422 furthermore as shown in fig4 b an additional reservoir 416 may be used to collect the u201c front end u201d of the suspension which is purged of microparticles and by using positive pressure at yet another pressure inlet 416 this solution may be transferred to a separate outlet 420 some of the substrate materials that may be used include but are not limited to silicon or a derived silicon surface such as silicon dioxide or silicon nitride glass quartz ceramics a wide variety of polymers such as pdms pmms pc coc or a combination of listed substrates such as a glass substrate with a coated film of pmma on the surface in accordance with an embodiment of the present invention a low cost plastic surface is used for fabricating the on chip bioparticle separator using a series of pressure pulses for a disposable biochip the substrate material may have a thickness ranging from 100 u03bcm to 5 mm the thickness of the substrate material should be sufficient to impart dimensional stability required for the various steps of the microfabrication process generally the surface has a hydrophobic surface characteristic specifically for the passive microfluidic dispensing schemes the concepts of the passive microvalves and the on chip dispensers are clearly detailed in u s provisional patent application 60 204 214 filed on may 12 2000 u s provisional patent application 60 209 051 filed on jun 2 2000 and u s patent application ser no 10 602 575 filed on jun 24 2003 all of which are incorporated herein by reference in their entirety the surfaces of the above listed substrates may be easily modified by.