Researchers found that spiders can very well adapt between dry and wet environments with their humidity-responsive web glue. In a new study, experts from the University of Akron (UA) and Virginia Polytechnic Institute examined the characteristics behind these arachnids' adhesion power.
Out of the 45,000 species of spiders, 7,500 spin webs to hunt down preys. The "capture silk" properties of spiral web strands help the species effectively trap preys and enhance the overall hunting experience.
The capture silk is composed of an axial fiber that is regularly covered in glue droplets. The said web glue is one-of-a-kind as its adhesive properties are enhanced under humid environments, which is totally opposite of synthetic adhesive materials. For example, in products like medical bandages, the more an individual sweats, the lesser the adhesive power of the bandage becomes and the band peels off easily.
The experts performed their research by measuring the bond of capture threads from five different spiders. Gaurav Amarpuri from UA said that the locations where these species settle range from dry to wet and humid hence, they identified the adhesion as a humidity component and utilized high-speed image capture to determine the quantitative rate of the species' glue droplets.
The manner with which the liquid droplets spread is in accordance to the "spreading power law," in which less sticky droplets expand more swiftly than the more sticky droplets. Amarpuri said that under usual humid foraging environments, the team found the adhesion power of the spiders' glue to be at its maximum.
The team also observed the spider web glue under the microscope and found that its spreading properties increase with humidity. The viscosities of the glue exuded modifications of more than five degrees with a change from 30 to 90 percent relative humidity - more or less the needed solution to transform the consistency of peanut butter to olive oil. Amarpuri explained that this demonstrates the spiders' unique ability to adjust the viscosity of its web glue to enhance adhesive power.
The way spiders adapt to changing surroundings, as well as how they change the viscosity of their web glue may aid the development of future adhesive products.
At present, the researchers are investigating the proteins and salts of the spider glue. "So now we're investigating the role of salts in controlling viscosity and adhesion," Amarpuri closed.
The results of the study were presented in the Society of Rheology's 87th Annual Meeting.
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