Spin-based properties, applications, and devices are commonly related to magnetic effects and to magnetic materials. Most of the development in spintronics is currently based on inorganic materials. Despite the fact that the magnetoresistance effect has been observed in organic materials, until now spin selectivity of organic based spintronics devices originated from an inorganic ferromagnetic electrode and was not determined by the organic molecules themselves. Here we show that conduction through double-stranded DNA oligomers is spin selective, demonstrating a true organic spin filter. The selectivity exceeds that of any known system at room temperature. The spin dependent resistivity indicates that the effect cannot result solely from the atomic spin-orbit coupling and must relate to a special property resulting from the chirality symmetry. The results may reflect on the importance of spin in determining electron transfer rates through biological systems.

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Chiral helicene, a fully conjugated system without stereogenic carbon, can filter spins effectively at room temperature, a consequence of the chiral-induced spin-selectivity effect. The chirality dictates the spin of the electrons transferred through helicene, and magnetoresistance devices based on these molecules show antisymmetric magnetoresistance versus H plots.

Human brain wrinkling has been implicated in neurodevelopmental disorders and yet its origins remain unknown. Polymer gel models suggest that wrinkling emerges spontaneously due to compression forces arising during differential swelling, but these ideas have not been tested in a living system. Here, we report the appearance of surface wrinkles during the in vitro development and self-organization of human brain organoids in a micro-fabricated compartment that supports in situ imaging over a timescale of weeks. We observe the emergence of convolutions at a critical cell density and maximal nuclear strain, which are indicative of a mechanical instability. We identify two opposing forces contributing to differential growth: cytoskeletal contraction at the organoid core and cell-cycle-dependent nuclear expansion at the organoid perimeter. The wrinkling wavelength exhibits linear scaling with tissue thickness, consistent with balanced bending and stretching energies. Lissencephalic (smooth brain) organoids display reduced convolutions, modified scaling and a reduced elastic modulus. Although the mechanism here does not include the neuronal migration seen in in vivo, it models the physics of the folding brain remarkably well. Our on-chip approach offers a means for studying the emergent properties of organoid development, with implications for the embryonic human brain.

The force required to separate a carbon nanotube from a solid polymer matrix has been measured by performing reproducible nanopullout experiments using atomic force microscopy. The separation stress is found to be remarkably high, indicating that carbon nanotubes are effective at reinforcing a polymer. These results imply that the polymer matrix in close vicinity of the carbon nanotube is able to withstand stresses that would otherwise cause considerable yield in a bulk polymer specimen.

cent reaction conditions. The mass yield is assigned as m(t)/m(¥) The data are fitted into the three-parameter Avrami equation (see text, Eq. 1) using Microcal Origin 4.1 software package on a PC-compatible computer.AFM experiments were performed using a Digital Instruments Nano-Scope III with a phase-extender module, operating in tapping mode. Samples were prepared on a graphite substrate by placing the substrate (for a few seconds) in the synthesis solution with a reactant mole ratio of 100 H 2 O : x HCl : 0.11 CTACl : 0.13 TEOS (for fiber, x = 7; for gyroid, x = 3.5), with subsequent gentle washing in distilled water. The A+B feedback signal was~3 V, whereas the root mean square (rms) signal was set at 0.3 V. Feedback gain parameters were set between 1 and 2 for both integral and proportional gains. UltraSharp NT-MDT silicon cantilevers SCS11 (resonance frequency is 300±380 kHz) were used throughout the study. The drive amplitude was set between 600 and 800 mV, whereas the working frequency was chosen to be~360 kHz. The D scan head (maximum scan area is 12.5´12.5 mm 2 , z-sensitivity is 9 nm/V) was employed throughout the study. Scan rates of~1 Hz were chosen.TEM experiments were performed using a Philips 430 microscope operating at 100 kV with 100 000´magnification. The samples were prepared by dipping a carbon-coated copper TEM grid into the aqueous solution with a mole ratio of 100 H 2 O : x HCl : 0.11 CTACl : 0.13 TEOS (for fiber, x = 7; for gyroid, x = 3.5). The excess solution was then blotted off from the grid and air dried. The white and black amorphous-like regions are probably adventitious surfactant and silicate residues, respectively, that had been incompletely removed from the seed during the blotting step.

The remarkable optoelectronic, and especially photovoltaic performance of hybrid-organicinorganic perovskite (HOIP) materials drives efforts to connect materials properties to this performance. From nano-indentation experiments on solution-grown single crystals we obtain elastic modulus and nano-hardness values of APbX 3 (A=Cs, CH 3 NH 3 ; X=I, Br). The Young's moduli are ~14, 19.5 and 16 GPa, for CH 3 NH 3 PbI 3 , CH 3 NH 3 PbBr 3 and CsPbBr 3 , respectively, lending credence to theoretically calculated values. We discuss possible relevance of our results to suggested 'self-healing', ion diffusion and ease of manufacturing. Using our results, together with literature data on elastic moduli, we classified HOIPs amongst relevant materials groups, based on their elasto-mechanical properties.

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