Materials change their properties in response to the environment in ways that are often detrimental to performance. However, a new generation of "smart materials" capitalizes on environmental responsiveness to improve performance in the laboratory. This project investigates how such "smart materials" evolve and function in nature, focusing on how adhesives adapt to fluctuating humidity in the environment. Spider capture threads are sophisticated composite structures that generate adhesion through multiple mechanisms that could respond synergistically or independently to the environment. Adhesion starts with the surface contact of sticky glycoproteins that are encased in liquid glue droplets and is then enhanced when those droplets and the underlying axial thread to which they are attached stretch and resist thread "pull-off" by forming a broad, suspension bridge-like interface. This whole process is controlled in part by cocktails of salts in the glue droplets that absorb atmospheric water, which then lubricates the glue and controls the extension of the droplets and axial threads. This project combines biology and materials science to compare the molecular compositions of glues, the adhesiveness of capture threads, and how webs capture insects across a community of spiders to understand how biological "smart" materials respond to their environments. It will inspire the development of new synthetic adhesive systems and "smart", environmentally responsive materials. The project will provide in depth training in interdisciplinary research to PhD, undergraduate and high school students. It will also develop new educational resources for K5-K12 summer camps and teacher workshops.
