Material inspired by dragonfly wings bursts bacteria

Prickly silicon could act as antimicrobial coating on medical devices

KILLER WINGS  Etched black silicon can mimic the nanoscale spikes that naturally occur on the wings of the dragonfly Diplacodes bipunctata (center). A synthetic surface with similar nanostructures, just 500 nanometers tall, can rupture bacterial cells and spores (scanning electron micrograph, lower right; computer-generated representation, upper left).

E. Ivanova et al./Nature Comm. 2013

Tiny spikes on a silicon surface can stab and kill any bacteria that make contact, researchers report November 26 in Nature Communications. Scientists could foil infectious bacteria by using the new surface architecture as a coating on medical devices and food-processing equipment.

Microbiologist Elena Ivanova of Swinburne University of Technology in Hawthorn, Australia, and colleagues designed the nanoarchitecture by taking cues from bacteria-free surfaces in nature such as insect wings. Using scanning electron microscopy, the team discovered that dragonfly wings have protrusions, just 240 nanometers tall, which appeared to pop bacterial cells that tried to attach to the wing.

By etching light-absorbing black silicon, Ivanova and her team created similar spikes, 500 nanometers tall and just 20 to 80 nanometers thick. When the researchers exposed bacteria or bacterial spores to the silicon surface, they found that it killed microbes quickly. On average, each square centimeter of silicon destroyed around half a million bacterial cells every minute.

Black silicon, which engineers typically use in solar panels and light sensors, is cheap and easy to manipulate, Ivanova says. Creating the nanostructured surface takes just five minutes, she says. The researchers believe that nanostructured silicon could coat items such as medical implants to prevent infectious bacteria from hitchhiking into patients.

The coating process “seems pretty straightforward and versatile,” says nanochemist Thomas Webster of Northeastern University in Boston. Though Webster would like to see more data on the physical forces that actually cause the bacteria to pop, he says modeling the new material from insect wings is a novel approach for finding ways to kill harmful bacteria. “There’s a lot of promise for nanoscale features to reduce bacterial growth without antibiotics,” he adds.

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