US Patent 7350397 - Porous cavity for nanoparticle detection

http://www.freepatentsonline.com/7350397.html

This patent teaches a device for detecting carbon nanoparticles in exhaust gas using a porous insulating film such as porous aluminum oxide. Claim 1 reads:

1. Device for detecting the amount or concentration of solid particles of nanometric or sub-micrometric size in a gas medium, in particular particulate matter in the exhaust gas of an internal combustion engine, comprising:

a structure for the deposit of solid particles present in the gas medium, at least a first and a second electrode associated to said structure, and

means for measuring an electric quantity between the first and second electrodes, wherein a plurality of cavities is defined in said structure, which act as collectors of solid particles present in the gas medium, the structure being arranged so as to enable collection of said particles inside said cavities, and wherein said structure comprises a porous body made of an electrically insulating material, the pores of said body constituting at least part of said cavities.