Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
  • A61C7/00—Orthodontics, i.e. obtaining or maintaining the desired position of teeth, e.g. by straightening, evening, regulating, separating, or by correcting malocclusions
  • A61C7/12—Brackets; Arch wires; Combinations thereof; Accessories therefor
  • A61C7/20—Arch wires
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/36—Removing material
  • B23K26/361—Removing material for deburring or mechanical trimming
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/02—Diffusing elements; Afocal elements
  • G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
  • G02B5/021—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures
  • G02B5/0215—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures the surface having a regular structure
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/02—Diffusing elements; Afocal elements
  • G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
  • G02B5/021—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures
  • G02B5/0221—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures the surface having an irregular structure
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/02—Diffusing elements; Afocal elements
  • G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
  • G02B5/0257—Diffusing elements; Afocal elements characterised by the diffusing properties creating an anisotropic diffusion characteristic, i.e. distributing output differently in two perpendicular axes
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/02—Diffusing elements; Afocal elements
  • G02B5/0268—Diffusing elements; Afocal elements characterized by the fabrication or manufacturing method
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/02—Diffusing elements; Afocal elements
  • G02B5/0273—Diffusing elements; Afocal elements characterized by the use
  • G02B5/0278—Diffusing elements; Afocal elements characterized by the use used in transmission
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/23—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  for the control of the colour
  • G02F1/25—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  for the control of the colour as to hue or predominant wavelength
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2101/00—Articles made by soldering, welding or cutting
  • B23K2101/32—Wires

Definitions

• Orthodontic therapy is a specialized area of dentistry concerning the supervised treatment of malpositioned (or crooked) teeth. Generally such treatment involves the judicious application of light continuous forces to the teeth using one or more orthodontic appliances. These forces stimulate changes in surrounding bone structure, thereby gradually directing teeth to their proper locations in the oral cavity. Orthodontic therapy can provide many benefits, including ease of maintaining hygiene, improved facial appearance, as well as improved bite function.
• Braces represent one type of orthodontic treatment in which tiny slotted appliances, called brackets, are attached to the teeth.
• a resilient, U-shaped (i.e., parabolic) archwire is then placed into the slots of the brackets.
• the archwire acts as a track that guides teeth toward their proper locations during the course of treatment.
• the archwire tends to have small cross-sectional dimensions to facilitate ligation and also keep forces imparted to the teeth relatively low as the teeth unravel.
• the teeth approach their target positions, allowing for progressively larger (and stiffer) wires to be used to improve the practitioner's control over the associated teeth.
• Orthodontic brackets may be made from a range of different materials such as metals (e.g., stainless steel), plastics (e.g., polycarbonate) and ceramic materials such as monocrystalline and polycrystalline aluminum oxide.
• Archwires may also be made from a range of metal or metal alloy materials including stainless steel, titanium, and shape memory alloys such as alloys of nickel-titanium and copper-nickel-titanium.
• Orthodontic archwires that are coated with a non-metallic aesthetic layer have been proposed in the past.
• US Patent No. 5,454,716 (Banerjee et al.) and International Publication No. WO 97/29712 (Sjoegren) describe orthodontic archwires that are coated with a thin coloring layer that matches the color of the teeth.
• Other coated orthodontic archwires are described in US Patent Nos. 4,050,156 (Chasanoff et al.) and 3,504,438 (Anthony et al.).
• US Patent No. 4,731,018 (Adelle et al.) describes an archwire with a metal part and a plastic part arranged so that the plastic part faces in a labial direction.
• US Patent No. 8,778,444 (Kim) describes the physically or chemically etching of a surface of the metal wire prior to coating the surface with a metal or other protective composition to impart a white or ivory color.
• the archwire is subsequently coated with a transparent parylene film, ostensibly so that the transparent metal material can be prevented from discoloration and coherence between the wire and the teeth.
• US Patent No. 8,726,510 (Voudouris) reports the use of large scale, laser created craters on a self igating bracket clip to generate a roughened surface texture for enhanced aesthetic coating adhesion.
• US Patent No. 5,882,193 sets forth a means for attaching auxiliary parts to an archwire, whereby a surface of an archwire is first de-oxidized by treatment with acid reducing agents. The cleaned surface is then plated with a noble metal e.g., gold, platinum, rhodium and palladium. The plated surface can provide some aesthetic improvement, while primarily providing a solderable or brazable surface for auxiliary attachment.
• a noble metal e.g., gold, platinum, rhodium and palladium.
• the present disclosure provides engineered, structured metal surfaces that exhibit reduced specular reflection and gloss while still providing a high intensity of reflected light at multiple incident angles.
• the structured metal surfaces include engineered topography that increases diffuse reflection, leading to a greater intensity of light perceived at multiple viewing angles. A viewer engaging such surfaces is likely to perceive a stronger 'white' reflection of the incident light and an improvement, particularly in orthodontic and other oral applications, of aesthetic appearance.
