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Written by: Soyoung Kang
Written on: November 1st, 2009
Tags: material science, biomedical engineering
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About the Author
Soyoung Kang was a third-year Biomedical Engineering student at University of Southern California in 2009. She enjoys traveling to new places and learning history and literature alongside her engineering studies.
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Volume XI Issue I > Biomimetics: Engineering Spider Silk
Spider silk has drawn much attention from engineers in the past 20 years for its toughness and elasticity, properties which may be utilized in applications such as suspension bridge wires, bulletproof vests, and medical adhesives. There remains, however, a mystery behind the production of spider silk. Scientists are intensively studying this process in order for engineers to replicate the silk in synthetic form. One of the first successful reproductions of spider silk was produced from genetically engineered goats. Such inventive approaches lead us closer to a mass-producible, commercializable material that may potentially be as common as ordinary silk. This paper explores the concept of biomimetics, which encompasses the study and engineering of spider silk, spiders and their production of spider silk, and the ways in which engineers approach this puzzle of spider silk reproduction.

Introduction

Conjure up the image of a spider in your mind, crawling around, cocooning its prey to devour later, creating intricate webs, gracefully repelling off ceilings and causing distress to people who might have arachnophobia. Most of your interactions with spiders might result in a disgusted facial expression and a squashed bug, but what if I told you that your children's children could be wearing a coat made with the same material that makes a spider's web, or that bridges could be suspended with that same material? The threads of silk that emerge from a spider are so tough that, on a human scale, a net made out of spider silk could stop a passenger plane in mid-flight (see Fig. 1) [1]. Scientists and engineers have been working together to unlock the secret of this incredible material and reproduce it for use in real-life applications such as bulletproof vests, medical adhesives, and military draglines.
Tom Friedel/Wikimedia Commons
Figure 1: A female Golden Orb Spider in her web.
The emerging field that seeks to study nature and its potential applications to engineering is known as biomimetics. Biomimeticists work toward mimicking mechanisms found in nature, such as the self-cleaning nature of the lotus leaf in order to produce a self-cleaning tile. Another goal of biomimetics is the replication of manufacturing methods found in nature, such as the replication of spider silk by artificial synthesis.

What is Spider Silk?

If you flip a spider on its back you can see a group of four to six spinnerets out of which the silk appears. Fig. 1 shows the silk emerging from the spinnerets located in the Yellow Garden Spider's lower abdomen. Each one of these spinnerets consists of six hundred or more spinning tubes which work like mini glue nozzles functioning as a part of a larger nozzle, as shown in Fig. 2. Inside each of these spinnerets is a viscous solution that sloshes around like syrup [2]. This solution, also called 'dope', is composed of globular protein molecules dissolved in water that are later found aligned in the silk fiber of the surrounding sheath. These protein components determine the core and the outer structures of the emerging fiber. How does this liquid solution turn into the solid silk fibers used to make webs and repelling thread? This is the complex process that is at the core of engineers' focus in reproducing spider silk.