This PhD project explores the principle of ratchet sieve technology and aims at application of this principle to separate and fractionate industrially relevant particle suspensions. Typically, suspensions with particles between 5 and 100 micron in diameter are treated using this technology. The separation device employs microsieves positioned such that suspended particles are deflected from the fluid streamlines on the basis of their size. The work involves experimental evaluation of the use of micro sieves to achieve so-called ratchet separation. This insight will be translated to the efficient recovery of valuable particle solids fractions with simultaneous removal of water (for example algae harvesting or spent grain or starch granule refining). This project is carried out in the framework of Wetsus, Centre of Excellence for Sustainable Water Technology in Leeuwarden.