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Posted: Apr 26, 2015

Simpler nanoscale bioreplication of beetle decoys

(Nanowerk News) Ash trees in 22 eastern states of U.S.A. are being decimated by emerald ash borers (EABs), an Asian beetle that arrived in Michigan more than two decades ago. The pest has even spread westwards into Kansas and Colorado.
Nothing seemed to be effective against EABs, until decoys designed to mimic female EABs were found in 2012 by a group of researchers at the Pennsylvania State University to be successful in enticing male EABs for mating. Last year, the same researchers found the decoys could be used to electrocute and kill the seduced males.
The iridescent green beetles are not vectors of any disease. Rather, their larvae bore tunnels in the trunks of the ash trees to feed on the sap, thereby starving the trees. Also, the numerous tunnels seriously weaken the trunks.
The electrocuting decoys could assist forestry managers in slowing the spread of the pest species. Industrial-scale production of these decoys would be necessary for success.
Penn State engineers led by Akhlesh Lakhtakia, Charles Godfrey Binder professor of engineering science and mechanics, had devised a nanofabrication technique to coat the upper parts of a dead female EAB with a dense assembly of 500-nm tall nanocylinders made of nickel. Having the same shape as the beetle, the coat is strengthened by an electrochemical process into a negative die. A matching positive die of epoxy is then made from the negative die. Numerous decoys can be made by hot stamping a specially prepared sheet of a common polymer between the pair of matching dies. The bioreplicated decoys are painted metallic green. Their success in luring male beetles is due to the replication of surface texture of the female beetle with very high resolution.
Although this technique was devised for mass production of decoys, improvements are needed for even faster production.
Tarun Gupta, a professor of industrial engineering at the Western Michigan University, visited Penn State for a sabbatical semester to work with Lakhtakia on making the negative nickel die not from just a single female EAB, but from an array of several female EABs instead. The production capacity was enhanced tenfold in Lakhtakia’s laboratory and can be scaled up hundredfold or more in factories. The researchers also eliminated the positive die, deciding to fill up the multiple cavities of the negative die with a liquid polymer that is thermally curable. Stephen Swiontek, a doctoral student working under Lakhtakia’s supervision, optimized the thermal curing step. Multiple decoys made simultaneously were painted metallic green.
“The new bioreplication technique is much simpler than the predecessor technique,” said Lakhtakia, “because a large number of decoys can be simultaneously made. Moreover, positive dies need not be fabricated at all.”
The researchers have published their work in the April 2015 issue of the Journal of Bionic Engineering ("Simpler Mass Production of Polymeric Visual Decoys for the Male Emerald Ash Borer (AgriAgrilus planipennis)"). Lakhtakia is confident that the new bioreplication technique is ready to combat the spread of many other insect pests in the same family as the EAB.
Source: Pennsylvania State University
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