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About "Ask A Scientist!"

On September 17th, 1998 the Ithaca Journal ran its first "Ask A Scientist!" article in which Professor Neil Ashcroft , who was then the director of CCMR, answered the question "What is Jupiter made of?" Since then, we have received over 1,000 questions from students and adults from all over the world. Select questions are answered weekly and published in the Ithaca Journal and on our web site. "Ask A Scientist!" reaches more than 21,000 Central New York residents through the Ithaca Journal and countless others around the world throught the "Ask a Scientist!" web site.

Across disciplines and across the state, from Nobel Prize winning scientist David Lee to notable science education advocate Bill Nye, researchers and scientists have been called on to respond to these questions. For more than seven years, kids - and a few adults - have been submitting their queries to find out the answer to life's everyday questions.

Published: 26 January, 2000

What makes Band-Aids sticky?

Everyone has been cut or scratched before and had to cover the wound with a bandage. The man who invented the Band-Aid® in 1920, Mr. Earle Dickson, worked at Johnson & Johnson and first made it to help family members who frequently got cuts and scrapes. His simple bandage consisted of 3 parts: a gauze patch made of cotton, a plastic strip and a sticky material, called an adhesive. The adhesive was coated on the plastic strip and then the gauze patch was put on the middle of the sticky part. All 3 parts are a different kind of polymer (or plastic).

The adhesive, unlike the other plastics, is a liquid like honey and will flow slowly and stick. If the adhesive touches another material, it must choose if it wants to stay in contact with the material or if it would rather remain in contact with air. Most good adhesives prefer to adhere (or stick) to a surface such as skin. If so, an adhesive bond is formed and the bandage covers the wound. If not, it falls off so that the adhesive can touch air instead of skin.

Other types of plastics that stick are coatings, such as paints. They are sticky when wet, but once they dry out they become hard. The adhesive plastics used in bandages are always sticky and never dry out. But they do not always stick. One way to make skin so that adhesives prefer contact with air (and will not stick) is to get the skin wet. So remember, if you ever need to apply a bandage, clean the wound, but make sure the skin is dry before you put it on.

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