Characterization of the selectivity of microsieves using a cross-flow microfiltration system

Abstract

-Filtration through membranes is a process largely employed in the food and chemical industry to separate particles. Sieves present some advantages in relation to conventional membranes such as high homogeneity in the pore sizes, smooth surfaces, straight-through pores, etc. In this paper we compare the selectivity in the exclusion of particles by size of sieves with circular and slit pores with the same porosity. The selectivity was investigated by filtering a mixture of rutin in water in a cross-flow filtration system. The particle-size distribution of the rutin solution was measured before and after microfiltration. The results showed a high efficiency in the size exclusion of particles for microsieves with circular pores. The filtration through a commercial membrane (net filter) with similar characteristics was also characterized for comparison.

Hierarchically Structured Assembly of Polymer Microsieves, made by a Combination of Phase Separation Micromolding and Float‐Casting

“…Microsieves were initially made from purely inorganic materials using photolithography, which facilitates the preparation of hierarchically structured microsieves via repeated cycles of lithographic structuring. The repertoire of methods to produce inorganic microsieves comprises furthermore non photo lithographic elements like the use of block copolymers as etch masks,13 the embedding of sacrificial particles as templates for pores,14 track etching,15 electroforming16, 17 and micromolding 18. Polymeric microsieves have been prepared by photolithography using directly the structured resist instead of transferring its structure into an underlying substrate 19.…”

Hierarchically Structured Microsieves Produced via Float-Casting

“…The high ratio of pore diameter to membrane thickness and the high area density of open pores give rise to a permeance of microsieves, which is higher than the permeance of other filtration membranes with comparable pore diameters. ,− The uniform diameter of the pores leads to a sharp size cut-off, which is of advantage in various filtration applications. , …”

“…Several groups characterized microsieves in relation to their mechanical properties, − permeance for gases, ,, liquids, ,,− and dissolved polymers, and their application in filtration, , and also with respect to filter cake build-up and fouling . They can also be used as support for nonporous membranes, , microcontactors, stencils, capturing and analyzing suspended living cells, , monitoring microbiological water quality, , and filtration of milk, , beer, and retention of tumor cells. , …”

“…There are various ways to prepare microsieves: most prominent is the lithography method, mainly photolithography, − ,,,,, laser interference lithography, ,, colloidal mask lithography, and e-beam lithography . Some other methods to name are holography, , focused ion beam etching and ion track etching, laser ablation, galvanoforming, ,, micromolding, − inkjet printing, , and float-casting. − …”

Modeling of fouling in cross‐flow microfiltration of suspensions

“…Cross‐flow filtration is a well‐established technique that has been used for decades to continuously separate solid‐liquid mixtures . While the difficulty of microfluidic solid‐liquid separations has been noted, there are numerous applications in this environment that could benefit from cross‐flow filtration . It has been successfully used for bacterial and yeast cell harvesting, as plasmapheresis for separating plasma from whole blood, for isolating macroscopic quantities of blood components for therapeutic purposes, and for nonbiological applications such as waste water recycling and latex separation .…”