  An essential element in the web-trap architecture, the capture silk spun by
ecribellate orb spiders consists of glue droplets sitting astride a silk
filament. Mechanically this thread presents a mixed solid-liquid behavior
unknown to date. Under extension, capture silk behaves as a particularly
stretchy solid, owing to its molecular nanosprings, but it totally switches
behavior in compression to now become liquid-like: It shrinks with no apparent
limit while exerting a constant tension. Here, we unravel the physics
underpinning the unique behavior of this "liquid wire" and demonstrate that its
mechanical response originates in the shape-switching of the silk filament
induced by buckling within the droplets. Learning from this natural example of
geometry and mechanics, we manufactured programmable liquid wires that present
previously unidentified pathways for the design of new hybrid solid-liquid
materials. This article is available in open access with supplementary
materials on the PNAS website.
