Ancient alternative for adhesion

摘要

It's one of the oldest scenes in the 'Horror' repertoire: a spider's web brushing a passing face! But spiders and their webs have been around longer than humans have been afraid of them. Today, most spiders' webs arc coated in a sticky glue to ensnare flics and other victims. But a few ancient species stuck to an older, drier alternative. They produce cribcllar threads: thousands of minute filaments coating a supporting thread that snag insects by their setae, like Velcro hoops over loops. Remarkably, the silk also sticks to glass and metal sheer surfaces through van der Waals molecular forces. But not all dry webbed spiders produce the same types of microscopic fibril. Some species produce lumpy fibrils, while the most ancient member of the cribellar family, the rare Hypochilidae. produce smooth fibrils. Intrigued by the differences between both types of silk. Brent Opell and his student Anya Hawthorn noticed that the lumpy fibre's adhesive properties improved under damp conditions, while the smooth fibres didn't. Wondering whether the knobbly fibres picked up water and adhered through hygroscopic forces, the team modelled the fibre's adhesive qualities under dry and damp conditions (p. 3905).