinct layouts of one causal graph is collected from 29 subjects using eye tracking and a print questionnaire. The evaluation of the collected data suggests that the layout of a graph does matter and that the Gestalt principles are a valuable tool for assessing partial aspects of a layout.}, language = {en} } @article{KrieglKrenkelShamoninChamonine, author = {Kriegl, Raphael and Krenkel, Lars and Shamonin (Chamonine), Mikhail}, title = {Preservation of wetting ridges using field-induced plasticity of magnetoactive elastomers}, series = {Journal of Colloid and Interface Science}, volume = {683}, journal = {Journal of Colloid and Interface Science}, publisher = {Elsevier}, issn = {0021-9797}, doi = {10.1016/j.jcis.2024.12.132}, pages = {1019 -- 1027}, abstract = {Hypothesis. The presence of a wetting ridge is crucial for many wetting phenomena on soft substrates. Conventional experimental observations of a wetting ridge require permanent presence of a droplet. The magnetic field-induced plasticity effect (FIPE) of soft magnetoative elastomers (MAEs) allows one to overcome this limitation. Depositing a droplet onto an MAE surface and applying a magnetic field fixes the wetting ridge in place due to the FIPE. The droplet can be removed to investigate the ridge with ease using conventional optical methods. Experiments. The wetting ridge is observed on MAEs with different shear moduli and different material thicknesses by confocal laser scanning microscopy (LSM). The preservation quality of the ridge is analyzed for several values of magnetic field from 10 mT to 270 mT. To verify the plausibilty of results obtained, the measured shape is compared to a theoretical model by Style \& Dufresne. Findings. Upon removal of the sessile droplet, the deformation remains embossed onto the MAE surface as long as the magnetic field remains applied. The height of the ridge peak on soft samples (effective shear modulus kPa) is close to the theoretical prediction for a magnetic flux density of 50 mT. The magnitude of the external magnetic field magnifies the height of the wetting ridge.}, language = {en} } @article{MuehlbauerKeinerGerhardsetal., author = {M{\"u}hlbauer, Andreas and Keiner, Dominik and Gerhards, Christoph and Caldera, Upeksha and Sterner, Michael and Breyer, Christian}, title = {Assessment of technologies and economics for carbon dioxide removal from a portfolio perspective}, series = {International Journal of Greenhouse Gas Control}, volume = {141}, journal = {International Journal of Greenhouse Gas Control}, publisher = {Elsevier}, doi = {10.1016/j.ijggc.2024.104297}, pages = {25}, abstract = {Carbon dioxide removal (CDR) is essential to achieve ambitious climate goals limiting global warming to less than 1.5◦C, and likely for achieving the 1.5◦C target. This study addresses the need for diverse CDR portfolios and introduces the LUT-CDR tool, which assesses CDR technology portfolios aligned with hypothetical societal preferences. Six scenarios are described, considering global deployment limitations, techno-economic factors, area requirements, technology readiness, and storage security for various CDR options. The results suggest the feasibility of large-scale CDR, potentially removing 500-1750 GtCO2 by 2100 to meet the set climate targets. For a 1.0◦C climate goal, CDR portfolios necessitate 12.0-37.5\% more primary energy compared to a scenario without CDR. Remarkably, funding a 1.0◦C target requires only 0.42-0.65\% of the projected global gross domestic product. Bioenergy carbon capture and sequestration and rainfall-based afforestation play limited roles, while secure sequestration of captured CO2 via direct air capture, electricity-based carbon sequestration, and desalination-based afforestation emerge as more promising options. The study offers crucial techno-economic parameters for implementing CDR options in future energy-industry-CDR system analyses and demonstrates the tool's flexibility through alternative assumptions. It also discusses limitations, sensitivities, potential tradeoffs, and outlines options for future research in the area of large-scale CDR.