On the other hand, soft materials achieve a lot of contact with surfaces, but - due to the larger amount of contact area - there is also a certain amount of adhesion or 'stick' not there with hard materials.
To solve this, stick insect's hairy friction pads employ three main tricks to allow contact area to increase quickly under pressure, creating a scale or 'hierarchy' of grip with absolutely no stick:
These design features work in harmony to generate large amounts of friction with comparatively tiny amounts of pressure from the insect. Importantly, there is hardly any contact area without some tiny amount of pressure - which means that the specialised 'frictional hairs' don't stick.
Arrays of tiny hairs have been found before, for example on the feet of geckos, beetles and flies. However, these hairs are designed to stick, and are used when creatures are vertical or hanging upside down.
Sticky hairs are completely aligned and have flat tips - meaning that they immediately make full contact that hardly changes with additional weight - as opposed to friction hairs, with their higgledy-piggledy height ranges and rounded tips.
"We investigate these insects to try and under
|Contact: Fred Lewsey|
University of Cambridge