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- ItemSelf‐assembled on‐chip‐integrated giant magneto‐impedance sensorics(Hoboken, NJ : Wiley, 2015) Karnaushenko, Daniil; Karnaushenko, Dmitriy D.; Makarov, Denys; Baunack, Stefan; Schäfer, Rudolf; Schmidt, Oliver G.A novel method relying on strain engineering to realize arrays of on‐chip‐integrated giant magneto‐impedance (GMI) sensors equipped with pick‐up coils is put forth. The geometrical transformation of an initially planar layout into a tubular 3D architecture stabilizes favorable azimuthal magnetic domain patterns. This work creates a solid foundation for further development of CMOS compatible GMI sensorics for magnetoencephalography.
- ItemPurely antiferromagnetic magnetoelectric random access memory(London : Nature Publishing Group, 2017) Kosub, Tobias; Kopte, Martin; Hühne, Ruben; Appel, Patrick; Shields, Brendan; Maletinsky, Patrick; Hübner, René; Liedke, Maciej Oskar; Fassbender, Jürgen; Schmidt, Oliver G.; Makarov, DenysMagnetic random access memory schemes employing magnetoelectric coupling to write binary information promise outstanding energy efficiency. We propose and demonstrate a purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) that offers a remarkable 50-fold reduction of the writing threshold compared with ferromagnet-based counterparts, is robust against magnetic disturbances and exhibits no ferromagnetic hysteresis losses. Using the magnetoelectric antiferromagnet Cr2O3, we demonstrate reliable isothermal switching via gate voltage pulses and all-electric readout at room temperature. As no ferromagnetic component is present in the system, the writing magnetic field does not need to be pulsed for readout, allowing permanent magnets to be used. Based on our prototypes, we construct a comprehensive model of the magnetoelectric selection mechanisms in thin films of magnetoelectric antiferromagnets, revealing misfit induced ferrimagnetism as an important factor. Beyond memory applications, the AF-MERAM concept introduces a general all-electric interface for antiferromagnets and should find wide applicability in antiferromagnetic spintronics.
- ItemHigh-performance magnetic sensorics for printable and flexible electronics(Hoboken, NJ : Wiley, 2014) Karnaushenko, Daniil; Makarov, Denys; Stöber, Max; Karnaushenko, Dmitriy D.; Baunack, Stefan; Schmidt, Oliver G.High‐performance giant magnetoresistive (GMR) sensorics are realized, which are printed at predefined locations on flexible circuitry. Remarkably, the printed magnetosensors remain fully operational over the complete consumer temperature range and reveal a giant magnetoresistance up to 37% and a sensitivity of 0.93 T−1 at 130 mT. With these specifications, printed magnetoelectronics can be controlled using flexible active electronics for the realization of smart packaging and energy‐efficient switches.
- ItemTuning the properties of magnetic thin films by interaction with periodic nanostructures(Frankfurt, M. : Beilstein-Institut zur Förderung der Chemischen Wissenschaften, 2012) Wiedwald, Ulf; Haering, Felix; Nau, Stefan; Schulze, Carsten; Schletter, Herbert; Makarov, Denys; Plettl, Alfred; Kuepper, Karsten; Albrecht, Manfred; Boneberg, Johannes; Ziemann, PaulThe most important limitation for a significant increase of the areal storage density in magnetic recording is the superparamagnetic effect. Below a critical grain size of the used CoCrPt exchange-decoupled granular films the information cannot be stored for a reasonable time (typically ten years) due to thermal fluctuations arbitrary flipping of the magnetization direction. An alternative approach that may provide higher storage densities is the use of so-called percolated media, in which defect structures are imprinted in an exchange-coupled magnetic film. Such percolated magnetic films are investigated in the present work. We employ preparation routes that are based on (i) self-assembly of Au nanoparticles and (ii) homogeneous size-reduction of self-assembled polystyrene particles. On such non-close-packed nanostructures thin Fe films or Co/Pt multilayers are grown with in-plane and out-of-plane easy axis of magnetization. The impact of the particles on the magnetic switching behavior is measured by both integral magnetometry and magnetic microscopy techniques. We observe enhanced coercive fields while the switching field distribution is broadened compared to thin-film reference samples. It appears possible to tailor the magnetic domain sizes down to the width of an unperturbed domain wall in a continuous film, and moreover, we observe pinning and nucleation at or close to the imprinted defect structures.
- ItemMonitoring microbial metabolites using an inductively coupled resonance circuit(London : Nature Publishing Group, 2015) Karnaushenko, Daniil; Baraban, Larysa; Ye, Dan; Uguz, Ilke; Mendes, Rafael G.; Rümmeli, Mark H.; de Visser, J. Arjan G.M.; Schmidt, Oliver G.; Cuniberti, Gianaurelio; Makarov, DenysWe present a new approach to monitor microbial population dynamics in emulsion droplets via changes in metabolite composition, using an inductively coupled LC resonance circuit. The signal measured by such resonance detector provides information on the magnetic field interaction with the bacterial culture, which is complementary to the information accessible by other detection means, based on electric field interaction, i.e. capacitive or resistive, as well as optical techniques. Several charge-related factors, including pH and ammonia concentrations, were identified as possible contributors to the characteristic of resonance detector profile. The setup enables probing the ionic byproducts of microbial metabolic activity at later stages of cell growth, where conventional optical detection methods have no discriminating power.
