Materials science

  • Letter |

    An insulator does not conduct electricity, and so cannot in general be used to transmit an electrical signal. But an insulator's electrons possess spin in addition to charge, and so can transmit a signal in the form of a spin wave. Here a hybrid metal–insulator–metal structure is reported, in which an electrical signal in one metal layer is directly converted to a spin wave in the insulating layer; this wave is then transmitted to the second metal layer, where the signal can be directly recovered as an electrical voltage.

    • Y. Kajiwara
    • , K. Harii
    •  & E. Saitoh
  • Letter |

    The addition of shear orthogonal to the tension-loading plane of crack propagation generates an instability that results in three-dimensional helical crack propagation, atomically rough surfaces and a fracture pattern resembling a series of lance shapes. Here numerical simulations reveal a new law that governs crack propagation in space for materials subject to general stress conditions.

    • Antonio J. Pons
    •  & Alain Karma
  • Letter |

    Many technological materials are intentionally 'doped' with foreign elements to impart new and desirable properties, a classic example being the doping of semiconductors to tune their electronic behaviour. Here lanthanide doping is used to control the growth of nanocrystals, allowing for simultaneous tuning of the size, crystallographic phase and optical properties of the hybrid material.

    • Feng Wang
    • , Yu Han
    •  & Xiaogang Liu
  • Letter |

    Ferroelectrics are electro-active materials that can store and switch their polarity, sense temperature changes, interchange electric and mechanical functions, and manipulate light. Subtle changes in the topology of certain chemical bonds have long been identified as a possible route for achieving ferroelectricity in organic molecular crystals. Ferroelectricity above room temperature is now demonstrated by applying an electric field to coherently align the molecular polarities in crystalline croconic acid.

    • Sachio Horiuchi
    • , Yusuke Tokunaga
    •  & Yoshinori Tokura
  • Letter |

    Many plants and animals make use of biological surfaces with structural features at the micro- and nanometre-scale that control the interaction with water. The appearance of dew drops on spider webs is an illustration of how they are one such material capable of efficiently collecting water from air. The water-collecting ability of the capture silk of the Uloborus walckenaerius spider is now shown to be the result of a unique fibre structure that forms after wetting.

    • Yongmei Zheng
    • , Hao Bai
    •  & Lei Jiang
  • Letter |

    Although deformation twinning in crystals controls the mechanical behaviour of many materials, its size-dependence has not been explored. Using micro-compression and in situ nano-compression experiments, the stress required for deformation twinning is now found to increase drastically with decreasing sample size of a titanium alloy single crystal, until the sample size is reduced to one micrometre; below this point, deformation twinning is replaced by dislocation plasticity.

    • Qian Yu
    • , Zhi-Wei Shan
    •  & Evan Ma
  • Letter |

    In the search to reduce our dependency on fossil-fuel energy, new plastic materials that are less dependent on petroleum are being developed, with water-based gels — hydrogels — representing one possible solution. Here, a mixture of water, 3% clay and a tiny amount of a special organic binder is shown to form a transparent hydrogel that can be moulded into shape-persistent, free-standing objects and that rapidly and completely self-heals when damaged.

    • Qigang Wang
    • , Justin L. Mynar
    •  & Takuzo Aida
  • Letter |

    From earthquakes to hard drives, frictional motion and its strength are involved in a wide range of phenomena. The strength of an interface that divides two sliding bodies is determined by both the real contact area and the contacts' shear strength. By continuous measurements of the concurrent local evolution of the real contact area and the corresponding interface motion from the first microseconds when contact detachment occurs, frictional strength is now characterized from short to long timescales.

    • Oded Ben-David
    • , Shmuel M. Rubinstein
    •  & Jay Fineberg