Femtosecond Laser Pulse Surface Structuring Methods and Materials Resulting Therefrom

Abstract

Embodiments of the present invention are generally directed to materials processing methods using femtosecond duration laser pulses, and to the altered materials obtained by such methods. The resulting nanostructured (with or without macro- and micro-structuring) materials have a variety of applications, including, for example, aesthetic applications for jewelry or ornamentation; biomedical applications related to biocompatibility; catalysis applications; and modification of, for example, the optical and hydrophilic properties of materials including selective coloring.

1 . A surface-structured metal, comprising:
 a base metal having at least one of a femtosecond laser pulse-induced nanostructured surface and a nanostructure-covered laser-induced periodic surface structure (NC-LIPSS).   
     
     
         2 . The surface-structured metal of  claim 1 , wherein the nanostructure-covered laser-induced periodic surface structure has a period that is less than a period of a non-nanostructure-covered laser-induced periodic surface structure (LIPSSs) in the metal surface. 
     
     
         3 . The surface-structured metal of  claim 1 , wherein the base metal has a polished surface. 
     
     
         4 . The surface-structured metal of  claim 1 , wherein the base metal includes substantially any metal and metal alloy. 
     
     
         5 . The surface-structured metal of  claim 1 , wherein the base metal is one of aluminum, gold, titanium, copper, platinum, tungsten, silver, titanium alloy, aluminum alloy, brass, and stainless steel. 
     
     
         6 . The surface-structured metal of  claim 1 , wherein the surface-structured metal has a colored appearance. 
     
     
         7 . The surface-structured metal of  claim 6 , wherein the surface-structured metal has at least one of a black color, a blue color, a gold color, a yellow color, a gray color, a red color, and a combination thereof. 
     
     
         8 . The surface-structured metal of  claim 6 , wherein the surface-structured metal has an iridescence. 
     
     
         9 . The surface-structured metal of  claim 1 , wherein the base metal is aluminum and the color is black. 
     
     
         10 . The surface-structured metal of  claim 1 , wherein the base metal is aluminum and the color is gold. 
     
     
         11 . The surface-structured metal of  claim 1 , wherein the base metal is titanium and the color is blue. 
     
     
         12 . The surface-structured metal of  claim 1 , wherein the base metal is platinum and the color is gold. 
     
     
         13 . The surface-structured metal of  claim 6 , having a color that changes as a function of viewing angle. 
     
     
         14 . The surface-structured metal of  claim 6 , having a color that is substantially constant as a function of viewing angle. 
     
     
         15 . The surface-structured metal of  claim 1 , having an absorptance equal to or greater than 0.8 for a wavelength that is equal to or greater than about 200 nanometers. 
     
     
         16 . The surface-structured metal of  claim 1 , having an absorptance equal to or greater than 0.2 for a wavelength that is equal to or greater than about 50 micrometers. 
     
     
         17 . The surface-structured metal of  claim 1 , having an absorptance equal to or greater than 0.9. 
     
     
         18 . The surface-structured metal of  claim 1 , having an absorptance equal to or greater than 0.5, wherein the base metal has an absorptance substantially less than 0.5 at normal incidence. 
     
     
         19 . The surface-structured metal of  claim 1 , wherein the surface structure further includes a plurality of microscale aggregates. 
     
     
         20 . The surface-structured metal of  claim 19 , wherein the microscale aggregates further comprise at least one of micropores, microgrooves, and microchannels. 
     
     
         21 . The surface-structured metal of  claim 19 , wherein the surface structure further includes a periodic plurality of elongate grooves. 
     
     
         22 . The surface-structured metal of  claim 1 , wherein the surface structure comprises a plurality of nanobranches. 
     
     
         23 . The surface-structured metal of  claim 22 , wherein the surface structure further comprises a plurality of spherical nanoparticles. 
     
     
         24 . The surface-structured metal of  claim 1 , wherein the surface structure comprises nanostructures having a shape of nanovoids. 
     
     
         25 . The surface-structured metal of  claim 1 , wherein the surface structure comprises redeposited nanoparticles of ablated base metal. 
     
