Abstract:Caddisfly (Trichopera) can glue diverse material underwater with a silk fiber. This makes it a particularly interesting subject for biomimetcs. Better understanding of silk composition and structure could lead to an adhesive capable to close bleeding wounds or to new biomaterials. However, while spiderweb or silkworm secretion is well researched, caddisfly silk is still poorly understood. Here we report a first nanomechanical analysis of H. Angustipennis caddisfly silk fiber. An Atomic Force Microscope (AFM) imaging shows dense 150 nm bumps on silk surface, which can be identified as one of features responsible for its outstanding adhesive properties. AFM force spectroscopy at the fiber surface showed, among others, characteristic saw like pattern. This pattern is attributed to sacrificial bond stretching and enhances energy dissipation in mechanical deformation. Similarities of some force curves observed on Tegenaria domestica spiderweb and caddisfly silk are also discussed. Steered Molecular Dynamics simulations revealed that the strength of short components of Fib-H HA species molecules, abundant in Trichoptera silk is critically dependent on calcium presence.

Nanostructures created by living organisms, optimized through millions of years of evolution, can be a valuable inspiration for nanotechnology. We employ atomic force microscopy to examine such structures in materials created by common organisms caddisy and diatoms. Caddisy larvae are well known for their ability to spin silk, which serves as an adhesive tape to glue various materials and collect food in aqueous environment. Atomic force microscopy imaging of caddisy silk, performed for the rst time by our team, has shown that its surface is patterned with 150 nm extensions a feature related to its exceptional underwater sticking abilities. Results of force spectroscopy of protein structures found on the surface are also shown. A characteristic feature of diatoms is that they are encased within a unique silica cell wall called frustules, patterned with 200 nm pores, which allow cellular interaction with the environment. We perform atomic force microscopy imaging of frustules in living diatoms as well as adhesion measurements inside pores.