Method of making a polymeric film having structured surfaces via replication

A method of making a desired microstructure surface film, the microstructure surface comprising a plurality of elongate geometric micro-features, the method comprising the steps of:

• (a) providing a tool comprising a negative version of the desired microstructure surface;
• (b) providing a polymeric resin to a gap formed between the master tool and a second surface;
• (c) forming a polymeric film having the desired microstructure surface in the gap, the film having (i) first and second in-plane axes that are mutually orthogonal with respect to each other and a third axes that is mutually orthogonal with respect to the first and second in-plane axes in a thickness direction of the film, and (ii) the desired microstructure surface having the elongate micro-features positioned in a direction substantially parallel to the first in-plane axis;
• (d) removing the polymeric film of step (c) from the tool;
• and
• (e) stretching the polymeric film in a direction substantially parallel to the first in-plane axis.