This paper presents a new concept of nano particle filtration module for lab-on-a-chip devices. This module is a perforated wall structure placed between two lateral fluid channels. Nanometer wide slots embedded in the wall connect both channels and allow only nano particles to flow through. By changing fabrication parameters, those highly uniformed nano slots can be adjusted from <100 nm to 2 ??m for different particle sizes. By expanding the filtration module into the silicon substrate, a 50% penetrable area over footprint is obtained when 500 nm wide slots are used. Finally, the fabrication process offers a convenient way to integrate it with other modules.