Using phase separation technique perforated as well as non-perforated polymeric structures can be made with high aspect ratios (>5). By varying the phase separation process the properties (e.g. porous, non-porous, dense, open skin) of the moulded product can be tuned. Applications are described in the field of micro fluidics (e.g. micro arrays, electrophoretic boards), optics, polymeric solar cells, ball grid arrays, and tissue engineering.