Gas chromotography and mass spectrometry are long-standing standard methods of chemical analysis.  If you want to know the composition of an airborne chemical, these methods are commonly used.  However, these methods traditionally require a lab setup and are of limited practical use in the real world.  So what about practical, real world situations like an airport detector of plastic explosive, or a industrial plant monitor to determine if toxins have entered the air -- how could these more complex in-the-field type uses be made reality?

One approach is to try to reinvent the wheel and develop new and exotic sensors.  Using neural networks, novel chemistry, and quirky algorithms are among the methods tried in this approach.  The far simpler, but more difficult to implement solution is to merely take the proven methods and shrink them to a microscopic scale.

Taking the latter approach is a daunting task, but engineers at MIT'S Microsystems Technology Laboratories (MTL) are determined to do just that, and already achieved significant progress in developing an portable electronic "nose".

MIT Professor Akintunde Ibitayo Akinwande envisions the final product to be a detector the size of a matchbox.  Akiwande restated the proven nature of the technology, saying, "Everything we're doing has been done on a macro scale. We are just scaling it down."

The key is converting macro scale into micro mechanical components and then integrating them with electrical devices.  These kinds of systems are known as Micro Electro Mechanical Systems (MEMS), a burgeoning field of technology.  The MTL lab is a leader in the development of these kinds of systems.

Dr. Akinwande and MIT research scientist Luis Velasquez-Garcia will present their work at a conference next week.  They will then present a further update on the progress in December.  Dr. Akinwande's team has the support of a large international group of participants including scientists at the University of Cambridge, the University of Texas at Dallas, Clean Earth Technology and Raytheon.

Currently, there are backpack-sized gas chromatography and mass spectrometry (GC-MS) sensors, but their large size makes them impractical and they are very slow. They can take up to 15 minutes to get a result and consume lots of energy -- 10 kJ of energy.  Dr. Akinwande and his team's matchbox-sized device consumes a scant 4 Joules and produces results in about 4 seconds.

The condensed version works by first breaking down the gas sample into fragments and ionizing these fragments, which are identified by specific charge (ratio of charge to molecular weight).    The gas molecules are broken apart by stripping their electrons or by the more novel approach of bombarding them with electrons stripped from carbon nanotubes; yet another use for the multifunctional nanotubes.  The resultant ion charges are converted to voltage after being sent through an electric field.  This voltage is measured and gives the molecule's unique electric fingerprint, revealing its identity.

One key advantage of taking the device to a micro scale is that the vacuum necessary in the chamber with the electric field is much more costly in terms of energy to maintain.  Batch production similar to IC production will allow the devices to be produced more easily and effectively than traditional macroscopic hand-assembled models.

The research started three years ago and is funded by Defense Advanced Research Projects Agency (DARPA) and the U.S. Army Soldier Systems Center in Natick, Mass.  The team states that the device will be complete and ready to be adapted for mass production within 2 years.  It will surely have a major impact on the fields of security, environmental science, public safety, and defense.