• the present disclosure provides an orthodontic appliance including an exterior surface including metal; and a plurality of recesses in the exterior surface, and wherein the surface including the plurality of recesses exhibits a Total CIE Chroma of no greater than 14 and a minimum L* value of at least 20 at an incident angle of 0 degrees and a view angle of 70 degrees.
• the present disclosure provides an orthodontic appliance including an exterior surface including metal; and a plurality of engineered features in the exterior surface, and wherein the surface including the plurality of engineered features exhibits a Total CIE Chroma of no greater than 14 and a minimum L* value of at least 20 at an incident angle of 0 degrees and a view angle of 70 degrees.
• the present disclosure provides an appliance including a body having an exterior surface including metal and a plurality of engineered features on the surface.
• the engineered surface exhibits a diffuse L* min70/maxl5 ratio of at least 0.2 at a Total CIE Chroma of less than 14, a minimum L* value of at least 20 at an incident angle of 0 degrees and a view angle of 70 degrees, as measured by the Diffuse Scattering Test.
• the present disclosure provides an appliance including an exterior surface including a metal and a plurality of recesses defined in the surface.
• the recesses have an average depth from the surface of at least 0.5 microns and are arranged in overlapping arrays such that a majority of the recesses overlap with adjacent recesses at boundary regions.
• the present disclosure provides a method for improving the aesthetic appearance of an article, the method including providing an article having an exterior surface, the surface including metal, and ablating at least a portion of the surface to create a plurality of features thereon, such that the surface exhibits a diffuse L* min70/maxl5 ratio of at least 0.2.
• geometric refers to the size and shape of an engineered feature.
• a “feature” is a structure or feature having a recognizable geometric shape defined by a volume that projects out the base plane of a surface or an indented volume which projects into the surface.
• an “engineered microstructure” and “engineered feature” shall mean a structure deliberately formed into and integral with a surface.
• An engineered microstructure or engineered feature are distinct from structures produced by random application of particles, by spraying, adhesive bonding, etc., to a surface.
• engineered surface and “structured surface” are generally used to refer to a surface that comprises engineered features.
• pitch means the average centroid to centroid distance between adjacent structures (e.g., recesses) on the engineered surface.
• the terms “height” , “base” and “top” are for illustrative purposes only, and do not necessarily define the orientation or the relationship between the surface and the microstructure.
• the "height” of a feature projected into a surface can be considered the same as the “depth” of recess created, and the “top” the “bottom” of said recess. Accordingly, the terms “height” and “depth”, as well as “top” and “bottom” should be considered interchangeable.
• an engineered surface comprising "a” pattern of recesses can be interpreted as an engineered surface comprising "one or more” patterns.
• the term "generally”, unless otherwise specifically defined, means that the property or attribute would be readily recognizable by a person of ordinary skill but without requiring absolute precision or a perfect match (e.g., within +/- 20 % for quantifiable properties).
• the term “substantially”, unless otherwise specifically defined, means to a high degree of approximation (e.g., within +/- 10% for quantifiable properties) but again without requiring absolute precision or a perfect match. Terms such as same, equal, uniform, constant, strictly, and the like, are understood to be within the usual tolerances or measuring error applicable to the particular circumstance rather than requiring absolute precision or a perfect match.
• Figure 1 illustrates an arrangement of engineered recesses on a surface, according to one embodiment of the present disclosure
• Figure 2 is a cross-sectional view of the engineered surface of Figure 1 ;
• Figure 3 is a schematic side-view of an engineered structure
• Figure 4 is an optical micrograph of a pattern of engineered recesses according to another embodiment of the present disclosure
• Figure 5 is an illustration of an arrangement of overlapping, engineered recesses according to another embodiment of the present disclosure
• Figure 6 is a block diagram detailing a method of creating patterns of engineered recesses on the surface of a substrate.
• Figure 7 is a schematic diagram of a laser ablation system according to an embodiment of the present disclosure.
• Figure 8A is an optical micrograph of a linear series of discreet recesses according to an embodiment of the present disclosure.
• Figure 8B is an optical micrograph of a first pattern of discreet recesses according to an embodiment of the present disclosure.
• Figure 9 is an illustration of a change in orientation of a laser pattern relative to a surface between first and second feature patterns according to an embodiment of the present disclosure.
• Figure 10 is a top view of an orthodontic arch wire
• Figure 11 is a cross-sectional view of the archwire of Figure 10.
• Figures 12-21 are laser intensity images obtained by confocal microscopy of engineered surfaces according to various embodiments of the present disclosure.
• the present disclosure provides engineered, structured metal surfaces that exhibit reduced specular reflection and gloss while still providing a high intensity of reflected light at a wide range of incident angles.
• the structured metal surfaces include engineered topography that increases diffuse reflection, leading to a greater intensity of light perceived at a wide range of viewing angles. A viewer engaging such surfaces is likely to perceive a strong 'white' reflection of the incident light and an improvement, particularly in orthodontic and other oral applications, of aesthetic appearance.
