Here come the Wireless Bio-Sniffers
By Mark Frauenfelder, Mon Jan 20 11:30:00 GMT 2003

The combination of wireless technology with biotechnology is taking both to the next level.

The diameter of a human hair is about 70 microns. That's about as wide as 20 anthrax spores lined up side-by-side. You can't even see an individual spore, but it takes just a few to work their way into your lungs and kill you in a matter of days.

Anthrax is just one of many nasty biological and chemical agents that have been keeping people up at night for the past year. Our cities are woefully unprepared to deal with the looming menace of bio-terrorism. The thought of invisible particles and vapors wafting through ventilation systems, subways, and other enclosed public areas is something that hardly anyone had thought about until the events following 911 had everyone running to their computers to search for "cipro" on Google. Now, governments are scrambling to come up with ways to protect people from another attack of anthrax, botulism, plague, smallpox, tularemia or other microscopic beastie.

Minimizing Exposure

Of course, the name of the game is preventing future incidents from happening again. That's not always easy to do, because making and using airborne pathogens isn't extraordinarily difficult, even for someone without access to an expensive laboratory. For instance, it's likely that a lone killer was responsible for the anthrax attacks last year. And in 1995, a Japanese religious cult was able to whip up a batch of sarin gas and disperse it in a subway system in Tokyo, killing 11 people and injuring over 5,500 others. In fact, soldiers who would catapult the corpses of bubonic plague victims over fortress walls were even practicing germ warfare in the Middle Ages. So while it's necessary to have an intelligence network to search for terrorists and stop them before they get started, it's unrealistic to believe that it's enough to keep us safe.

Vaccinations can certainly help, but it's just not feasible to vaccinate every person against every conceivable bio-warfare agent. For one thing, some vaccines can cause serious problems in the young, the elderly, and people with weakened immune systems. For another, some bio-weapons have no known vaccine. And some vaccines require frequent booster shots and are impractical to issue on a massive scale. Until the day comes when there's a one-shot, long lasting "super-vaccine" with no side effects, it's likely that military forces, disease control workers, and other government personnel will be the only ones to receive vaccinations for hazardous microbes and poisonous chemicals.

Early Detection

In addition to intelligence and vaccination, there's another way to fight bio-terrorism, and that's through the use of early detection systems capable of sensing and identifying minute quantities of lethal airborne pathogens in time to quarantine contaminated areas and give immediate treatment to people suspected of exposure.

Today, it's possible to go out and buy systems that can detect different kinds of airborne pathogens, but most of them are bulky, slow acting, and expensive. Most of these systems use antibodies to detect traces of biological pathogens. For example, Alexeter Technologies ( in Wheeling, Illinois, makes plastic strips coated with antibodies that react to specific bio-toxins. But they aren't the kind of thing you can leave hanging from the wall like an air freshener. Trained personnel, who arrive on the scene in a HAZMAT suit, use them. They collect some of the suspect material (if there is indeed enough material to be collected), mix it with a special liquid, and apply it to the strip. Fifteen minutes later, the specialist will examine the strip. If there's a colored line, beware. That means the material is anthrax (or some other bio-toxin, depending on the type of antibody on the strip.) Twenty-five strips will run you $500.

Such a system is useful in certain situations, but it doesn't come close to having the convenience of something like a home smoke alarm, which can be installed by anyone, and is always on, sniffing the air for the first sign of danger. Today's bio-terrorism detectors are sadly lacking, but that's all about to change, now that the US federal budget for bio-terrorism countermeasures has ballooned from $300 million to $3 billion in the past year. With all those dollars dangling from the tree, hundreds of companies are competing to build bio-detectors that are smaller, faster, and cheaper than the current crop.

MEMS to the Rescue

The most significant breakthrough in counter-bioterrorism is in the use of MEMS (Micro Electro-Mechanical Systems) to detect hazardous biomaterials. MEMS are microscopic machines that are built in much the same way computer chips are fabricated. MEMS are already in use in a number of applications. Car airbags use them to detect collisions. Microdisplay companies use MEMS that contain tiny swiveling mirrors to project laser images on viewers' retinas. One of the most exciting areas in MEMS research is biotechnology. MEMS are being used to create "laboratories on a chip," in which an array of tiny reservoirs containing chemical reactants senses the presence of minute amounts of specifics kinds of chemicals. As it turns out, they're ideally suited to detect dangerous microbes and toxic gases.

