A microsieve for leukocyte depletion of erythrocyte concentrates

A new ultra thin filtration membrane has been used for leukocyte removal from erythrocyte concentrates. This filtration membrane, an Aquamarijn Microsieve(R), has a high pore density and a narrow pore size distribution and shows good separation behaviour. The low surface roughness of the microsieve will contribute to the biocompatibility and will reduce cell rupture, in particular hemolysis, during filtration. In this paper a brief overview of the effects that occur during filtration will be given. Also the results of the experiments of leukocyte removal from erythrocyte concentrates will be discusse

Fabrication of microsieves with sub-micron pore size by laser interference lithography

Laser interference lithography is a low-cost method for the exposure of large\ud surfaces with regular patterns. Using this method, microsieves with a pore\ud size of 65 nm and a pitch of 200 nm have been fabricated. The pores are\ud formed by inverting a square array of photoresist posts with a chromium\ud lift-off process and by subsequent reactive-ion etching using the chromium\ud as an etch mask. The method has wider process latitude than direct\ud formation of holes in the resist layer and the chromium mask allows for\ud etching of pores with vertical sidewalls

Wet and dry etching techniques for the release of sub-micrometre perforated membranes

For the production of microsieves we studied the release of perforated silicon nitride membranes from a silicon substrate. During the release by KOH etching the pressure build-up due to hydrogen gas formation can be quite large and cause rupture of the membrane. We explored the use of anisotropic etching with an SF6/O2 plasma to replace KOH etching. For sub-micrometre pores excellent results were obtained

Filtration of lager beer with microsieves: flux, permeate, haze and in-line microscope observations

Membrane fouling during filtration of lager beer with microsieves was studied through in-line microscope observations. It was observed that the main fouling was caused by micrometre-sized particles, presumably aggregated proteins. These particles formed flocks covering parts of the membrane surface. Most of the flocks could be removed by a strong temporary increase in crossflow. Underneath the flocks a permanent fouling layer was formed inside the pores. This made frequent removal of the flocks crucial in delaying the process of permanent in-pore fouling.\ud \ud Besides the fouling process the influence of pore size on permeate flux and turbidity was investigated. Centrifuged beer appeared to give a significantly clearer permeate than rough beer. For centrifuged beer and a microsieve with a pore diameter of 0.55 μm a haze of 0.23 EBC was obtained during 10.5 h of filtration at an average flux of 2.21×103 l/m2 h. For a sieve with slit-shaped perforations of 0.70 μm×3.0 μm a haze of 0.46 EBC was obtained during 9 h of filtration at an average flux of 1.43×104 l/m2 h. This flux is more than two-orders of magnitude higher than is commonly obtained with membrane-filtration of lager beer. Concentration of the beer by a factor of 12 hardly influenced the magnitude of the flux. \u

Microsieves made with laser interference lithography for micro-filtration applications

A microsieve with a very uniform pore size of 260 nm and a pore to pore spacing of 510 nm has been fabricated using multiple exposure interference lithography and (silicon) micro-machining technology.\ud \ud The sieve consists of a 0.1 µm thick silicon nitride membrane perforated with sub-micron diameter pores and a macro perforated silicon support. The calculated clean water flux is at least one to two orders higher than that of conventional inorganic membranes