Methods and systems for forming flexible multilayer structures
Techniques are described for fabricating multilayer structures having arrays of conducting elements or apertures in a conductive grid which can be used to form frequency selective surfaces (FSSs), antenna arrays and the like on flexible substrates. Fabrication techniques can include use of a polymer mask or direct dielectric molding. In embodiments utilizing a polymer mask, a temporary 3D polymeric relief pattern is formed on a substrate and used as a mask or stencil to form the desired pattern elements. In an additive process, the conductive material is deposited over the masked surface. Deposition can be followed by mask removal In the subtractive process, the conductive layer can be deposited prior to formation of the polymer mask, and the exposed parts of the underlying conductive layer can be etched. Other embodiments utilize dielectric molding in which the molded structure itself becomes an integral and permanent part of the FSS structure.
1. A method of construction of a frequency selective surface (FSS) on a flexible substrate, the method comprising:
providing a binary molding template having a surface with a three dimensional pattern including a pattern depth;
applying a dielectric material layer to the binary molding template;
molding the dielectric material layer with a desired pattern that is complementary to the pattern of the binary molding template, to form a patterned dielectric material layer that is disposed on or comprises a flexible substrate;
forming a FSS structure on the flexible substrate, wherein the FSS structure comprises a patterned conductive element layer, an insulating material layer, and an electrically conductive ground plane; and
utilizing the pattern depth of the molded dielectric material layer to form a spatial separation between the patterned conductive element layer and the ground plane.
2. The method of claim 1 , wherein the conductive element layer comprises a metal.
3. The method of claim 2 , wherein the metal is selected from a group consisting of as gold, silver, copper, aluminum, manganese, and titanium.
4. The method of claim 1 , wherein the conductive element layer comprises indium tin oxide.
5. The method of claim 2 , wherein the conductive element layer comprises a conductive polymer or conductive particles in a polymer binder.
6. The method of claim 1 , wherein the patterned dielectric material layer comprises a polymeric material or dielectric particles in a polymeric binder.
7. The method of claim 1 , wherein the electrically conductive element is formed by the addition of material to the substrate.
8. The method of claim 7 , wherein adding material includes vacuum deposition or solution coating or electroplating or electroless deposition or chemical vapor deposition (CVD).
9. The method of claim 1 , wherein the patterned conductive element layer on the flexible substrate is formed by selectively removing material from the conductive material layer on the substrate.
10. The method of claim 9 , wherein the patterned conductive element layer on the flexible substrate is formed by selectively removing material from the conductive material layer through openings in a mask layer.
11. The method of claim 10 , wherein removing material includes chemical, solvent, or plasma etching or electroetching.
12. The method of claim 1 , wherein the patterned conductive element layer is formed as a plurality of antenna elements.
13. The method of claim 12 , wherein the plurality of antenna elements is formed as a component of an energy harvesting device.
14. The method of claim 1 , wherein the flexible substrate further comprises a protective layer.