• the creation of structures according to the methods and concepts below eliminates or substantially reduces any deleterious effect on the mechanical performance of the substrate or an article containing the substrate.
• a structured surface region extends generally along orthogonal in-plane directions, which can be used to define a local Cartesian x-y-z coordinate system.
• the topography of the structured surface region can then be expressed in terms of deviations along a thickness direction (z-axis), relative to a reference plane (the x-y plane) lying parallel to the structured surface.
• the engineered or structured surface region of the substrate can also be generally described in terms of an average elevation.
• the average elevation of the structured surface region can be defined as an imaginary surface associated therewith i) lacking protrusive features or intrusive features and ii) being parallel to a major surface contour of the substrate in the structured surface region.
• the major surface contour of the substrate can be referred to as the shape of the surface of the substrate surface, regardless of the shape of the protrusive features and the intrusive features of the structured surface region.
• Engineered surface regions of the present disclosure comprise intrusive features and, in certain embodiments, protrusive features.
• Protrusive features of an engineered surface region can generally be described as features having surface points that lie above the average elevation of the structured surface region.
• Intrusive features (e.g., recessed features) of the structured surface region can generally be described as features having surface points that lie below the average elevation of the structured surface region.
• protrusive features and intrusive features are features commonly referred to as topographical features.
• Engineered surfaces or surface regions having intrusive features can be referred to as recessed features or recesses.
• Recessed features for example, can be referred to as recesses, wells, cavities, concavities, pockets, channels, and the like.
• Recessed features can have a volume with dimensions such as diameter, radius, depth, length, and width.
• a base of the recessed feature can generally refer to a location within the recessed feature having points lying closest to an average elevation, while the surface or region of the recess farthest from the average elevation is considered an apex.
• a recessed feature can be separated from another recessed feature by adjacent protrusive features.
• each topographical feature may comprise a variety of cross-sectional shapes including, but not limited to, parallelograms, parallelograms with rounded corners, rectangles, squares, circles, half-circles, ellipses, half-ellipses, triangles, trapezoids, stars, other polygons (e.g., hexagons), etc., and combinations thereof.
• cross-sectional shapes including, but not limited to, parallelograms, parallelograms with rounded corners, rectangles, squares, circles, half-circles, ellipses, half-ellipses, triangles, trapezoids, stars, other polygons (e.g., hexagons), etc., and combinations thereof.
• the relevant cross-sectional dimension will be understood to be the diameter of a circle of equivalent area.
• Protrusive features of the structured surface regions can be features that represent a departure or deviation away from an otherwise flat surface region.
• protrusive features separate recessed features.
• the geometry of the structured surface region can be described as hierarchical.
• recessed features can have random, partially random, or precisely spaced features positioned on the surfaces or walls of the recessed features, on raised regions of the recessed features, and within the recessed features.
• the surfaces of the recessed features can include protrusive features on a shorter height or narrower width scale than that characteristic of the recessed feature itself, for example.
• the topographical features are distributed as a periodic array across a structured surface region (e.g., a one-dimensional array or a two-dimensional array, for example a square array, hexagonal, or other regular array).
• the structured surface includes an arranged pattern of recesses.
• An "arranged pattern of recesses" is a plurality of recesses arranged at predetermined positions, arranged with some degree of regularity, or arranged in any desired manner.
• the arranged pattern of recesses can include an arranged row pattern, an arranged lattice pattern such as an arranged square lattice pattern, an arranged zigzag pattern, or an arranged radial pattern.
• the arranged pattern of recesses need not be formed evenly on the entire surface but may be formed in only a portion of the article surface.
• the pattern of recesses may vary or remain the same over any portion of the article. For example, similar or different patterns can be used within the same plane.
• the recesses within the pattern can be of similar size and shape or can have different sizes and shapes.
• features of the structured surface region can be present on a regular repeating basis, on a random basis, and the like, or combinations thereof. In other embodiments, the features can be present over a portion of the entire area of the structured surface region, or present over the entire area of the structured surface region. In some embodiments, features can be present in the recessed features of the structured surface region, present on the protrusive features of the structured surface region, and the like, or combinations thereof.
• the structures may also in some cases be closely packed, i.e., arranged such that at least portions of boundaries of many or most adjacent structures substantially meet, coincide, of substantially overlap.
• the structures can be irregularly or non-uniformly dispersed on the structured surface.
• some, most, or substantially all (e.g., > 90%, or > 95%, or > 99%) of the structures may be curved or comprise a rounded or otherwise curved base surface.
• the size of a given structure may be expressed in terms of an equivalent circular diameter (ECD) in plan view, and the structures of a structured surface may have an average ECD of less than 70 microns, or less than 60 microns, or in a range from 5 to 50 microns, for example.
• ECD equivalent circular diameter
• the structured surface region and structures can also be characterized with other parameters as discussed elsewhere herein, e.g., by an aspect ratio of the depth or height to a characteristic transverse dimension such as ECD.
• An engineered surface 110 is illustrated in Figures 1-2 and includes a plurality of discreet engineered recesses 120 projecting into at least a portion of a metal substrate 100.
