Spiders spin adhesive threads to capture prey

1. Role of Structure and Dynamics of Molecules at the Interface in Controlling Friction, Adhesion and Adhesion HysteresisAli N. Dhinojwala, University of Akron, DMR 0512156 Spiders spin adhesive threads to capture prey Modern orb-weaving spiders use adhesive silk threads to capture prey. These threads consist of highly evolved intricate composites of viscoelastic axial silk fibers covered by micron-sized glue droplets. These glue droplets are composed of granules of glycoproteins surrounded by viscous aqueous coats of salts that regulate water content. Although the glycoproteins are hypothesized to cause adhesion, the mechanism is not understood. This is partly due to an inability to probe the glycoproteins through the viscous coat and partly due to the difficulty in separating the contribution of the glue droplets from the highly extensible axial silk for the force required to peel a single thread off a surface. In this research we show that the glycoprotein behaves like a viscoelastic solid (just like a sticky chewing gum) – a property that has important consequences in enhancing the adhesion of these almost invisible threads. At slow extension rates similar to the movements of already entangled insects, the drops deform like an ideal elastic rubber band, which is essential in retaining trapped insects long enough to be subdued by the spider. The elegant use of elasticity to enhance adhesive forces also occurs in marine mussels and therefore suggests a common design principle in the evolution of natural adhesives. Published in Nat. Commun. 1:19 doi: 10.1038/ ncomms1019 (2010).

2. Broader ImpactAli N. Dhinojwala, University of Akron, DMR 0512156 Based on the work supported by the NSF grant, we have started a company to commercialize the carbon nanotube-based gecko adhesive technology. The start-up company, ADAP Nanotech, has currently secured an Airforce STTR Phase I and Lorian County grants to develop thermal interface materials. The graduate student, Sunny Sethi, who was working on this project is now working in this start-up company. Three patents have been filed and this NSF-funded research has resulted in technology that will provide a solution for dissipating heat in high end computer processors. From last twelve years, I have also been involved in organizing District 5 Science Day at the University of Akron. This year we had 300 poster presentations and we selected 90 projects to advance to the State Science Day. We have also started a mentorship program this year to pair the school kids with scientists from industry and Universities to assist them in their Science Project. We are expecting the mentorship program to encourage school students to work on science projects and learn more about career opportunities in science. This summer I have also supervised two undergraduate NSF-REU students (Megan Forshney and Tyler Pizzute) and one undergraduate student (Disha Labhashetwar) using the DMR support. As a result of their work during the summer, we have filed one disclosure and one paper is under preparation. Gecko-Inspired Adhesives