Penn State researchers, in conjunction with Ultran Laboratories, Inc., of Boalsburg, have created the world's first ultrasound device that could potentially decontaminate all mail sent in the United States.

Using a technology called 'phenomenally high efficiency non-contact ultrasonic (NCU) transducers,' the researchers were able to kill 99.99 percent of Bacillus thuringiensis, a close cousin of Bacillus anthracis, commonly known as anthrax.

Kelli Hoover, an assistant professor of entomology, was one of the main researchers on the project. She said anthrax spores are extremely hardy and resistant to sterilization. Microwaves are unsuccessful because the spores are completely dry.

Another method of killing anthrax, which uses electron beams, is ineffective for large packages. Although radiation such as x-rays generated by cobalt-60 works, it is dangerous, requires expensive shielding, and is very time-consuming.

Currently, all mail sent to government offices is exposed to gamma radiation, creating lengthy delays in the mail being delivered.

Sonication, a process by which sound waves are carried through a contact medium such as water, gel, or grease in order to kill microbes, is also effective but is impractical for letters and packages. The device the researchers created is the first one capable of using ultrasound, in the range of 50 kHz to 10 Mhz, without a contact medium to destroy bacterial spores.

Ultrasound comes in two varieties: diagnostic and destructive. Diagnostic ultrasound is the traditional type used to observe a fetus in the womb, view a kidney stone, and to detect other medical issues. It also has novel uses, such as detecting bodies behind walls, contraband items in luggage, fat content in food, or even cracks in the tail of an airplane.

Destructive ultrasound actually destroys cells, although in this case, the particular mechanism of killing is unknown. Hoover hypothesized that it may cause the destruction of DNA or membranes or may be the result of incredibly intense heat or pressure.

Hoover said the ultrasound device creates "waves so intense, it causes the envelope to jump."

Hoover said the developers own the rights to the transducer, and a patent has been filed.

Mahesh Bhardwaj, president and chief technology officer at Ultran Labs, says ultrasound does not travel well through gases. Although the precise workings of the transducer are proprietary, he said it involves a unique combination of materials on the transducer that allow the ultrasound waves to travel unimpeded through the air.

Besides killing anthrax in the mail, the device can also be used to clean environments such as congressional offices. The researchers also want to test the device on other bacteria and viruses, including smallpox.

Linda Bartraw, State College postmaster since 2001, said local post offices have completed several low-tech steps to increase security, including reinforcing doors and training employees, especially letter carriers.

Bhardwaj said Ultran is still trying to understand the full capabilitites of its development. Then it will develop practical applications.

Penn State holds a share in a company owning the technology, and will profit from its commercialization.

Hoover said it may take several more years of engineering before the device is ready for sale, but the potential for success is very large.

Bhardwaj has been working on NCU technologies since the late 1970s.

"My goal was to throw out everything that was known about ultrasound. We have literally created a whole new field," he said. "Even I do not know how far it will go."