60 results
Search Results
Now showing 1 - 10 of 60
- ItemBiofunctionalized self-propelled micromotors as an alternative on-chip concentrating system(Cambridge : Royal Society of Chemistry, 2014) Restrepo-Pérez, Laura; Meyer, Anne K.; Helbig, Linda; Sanchez, Samuel; Schmidt, Oliver G.Sample pre-concentration is crucial to achieve high sensitivity and low detection limits in lab-on-a-chip devices. Here, we present a system in which self-propelled catalytic micromotors are biofunctionalized and trapped acting as an alternative concentrating mechanism. This system requires no external energy source, which facilitates integration and miniaturization.
- 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.
- ItemSperm-Hybrid Micromotor for Targeted Drug Delivery(Washington, DC : Soc., 2017-12-13) Xu, Haifeng; Medina-Sánchez, Mariana; Magdanz, Veronika; Schwarz, Lukas; Hebenstreit, Franziska; Schmidt, Oliver G.A sperm-driven micromotor is presented as a targeted drug delivery system, which is appealing to potentially treat diseases in the female reproductive tract. This system is demonstrated to be an efficient drug delivery vehicle by first loading a motile sperm cell with an anticancer drug (doxorubicin hydrochloride), guiding it magnetically, to an in vitro cultured tumor spheroid, and finally freeing the sperm cell to deliver the drug locally. The sperm release mechanism is designed to liberate the sperm when the biohybrid micromotor hits the tumor walls, allowing it to swim into the tumor and deliver the drug through the sperm–cancer cell membrane fusion. In our experiments, the sperm cells exhibited a high drug encapsulation capability and drug carrying stability, conveniently minimizing toxic side effects and unwanted drug accumulation in healthy tissues. Overall, sperm cells are excellent candidates to operate in physiological environments, as they neither express pathogenic proteins nor proliferate to form undesirable colonies, unlike other cells or microorganisms. This sperm-hybrid micromotor is a biocompatible platform with potential application in gynecological healthcare, treating or detecting cancer or other diseases in the female reproductive system.
- ItemHigh-performance giant magnetoresistive sensorics on flexible Si membranes(Melville, NY : American Inst. of Physics, 2015) Pérez, Nicolás; Melzer, Michael; Makarov, Denys; Ueberschär, Olaf; Ecke, Ramona; Schulz, Stefan E.; Schmidt, Oliver G.We fabricate high-performance giant magnetoresistive (GMR) sensorics on Si wafers, which are subsequently thinned down to 100 μm or 50 μm to realize mechanically flexible sensing elements. The performance of the GMR sensors upon bending is determined by the thickness of the Si membrane. Thus, bending radii down to 15.5 mm and 6.8 mm are achieved for the devices on 100 μm and 50 μm Si supports, respectively. The GMR magnitude remains unchanged at the level of (15.3 ± 0.4)% independent of the support thickness and bending radius. However, a progressive broadening of the GMR curve is observed associated with the magnetostriction of the containing Ni81Fe19 alloy, which is induced by the tensile bending strain generated on the surface of the Si membrane. An effective magnetostriction value of λs = 1.7 × 10−6 is estimated for the GMR stack. Cyclic bending experiments showed excellent reproducibility of the GMR curves during 100 bending cycles.
- ItemHigh-rate amorphous SnO2 nanomembrane anodes for Li-ion batteries with a long cycling life(Cambridge : RSC Publ., 2014) Liu, Xianghong; Zhang, Jun; Si, Wenping; Xi, Lixia; Oswald, Steffen; Yan, Chenglin; Schmidt, Oliver G.Amorphous SnO2 nanomembranes as anodes for lithium ion batteries demonstrate a long cycling life of 1000 cycles at 1600 mA g−1 with a high reversible capacity of 854 mA h g−1 and high rate capability up to 40 A g−1. The superior performance is because of the structural features of the amorphous SnO2 nanomembranes. The nanoscale thickness provides considerably reduced diffusion paths for Li+. The amorphous structure can accommodate the strain of lithiation/delithiation, especially during the initial lithiation. More importantly, the mechanical feature of deformation can buffer the strain of repeated lithiation/delithiation, thus putting off pulverization. In addition, the two-dimensional transport pathways in between nanomembranes make the pseudo-capacitance more prominent. The encouraging results demonstrate the significant potential of nanomembranes for high power batteries.
