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Fulleretic well-defined scaffolds: Donor–fullerene alignment through metal coordination and its effect on photophysics

2016, Williams, Derek E., Dolgopolova, Ekaterina A., Godfrey, Danielle C., Ermolaeva, Evgeniya D., Pellechia, Perry J., Greytak, Andrew B., Smith, Mark D., Avdoshenko, Stanislav M., Popov, Alexey A., Shustova, Natalia B.

Herein, we report the first example of a crystalline metal–donor–fullerene framework, in which control of the donor–fullerene mutual orientation was achieved through chemical bond formation, in particular, by metal coordination. The 13C cross‐polarization magic‐angle spinning NMR spectroscopy, X‐ray diffraction, and time‐resolved fluorescence spectroscopy were performed for comprehensive structural analysis and energy‐transfer (ET) studies of the fulleretic donor–acceptor scaffold. Furthermore, in combination with photoluminescence measurements, the theoretical calculations of the spectral overlap function, Förster radius, excitation energies, and band structure were employed to elucidate the photophysical and ET processes in the prepared fulleretic material. We envision that the well‐defined fulleretic donor–acceptor materials could contribute not only to the basic science of fullerene chemistry but would also be used towards effective development of organic photovoltaics and molecular electronics.

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Controllable sliding transfer of wafer‐size graphene

2016, Lu, Wenjing, Zeng, Mengqi, Li, Xuesong, Wang, Jiao, Tan, Lifang, Shao, Miaomiao, Han, Jiangli, Wang, Sheng, Yue, Shuanglin, Zhang, Tao, Hu, Xuebo, Mendes, Rafael G., Rümmeli, Mark H., Peng, Lianmao, Liu, Zhongfan, Fu, Lei

The innovative design of sliding transfer based on a liquid substrate can succinctly transfer high‐quality, wafer‐size, and contamination‐free graphene within a few seconds. Moreover, it can be extended to transfer other 2D materials. The efficient sliding transfer approach can obtain high‐quality and large‐area graphene for fundamental research and industrial applications.

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Wearable magnetic field sensors for flexible electronics

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.

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Chemotactic behavior of catalytic motors in microfluidic channels

2013, Baraban, Larysa, Harazim, Stefan M., Sanchez, Samuel, Schmidt, Oliver.G.

Chemotaxis in practice: Two different artificial catalytic micromotors (tubular and spherical, see scheme) show chemotactic behavior in microfluidic channels demonstrating that catalytic micromotors can sense the gradient of chemical fuel in their environment and be directed towards desired locations.

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Stimuli‐responsive microjets with reconfigurable shape

2014, Magdanz, Veronika, Stoychev, Georgi, Ionov, Leonid, Sanchez, Samuel, Schmidt, Oliver.G.

Flexible thermoresponsive polymeric microjets are formed by the self‐folding of polymeric layers containing a thin Pt film used as catalyst for self‐propulsion in solutions containing hydrogen peroxide. The flexible microjets can reversibly fold and unfold in an accurate manner by applying changes in temperature to the solution in which they are immersed. This effect allows microjets to rapidly start and stop multiple times by controlling the radius of curvature of the microjet. This work opens many possibilities in the field of artificial nanodevices, for fundamental studies on self‐propulsion at the microscale, and also for biorelated applications.

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Carbons and electrolytes for advanced supercapacitors

2014, Presser, Volker

Electrical energy storage (EES) is one of the most critical areas of technological research around the world. Storing and efficiently using electricity generated by intermittent sources and the transition of our transportation fleet to electric drive depend fundamentally on the development of EES systems with high energy and power densities. Supercapacitors are promising devices for highly efficient energy storage and power management, yet they still suffer from moderate energy densities compared to batteries. To establish a detailed understanding of the science and technology of carbon/carbon supercapacitors, this review discusses the basic principles of the electrical double-layer (EDL), especially regarding the correlation between ion size/ion solvation and the pore size of porous carbon electrodes. We summarize the key aspects of various carbon materials synthesized for use in supercapacitors. With the objective of improving the energy density, the last two sections are dedicated to strategies to increase the capacitance by either introducing pseudocapacitive materials or by using novel electrolytes that allow to increasing the cell voltage. In particular, advances in ionic liquids, but also in the field of organic electrolytes, are discussed and electrode mass balancing is expanded because of its importance to create higher performance asymmetric electrochemical capacitors.

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Funnel-shaped microstructures for strong reversible adhesion

2017, Fischer, Sarah C.L., Groß, Katja, Abad, Oscar Torrents, Becker, MIchael M., Park, Euiyoung, Hensel, René, Arzt, Eduard

The potential of a new design of adhesive microstructures in the micrometer range for enhanced dry adhesion is investigated. Using a two-photon lithography system, complex 3D master structures of funnel-shaped microstructures are fabricated for replication into poly(ethylene glycol) dimethacrylate polymer. The diameter, the flap thickness, and the opening angle of the structures are varied systematically. The adhesion of single structures is characterized using a triboindenter system equipped with a flat diamond punch. The pull-off stresses obtained reaches values up to 5.6 MPa, which is higher than any values reported in literature for artificial dry adhesives. Experimental and numerical results suggest a characteristic attachment mechanism that leads to intimate contact formation from the edges toward the center of the structures. van der Waals interactions most likely dominate the adhesion, while contributions by suction or capillarity play only a minor role. Funnel-shaped microstructures are a promising concept for strong and reversible adhesives, applicable in novel pick and place handling systems or wall-walking robots.

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High-performance Li-O2 batteries with trilayered Pd/MnOx/Pd nanomembranes

2015, Lu, Xueyi, Deng, Junwen, Si, Wenping, Sun, Xiaolei, Liu, Xianghong, Liu, Bo, Liu, Lifeng, Oswald, Steffen, Baunack, Stefan, Grafe, Hans Joachim, Yan, Chenglin, Schmidt, Oliver G.

Trilayered Pd/MnOx/Pd nanomembranes are fabricated as the cathode catalysts for Li‐O2 batteries. The combination of Pd and MnOx facilitates the transport of electrons, lithium ions, and oxygen‐containing intermediates, thus effectively decomposing the discharge product Li2O2 and significantly lowering the charge overpotential and enhancing the power efficiency. This is promising for future environmentally friendly applications.

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Direct transfer of magnetic sensor devices to elastomeric supports for stretchable electronics

2015, Melzer, Michael, Karnaushenko, Daniil, Lin, Gungun, Baunack, Stefan, Makarov, Denys, Schmidt, Oliver G.

A novel fabrication method for stretchable magnetoresistive sensors is introduced, which allows the transfer of a complex microsensor systems prepared on common rigid donor substrates to prestretched elastomeric membranes in a single step. This direct transfer printing method boosts the fabrication potential of stretchable magnetoelectronics in terms of miniaturization and level of complexity, and provides strain‐invariant sensors up to 30% tensile deformation.

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Biomimetic microelectronics for regenerative neuronal cuff implants

2015, Karnaushenko, Daniil, Münzenrieder, Niko, Karnaushenko, Dmitriy D., Koch, Britta, Meyer, Anne K., Baunack, Stefan, Petti, Luisa, Tröster, Gerhard, Makarov, Denys, Schmidt, Oliver G.

Smart biomimetics, a unique class of devices combining the mechanical adaptivity of soft actuators with the imperceptibility of microelectronics, is introduced. Due to their inherent ability to self‐assemble, biomimetic microelectronics can firmly yet gently attach to an inorganic or biological tissue enabling enclosure of, for example, nervous fibers, or guide the growth of neuronal cells during regeneration.