}, language = {en} } @article{MonkmanSindersbergerPremetal., author = {Monkman, Gareth J. and Sindersberger, Dirk and Prem, Nina and Diermeier, Andreas and Szecsey, Tamara}, title = {Dielectric behaviour of magnetic hybrid materials}, series = {Physical Sciences Reviews}, volume = {7}, journal = {Physical Sciences Reviews}, number = {10}, publisher = {de Gruyter}, doi = {10.1515/psr-2019-0121}, pages = {1169 -- 1185}, abstract = {The objectives of this work include the analysis of electrical and magnetic properties of magneto-elastic hybrid materials with the intention of developing new techniques for sensor and actuator applications. This includes the investigation of dielectric properties at both low and high frequencies. The behaviour of capacitors whose dielectrics comprise magnetic hybrid materials is well known. Such interfacial magnetocapacitance can be varied according to magnetic content, magnetic flux density and the relative permittivity of the polymer matrix together with other dielectric content. The basic function of trapping electrical charges in polymers (electrets) is also established technology. However, the combination of magnetoactive polymers and electrets has led to the first electromagnetic device capable of adhering to almost any material, whether magnetically susceptible or not. During the course of this research, in addition to dielectrics, electrically conductive polymers based on (PDMS) matrices were developed in order to vary the electrical properties of the material in a targeted manner. In order to ensure repeatable results, this demanded new fabrication techniques hitherto unavailable. The 3D printing of silicones is far from being a mature technology and much pioneering work was necessary before extending the usual 3 d.o.f. to include orientation about and diffusion of particles in these three axes, thus leading to the concept of 6D printing. In 6D printing, the application of a magnetic field can be used during the curing process to control the particulate distribution and thus the spatial filler particle density as desired. Most of the devices (sensors and actuators) produced by such methods contain levels of carbonyl iron powder (CIP) embedded magnetic filler of up to 70 wt\%. Contrary to this, a hitherto neglected research area, namely magnetoactive polymers (MAPs) having significantly lower magnetic particle concentrations (1 to 3 wt\% CIP) were also investigated. With filler concentrations lower than 3 wt\%, structures are formed which are completely absent at higher filler levels. CIP concentrations in the range of 1wt\% demonstrate the formation of toroidal structures. Further development of coherent rings with a compact order results as filler concentrations increase towards 2 wt\%. Above 3 wt\% the structure eventually disintegrates to the usual random order found in traditional MAP with higher CIP content. Structured samples containing 1\%-3 wt\% CIP were investigated with the aid of X-ray tomography where solitary ring structures can be observed and eventually the formation of capillary doubles. Over wavelengths ranging from 1 to 25 µm, spectroscopic analysis of thin film MAP samples containing 2 wt\% CIP revealed measurable magnetic-field-dependent changes in IR absorption at a wavenumber 2350 (λ = 4.255 µm). This was found to be due to the diamagnetic susceptibility of atmospheric carbon dioxide (CO2). Consequently, the first potential application for sparse matrix MAPs was found.}, language = {en} } @article{SchmidtStraubSindersbergeretal., author = {Schmidt, Henrik and Straub, Benedikt B. and Sindersberger, Dirk and Br{\"o}ckel, Ulrich and Monkman, Gareth J. and Auernhammer, G{\"u}nter}, title = {Collision and separation of nickel particles embedded in a Poly dimethylsiloxan matrix under a rotating magnetic field: A strong magneto active function}, series = {Colloid and Polymer Science}, volume = {299}, journal = {Colloid and Polymer Science}, publisher = {Springer}, doi = {10.1007/s00396-020-04784-4}, pages = {955 -- 967}, abstract = {In order to function as soft actuators, depending on their field of use, magnetorheological elastomers (MREs) must fulfill certain criteria. To name just a few, these can include rapid response to external magnetic fields, mechanical durability, mechanical strength, and/or large deformation. Of particular interest are MREs which produce macroscopic deformation for small external magnetic field variations. This work demonstrates how this can be achieved by just a small change in magnetic field orientation. To achieve this, (super)paramagnetic nickel particles of size ≈ 160 μm were embedded in a non-magnetic polydimethylsiloxan (PDMS) (661-1301 Pa) and their displacement in a stepwise rotated magnetic field (170 mT) recorded using a video microscope. Changes in particle aggregation resulting from very small variations in magnetic field orientation led to the observation of a new strongly magneto-active effect. This configuration is characterized by an interparticle distance in relation to the angle difference between magnetic field and particle axis. This causes a strong matrix deformation which in turn demonstrates hysteresis on relaxation. It is shown that the occurrence strongly depends on the particle size, particle distance, and stiffness of the matrix. Choosing the correct parameter combination, the state can be suppressed and the particle-matrix system demonstrates no displacement or hysteresis. In addition, evidences of non-negligible higher order magnetization effects are experimentally ascertained which is qualitatively in agreement with similar, already theoretically described, particle systems. Even at larger particle geometries, the new strongly magneto-active configuration is preserved and could create macroscopic deformation changes.