13. Spider Silk: A Sticky Situation

This chapter takes a look at the structural and surface properties of various types of spider silk that enable such remarkable performance as a fiber, as well as its past and potential uses in engineering. Though there are various types of spider webs such as tangle and sheet webs, the orb web is the most common and is spun and constructed by orb-weaving spiders, Araneus and Nephila. Orb-weaving spiders are capable of producing seven different types of silk threads, each with distinct combinations of amino acid composition, function, and gland and spinneret used in production (Saravanan, J Textile Apparel Technol Manag 5(1):1–20, 2006). Dragline silk, known to be the toughest of all types of silk, serves as the framework of the spider’s web, as well as its lifeline (Heim et al., Angew Chem Int Ed 48:3584–3596, 2009). Despite inevitable variations in the material properties of dragline silk across different species of spiders, it is still found to be tougher than most biological fibers and even man-made fibers (Swanson et al., Evolution 60(12):2539–2551, 2007). While spiders use dragline silk for web framework and as a lifeline, they also spin threads to capture their prey, which are called capture threads (Vollrath, Rev Mol Biotechnol 74(2):67–83, 2000). The adhesive properties of capture threads are made possible by an interlocking mechanism (Hawthorn, Biol J Linn Soc 77(1):1–8, 2002) and van der Waals and capillary forces (Sahni et al., J Adhes 87:595–614, 2011). Spider silk has numerous future engineering applications. New biopolymer materials to be used in the medical field are a possibility with the manipulation of spider silk proteins (Römer and Scheibel, Prion 2(4):154–161, 2008). Also, spider silk is being applied to a diverse array of applications within the military arena, including, but not limited to, being used as an underwater anchoring adhesive (Military Times, Navy bets on spider silk research with USU funding, http://​www.​militarytimes.​com/​article/​20130807/​NEWS04/​308070038/​Navy-bets-spider-silk-research-USU-funding, 2013).