The recent anthrax attacks posed a tough question to the people charged with safeguarding public health: How do you stop an enemy you can't see? Some scientists and engineers have taken up the challenge by developing a variety of ways to expose and destroy rogue bacteria and chemical agents. The technologies could also prove useful against conventional mold and pollutants.
Liquid crystals: Chemical engineers Rahul Shah, now at 3M Corporation, and Nicholas Abbott of the University of Wisconsin coat a small plate with liquid crystals. If viruses, proteins, or other chemical targets are present, they displace the crystals, causing them to change color or brightness. Such a detector could be designed as a badge that requires no batteries.
Light into sound: Chemist Jeanne Small of Eastern Washington University sucks bacterial spores into water and bombards them with laser pulses. The spores heat up and expand the surrounding water, creating a pattern of ultrasound waves that are picked up by a microphone. A system that continuously samples the air could flag a suspicious contaminant in about a half hour.
Synthetic muscles: Dan Nicolau of Swinburne University of Technology in Melbourne, Australia, and Cristobal dos Remedios of the University of Sydney place actin and myosin—proteins in human muscle—on a polymer-coated silicon chip. They attach antibodies and microscopic magnetic beads to the actin molecules. Normally the actin bounces along the myosin molecules, dragging the magnets and generating a tiny current. If the actin antibodies bind to anthrax or another chemical target, the current stops, setting off an alarm.
Mouse cells: Guenter W. Gross of the University of North Texas takes nerve cells from mouse embryos and places them on a glass plate embedded with electrodes. When the cells encounter a toxin, it alters their natural electrical signals. A group led by Greg Kovacs of Stanford University has built a handheld detector that responds to similar toxin-induced changes in mammalian heart cells.
Killer oxidants: Yogi Goswami of the University of Florida has a way to kill bacteria using a technique he developed for allergy sufferers. He shines an ultraviolet light on to titanium dioxide, a compound that catalyzes the production of oxidizing molecules. These molecules break up DNA and destroy bacterial spores. The system can be added to existing heating or air-conditioning systems.
Killer plasma: Kurt Kovach and his colleagues at PlasmaSol Corporation in New Jersey can create a sterilizing plasma—a mix of electrons and other charged particles—at room temperature. Reactive atom fragments in the plasma penetrate and disintegrate bacterial spores. The system could be incorporated into building air-filtration systems or used directly on surfaces.