- Senior Lecturer SOE, Ecology & Evolutionary Biology
- School of Biological Sciences
- Microfabricated Surfaces For The Physical Capture Of Bed Bugs And Other Insects
- Tech ID: 23533
The background on bedbugs
Bed bugs (Cimex lectularius), apple seed-sized insects that hide in cracks and emerge at night to suck blood from sleeping humans, have experienced a resurgence in recent years. Assiduous hitchhikers on luggage, used clothes, and furniture, bed bugs are hard to get rid of. They infest the best hotels and apartment buildings, and spread as well in schools, homeless shelters, movie theaters, nursing homes and hospitals. Bed bugs are an underreported problem, as only one in 20 people have obvious reactions to their bites.
Although well controlled by DDT in the 1940s, bed bugs acquired resistance to the modern insecticides used by exterminators. Other treatments such as heat, cold, and vacuuming are costly, tedious, and unreliable. Unfortunately, many bed bug sufferers resort to ineffective and potentially dangerous measures, including spraying pesticides at home.
Bed bugs can have a life cycle as short as 50 days, but adult bed bugs can live for 3 to 12 months and produce up to 500 eggs over their lifetime. They feed every 3 to 7 days but also go for weeks without a blood meal. They are attracted to humans by body odor, heat, and carbon dioxide in breath.
Plate with bedbugs.
Catherine Loudon, professor of biomechanics at the UCI School of Biological Sciences, is developing a biomimetic trap to snare bed bugs without the use of toxic chemicals. “It all started when two colleagues at the University of Kentucky, Ken Haynes and Mike Potter, approached me at a meeting.” said Loudon. “They wanted to know if I knew about this historical approach for trapping bed bugs, to use leaves from bean plants. This was apparently a method used hundreds of years ago in Eastern Europe. I had never heard of this. It sounded quite extraordinary.” People scattered kidney bean leaves under beds at night, then scooped them up with their loads of parasites in the morning and destroyed them.
Loudon grew some bean plants and then took some bed bugs and dropped them on the leaves. “Sure enough, after taking just a few steps, in a few seconds, the bed bug gets trapped on the leaf.” Loudon recalled.
Using a scanning electron microscope (SEM), Loudon and her collaborators observed that the surface of the bean leaves were covered with sharp, flexible, microscopic hairs called trichomes. “After hundreds of incidents we could verify, in fact, that the mechanism of capture is to be impaled,” said Loudon. “There were little tiny microscopic pointy sharp hairs on the leaf of the plant that you can’t feel.” There is no known evolutionary relationship between kidney bean leaves and blood-sucking bed bugs, although the bean plant could have developed that surface to protect itself against sap-sucking aphids.
While bed bugs are highly armored, they are vulnerable in their joints and in their feet, called tarsi. When the bed bug struggles on the kidney bean leaf, the trichomes’ flexible and sharp prongs puncture the tarsi in multiple places. “There is a certain irony to it,” said Loudon, “Its movements generate the force for impaling and the bug is unable to generate enough force to break this bond.”
While bean leaves are not a practical solution for the massive problem of bed bug infestations, Loudon saw an opportunity to develop a solution based on mechanical forces. She could also exploit bed bug behavior. They love to hide and keep in physical contact with a surface; they burrow in mattress crannies and behind baseboards. “Our goal is to develop a synthetic surface that acts like a bean leaf that can also be incorporated into products and surfaces.” Loudon said.
Using microfabricated surfaces to entrap insects could provide effective pest control, especially in the critical early stages of infestation. Bed bug-trapping surfaces could conceivably be incorporated into surfaces within dwellings, avoiding the issues of pesticide toxicity and resistance.
In a study funded by the National Science Foundation, Loudon and a graduate student, Megan Szyndler, along with their University of Kentucky collaborators, developed a biomimetic microfabricated surface that functionally duplicated the shape, spacing, and orientation of the natural bean leaf surface microstructures.
Their research results were published in the Journal of the Royal Society Interface, (M. W. Szyndler et al., J. R. Soc. Interface 2013; 10 (83):20130174), and received international coverage from the New York Times, BBC News, Business Week, Scientific American, among others. But while natural bean leaf trichomes skewered the bugs within seconds, under SEM scrutiny, the team realized that their efforts to precisely duplicate the bean leaf microstructures had failed. The difference seemedto be in the ability of the natural hooks to flex and twist. These structural properties are a function of geometry and mechanical properties of the natural trichomes. As Loudon notes, biomimetic design doesn’t necessarily mean duplicating the form of a natural surface, but its function.
Since that 2013 paper, Loudon has verified the mechanism of entrapment and built patent protection. She has been working with material scientists to develop the next generation of bean leaf analogues. Now she is ready to discuss results with companies interested in commercializing an effective, non-toxic, and passive bed bug entrapment surface.