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From Nano to Micro to Macro: Importance of Structure and Architecture in Spider Silk Adhesives

Sahni, Vasav
http://rave.ohiolink.edu/etdc/view?acc_num=akron1342412634

Abstract Details

2012, Doctor of Philosophy, University of Akron, Polymer Science.
Spiders employ clever behavioral strategies combined with almost invisible custom-made adhesives for locomotion and prey-capture. The adhesive produced by modern orb-weaving spiders to capture prey (viscid glue) is laid on a pair of extensible axial silk fibers as micron-size glue droplets that are composed of a mixture of salts and polymeric glycoproteins. Each glue droplet is composed of a dense core surrounded by a sparse shell. We discuss the importance of the structure at nano-, micro-, and macro level in adhesion. At the nano level, we show that the inherent elasticity in the glue enhances adhesion caused by specific adhesive ligand by over two orders of magnitude.Furthermore, we describe how the viscoelastic solid nature of the glue drops help in capturing and retaining prey. We also develop an energy model to separate the axial silk contributions from glue droplet contribution in the force required to separate a whole thread from a surface. We describe the functions of the salts that are present in large quantities in the web, and are nutritionally and physiologically essential for the spider. Previously, it was assumed that the main function of the salts is to sequester water. We show that salts play a major role in adhesion itself and how the core-shell microstructure developed within each drop facilitates reversible usage of this glue. We compare the properties and humidity-responses of orb-weaving glue with the gumfoot glue produced by cob-weavers, the evolutionary descendants of orb-weavers and despite being produced in homologous glands, we find very interesting differences.We mimic the common macro-architecture of these capture threads: Beads-on-a-string (BOAS) architecture, and understand why spiders employ this architecture for capturing prey. Lastly, we discuss the attachment discs produced by spiders, which make it possible for spiders to move, defend, and capture prey. We comment on how the macro architecture of these attachment discs affects their adhesion, thus enabling different functions in a web. This research, thus shows the importance of structure at different length scales in influencing adhesion and shall inspire future efforts directed towards tunable adhesives.
Ali Dhinojwala, Dr. (Advisor)
Todd A. Blackledge, Dr. (Committee Member)
Gary Hamed, Dr. (Committee Member)
Toshi Miyoshi, Dr. (Committee Member)
Jutta Luettmer -Strathmann, Dr. (Committee Member)
Biology; Biomechanics; Biophysics; Materials Science; Mechanics; Polymers
Spider Silk; Adhesion; Glycoproteins; Viscoelastic Solid; Elasticity; Pyriform Silk; Capture Silk; Prey Capture; Beads on a string

Recommended Citations

Citations

  • Sahni, V. (2012). From Nano to Micro to Macro: Importance of Structure and Architecture in Spider Silk Adhesives [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1342412634

    APA Style (7th edition)

  • Sahni, Vasav. From Nano to Micro to Macro: Importance of Structure and Architecture in Spider Silk Adhesives. 2012. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1342412634.

    MLA Style (8th edition)

  • Sahni, Vasav. "From Nano to Micro to Macro: Importance of Structure and Architecture in Spider Silk Adhesives." Doctoral dissertation, University of Akron, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1342412634

    Chicago Manual of Style (17th edition)

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© 2012, all rights reserved.
This open access ETD is published by University of Akron and OhioLINK.