Small-scale sensor heading for the wrist

Da-Ren Chen, Ph.D., a mechanical engineer at Washington University in St. Louis, is working on a bracelet-sized device that monitors the air quality around the wearer.

Da-Ren Chen, Ph.D., mechanical engineer at Washington University in St. Louis, is working on a bracelet-sized device that monitors the air quality about the wearer. Conceivably, one could attach the device to a bracelet or belt and be assured that the air is good or warned if it’s bad.

The device is currently in the working stage but Chen has recently received a US patent on a larger device that does the same thing.

The device, which Chen designed and invented, is called the Nanometer Differential Mobility Analyser. At about seven inches tall with a circumference of a cereal bowl, Chen’s analyser is said to be nine times smaller than similar devices already available.

The device records aerosols (air particles) in the nanometer size range; the size that increasing evidence suggests is most dangerous to health.

Chen’s analyser can reportedly measure nanoparticles as tiny as two nanometers. Its resolution is 0.2 percent compared with 10 percent for traditional analysers, so it can distinguish differences between two nanoparticles with close diameters.

Particles with the sizes of 20 and 21 nanometers, which would be not distinguished by traditional analysers, will be able to be classified in Chen’s device. Moreover, Chen’s analyser will charge a high percentage of nanoparticles thanks to a separate charger that he also has patented.

Charging the nanoparticles allows for a higher level of detection or sensitivity. A conventional apparatus will charge only eight particles out of a thousand, whereas Chen’s device will charge 400 out of 1,000 particles in the three nanometer range; at a seven nanometer range 100 percent of nanoparticles will be charged.

‘The device is not only for measuring but it’s for classifying, too, ‘ said Chen, who noted that burning materials, such as coal and fuels, produces particles in the nanometer range. ‘Essentially anything in the nanoparticle size can be sized with it, and it shows great promise for a number of applications. ‘

Chen said that his analyser is one-third less expensive to manufacture than current ones, and that many units have been sold to industry through a Minneapolis-based company, TSI. ‘I’ve designed the instrument to be able to do as much as it possibly can,’ Chen said. ‘Fire detection is one possibility, and it’s being tested now in that capacity at the National Institute of Tests and Standards. This application will provide more insight into the initiation of a fire.’