Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: In-drop capillary spooling of spider capture thread inspires highly
  extensible fibres   Spiders' webs and gossamer threads are often paraded as paradigms for
lightweight structures and outstanding polymers. Probably the most intriguing
of all spider silks is the araneid capture thread, covered with tiny
glycoprotein glue droplets. Even if compressed, this thread remains
surprisingly taut, a property shared with pure liquid films, allowing both
thread and web to be in a constant state of tension. Vollrath and Edmonds
proposed that the glue droplets would act as small windlasses and be
responsible for the tension, but other explanations have also been suggested,
involving for example the macromolecular properties of the flagelliform silk
core filaments. Here we show that the nanolitre glue droplets of the capture
thread indeed induce buckling and coiling of the core filaments: microscopic
in-vivo observations reveal that the slack fibre is spooled into and within the
droplets. We model windlass activation as a structural phase transition, and
show that fibre spooling essentially results from the interplay between
elasticity and capillarity. This is demonstrated by reproducing artificially
the mechanism on a synthetic polyurethane thread/silicone oil droplet system.
Fibre size is the key in natural and artificial setups which both require
micrometer-sized fibres to function. The spools and coils inside the drops are
further shown to directly affect the mechanical response of the thread,
evidencing the central role played by geometry in spider silk mechanics. Beside
shedding light on araneid capture thread functionality, we argue that the
properties of this biological system provide novel insights for bioinspired
synthetic actuators.

12
The categories of this paper are: nucl-th
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The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
20
The categories of this paper are: acc-phys
16
The categories of this paper are: stat
25
The categories of this paper are: patt-sol
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The categories of this paper are: bayes-an
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The categories of this paper are: comp-gas
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The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
1
The categories of this paper are: cs
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The categories of this paper are: funct-an
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The categories of this paper are: econ
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The categories of this paper are: eess
10
The categories of this paper are: q-bio