- ItemMagnetic suspension array technology: Controlled synthesis and screening in microfluidic networks(Hoboken, NJ : Wiley, 2016) Lin, Gungun; Karnaushenko, Dmitriy D.; Cañón Bermúdez, Gilbert Santiago; Schmidt, Oliver G.; Makarov, DenysInformation tagging and processing are vital in information‐intensive applications, e.g., telecommunication and high‐throughput drug screening. Magnetic suspension array technology may offer intrinsic advantages to screening applications by enabling high distinguishability, the ease of code generation, and the feasibility of fast code readout, though the practical applicability of magnetic suspension array technology remains hampered by the lack of quality administration of encoded microcarriers. Here, a logic‐controlled microfluidic system enabling controlled synthesis of magnetic suspension arrays in multiphase flow networks is realized. The smart and compact system offers a practical solution for the quality administration and screening of encoded magnetic microcarriers and addresses the universal need of process control for synthesis in microfluidic networks, i.e., on‐demand creation of droplet templates for high information capacity. The demonstration of magnetic suspension array technology enabled by magnetic in‐flow cytometry opens the avenue toward point‐of‐care multiplexed bead‐based assays, clinical diagnostics, and drug discovery.
- ItemEntirely flexible on-site conditioned magnetic sensorics(Hoboken, NJ : Wiley, 2016) Münzenrieder, Niko; Karnaushenko, Daniil; Petti, Luisa; Cantarella, Giuseppe; Vogt, Christian; Büthe, Lars; Karnaushenko, Dmitriy D.; Schmidt, Oliver G.; Makarov, Denys; Tröster, GerhardThe first entirely flexible integrated magnetic field sensor system is realized consisting of a flexible giant magnetoresistive bridge on‐site conditioned using high‐performance IGZO‐based readout electronics. The system outperforms commercial fully integrated rigid magnetic sensors by at least one order of magnitude, whereas all components stay fully functional when bend to a radius of 5 mm.
- ItemImperceptible magnetoelectronics(London : Nature Publishing Group, 2015) Melzer, Michael; Kaltenbrunner, Martin; Makarov, Denys; Karnaushenko, Dmitriy; Karnaushenko, Daniil; Sekitani, Tsuyoshi; Someya, Takao; Schmidt, Oliver G.Future electronic skin aims to mimic nature’s original both in functionality and appearance. Although some of the multifaceted properties of human skin may remain exclusive to the biological system, electronics opens a unique path that leads beyond imitation and could equip us with unfamiliar senses. Here we demonstrate giant magnetoresistive sensor foils with high sensitivity, unmatched flexibility and mechanical endurance. They are <2 μm thick, extremely flexible (bending radii <3 μm), lightweight (≈3 g m−2) and wearable as imperceptible magneto-sensitive skin that enables proximity detection, navigation and touchless control. On elastomeric supports, they can be stretched uniaxially or biaxially, reaching strains of >270% and endure over 1,000 cycles without fatigue. These ultrathin magnetic field sensors readily conform to ubiquitous objects including human skin and offer a new sense for soft robotics, safety and healthcare monitoring, consumer electronics and electronic skin devices.
- ItemCompact helical antenna for smart implant applications(London : Nature Publishing Group, 2015) Karnaushenko, Dmitriy D.; Karnaushenko, Daniil; Makarov, Denys; Schmidt, Oliver G.Smart implants are envisioned to revolutionize personal health care by assessing physiological processes, for example, upon wound healing, and communicating these data to a patient or medical doctor. The compactness of the implants is crucial to minimize discomfort during and after implantation. The key challenge in realizing small-sized smart implants is high-volume cost- and time-efficient fabrication of a compact but efficient antenna, which is impedance matched to 50 Ω, as imposed by the requirements of modern electronics. Here, we propose a novel route to realize arrays of 5.5-mm-long normal mode helical antennas operating in the industry-scientific-medical radio bands at 5.8 and 2.4 GHz, relying on a self-assembly process that enables large-scale high-yield fabrication of devices. We demonstrate the transmission and receiving signals between helical antennas and the communication between an antenna and a smartphone. Furthermore, we successfully access the response of an antenna embedded in a tooth, mimicking a dental implant. With a diameter of ~0.2 mm, these antennas are readily implantable using standard medical syringes, highlighting their suitability for in-body implant applications.
- ItemWearable magnetic field sensors for flexible electronics(Hoboken, NJ : Wiley, 2014) Melzer, Michael; Mönch, Jens Ingolf; Makarov, Denys; Zabila, Yevhen; Bermúdez, Gilbert Santiago Cañón; Karnaushenko, Daniil; Baunack, Stefan; Bahr, Falk; Yan, Chenglin; Kaltenbrunner, Martin; Schmidt, Oliver G.Highly flexible bismuth Hall sensors on polymeric foils are fabricated, and the key optimization steps that are required to boost their sensitivity to the bulk value are identified. The sensor can be bent around the wrist or positioned on the finger to realize an interactive pointing device for wearable electronics. Furthermore, this technology is of great interest for the rapidly developing market of eMobility, for optimization of eMotors and magnetic bearings.