EAPSI: New insights into the effects of chemical composition and surface structure on spider silk adhesion and prey retention

Diaz Candido, Akron OH

Investigators

Abstract

Adhesion is an important consideration in construction and repair. Organisms have evolved different adhesives for survival in nearly every environment on earth. In chemical adhesion the formation of chemical bonds and sharing of electrons create attractive forces between surfaces. For example, spiders utilize a sticky aggregate glue to keep their prey ensnared in their webs. This project will test how adhesion strength of aggregate glue varies based on surface roughness, hydrophilicity, and chemical composition. In collaboration with Dr. Tadashi Miyashita at the Unversity of Tokyo - the only researcher to have previously studied the silk of the spider Cytarachne - the research will be determined which surface characteristics have served as evolutionary pressures, leading to optimal glue adhesion. Identification of the chemical composition of glue droplets will be conducted. By studying spiders, it can lead to the utilization and mimicking of aggregate glue chemical compounds leading to substrate specific synthetic adhesive products. Aggregate silk is composed of a glycoprotein core and an aqueous droplet of salts. The combination of salts and the glycoproteins act together to form a bond between the silk threads and prey. Spiders from the genus Cyrtarachne are specialized moth-hunting orb-weavers, only found within Asia and more commonly in Japan. These spiders have evolved to prey on moths by utilizing reduced orb webs with unusually large, viscous droplets of glue. Successful prey capture relies primarily on the prolonged adhesion between the glue and exoskeleton. Varying surface structures and chemical compositions may react with glycoproteins and hydroscopic salts differently resulting in scenarios in which Cyrtarachne aggregate glue under or over performs. Adhesion tests will be conducted by the pull-off method. Information will be gained on what chemicals they contain, and when they are strongest. This NSF EAPSI award is funded in collaboration with the Japan Society for the Promotion of Science.