• the metal substrate 100 may be planar, substantially planar, or include varying topography (e.g., undulations).
• Suitable metals for use as the substrate include, but are not limited to, stainless steel alloys, chromium-cobalt-molybdenum alloys, titanium alloys, zirconium alloys, shape memory nickel-titanium alloys, super elastic nickel-titanium alloys, aluminum alloys, copper alloys, and combinations thereof. Additional metals may be used depending on the desired application for the engineered surface.
• the thickness of the substrate 100 can vary depending on the intended use of the engineered surface.
• the engineered features are typically made from the same materials as the substrate, as further described below.
• the engineered recesses 120 are arranged in an array having a defined spacing or pitch between adjacent recesses 120.
• the configuration of recesses in any given region is chosen so that the pitch 126 (i.e., the average centroid to centroid distance between adjacent features) is at least 5 microns, in other embodiments at least 15 microns, in other embodiments at least 20 microns, in other embodiments at least 25 microns, and in yet other embodiments at least 30 microns.
• the pitch 126 is no greater than 70 microns, in some embodiments no greater than 60 microns, in some embodiments no greater than 50 microns, and in certain embodiments no greater than 45 microns.
• Engineered surfaces having feature pitches outside this range, depending on the cross-sectional dimensions of the recesses, may result in topographies that do not sufficiently reduce specular reflection or do not provide sufficient topographical hierarchy, leading to a glossy or metallic appearance.
• the pitch when the pitch is too large, the perceived brightness and gloss will be more dependent on the non-patterned surfaces than the engineered structures, particularly when the feature geometry (e.g., diameter, height) is small.
• a pitch below 5 microns can result in excess thermal energy introduced over a given surface area at high repetition rates. This excess introduction of thermally energy may, in certain circumstances oxidize the metal and/or may distort the grain structure, potentially altering mechanical properties of the engineered surface and the attendant article.
• a Cartesian x-y-z coordinate system is included in Figure 1 for reference purposes.
• the substrate extends generally parallel to the x-y plane, and an optical axis of the system may correspond to the z-axis.
• the lattice array of engineered recesses 120 includes a transverse direction, generally along the x-axis and a longitudinal direction, generally along the y-axis.
• the pitch between adjacent recesses in an array or pattern may be the same in both the traverse direction and longitudinal direction. In other potentially advantageous embodiments, the pitch along the longitudinal direction is less than the pitch along the transverse direction and vice versa.
• the ratio between the pitch along the transverse direction and the pitch along the longitudinal direction is defined herein as the spacing ratio.
• the spacing ratio is not 1 : 1, as a spacing ratio of 1 : 1 may produce a visible Moire pattern perceptible on the surface and potentially distracting from the desired aesthetic appearance.
• the spacing ratio is 0.7: 1, in some embodiment 0.9: 1, in some embodiments 1.1 : 1, in some embodiments 1.3: 1, and in yet other embodiments 1.5: 1.
• the engineered recesses 120 in the depicted embodiment are arranged in a cubic array, in that the boundary regions 123 of adjacent recesses 120 are directly adjacent or slightly overlapping (i.e., a discreet diameter of the recesses may be calculated in non-overlapping regions).
• the engineered recesses 120 are essentially discreet and include interstitial space 130 between adjacent recesses 120.
• the interstitial space 130 is, in this implementation, un-patterned in that it generally lacks any topographical or hierarchical features.
• un-patterned bare metal substrate between adjacent recesses may, in some circumstances, deleteriously affect the appearance of the substrate or article, as the un-patterned regions allow for more specular reflection of incident light (i.e., gloss).
• an engineered surface may include an arrangement of recesses in a hexagonal close packed array to further minimize the interstitial space between adjacent recesses.
• the area of the engineered surface contained within the plurality of recesses is typically substantially greater than the area bound within interstitial spaces. In some embodiments, 75% of the area of the engineered surface is contained within the recesses, in some embodiments at least 80%, in some embodiments at least 85%, in some embodiments at least 90%, and in yet additional embodiments at least 95% of the area is contained within the recesses.
• recesses 120 comprise a base 121 adjacent the engineered surface 110 and a bottom surface or apex 122 separated from base 121 by a depth 124.
• a recess 120 typically includes a spherical surface or concavity such that the depth near the perimeter or boundary is less than that near the center.
• the term "spherical surface” means that the surface can be considered to be a portion of a sphere or the surface has a generally spherical curvature. Some spherical surfaces can be considered to be dome-shaped or hemispherical. Other spherical surfaces can cover a smaller portion of a sphere than a hemisphere.
• the spherical curvature of the recess 120 is generally continuous, such that the recess lacks sidewalls that are orthogonal or substantially orthogonal (e.g., 80 - 89 degrees) to the engineered surface.
• the general spherical curvature in such implementations can be considered independent of hierarchical protrusive features within the recess.
