Suspension separation with deterministic ratchets at moderate Reynolds numbers

Deterministic ratchets were evaluated in this study as continuous separation devices for suspensions. Compared to conventional microfluidic ratchets (gap width ≈10 μm), ratchet designs in this study were 70 times larger. Apart from the hydrodynamic regime (21), which lead to additional displacement. Furthermore, there was a maximum concentration of particles in the device above which the separation decreased, e.g., 12 v/v% for a design with cylindrical-shaped obstacles. The high suspension concentrations did not lead to blockage of the device and were much higher compared to concentrations normally achieved for membrane separations.The up-scaled deterministic ratchets show potential for fractionation. Particles above a critical particle size were better separated than particles below that critical particle size.

► Novel up-scaled deterministic ratchets were constructed and evaluated as continuous separation devices for suspensions. ► Different ratchet designs using circular and quadrilateral obstacle designs appeared to affect separation behavior. ► Separation surprisingly improved with increasing flow rates up to a maximum concentration factor of 45. ► Separation behavior and efficiency of the devices were not influenced by high particle concentrations up to 12 v/v%. ► The ratchets were capable to both concentrate suspensions and fractionate suspended particles on size.