Viscid silk in spider orb webs adheres strongly across surfaces with different roughnesses and surface energies

Orb spiders use glue-coated viscid silk in their webs that maximizes adhesive forces by optimizing spreading across insect surfaces while maintaining strong bulk cohesion. While glue adhesion on smooth hydrophilic glass is well understood, insect cuticles vary in wettability and wax coatings that resist glue spreading, potentially allowing insects to escape webs. Here, we tested the adhesiveness of viscid silk on the superhydrophobic lotus leaf, an extreme case of a hydrophobic surface, to explore whether hydrophobic cuticles can help insects evade webs. We compared adhesion of viscid silk on three substrates: natural lotus leaves (superhydrophobic due to waxes and microtopography), lotus leaves treated with oxygen plasma (hydrophilic but maintaining microtopography), and smooth hydrophilic glass. We found that viscid silk adheres better to the superhydrophobic lotus leaves than to other surfaces, but that adhesion was always higher on the lotus leaves, regardless of surface energy. These findings demonstrate that viscid silk is resilient to a wide range of surface hydrophobicity and leverages microtopography to increase adhesion, both of which are vital for generalist predators like orb-weaving spiders and may inspire the development of tunable adhesives with multifunctional applications in biomedical, industrial, and robotic fields.