• each engineered recess 120 may comprise a variety of cross-sectional shapes including, but not limited to, parallelograms, parallelograms with rounded corners, rectangles, squares, circles, half-circles, ellipses, half-ellipses, triangles, trapezoids, stars, other polygons (e.g., hexagons), etc., and combinations thereof.
• each engineered feature comprises a largest cross-sectional dimension at the base 121.
• the largest cross-sectional dimension of the base 121 may be no greater than 80 microns, in some embodiments no greater than 70 microns, and in some embodiments no greater than 60 microns.
• the largest cross- sectional dimension may be at least 10 microns, in some embodiments at least 15 microns, and in some embodiments at least 20 microns. As will be set forth in the Examples below, recesses having a largest cross-sectional dimension outside this range can be either perceivable by the naked eye and/or can result in insufficient modification of the substrate surface.
• a recess 120 typically includes a depth no greater than the pitch or largest cross-sectional dimension 127, though it certain embodiments the recess depth is significantly less than the pitch or cross-sectional dimension.
• each recess of the plurality of recesses has a depth that is at least 0.5 microns.
• recesses have a depth of at least 1 micron, in other embodiments at least 1.5 microns, in other embodiments at least 2 microns, in other embodiments at least 3 microns and in other embodiments at least 5 microns.
• the recess depth is no greater than 30 microns, in some embodiments no greater than 25 microns, in some embodiments no greater than 20 microns, and in certain embodiments no greater than 15 microns.
• Recesses having a depth greater than 30 microns may trap certain wavelengths of light, leading to less available intensity for the surface to appear sufficiently white. It may be noted, however, that not all recesses of the plurality of recesses need fall within the depth range listed above.
• Each recess 120 of the plurality of recesses includes a particular aspect ratio.
• the aspect ratio is defined herein as the ratio of the depth to the largest cross-sectional dimension (e.g., width, length, diameter) at the base.
• the largest cross-sectional dimension will be understood to be the diameter of a circle of equivalent area.
• each recess of the plurality of recesses typically includes an aspect ratio of no greater than 0.75 and at least 0.08.
• certain recesses of the plurality of recesses 120 can include hierarchical protrusive features thereon or therein.
• the protrusive features are typically submicron scale or at least include height and cross-sectional dimensions appreciably smaller than the cross-sectional dimension 127 or depth 124 of the recess 120.
• these hierarchal features may be created as a result of the methods used to create the recess 120, particularly those methods featuring laser ablation as further described below.
• the protrusive features may be added subsequent to the creation of the recesses by known methods for disposing microscale and nanoscale structures on a surface.
• the protrusive features may enhance the diffuse reflection of light and may interfere with an otherwise perceivable pattern of features that can otherwise detract from the aesthetic appearance of the engineered surface 110.
• FIG. 3 is a schematic side-view of a portion of an article including an engineered surface.
• Figure 3 shows an engineered feature 160 that has a slope distribution across the surface of the feature.
• Slope ⁇ is also the angle between tangent line 168 and a planar, major surface of the article 170.
• Slope of the structured surface can be taken along an x direction, and then along a y direction, such that:
• H(x,y) the height profile of the surface.
• Average x-slope and y-slope were evaluated in a 1.65 micron interval about each pixel.
• the interval may be chosen to be larger, such as 2 microns, or 3 microns, so long as a constant interval is used.
• X and y slope distributions were generated with a bin size of 0.5 degrees. From the x-slope and y-slope data, it is possible to determine a gradient magnitude. This may be understood as follows:
• Average gradient magnitude was then capable of being evaluated in a 1.65 ⁇ x 1.65 ⁇ box centered at each pixel.
• Gradient magnitude distribution was generated with a bin size of 0.5 degrees. It should be understood that in order to find the angle degree value of the x-slope, y-slope and gradient magnitude angles that corresponds to the values above, the arctangent of the values in Equations 1 , 2, and 3 should be taken. Gradient magnitude corresponds to a combination of the x and y-slopes, and therefore, gradient magnitude may be understood as a general slope magnitude.
• the minimum full width at half maximum (FWHM) between the x-slope distribution and the y-slope distribution is at least 10 degrees, in other embodiments at least 20 degrees, and in yet other embodiments at least 30 degrees.
• a minimum FWHM of at least 20 degrees evinces a variety of features that tend to increase the intensity of diffuse, reflected light.
• Other exemplary slope distributions include Lorentzian distributions, parabolic distributions, and combinations of different, distributions.
• the surface roughness of the engineered surface can also impact the light reflective properties.
• surface roughness is a measure of the roughness of a surface. Surface roughness can be measured using a technique such as confocal microscopy that can resolve features in the micrometer range.
• average roughness (Ra) or root-mean-square roughness (Rq) can be used, though Rq is presently preferred.
• Rq is the root mean square average of height deviations taken from the mean image data plane, expressed as:
• N is the total number of points and H is the height at each point (relative to the mean height).
• a high spatial frequency filter can be used to remove waviness.
• a low pass spatial frequency filter can be used to remove noise introduced by the measuring instrument.
