Programmable soft lithography: solvent-assisted nanoscale embossing
A method of forming a nanoscale pattern on a substrate is provided, wherein the method increases or decreases the spacing of patterns on the substrate relative to a master, while keeping the pattern feature size constant. The method can alternatively reduce the pattern feature size of the substrate relative to a master, while keeping the spacing patterns constant.
1. A method of forming a master mold, the method comprising:
casting an elastomer against a nanoscale master template surface having a template surface pattern array;
removing the cast elastomer from the template surface as an elastomer mold;
wetting the elastomer mold with a suspended polymer;
contacting the wet elastomer mold with a thermoplastic master mold substrate;
removing the contacted substrate from the elastomer mold as a suspended polymer patterned master mold having an initially constant pattern feature size and spacing with respect to pattern features of the template surface pattern array and having a tunable pattern density across a range from 50% less than to 100% greater than the initial pattern density; and
manipulating the master mold so as to either increase or decrease the initial pattern density.
2. The method according to claim 1 , wherein the master template comprises a polymer.
3. The method according to claim 2 , wherein the master template polymer is polyurethane.
4. The method according to claim 1 , wherein the elastomer is poly(dimethylsiloxane).
5. The method according to claim 1 , wherein said manipulating comprises heating the master mold so as to increase pattern feature density by decreasing separation between pattern features thereof.
6. The method according to claim 5 , wherein said heating is uniformly applied at 115° C. for 20-40 minutes.
7. The method according to claim 5 , wherein pattern feature sizes of the master mold remain constant with respect to pattern features of the template array after said manipulating.
8. The method according to claim 1 , wherein said manipulating comprises mechanically stretching the master mold so as to decrease pattern density by increasing separation between pattern features thereof.
9. The method according to claim 8 , further comprising heating the master mold prior to said mechanical stretching.
10. The method according to claim 8 , wherein said stretching is in only one direction of the master mold.
11. The method according to claim 8 , wherein pattern feature sizes of the master mold remain constant with respect to pattern features of the template array after said manipulating.
12. The method according to claim 1 , wherein the master mold substrate comprises one or more of a polymer selected from the group consisting of polystyrene, polypropylene, polyethylene, polyethylene terephthalate, polyester, polycarbonate and polyamide.
13. The method according to claim 1 , wherein the template array comprises a hexagonal array of posts.
14. The method according to claim 1 , wherein the suspended polymer is a photoresist.
15. The method according to claim 1 , wherein the suspended polymer comprises one or more polymers selected from the group consisting of polymers of (meth)acrylic acid, (meth)acrylamides, alkyl (meth)acrylates, alkenyl (meth)acrylates, aromatic (meth)acrylates, vinyl aromatic monomers, nitrogen-containing compounds and their thio-analogs, substituted ethylene monomers, cyclic olefins, and substituted cyclic olefins.