Process for fabricating precise microstructures
There is disclosed a method and apparatus for producing a polymeric film that accurately replicates a mold surface at least a portion of which surface has a complex pattern of microstructured or nano-structured dimensions. A polymeric powder is electrodeposited on an underlying mold surface and heated to its molten state to replicate a pattern on the mold surface. Then the powder can be cured to create a polymeric film. Finally the film is removed from the mold surface.
1. A method of continuously producing a polymeric object having a complex pattern formed on a surface thereof, the complex pattern comprising elements of predetermined microstructured or nano-structured dimensions, the method comprising the steps of:
a) providing a mold that moves along a continuous path, at least a portion of which path is substantially planar, said mold having a complex pattern including recesses of microstructures or nanostructures formed on at least a portion of a surface thereof;
b) depositing a polymeric powder comprising either a thermosetting or thermoplastic resin on said moving mold surface, the particle size of said polymer powder being sufficiently small so that said polymer powder particles fill the recesses of said complex pattern in said mold surface from the bottom up so as substantially to avoid any air entrapment;
c) melting the powder on said moving mold surface;
d) cooling said melted polymer at the substantially planar portion of the continuous path to create a polymeric object having a complex pattern on a surface thereof, said complex pattern on said polymeric object being complementary to the complex pattern on said mold surface; and
e) continuously removing said polymer object having said complex pattern from said moving mold,
wherein the mold surface provides a throughhole in the polymeric object.
2. The method of claim 1 , wherein said resin comprises a thermoplastic resin selected from one or more of: acrylic, polycarbonate, polyester, urethane, nylon, polypropylene, polyethylene, polyvinylchloride and silicones.
3. The method of claim 1 , wherein said resin comprises a thermosetting resin selected from one or more of : functional epoxy, epoxy-polyester, silicone and UV curable polymer.
4. The method of claim 1 , wherein said polymeric powder is substantially free of additives.
5. The method of claim 1 , wherein the polymeric powder further comprises a further phase or filler material.
6. The method of claim 1 , wherein the step of providing said mold having a complex pattern on a surface thereof comprises first forming the mold of a polymeric material by depositing a polymer powder against a substrate having the desired complex pattern formed therein.
7. The method of claim 1 , wherein said particles have a maximum dimension no greater than about 50 microns.
8. The method of claim 7 , wherein said particles have a maximum dimension in the range of about 5-20 microns.
9. The method of claim 1 , wherein throughholes are formed in said object by partially filling the depth of the complex pattern on the mold with the polymeric powder, said method including the further steps of pressing a resilient layer of material over the deposited powder to press the polymeric powder to a substantially uniform level, and then curing the polymeric powder to form said object.
10. The method of claim 1 , wherein the thickness of said object is between about 0.001 inch (25 microns) and about 0.020 inch (500 microns).
11. The method of claim 1 , wherein said mold moves at a speed of between about 50 and 100 ft./min.
12. The method of claim 1 , comprising forming a plurality of objects produced as part of a single layer film, and separating said objects into discrete components.