October 3, 2012
One Spider Glue Used To Make Two Types Of Webs
April Flowers for redOrbit.com - Your Universe Online
The common house spider is creepy, no doubt. It is also inspiring, at least according to scientists from the University of Akron. Researchers there have been inspired to find new and better ways to develop adhesives for human applications as diverse as wound healing and industrial strength tape. Consider being able to use the same adhesive to help heal a fractured collar bone and create "ouch-free" bandages.
Polymer scientists and biologists from UA have discovered that the common house spider performs an uncommon feat in order to catch different types of prey more efficiently. It tailors one glue into two different adhesive strengths: firm and weak.
In a study published in Nature Communications, the researchers have demonstrated that cobweb spiders use adhesive discs to anchor webs to various surfaces. They use the same glue on all surfaces, however, but they create it using two different designs to give it either a strong or weak grip depending on whether the prey is flying or crawling.
The research team that made this discovery is already working on human applications for this technology by trying to develop a synthetic adhesive that mimics this intelligent design strategy.
"We were intrigued by how cleverly spiders use silk to create a beautifully multifaceted adhesive and how they do so with very little glue," says Ali Dhinojwala, UA Department of Polymer Science chair and Morton Professor of Polymer Science.
"It teaches us how to take something minimal and make the most of it — how to design an attachment to hold things together in unique ways."
The adhesive discs that anchor webs to ceilings and vertical surfaces are super sticky, allowing the web to stay mounted in place when struck by a flying insect moving at a high velocity. In contrast, the discs used to anchor the webs to the ground in order to capture walking insects have a much weaker grip. When a walking insect strikes the web, the weaker discs snap away from the ground, leaving the prey suspended in the air by a silken thread.
Vasav Sahni, a recent PhD graduate from the UA department of polymer science and a senior research engineer at the company 3M explained the phenomenon in terms of a beloved comic book character.
"When Spiderman jumps from one building to another, he throws a thread that sticks to a building and then he jumps. The thread has to be very strong and also equally sticky — sticky enough to support him."
Spiderman's threads do not lose their grip as the fast-moving hero springs from building to building. Likewise, cobweb spiders use a "staple-pin" adhesive disc to keep their webs' draglines firmly attached to the ceiling and walls. The branching discs that mount the webs' so-called ℠gumfoot threads´ to the ground, on the other hand, have a loose grip that can easily break away.
"When we made the discovery of the gumfoot adhesive disc that binds cobwebs lightly to the ground and compared it to the scaffolding adhesive discs, which attach cobwebs very firmly to walls and ceilings, we thought, 'How is this spider using the same glue to design both a weak and a strong attachment disc,'" Sahni says.
"What we have also discovered is a key design principle," Sahni says. "It's not a question of the inherent chemistry of the glue, but how the same glue can have different degrees of adhesion."
The study asserts that the differences in the two disc types must arise purely from the spider's spinning behaviors as both are built from silk from the same set of glands. This research could result in the development of synthetic adhesives, particularly for biomedical applications.