Combimatrix (, in Mukilteo, Washington, has developed a handheld bio-warfare detector that uses MEMS that react to a large number of hazardous substances. Combimatrix vice president Bret Undem says the detectors are capable of sensing as few as ten anthrax spores. The company is currently talking to a number of possible partners to build a commercial device (it's already delivered working prototypes to the US military), and is receiving a $3.6 million dollar federal grant for the program.

Wireless MEMS Sensors

But MEMS are only the beginning when it comes to the new breed of anti-bio-terrorism detectors. Sure, a smoke-alarm-style or handheld biohazard detector is a great leap forward from today's technology, but they'll be an order of magnitude more useful when they're wirelessly connected. Imagine a network of hundreds or thousands of small, ultra-sensitive detectors stationed around a hotel, hospital or airport. With their MEMS chips waiting for a handful of spores to activate them, the detectors could continuously transmit their status to a central computer. In the event of an attack, each affected detector could inform the computer of the concentration of the hazardous material, thus giving the computer the information it needs to home in on the exact spot where the material was released. How about putting MEMS-based bio-toxin sensors on soldiers' uniforms that would instantly alert field command to the presence of poison gas or deadly germs? With MEMS small size and the portability of wireless transceivers, the possibilities are endless.

A Flock of Virtual Canaries in the Coal Mine

One company already at work in making wireless sensor systems is Sensicast, based in Needham, MA. Started with $3 million in funding from Ardesta (an Ann Arbor company that starts and funds companies that use MEMS technology), Sensicast is developing battery-operated wireless sensor network systems for a variety of applications, including security and environmental monitoring. Sensicast is one of several startups trying to commercialize "mesh networking," a relatively new way to propagate information from one point to another.

Unlike standard 802.11 networks, which route all traffic to a central hub, every device in a mesh network has the capability of functioning like a router. That way, you could stick dozens or hundreds of matchbox-sized sensors all over a building or enclosed public area and not have to worry that each sensor be in range of a central router - Sensicast's software creates an ad-hoc self-healing network. You can also add repeaters throughout the facility to boost the signals of the remote sensors. This is important, because when you're using battery-powered sensors, you don't want to have to worry about draining a sensor's power to make sure the signal doesn't get lost.

Shake Your Way to Energy

Of course, no matter how miserly a device is, batteries don't last forever. And that's a problem when you are talking about thousands of battery-powered sensors attached to the ceilings, ventilation systems, and other hard-to-reach areas of a single large facility. That's why researchers at several universities are looking into ways to scavenge the ambient vibration of buildings and convert it into electrical energy. All building surfaces vibrate to some degree, due to heating, air conditioning, machinery, noise, wind, and other factors. These vibrations are usually so small that we don't notice them. But they're strong enough to generate a small amount of power by stimulating a MEMS device with containing piezoelectric crystal, which produces electrical energy when it is deformed. These scavengers could be used to power small wireless biosensors, eliminating the need to replace batteries every couple of months.

A Germ Free Spaceship is a Happy Spaceship

Bad germs just don't happen on earth. At the University of Tennessee's Center for Environmental Biotechnology, researchers are developing wireless biosensors that can be used to monitor microbial contamination and radiation exposure in future manned space missions. The researchers are using "bioluminescent biosensor organisms" built directly onto wireless integrated circuits. They call them Bioluminescent Bioreporter Integrated Circuits (BBIC). Bioluminescent biosensors are bacteria that glow when they come into contact with a specific toxic compound. The more poison the bacteria receive, the more brightly they shine. The BBIC uses this light to determine the level of toxicity present in the spacecraft, sending a wireless message to a central computer. "The ultimate goal," say the researchers, "is to create an array or network of small, unobtrusive, low cost, low power BBICs for intelligent distributed monitoring of the space craft environment, as well as for planetary-based surface habitats."

It may sound like science fiction, but this is one technology that's coming down to Earth, and not a moment too soon.

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Mark Frauenfelder is a writer and illustrator from Los Angeles.