(484b) Control of Packed-Particle Flow Resistances During Cross-Flow Filtration In Microchannels

Cross-flow filtration of fine suspensions through microsieves is a logical, sometimes necessary step in micro-processing.  The observed limitation on steady-state filtrate flux accompanying this operation is generally attributed to particle accumulation upon the sieve.  We consider two mechanisms: (1) blockage of filter pores by particles in contact with the filter surface, and (2) formation of a packed bed of particles that intrudes upon and is regulated by shear flow within the microchannel.   This study examines the conditions under which a packed bed forms on a sieve, and provides a simple model for predicting its thickness when formed by hard non-interacting microspheres.  Extensive experimental data are reported that corroborate the model.  The good fit of these data lay a firm basis for the semi-quantitative analysis of the behavior of more complex suspensions.