Letter

Nature 463, 640-643 (4 February 2010) | doi:10.1038/nature08729; Received 5 October 2009; Accepted 10 November 2009

Directional water collection on wetted spider silk

Yongmei Zheng1,4, Hao Bai2,4, Zhongbing Huang3, Xuelin Tian3, Fu-Qiang Nie3, Yong Zhao3, Jin Zhai1 & Lei Jiang3

  1. School of Chemistry and Environment, Beijing University of Aeronautics and Astronautics, Beijing 100191, China
  2. National Center for Nanoscience and Technology, Beijing 100190, China
  3. Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
  4. These authors contributed equally to this work.

Correspondence to: Yong Zhao3Lei Jiang3 Correspondence and requests for materials should be addressed to L.J. (Email: jianglei@iccas.ac.cn) or Y. Zhao (Email: zhaoyong@iccas.ac.cn).

Many biological surfaces in both the plant and animal kingdom possess unusual structural features at the micro- and nanometre-scale that control their interaction with water and hence wettability1, 2, 3, 4, 5. An intriguing example is provided by desert beetles, which use micrometre-sized patterns of hydrophobic and hydrophilic regions on their backs to capture water from humid air6. As anyone who has admired spider webs adorned with dew drops will appreciate, spider silk is also capable of efficiently collecting water from air. Here we show that the water-collecting ability of the capture silk of the cribellate spider Uloborus walckenaerius is the result of a unique fibre structure that forms after wetting, with the ‘wet-rebuilt’ fibres characterized by periodic spindle-knots made of random nanofibrils and separated by joints made of aligned nanofibrils. These structural features result in a surface energy gradient between the spindle-knots and the joints and also in a difference in Laplace pressure, with both factors acting together to achieve continuous condensation and directional collection of water drops around spindle-knots. Submillimetre-sized liquid drops have been driven by surface energy gradients7, 8, 9 or a difference in Laplace pressure10, but until now neither force on its own has been used to overcome the larger hysteresis effects that make the movement of micrometre-sized drops more difficult. By tapping into both driving forces, spider silk achieves this task. Inspired by this finding, we designed artificial fibres that mimic the structural features of silk and exhibit its directional water-collecting ability.

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