- 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-defect hydrophilic carbon cuboids anchored with Co/CoO nanoparticles as highly efficient and ultra-stable lithium-ion battery anodes(Cambridge : Royal Society of Chemistry, 2016) Sun, Xiaolei; Hao, Guang-Ping; Lu, Xueyi; Xi, Lixia; Liu, Bo; Si, Wenping; Ma, Chuansheng; Liu, Qiming; Zhang, Qiang; Kaskel, Stefan; Schmidt, Oliver G.We propose an effective strategy to engineer a unique kind of porous carbon cuboid with tightly anchored cobalt/cobalt oxide nanoparticles (PCC–CoOx) that exhibit outstanding electrochemical performance for many key aspects of lithium-ion battery electrodes. The host carbon cuboid features an ultra-polar surface reflected by its high hydrophilicity and rich surface defects due to high heteroatom doping (N-/O-doping both higher than 10 atom%) as well as hierarchical pore systems. We loaded the porous carbon cuboid with cobalt/cobalt oxide nanoparticles through an impregnation process followed by calcination treatment. The resulting PCC–CoOx anode exhibits superior rate capability (195 mA h g−1 at 20 A g−1) and excellent cycling stability (580 mA h g−1 after 2000 cycles at 1 A g−1 with only 0.0067% capacity loss per cycle). Impressively, even after an ultra-long cycle life exceeding 10 000 cycles at 5 A g−1, the battery can recover to 1050 mA h g−1 at 0.1 A g−1, perhaps the best performance demonstrated so far for lithium storage in cobalt oxide-based electrodes. This study provides a new perspective to engineer long-life, high-power metal oxide-based electrodes for lithium-ion batteries through controlling the surface chemistry of carbon host materials.
- ItemCharge transport in organic nanocrystal diodes based on rolled-up robust nanomembrane contacts(Frankfurt, M. : Beilstein-Institut zur Förderung der Chemischen Wissenschaften, 2017-6-19) Bandari, Vineeth Kumar; Varadharajan, Lakshmi; Xu, Longqian; Jalil, Abdur Rehman; Devarajulu, Mirunalini; Siles, Pablo F.; Zhu, Feng; Schmidt, Oliver G.The investigation of charge transport in organic nanocrystals is essential to understand nanoscale physical properties of organic systems and the development of novel organic nanodevices. In this work, we fabricate organic nanocrystal diodes contacted by rolled-up robust nanomembranes. The organic nanocrystals consist of vanadyl phthalocyanine and copper hexadecafluorophthalocyanine heterojunctions. The temperature dependent charge transport through organic nanocrystals was investigated to reveal the transport properties of ohmic and space-charge-limited current under different conditions, for instance, temperature and bias
- ItemEffect of surfactants on the performance of tubular and spherical micromotors-a comparative study(Cambridge : Royal Society of Chemistry, 2014) Simmchen, Juliane; Magdanz, Veronika; Sanchez, Samuel; Chokmaviroj, Sarocha; Ruiz-Molina, Daniel; Baeza, Alejandro; Schmidt, Oliver G.The development of artificial micromotors is one of the greatest challenges of modern nanotechnology. Even though many kinds of motors have been published in recent times, systematic studies on the influence of components of the fuel solution are widely missing. Therefore, the autonomous movement of Pt-microtubes and Pt-covered silica particles is comparatively observed in the presence and absence of surfactants in the medium. One representative of each of the three main surfactant classes – anionic (sodium dodecyl sulfate, SDS), cationic (benzalkonium chloride, BACl) and non-ionic (Triton X) – has been chosen and studied.
- 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.