Tikalon Blog by Dev Gualtieri

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Insect Velcro

April 22, 2013

Louis Pasteur is credited with the quotation, "Chance favors a prepared mind ."[1] I've experienced this myself when the results of an experiment were not what I so fervently expected, but they led to an important discovery, at least in the "normal science " meaning of important.

The Swiss electrical engineer , George de Mestral, noticed something interesting while hunting in the alps in 1941. He noticed how well burdock burrs , which cover the seeds of burdock as an aid to their dispersal , stuck to his clothing.

Not letting such a chance observation pass without an investigation of the mechanism, de Mestral used a microscope to see that the burrs were covered with hooked spines. He developed a fastener based on the burdock principle, and received patents for Velcro™.[2] I wrote about the fiftieth anniversary of Velcro in a previous article (Fifty Years of Velcro, June 16, 2008).

Figure caption

Detail of the seed of the Arctium lappa (burdock), and the hooks of a piece of Velcro. (Source images, left and right , via Wikimedia Commons. Right image by Flickr User Olivepixel.)

De Mestel's trade name for his invention, Velcro, was derived from a combination of two French words, velours (velvet ) and crochet (hook). As is typical for important inventions, expiry of the Velcro patent in 1978 unleashed a flood of like products into the world. The original Velcro US patent is currently cited by 116 other US patents.[2]

Not just useful for clothing fasteners, Velcro keeps object in place. The US space shuttles contained hundreds of feet of Teflon -polyester Velcro strips to hold objects in weightlessness . Vulcan Velcro (Vulcro?) is an important plot element in an episode of Star Trek: Enterprise ( Carbon Creek , Season 2, Episode 2, September 25, 2002).

Figure 4 of US Patent No. 3,009,235, 'Separable Fastening Device,' by George de Mestral, November 21, 1961

Figure four of US Patent No. 3,009,235, 'Separable Fastening Device,' by George de Mestral, November 21, 1961.

(Via Google Patents.[2])

A team of scientists from the Department of Chemistry and the Department of Ecology and Evolutionary Biology of the University of California, Irvine , and the Department of Entomology , the University of Kentucky (Lexington, KY ), have followed-up on a Balkan old wives prescription for ridding a residence of bedbugs .[3-6]

According to the folk practice , bedbugs are trapped on the surface of kidney bean leaves placed on the floor next to beds. The leaves are later collected and burned.[4] There were a few publications about this method, including a 1927 paper by a German entomologist , and a 1943 paper by a scientist at the United States Department of Agriculture .[5]

The motivation for this research is easy to understand, since there's been a resurgence of bedbug infestation in the US. The insect's ability to breed rapidly and "hitchhike" from place to place make their extermination difficult. The established extermination methods include chemical pesticides , freezing , heating , and vacuuming . Chemicals have their toxicity , the bugs have developed pesticide resistance , and the other methods are expensive.[4]

By using scanning electron microscopy and videography , the research team found that the mechanism is not the Velcro mechanism; rather, there's a physical impaling of bedbug feet (called tarsi) by the hairlike trichomes on a leaf surface. The initial capture happens in just a few seconds; and, in their struggles to free themselves, the bedbugs are impaled by other trichomes.[3-4]] There is a similarity to Velcro, however, in the hooks at the ends of the trichomes (see photomicrograph ).[4]

Figure caption

Photomicrograph of a bedbug leg trapped by the hairlike trichomes on a leaf surface.

Although the US Irvine study focused on bedbugs and kidney bean leaves, other plants have insect-trapping trichomes.

(University of California Irvine image by M. Szyndler and C. Loudon.)[4]

Not all regions of the leg are pierced by the trichomes; rather, it is only the thinner areas of the exoskeleton where the legs flex and the claws protrude.[5] Close microscopic examination of the impaling process showed that it happens as the foot is lifted, since the hooks point downwards.[5] The trichomes and their hooks are located at an optimal height for the impaling.[3]

Kidney bean leaves could be cultivated for this purpose; but, as all leaves, they dry out and lose effectiveness. Also, they can't be applied easily to areas other than the floor.[4] The next step was some materials engineering to create a surface that mimics kidney bean leaves, so the research team microfabricated materials with surfaces that closely resembled the leaf surface. A casting process was used with a variety of polymers .[5]

Unfortunately, the artificial leaves are not as effective. They entrap the bedbugs just temporarily. The bugs could walk 39 steps on average before being snagged, but their exoskelton was never pierced, and they moved on.[3,5] This suggests that the mechanical stiffness of the artificial trichomes needs to be optimized.[4-5]

Says Michael Potter of the University of Kentucky,

"Nature is a hard act to follow, but the benefits could be enormous...Imagine if every bedbug inadvertently brought into a dwelling was captured before it had a chance to bite and multiply."[4]

A patent is pending on this technology, which has garnered the interest of a company for possible commercialization.[5] Funding for the study was provided by the National Science Foundation .[3-4]

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