Fibrillar structures to reduce viscous drag on aerodynamic and hydrodynamic wall surfaces

1. An aerodynamic or hydrodynamic wall surface comprising:

the aerodynamic or hydrodynamic wall surface comprises at least a portion of wind turbine blade, a propeller, a wing, an airfoil, a flight control surface, a hull of a ship or a submarine, a land-based vehicle, an manned or unmanned aerial vehicle or a pipeline;

an array of spaced-apart individual fibers attached to and extending from the aerodynamic or hydrodynamic wall surface, wherein each individual fiber comprises a stalk and a tip made of a single moldable material;

each stalk having a first end and a second end, wherein the first end is attached to the aerodynamic or hydrodynamic wall surface, and the stalk is oriented with respect to the aerodynamic or hydrodynamic wall surface at a stalk angle between approximately 1 degree and 179 degrees, each stalk has a stalk diameter of approximately 10 nm to 1000 μm, and a length of approximately 10 nm to 1000 μm, and a center of each stalk is separated from a center of an adjacent stalk by approximately 10 nm to 5000 μm;

each tip having a first side and a second side, wherein the first side is attached proximate to the second end of the stalk, the tip has a larger cross-sectional area than the stalk, and the second side comprises a substantially planar surface that is oriented with respect to the stalk at a tip angle between approximately 0 degrees and 90 degrees, and each tip has a tip diameter of approximately 10 nm to 2000 μm; and

wherein the array of spaced-apart individual fibers reduce a drag of the aerodynamic or hydrodynamic wall surface by at least 30%.

2. The wall surface as recited in claim 1 , wherein the stalk angle is between approximately 45 degrees and 90 degrees.

3. The wall surface as recited in claim 1 , wherein a cross section of the stalk is substantially square shaped, rectangular shaped, circular shaped, elliptically shaped, triangular shaped, hexagonally shaped or multi-sided prism shaped.

4. The wall surface as recited in claim 1 , wherein the second side of the tip is substantially square shaped, rectangular shaped, circular shaped, elliptically shaped, triangular shaped, hexagonally shaped or multi-sided prism shaped.

5. The wall surface as recited in claim 1 , wherein the stalk and tip form a mushroom shape.

6. The wall surface as recited in claim 1 , wherein the wall surface, each stalk and each tip are formed from a single material.

7. The wall surface as recited in claim 1 , wherein each stalk and tip are made of a silicone rubber, a polyurethane plastic, a thermoplastic, a thermoset, a UV curable material, a polymer or a combination thereof.

8. The wall surface as recited in claim 1 , wherein the each stalk and tip are formed by micro/nano-molding one or more templates.

9. The wall surface as recited in claim 8 , wherein the one or more templates are produced using a photolithography process and/or etching process.

10. The wall surface as recited in claim 1 , wherein:

each stalk has a stalk diameter of approximately 50 μm and a length of approximately 100 μm;

each tip has a tip diameter of approximately 100 μm; and

a center of each stalk is separated from a center of an adjacent stalk by approximately 120 μm.

11. The wall surface as recited in claim 1 , wherein the stalks in the array of spaced-apart individual fibers are arranged in a square packing, a hexagonal packing or a random packing.

12. The wall surface as recited in claim 1 , wherein the spaced-apart individual fibers within the array have varying cross-sectional shapes, diameters and/or spacings.

13. The wall surface as recited in claim 1 , wherein the array of spaced-apart individual fibers increase a lift of the aerodynamic or hydrodynamic wall surface.

14. The wall surface as recited in claim 1 , wherein the array of spaced-apart individual fibers increase a lift-to-drag ratio of the aerodynamic or hydrodynamic wall surface.

15. The wall surface as recited in claim 1 , wherein at least a portion of the aerodynamic or hydrodynamic wall surface comprise a curved surface.

16. The wall surface as recited in claim 1 , further comprising one or more additional arrays of spaced-apart individual fibers having one or more of a different stalk angle, a different stalk shape, a different stalk length, a different stalk diameter, a different tip angle, a different tip shape, a different tip length, a different tip diameter, a different spacing, a different packing or a different backing layer thickness.

17. A method for reducing a drag of an aerodynamic or hydrodynamic wall surface comprising:

providing the aerodynamic or hydrodynamic wall surface comprising at least a portion of wind turbine blade, a propeller, a wing, an airfoil, a flight control surface, a hull of a ship or a submarine, a land-based vehicle, an manned or unmanned aerial vehicle, a pipeline or a stationary structure;

attaching an array of spaced-apart individual fibers to the aerodynamic or hydrodynamic wall surface, wherein each individual fiber comprises a stalk and a tip made of a single moldable material, and each stalk extends outward from the aerodynamic or hydrodynamic wall surface;

wherein each stalk having a first end and a second end, wherein the first end is attached to the aerodynamic or hydrodynamic wall surface, and the stalk is oriented with respect to the aerodynamic or hydrodynamic wall surface at a stalk angle between approximately 1 degree and 179 degrees, each stalk has a stalk diameter of approximately 10 nm to 1000 μm, and a length of approximately 10 nm to 1000 μm, and a center of each stalk is separated from a center of an adjacent stalk by approximately 10 nm to 5000 μm;

wherein each tip having a first side and a second side, wherein the first side is attached proximate to the second end of the stalk, the tip has a larger cross-sectional area than the stalk, and the second side comprises a substantially planar surface that is oriented with respect to the stalk at a tip angle between approximately 0 degrees and 90 degrees, and each tip has a tip diameter of approximately 10 nm to 2000 μm; and

reducing the drag of the aerodynamic or hydrodynamic wall surface by at least 30% using the array of spaced-apart individual fibers.

18. The method as recited in claim 17 , further comprising increasing a lift of the aerodynamic or hydrodynamic wall surface using the array of spaced-apart individual fibers.

19. The method as recited in claim 17 , further comprising increasing a lift-to-drag ratio of the aerodynamic or hydrodynamic wall surface using the array of spaced-apart individual fibers.