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Volume 476 Issue 7360, 18 August 2011

When a drop of coffee dries, a halo of particles accumulates at the drop’s edge. This ‘coffee-ring effect, first described formally in a Nature paper in 1997, is a common occurrence when a solution of suspended colloidal particles evaporates. Far from being just a household curiosity, it has turned out to have relevance for many applications in which a uniform particle deposition is required, such as inkjet printing, assembly of photonics components and manufacture of DNA chips. In this issue, Peter Yunker and colleagues show that ellipsoidal particles suppress the coffee-ring effect. Attractive interparticle interactions between ellipsoids are sufficiently strong to counteract the forces that drive spherical particles towards the drop's edge as the drop evaporates. The coffee-ring effect can be restored for ellipsoids in solution containing surfactant, and ‘designed mixtures of spheres and ellipsoids can lead to uniform deposition. Cover photo: Annthea Lewis.


  • Editorial |

    The United Kingdom and others must not overlook the potential for nanotechnology to boost regenerative medicine.

  • Editorial |

    Integrity guidelines are a good start, but they must be clear and appropriately enforced.

World View

Research Highlights

Seven Days

  • Seven Days |

    The week in science: the search for extraterrestrial life resumes; chemists campaign against UK cuts; and the Mars rover reaches its new home.


News Feature

  • News Feature |

    For decades, the Armed Forces Institute of Pathology has been a leader in disease diagnosis. Now it is closing, and its legacy is in jeopardy.

    • Alison McCook


Books & Arts

  • Books & Arts |

    Hugh Gusterson enjoys a history of the quirky group that pursued quantum physics when it was unfashionable.

    • Hugh Gusterson
  • Books & Arts |

    Jay Pasachoff relishes a novel that brings to life the scientific stars of the 1600s.

    • Jay M. Pasachoff
  • Books & Arts |

    Daphne Sheldrick was the first person to rear baby elephants successfully by hand, and has worked with animals for 50 years in Kenya. As she stars in an IMAX film chronicling her efforts, she describes her experience of conservation and animal husbandry.

    • Daniel Cressey



News & Views

  • News & Views |

    The well-known boundaries of coffee stains are caused by the outward flow of particles suspended in the liquid. Experiments show that ellipsoidal particles can prevent the formation of such boundaries. See Letter p.308

    • Jan Vermant
  • News & Views |

    The protein Lgr5 has been valuable as the undisputed marker of intestinal and other stem cells. It emerges that Lgr5 and its relatives also have essential signalling roles of relevance to health and disease. See Article p.293

    • Walter Birchmeier
  • News & Views |

    Polarized emission has been detected from the largest Lyman-α gas cloud, known as blob 1. This result strongly suggests that such clouds are powered by a central source of ionizing radiation. See Letter p.304

    • Richard Bower
  • News & Views |

    Images of the sea floor in Pine Island Bay, West Antarctica, reveal impressive evidence that a massive ice-shelf break-up occurred before about 12,000 years ago, and point to a tidal influence on sea-floor features produced during deglaciation.

    • Colm Ó Cofaigh
  • News & Views |

    Tracing a common ancestry between languages becomes harder as the connection goes further back in time. A new test has revealed a surprisingly ancient relationship between a central Siberian and a North American language family.

    • Jared Diamond





Career Brief

  • Career Brief |

    International graduate student fellowship aims to identify future scientific leaders.

  • Career Brief |

    Analysis suggests widespread nepotism in Italian academia.

  • Career Brief |

    Number receiving physics PhD degrees is on the rise in the United States.


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