Air Date: Week of April 12, 2002

Living on Earth’s Cynthia Graber reports on how engineers are designing a painless needle by learning from mosquitoes.

Transcript

CURWOOD: Coming up, why turkeys are hot to trot right now. First, this environmental Technology Note from Cynthia Graber.

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GRABER: When a mosquito bites us its stinger, or proboscis, goes in and out of our skin painlessly. That painful pinch we feel is the anti-coagulant saliva that irritates our skin, and then makes the spot itchy and scratchy. The reason the sting itself is painless is that a mosquito's stinger isn't smooth. Its edges are actually serrated, so fewer points meet sensitive nerve endings. Unlike a mosquito stinger, medical needles are made of smooth metal, and come in contact with nerve endings at every possible point during insertion into our skin.

So engineers in Japan decided to make a painless needle by mimicking the mosquito's design. They cut microscopic jagged edges into silicon dioxide, and then bonded the pieces together. The end result: a needle that's only one millimeter long, and one-tenth of a millimeter in diameter. In preliminary tests, it pierced through a piece of silicone rubber, used to imitate skin.

Right now, this painless needle is too brittle, and could break off after piercing human skin. So engineers are still refining their design for human tests. That's this week's Technology Note. I'm Cynthia Graber.

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CURWOOD: And you're listening to Living on Earth.

[MUSIC: Medeski, Martin & Wood, "Smoke," UNINVISIBLE (Blue Note - 2002)]