Polydimethylsiloxane (PDMS) microfluidic devices have been used to filter and separate particles of different sizes, especially cells, from various mixtures. These microfluidic devices rely on fine lateral (XY) resolution for trapping microparticles. For example, a set of pillars with an inter distance of 25 µm will collect particles bigger than 25 µm while smaller particles will pass through. For achieving such a lateral resolution (XY), soft lithography must be used. This means spin coating a photopolymer, fabricating a mask with high resolution, mask alignment and UV developing, baking, and washing steps to make a PDMS mold.