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Science Projects From Yesterday - Ultrasonic Sound Kills Bacteria
by Jeanette Cain
Frederick Dana Hess received the Second Award at the 16th ISF with a project on bacterial cultures exposed to ultrasonic sound. Hess said the topic was easy for him to choose, since after reading a physics assignment, he realized that ultrasonic sound has been used in killing bacteria. The project began and ended at the International Science Fair in St. Louis, Missouri.
Hess began searching for any information he came upon, first at the local library, then to Washington State University library, and finally the Department of Bacteriology. Hess began reading all the ultrasonic sound and bacteria material at his local library before contacting the Washington State University science library. It was at WSU that Hess acquired his first ultrasonic cavitation of bacteria information. At first, this information did not register with Hess, which was the time he contacted WSU requesting the specifics on bacteria and ultrasonic destruction. Hess then used a microbiology book to find the specifics for handling bacteria, and the authors allowed Hess to receive cultures of bacteria, after he made sufficient preparations for using and handling the cultures.
A teacher suggested contacting the Department of Commerce in Washington, D.C. for a bibliography of ultrasonic sound effects on the culture. Hess said he even went so far as to contact Walt Disney Studios for information on cartoon characters he hoped to use in his project. Hess also received a reprint from the Department of Commerce on a Russian research paper.
Washington State University was of immense help to Hess: allowed access to the library, professors were willing to talk, and they gave permission for Hess to use their electron microscope for his experimental results. Hess said the most important part of any science project is the research. He then took a stance on an experiment that had never been performed before "Can Ultrasonic Sound Kill Bacteria?"
Hess limited his experiment to only two different types of bacteria. These two types of bacteria were exposed four different times to ultrasonic sound with the time ranging from one to thirty minutes. Every exposure was repeated many times to insure accuracy. Hess was very careful in recording his data, which required the most time for this project.
The construction of the display and experimentation were handmade by Hess. He made an incubator to keep the bacteria at the desired temperature, and an oscillator used to drive the transducer unit producing the ultrasonic waves. The two times he needed assistance: an electron microscope for photographing the bacteria, and the cartoon characters from Walt Disney Studios.
Hess said he had his setbacks when working on the project: one morning he awoke to find the previous day's experiments contaminated in the incubator. He finally found two small cultures that had not been contaminated and began to transfer these to a sterile medium. He had to sterilize everything and begin at the beginning again, but Hess said it was worth it.
Hess said he was told that the only way to win awards in high school was from sports, but he proved the theory wrong. Hess won four grand awards at his high school science fair; first, fourth, and grand award at the District Science Fair; and, second place at the National Science Fair International. During his high school years he was awarded seven ribbons, four trophies, and eight medals. But, which was best the ribbons or the trophies? Hess said it was the places he went and the people he met.
Source:
1. Sawyer, Roger Williams and Robert A Farmer. New Ideas for Science Fair Projects: "Frederick Dana Hess: Can Ultrasound Kill Bacteria?" Arco Publishing Company, Inc.: NY 1977. pps.86-89
Bacteria Experiments
Rate of growth at different temperatures, antibacterial soaps on bacteria, light effects on bacterial growth, household cleaners with bacteria characteristics. Class experiments with quick-time movies.
Khuri-Yakub Ultrasonics Group
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