• a high pass spatial frequency filter may be used in conjunction with the low pass filter to remove waviness and noise in the surface height map of the sample (i.e., a band pass filter).
• a Gaussian Fourier filter window is typically used to avoid ringing artifacts as is known in the art. See for example, ASME standard B46.1- 2009: "Surface Texture: Surface Roughness, Waviness, and Lay" and ISO 25178-2:2012.
• the roughness measurements should typically be taken in a region of the sample without debris or defects (e.g., unintentional bubbles, pits, scratches, etc.) to be meaningful.
• Software programs such as those available under the trade designation "VISION” from Bruker Corp., Santa Barbara, CA may be used or data processing software such as those programs available under the trade designation " MATLAB” from Math Works, Natick, MA may be used.
• the Rq value for the engineered surface is greater than 0.5, 0.8, 1, 1.5 or even 2 microns. In presently preferred circumstances, the Rq value of the engineered surface is at least 1 micron.
• An engineered surface 210 according to another embodiment of the present disclosure is shown in the optical micrograph of Figure 4.
• the engineered surface 210 includes an arrangement of disrupted recesses 220 having a modified cross-sectional dimension at the recess base 234.
• Disrupted recesses 220 according to the present disclosure can be the result of overlap of boundary regions between adjacent recesses. To create such overlap, disrupted recesses 220 are created based on an expected diameter that is greater than the pitch 230.
• An "expected diameter" as used herein means the diameter or ECD at the base of a single recess according to the selected method and process parameters used in creating the engineered surface. For example, a recess 220 created via laser ablation according to the methods described below may have an expected diameter of 40 microns.
• multiple recesses 220 are arranged along a transverse direction of the metal surface at a pitch of 30 microns, there will be roughly 10 microns of overlap between adjacent recesses 220. Additional overlapping regions may be created by adjacent recesses in the longitudinal direction as well. The overlapping region may result in protrusive or intrusive features created between discreet recesses, and alternatively may appear to the naked eye as part of a recess or as interstitial space.
• Figure 5 depicts a plurality of spherical recesses 320 having an expected diameter 334.
• the recess are arranged in a linear, grid array, such that any recess 320 not disposed on an edge region 350 of the engineered surface 310 will have one or more adjacent recesses 320 in the x and y directions.
• Certain recesses 320 within the array include a plurality of overlapping boundary regions 323 between multiple adjacent recesses, creating a discrete interior recesses 321 defined by the plurality of overlapping boundary regions.
• the discreet interior recess 321 accordingly includes cross-sectional dimensions smaller than the expected diameter. Disruption via substantial overlap between adjacent recesses can modify one or more characteristics of the recess including, but not limited to depth, volume, curvature, slope distribution, and cross-sectional dimensions at the base.
• the engineered surfaces of the present disclosure can exhibit a minimum L* value of at least 20 at a 70 degree view angle with normally incident illumination.
• view angle i.e., scatter angle
• sample normal i.e., line 164 in Figure 3
• Whiteness is an attribute of colors of high luminous reflectance and low purity, situated in a relatively small region of the color space. Lightness describes the overall intensity of the color in terms of how light or dark a color is. Under the Commission Internationale de l'Eclairage L*a*b* scoring system, the color white is distinguished by its high lightness, and surface having a perfectly white appearance has an L* of 100 (or greater if measured only at a specific view angle).
• the L* value at a scatter angle of 30 degrees is greater than 60, in some embodiments greater than 75, and in yet other embodiments greater than 80.
• the engineered surfaces of the present disclosure have a reduced L* value at an incident angle normal to the surface in comparison to stainless steel.
• the reflected intensity provided by the engineered surfaces of the present disclosure does not substantially decrease as view angle changes, contributing to a relatively high L Ratio.
• the "L Ratio" or “L* Ratio” is the L* value between the minimum L* value at a view angle of 70 degrees over the maximum L* value at a 15 degree view angle.
• a surface exhibiting a low or incalculable L Ratio can produce a dramatic change in lightness as the viewing angle or angle of incident light is rotated relative to the substantially orthogonal view, particularly when the surface is not black.
• Non-etched and otherwise untextured stainless steel can exhibit an L Ratio of 0. Surfaces having a moderate to high L Ratio, exhibit a more uniform lightness (i.e., L*) as a function of view angle.
• the present disclosure provides a method for creating a pattern of microscale, engineered features in a surface using laser energy.
• a flow diagram for this process is depicted in Figure 6.
• step 500 an article having a metal surface is provided and oriented relative to a laser source or scanner. Contaminants on the metal surface may be removed at this point, according to methods well known in the art.
• step 510 laser pattern parameters relating to a first feature pattern are defined to control the initial location, spacing, and size of the ablation-created features on the surface.
• Relevant pattern parameters include: 1) distance (i.e., spacing) between target locations (i.e., target sites on the surface for receipt of laser energy) in both x and y directions; 2) portion or extent of the metal surface that will include engineered features; 3) laser power and/or wavelength; 4) focal point position of the laser beam relative to the substrate; and 5) repetition rate of laser energy (pulses) directed at the surface.