}, language = {en} } @article{KinoshitaDelcroixGannotetal., author = {Kinoshita, Keisuke and Delcroix, Marc and Gannot, Sharon and Habets, Emanuel A. P. and Haeb-Umbach, Reinhold and Kellermann, Walter and Leutnant, Volker and Maas, Roland and Nakatani, Tomohiro and Raj, Bhiksha and Sehr, Armin and Yoshioka, Takuya}, title = {A summary of the REVERB challenge: state-of-the-art and remaining challenges in reverberant speech processing research}, series = {Eurasip journal on advances in signal processing}, volume = {2016}, journal = {Eurasip journal on advances in signal processing}, publisher = {Springer Nature}, doi = {10.1186/s13634-016-0306-6}, abstract = {In recent years, substantial progress has been made in the field of reverberant speech signal processing, including both single- and multichannel dereverberation techniques and automatic speech recognition (ASR) techniques that are robust to reverberation. In this paper, we describe the REVERB challenge, which is an evaluation campaign that was designed to evaluate such speech enhancement (SE) and ASR techniques to reveal the state-of-the-art techniques and obtain new insights regarding potential future research directions. Even though most existing benchmark tasks and challenges for distant speech processing focus on the noise robustness issue and sometimes only on a single- channel scenario, a particular novelty of the REVERB challenge is that it is carefully designed to test robustness against reverberation, based on both real, single- channel, and multichannel recordings. This challenge attracted 27 papers, which represent 25 systems specifically designed for SE purposes and 49 systems specifically designed for ASR purposes. This paper describes the problems dealt within the challenge, provides an overview of the submitted systems, and scrutinizes them to clarify what current processing strategies appear effective in reverberant speech processing.}, language = {en} } @article{SternerBauer, author = {Sterner, Michael and Bauer, Franz}, title = {Power-to-X im Kontext der Energiewende und des Klimaschutzes in Deutschland}, series = {Chemie-Ingenieur-Technik}, volume = {92}, journal = {Chemie-Ingenieur-Technik}, number = {1-2}, publisher = {Wiley}, issn = {0009-286X}, doi = {10.1002/cite.201900167}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-11669}, pages = {85 -- 90}, abstract = {Um den Einfluss verschiedener Power-to-X-Verfahren auf die Transformation des deutschen Energiesystems und das Erreichen der Klimaschutzziele zu {\"u}berpr{\"u}fen, wurde ein sektor{\"u}bergreifendes Energiesystemmodel entwickelt. Die daraus gewonnenen Ergebnisse zeigen: F{\"u}r eine erfolgreiche Energiewende ist der Einsatz von Power-to-X in Zukunft unverzichtbar. Vor allem in Bereichen und Sektoren, in denen hohe Energiedichten erforderlich und nur wenig andere Optionen zur Defossilisierung vorhanden sind, werden Power-to-X-Technologien zwingend notwendig.}, subject = {Power-to-Gas}, language = {de} } @article{KeinerWalterBogdanovetal., author = {Keiner, Dominik and Walter, Lukas and Bogdanov, Dmitrii and Peters, Ian Marius and Breyer, Christian}, title = {Assessing the impact of bifacial solar photovoltaics on future power systems based on capacity-density-optimised power plant yield modelling}, series = {Solar Energy}, volume = {295}, journal = {Solar Energy}, publisher = {Elsevier}, doi = {10.1016/j.solener.2025.113543}, pages = {35}, abstract = {Bifacial solar photovoltaic (PV) technology is currently taking over the solar PV module market, exceeding a 90\% share in 2025. This important technology must be included in energy system modelling. This study provides a method for calculating the yield of monofacial and bifacial power plants in fixed-tilted, single-axis tracking, and east-west facing vertical setup. A novel method is introduced to maximise the capacity density of solar PV power plants without the need for detailed land cost for the most efficient use of the occupied area. The results indicate a 15-20\% yield gain from single-axis tracking compared to fixed-tilted power plants, and a limited bifacial gain