     
         26 . The surface-structured metal of  claim 1 , wherein the base metal is a bulk metal. 
     
     
         27 . The surface-structured metal of  claim 1 , wherein the base metal is a thin film. 
     
     
         28 . A surface-structured metal having an induced absorptance that is equal to or greater than 0.8 for a wavelength that is equal to or greater than about 200 nanometers. 
     
     
         29 . The surface-structured metal of  claim 28 , comprising an induced nanostructure in a surface of the metal. 
     
     
         30 . The surface-structured metal of  claim 28 , comprising substantially any metal and metal alloy. 
     
     
         31 . The surface-structured metal of  claim 29 , wherein the induced nanostructure is a nanostructure-covered laser-induced periodic surface structures (NC-LIPSS). 
     
     
         32 . The surface-structured metal of  claim 29 , wherein the induced nanostructure comprises a plurality of nanobranches. 
     
     
         33 . The surface-structured metal of  claim 32 , wherein the induced nanostructure further comprises a plurality of spherical nanoparticles. 
     
     
         34 . The surface-structured metal of  claim 28 , wherein the metal is a bulk metal. 
     
     
         35 . The surface-structured metal of  claim 28 , wherein the metal is a thin film. 
     
     
         36 . A method for treating a base metal, comprising:
 exposing a surface region of the base metal to a femtosecond duration laser pulse having a fluence, F, that is sufficient to alter a surface structure of the base metal; and   altering the surface structure of the base metal by creating a nanostructure in the surface.   
     
     
         37 . The method of  claim 36 , comprising exposing the surface region of the base metal to a single femtosecond duration laser pulse. 
     
     
         38 . The method of  claim 36 , comprising creating a plurality of nanobranch structures. 
     
     
         39 . The method of  claim 38 , further comprising creating a plurality of spherical nanoparticle structures. 
     
     
         40 . The method of  claim 38 , further comprising creating a plurality of nanovoids. 
     
     
         41 . The method of  claim 38 , further comprising creating surface microstructures. 
     
     
         42 . The method of  claim 36 , further comprising creating at least one of micropores, arcuate microgrooves, and central microchannels. 
     
     
         43 . The method of  claim 36 , comprising creating a plurality of nano-covered laser-induced periodic surface structures (NC-LIPSSs). 
     
     
         44 . The method of  claim 43 , further comprising creating a plurality of surface macrostructures. 
     
     
         45 . The method of  claim 44 , comprising scanning a femtosecond duration pulsed laser beam across the surface of the base metal at a selected velocity. 
     
     
         46 . The method of  claim 45 , comprising creating a periodic plurality of grooves. 
     
     
         47 . The method of  claim 46 , wherein the periodic plurality of grooves has a period equal to a translation step between two adjacent laser scanning lines. 
     
     
         48 . The method of  claim 36 , further comprising ablating material from a region of the surface and redepositing the ablated material on the surface. 
     
     
         49 . The method of  claim 37 , comprising exposing the surface region of the base metal to between 1-10 additional femtosecond duration laser pulses. 
     
     
         50 . The method of  claim 49 , comprising exposing the surface region of the base metal to between 10-100 additional femtosecond duration laser pulses. 
     
     
         51 . The method of  claim 50 , comprising exposing the surface region of the base metal to between 100-300 additional femtosecond duration laser pulses. 
     
     
         52 . The method of  claim 51 , comprising exposing the surface region of the base metal to greater than 300 additional femtosecond duration laser pulses. 
     
     
         53 . The method of  claim 44 , wherein the NC-LIPSS has a period, d, that is less than the laser wavelength, λ. 
     
     
         54 . The method of  claim 53 , comprising controlling the period of the NC-LIPSS by controlling at least one of λ, the incidence angle, θ, and the real part of the effective refractive index of an air-metal interface, η, according to the equation d=λ/(η±sin θ). 
     
     
         55 . The method of  claim 36 , comprising polishing the base metal surface prior to exposing the surface to the femtosecond duration laser pulse.