Engineering Commons^™

How Super Is Supercontraction? Persistent Versus Cyclic Responses To Humidity In Spider Dragline Silk, Todd Blackledge, Cecilia Bountry, Shing-Chung Wong, Avinash Baji, Ali Dhinojwala, Vasav Sahni, Ingi Agnarsson

Ali Dhinojwala

Spider dragline silk has enormous potential for the development of biomimetic fibers that combine strength and elasticity in low density polymers. These applications necessitate understanding how silk reacts to different environmental conditions. For instance, spider dragline silk ;supercontracts' in high humidity. During supercontraction, unrestrained dragline silk contracts up to 50% of its original length and restrained fibers generate substantial stress. Here we characterize the response of dragline silk to changes in humidity before, during and after supercontraction. Our findings demonstrate that dragline silk exhibits two qualitatively different responses to humidity. First, silk undergoes a previously unknown cyclic relaxation-contraction response to …