W e present a particle separator that works on micro scales and that can be implemented on-chip. The working principle is based on the motion of particles or species in thermal gradients, the so called thermophoresis. A study of the feasibility of thermophoretic separation in microfluidics has been conducted. The efficiency of separation is observed by particle imaging. An integrated thermophoretic separator has been micro fabricated in silicon. Tests show that separation of 83% of the particles can be achieved in 100 s, using only 1 W of electrical power. Separation appears to be an order of magnitude faster than predicted. This separator will serve as a micro laboratory to further investigate the thermophoretic separation.