of up to 10\% for most areas of the world. Higher bifacial gains are sporadically possible in specific conditions. Fixed-tilted systems show higher bifacial gains. Optimising tilt angles and row pitch would allow for 147 MW/ km2 capacity density today, though on average 70-110 MW/km2 can be achieved for 20.2\% module efficiency. The impact on the power system, studied in a free cost optimisation scenario and forcing vertical bifacial PV scenario, implying agrivoltaics, is not significant with a +/- 10\% change in total solar PV capacity, change in installed wind power of on average-10\%, increase of installed battery capacity of on average 5\%, and an on average changed levelised cost of electricity of-2\% globally. Bifacial solar PV technology has been found to be beneficial but no game changer for future power systems; system improvements are widely possible underlining the important role of this technology.}, language = {en} } @article{DoepfertCandasKrausetal., author = {Doepfert, Markus and Candas, Soner and Kraus, Hermann and Tzscheutschler, Peter and Hamacher, Thomas}, title = {Assessing the techno-economic benefits of LEMs for different grid topologies and prosumer shares}, series = {iScience}, volume = {28}, journal = {iScience}, number = {6}, publisher = {Elsevier - Cell Press}, doi = {10.1016/j.isci.2025.112493}, abstract = {The shift toward decentralized and renewable energy sources has introduced significant challenges to traditional power systems, necessitating innovative market designs. Local energy markets present a viable solution for integrating distributed energy resources such as photovoltaic systems, electric vehicles, and heat pumps. This study investigates the techno-economic implications of local energy markets compared to conventional market designs, focusing on their impact on average energy prices and operational peak power. Through comprehensive simulations across various grid topologies with varying penetration levels of the distributed energy resources, totaling 400 simulation setups, we demonstrate that local energy markets can enhance economic efficiency and grid stability with 99\% of the scenarios boasting lower average energy prices and 80\% lower operational peak power levels. The findings suggest that local energy markets can play a role in the future energy system, provided that additional infrastructure, management costs, and bureaucratic complexity are kept to a minimum.}, language = {en} } @article{ThemaBauerSterner, author = {Thema, Martin and Bauer, Franz and Sterner, Michael}, title = {Power-to-Gas: Electrolysis and methanation status review}, series = {Renewable and Sustainable Energy Reviews}, volume = {112}, journal = {Renewable and Sustainable Energy Reviews}, number = {7}, publisher = {Elsevier}, doi = {10.1016/j.rser.2019.06.030}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-26238}, pages = {775 -- 787}, abstract = {This review gives a worldwide overview on Power-to-Gas projects producing hydrogen or renewable substitute natural gas focusing projects in central Europe. It deepens and completes the content of previous reviews by including hitherto unreviewed projects and by combining project names with details such as plant location. It is based on data from 153 completed, recent and planned projects since 1988 which were evaluated with regards to plant allocation, installed power development, plant size, shares and amounts of hydrogen or substitute natural gas producing examinations and product utilization phases. Cost development for electrolysis and carbon dioxide methanation was analyzed and a projection until 2030 is given with an outlook to 2050. The results show substantial cost reductions for electrolysis as well as for methanation during the recent years and a further price decline to less than 500 euro per kilowatt electric power input for both technologies until 2050 is estimated if cost projection follows the current trend. Most of the projects examined are located in Germany, Denmark, the United States of America and Canada. Following an exponential global trend to increase installed power, today's Power-to-Gas applications are operated at about 39 megawatt. Hydrogen and substitute natural gas were investigated on equal terms concerning the number of projects.