Deterministic Ratchets for Particle Separation Fabricated With Si MEMS Technology

This paper presents the design, fabrication and testing of deterministic ratchets which are used for fractionation purpose. Ratchets with different configuration are prepared to determine particle trajectories with different sizes. Silicon based MEMS technology is used to fabricate devices containing arrays of obstacles with varying size, spacing and number. The arrays of high aspect ratio, 7-20 mu m wide, silicon pillars are defined and etched in 60 to 80 mu m deep microchannels using Deep Reactive Ion Etching (DRIE). The working modes of the ratchets are demonstrated using colloidal suspensions of latex particles which have an average diameter ranging between 2 and 6 mu m.