To reduce particle emissions from diesel engines, sensors based on resistance change of soot collected on interdigitated electrodes have been introduced . Sensitivity depends on the known mechanisms of soot deposition (convection, diffusion, impact and thermo- phoretic effects). Thermophoresis is a force affecting particles suspended in a gas having a temperature gradient . Collisions with gas molecules coming from the hotter zone result in net movement toward the colder zone for the particles. Sensor surfaces maintained at a cooler temperature than the exhaust gas will thus achieve an effective collection of soot particles less than 100 nm.Thermophoresis show potential for high sensitivty soot sensing for applications such as OBD, On Board Diagnostics.