• the first feature pattern can include, but is not limited to, Cartesian grid arrays, hexagonal arrays, and other structured and unstructured arrays.
• the laser beam is moved across a surface of the article at a predetermined path of travel. In other implementations, the surface may be moved relative to the laser beam.
• the laser source discharges laser energy at predetermined time intervals (i.e., generates pulses) according to the determined first feature pattern parameters, thereby creating a first portion of the first feature pattern on the surface.
• the first portion may be a generally horizontal, vertical, diagonal, sinusoidal, spiral or other linear or non-linear series of features, depending on the first feature pattern and the desired orientation of the first feature pattern on the substrate surface.
• the process proceeds to step 530, in which the laser beam is offset from the first series according to the first pattern parameters (e.g., pitch) and the laser beam proceeds to traverse the surface again at the same relative orientation between the laser beam and the substrate to create a second, subsequent portion of the first feature pattern.
• steps 500-530 may be used to create additional feature patterns that at least partially overlap with the first feature pattern as set out in steps 540-560.
• the additional feature patterns as selected in step 540 maintain or approximate at least some of the laser pattern parameters of the first feature pattern.
• the orientation of the laser pattern relative to the surface can be modified, however, between or amongst feature patterns.
• the position of the laser beam's path of travel relative to the surface may be rotated, which results in rotation of the laser pattern.
• the laser beam travels across the surface in the y-direction in creating first feature pattern 910, resulting in series of features generally along longitudinal lines 920.
• pattern parameters Prior to creation of the second feature pattern 930, however, pattern parameters are modified such that the intended path of travel for the laser beam is rotated by 90 degrees. This rotation, as illustrated in Figure 9, ensures that the beam will travel across the surface in the x-direction in creating the second feature pattern 930, exposing the surface to laser energy along transverse lines 940.
• first and second feature pattern parameters include the same pitch in the x-direction and the same pitch in the y-direction prior to pattern rotation
• the pitch of the second feature pattern in the x and y directions will be the opposite of x and y direction pitches of the first feature pattern.
• the rotation of the laser pattern by 90 degrees will cause the second feature pattern to include a pitch in the x-direction of 25 microns and a pitch in the y-direction of 20 microns.
• the surface may be rotated by, for example, 90 degrees relative to the laser beam to effectuate the same distinction in pattern parameters and/or feature spacing.
• the second feature pattern may include a mirror of the first feature pattern, in that the pitch of the second pattern in the x-direction is the same as the pitch of the first pattern in the y- direction, for example.
• the modification in the pitch of the first and second patterns can cause significant disruption of the engineered features.
• this disruption is caused by overlapping boundary regions of features that exceed an expected cross-sectional dimension (typically diameter).
• Disruption via substantial overlap between adjacent features can modify one or more characteristics of the features including, but not limited to depth, volume, curvature, slope, slope distribution and cross-sectional dimensions at the base.
• disruption of recesses can create protrusive features in interstitial space and within the recesses. As seen in Figures 14 and 21 and depending on the extent of overlapping regions between adjacent features, the resulting engineered surface may appear to include aperiodic features despite any periodic character of the selected first feature pattern.
• the disruption of features can reduce gloss and other expected optical features of the metal surface, as protrusive and intrusive features account for a greater degree of diffuse reflection.
• the disrupted structures may still be characterized, in certain implementations, by equivalent circular diameters (ECDs) in the reference plane and by mean heights relative to the average elevation.
• ECDs equivalent circular diameters
• substantial disruption may be effected with increased laser energy over the same ablation period.
• recesses in a first feature pattern may not substantial overlap at an average power of 2.25 W. If other pattern parameters are held constant and the power is increased to, for example, 3.9 W, adjacent recesses will substantially overlap at boundary regions due to higher energy at the substrate surface. The increased energy results in a recess with a larger expected cross-sectional dimension.
• a metal or other coating is to be included on the surface of the engineered features according to methods described below, it can be advantageous to increase the expected cross-sectional dimension to a dimension greater than desired in the end state.
• a thickness of coating may result in a filling in of certain recesses or features, essentially flattening the surface by reducing the depth and other characteristics of features. This behavior can be countered or otherwise accommodated by adjusting the laser pattern to increase the dimension of the engineered feature.
• (Wf) of the engineered feature after depositing a coating of thickness (t) can be at least roughly determined as follows, assuming a spherical engineered feature as a part of a circular segment, with the feature width defining a chord making a central angle ⁇ :
• Wi 2(R+t) sin(O.50)
• w f 2R sin(0.5 ⁇ )
• R df + 0.5 Wf cot(0.5 ⁇ )
• R + 1 di + 0.5 Wi cot(0.5 ⁇ )
• the initial width of the engineered recess should be 45 microns.
• the corresponding initial depth if the final depth of the engineered feature is 6.78 microns is 10.17 microns.
• laser energy is generated using a laser source such as, for example, a fiber laser.
• Laser ablation of an article surface 700 can be carried out using a laser system as depicted in Figure 7.
