“…The pore size distribution of membranes can be measured by several methods (Calvo et al, 1995); among these, the most usual is the Bubble Point (Hernandez and et al, 1996) For pore sizes on the scale of tenths of microns, the Net Filter (Millipore, 2002) presents the best homogeneity in terms of pore size distribution among the available commercial membranes. With the development of micro-machining fabrication techniques (Madou, 2002), however, smooth surface sieves with controlled shape of pores and porosity can be fabricated using Si technology (Tong et al, 2005;Rijn et al, 1999), LIGA technologyLithographie Galvanoformung Abformung (Malek and Saile, 2004;Storkveco Inc, 2009) or Soft Lithography (Madou, 2002;. Besides the homogeneity in the pore sizes and pore distribution, the sieves present a very smooth surface and they can be fabricated with a thickness much smaller than the pore diameter, forming a screen filter (Kuiper et al, 1998).…”