The next-generation device should extend the distance at which TNT vapors can be detected and allow operation in cold temperatures, such as in the mountains of Afghanistan. It will use a polymer-based sensing element, also developed at MIT, that instead of merely glowing, produces a much more intense light in the form of a laser. When TNT vapors touch the material, it suddenly stops lasing, causing a dramatic drop-off in the amount of light. "As a consequence, you can amplify the recognition of the presence of TNT," increasing the detector's sensitivity, says Vladimir Bulovic, an electrical engineering professor at MIT who was involved with developing the more-sensitive device.

Rose is now adapting the device, described last April in the journal Nature, for low-power applications, by containing the polymer in micro- or nano-sized structures that lower the amount of light needed to trigger the lasing. Nomadics is also making the detector more versatile, with the goal of being able to sense more kinds of chemicals, such as the RDX used in plastic explosives. According to Rose, RDX, the second-most common explosive, after TNT, has three orders of magnitude less vapor around it than TNT, requiring the higher sensitivity for detection.

As good as bomb-detection technology may get, however, it alone will not be able to solve the IED problem. Loren Thompson, CEO of the Lexington Institute, a nonpartisan think tank in Arlington, VA, says the effectiveness of Nomadics' technology will be limited by soldiers' ability to control traffic in a city, which, in turn, is limited by the number of troops available. "To create a checkpoint, to continuously monitor a neighborhood for a bomb factory -- we just don't have enough personnel to do that," he says. "You would have to rely on some sort of prior intelligence-gathering or sensor surveillance to reduce the number of prospective areas where you are going to apply the technology, otherwise it would be an insurmountable challenge."

The U.S. military is thus pursuing efforts that can complement detection. By Thompson's estimate, there are a somewhere around a hundred different concepts -- most of them classified -- for defeating IEDs. Right now, he says, the most prevalent technologies in Iraq are devices for detecting magnetic anomalies created by artillery-shell-based IEDs or jamming the signals from garage-door openers and cell phones.

The U.S. is also working to improve the way its military communicates. On the army's Company Command website, thousands of army commanders are sharing their experiences in responding to the rapidly changing techniques of terrorist bombers.

All these combined efforts might be helping. At the end of December, Major General William Webster, commander of the Multinational Division-Baghdad, said the military is "finding nearly half of the roadside bombs, the IEDs, that the enemy is emplacing, and we've had a 92% increase in weapons caches found." He said their efforts had forced insurgents to try different, less deadly tactics, such as drive-by shootings. Indeed, in January, according to the nonprofit icasualties.org, which compiles data from DOD releases, 25 soldiers died from IEDs, down from an average 40 in several previous months.

Whatever solutions work for fighting IEDs, it's clear they will have to adapt constantly to new tactics by the bombers. The decrease in IED-related deaths in January could turn out to be a temporary downturn, if the pace of such deaths this month continues. "The basic problem you have with the IED threat," Thompson says, "is it continuously morphs in order to circumvent solutions that we've developed."