}, language = {en} } @article{SternerHofrichterMeisingeretal., author = {Sterner, Michael and Hofrichter, Andreas and Meisinger, Alexander and Bauer, Franz and Pinkwart, Karsten and Maletzko, Annabelle and Dittmar, Felix and Cremers, Carsten}, title = {19 Import options for green hydrogen and derivatives - An overview of efficiencies and technology readiness levels}, series = {International Journal of Hydrogen Energy}, volume = {90}, journal = {International Journal of Hydrogen Energy}, publisher = {Elsevier}, issn = {0360-3199}, doi = {10.1016/j.ijhydene.2024.10.045}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-77756}, pages = {1112 -- 1127}, abstract = {The import of hydrogen and derivatives forms part of many national strategies and is fundamental to achieving climate protection targets. This paper provides an overview and technical comparison of import pathways for hydrogen and derivatives in terms of efficiency, technological maturity and development and construction times with a focus on the period up to 2030. The import of hydrogen via pipeline has the highest system efficiency at 57-67 \% and the highest technological maturity with a technology readiness level (TRL) of 8-9. The import of ammonia and methanol via ship and of SNG via pipeline shows efficiencies in the range of 39-64 \% and a technological maturity of TRL 7 to 9 when using point sources. Liquid hydrogen, LOHC and Fischer-Tropsch products have the lowest efficiency and TRL in comparison. The use of direct air capture (DAC) reduces efficiency and TRL considerably. Reconversion of the derivatives to hydrogen is also associated with high losses and is not achievable for all technologies on an industrial scale up to 2030. In the short to medium term, import routes for derivatives that can utilise existing infrastructures and mature technologies are the most promising for imports. In the long term, the most promising option is hydrogen via pipelines.}, language = {en} } @article{KovalevBelyaevavonHofenetal., author = {Kovalev, Alexander and Belyaeva, Inna A. and von Hofen, Christian and Gorb, Stanislav and Shamonin (Chamonine), Mikhail}, title = {Magnetically Switchable Adhesion and Friction of Soft Magnetoactive Elastomers}, series = {Advanced Engineering Materials}, volume = {24}, journal = {Advanced Engineering Materials}, number = {10}, publisher = {WILEY-VCH}, doi = {10.1002/adem.202200372}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-45283}, pages = {1 -- 8}, abstract = {Herein, the effect of an applied moderate (~240 mT) magnetic field on the work of adhesion (WoA) of mechanically soft (the shear modulus ~10 kPa) magnetoactive elastomer (MAE) samples with two different mass fractions (70 and 80 wt\%) of carbonyl iron powder (CIP) is concerned. The unfilled elastomer sample is used for comparison. Due to some sedimentation of filling particles, the concentration of inclusions in thin (~10 μm) subsurface layers is different. It is shown that the WoA increases (up to 1.8-fold) on the particle-enriched side (PES) in the magnetic field and its value is higher for higher filler concentration. On the particle-depleted side (PDS), WoA does not depend on particle concentration and on the magnetic field. Adhesion and friction are coupled in MAEs. No statistically significant difference in the friction coefficient, determined from the extended Amontons´ law, depending on sample side, CIP concentration, or presence of magnetic field is found. However, the PDS in the magnetic field demonstrates significantly higher critical shear stress compared to that for the PES or PDS in the absence of magnetic field. Correlations between different surface properties are discussed. Obtained results are useful for the development of magnetically controllable soft robots.}, 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{KravanjaBelyaevaHribaretal., author = {Kravanja, Gaia and Belyaeva, Inna A. and Hribar, Luka and Drevenšek-Olenik, Irena and Shamonin (Chamonine), Mikhail and Jezeršek, Matija}, title = {Laser Micromachining of Magnetoactive Elastomers as Enabling Technology for Magnetoresponsive Surfaces}, series = {Advanced Materials Technologies}, volume = {7}, journal = {Advanced Materials Technologies}, number = {5}, publisher = {Wiley}, doi = {10.1002/admt.202101045}, pages = {1 -- 8}, abstract = {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.}, language = {en} } @article{KravanjaBelyaevaHribaretal., author = {Kravanja, Gaia and Belyaeva, Inna A. and Hribar, Luka and Drevenšek-Olenik, Irena and Jezeršek, Matija and Shamonin (Chamonine), Mikhail}, title = {Tunable Drop Splashing on Magnetoactive Elastomers}, series = {Advanced Materials Interfaces}, volume = {8}, journal = {Advanced Materials Interfaces}, number = {11}, publisher = {Wiley}, doi = {10.1002/admi.202100235}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-24504}, pages = {1 -- 7}, abstract = {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.}, 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{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} }