• the system 600 includes a laser source 602, a laser beam delivery fiber 604, and a controller 608.
• the laser source 602 is configured to generate pulses of laser energy.
• a moveable scanner 605, typically an optical scanner, is configured to position the laser beam 610 relative to the target location.
• the laser delivery fiber 604 is optically coupled to the laser source 602, and is configured to direct the laser energy 610 generated by the laser source 602 through the scanner 605 to a targeted substrate.
• the controller 608 is configured to control the laser source 602 and the scanner 605 based on the output signal from patterning software or direct manipulation of the scanner or substrate position by a user.
• the laser source 602 may comprise one or more laser sources which are used to produce the laser energy.
• the system 600 may also comprise conventional components, such as a beam expander 614, to produce the laser beam having the desired focal spot size.
• the laser energy has a wavelength of approximately 532 nm (green).
• Other wavelengths of the laser energy 610 may also be used, such as laser energy having a wavelength of approximately 400-475 nm (blue), about 355 nm (near UV), or laser energy having a wavelength of approximately 1000-1100 nm (near IR). These and other wavelengths may be used for the laser beam 610 depending on geometries of the recesses or other features to be created in the substrate surface.
• the laser beam 610 generated by the laser source 602 is optically coupled to the laser beam delivery fiber 604 equipped with a conventional optical isolator 612.
• the laser beam delivery fiber 604 may further include any conventional optical components to shape and deliver the laser beam.
• the distal end of the laser fiber 604 may include optical components to discharge the laser energy 610 laterally (i.e., side -fire laser), along the axis of the laser fiber 604 (i.e., end-fire laser), or in another conventional manner.
• the laser beam 610 discharged from distal end of 616 the optical isolator 612 may be directed into the scanner port 620 via mirror 618, as depicted, when the optical isolator 612 is oriented substantially perpendicular to the axis of the port 620.
• Such a construction can, in certain circumstances, protect the optical isolator 612 from inadvertent collisions with other components of the system.
• the beam 610 may be discharged parallel to the axis of port 620.
• the controller 608 includes or has access via network to a software program to control scan parameters (e.g., speed, angle, etc.).
• the controller may include the LaserDESK® software program, available from SCANLAB America, St. Charles, IL.
• a first series of features is made along at least a portion of the metal surface (e.g., in the transverse direction) according to the selected initial spacing.
• the series may be created by holding the surface fixed and modifying the position of the laser beam or vice versa.
• a series of small recesses is created with the distance between consecutive recess dependent on the scan speed and the repetition rate of the laser.
• the series can form a linear array of recesses (as shown in Figure 8A) with a pitch between adjacent recesses in the array varying from the initial feature spacing depending on the laser beam parameters selected, particularly repetition rate and scan rate.
• a second series of recesses is created, with each recess spaced from the first according to the predetermined pitch in the y-direction.
• the creation of a third series of recesses is shown in Figure 8B. The creation of additional series is repeated until the first feature pattern is complete over the desired portion of the substrate surface.
• Recesses may be created in a sinusoidal, spiral, speckle, fractal, and myriad other patterns.
• the laser beam is aperiodically moved and fired relative to the surface.
• Additional feature patterns at least partially overlapping the first feature pattern may be created in steps 540-560, typically by modifying certain pattern parameters.
• the laser patterning process illustrated in Figure 6 only envisions the creation of two overlapping feature patterns, one skilled in the art will appreciate that any number of overlapping patterns may be created. For example, it is possible to create substantial disruption of the surface with three, four, six, and eight overlapping arrays and patterns of recesses.
• the orientation of the laser pattern i.e., relative position of the laser beam's path of travel
• the surface is modified (e.g., rotated) after the creation of each pattern.
• the focal point of the laser may be adjusted to a point below the surface of the target substrate. In certain implementations the focal point is at least 50 microns below the surface of the article. In other implementations, the focal point is about 200 microns below the surface. Adjusting the focal point below the surface of the substrate can increase the size of the recesses or other features created. In other embodiments, the focal point of the laser is adjusted to be at or slightly above the surface of the article.
• the creation of a pattern of microscale features can be performed in the presence of an assist gas.
• a generating gas used to perform the ablation may vary according to predetermined processing conditions, any one of argon (Ar), oxygen (O2) and nitrogen (N2), helium, carbon dioxide (CO2), or a mixed gas of at least two thereof can be used.
• an inert gas is used to minimize oxide formation on the ablated surface.
• an engineered surface can be formed by a variety of methods, including a variety of microreplication methods, including, but not limited to, casting, coating, and/or compressing techniques.
• the engineered surface can be created by at least one of (1) casting a molten thermoplastic using a tool having a first feature pattern, (2) coating of a fluid onto a tool having a first feature pattern, solidifying the fluid, and removing the resulting film, (3) passing a thermoplastic film through a nip roll to compress against a tool having a first feature pattern (i.e., embossing), and/or (4) contacting a solution or dispersion of a polymer in a volatile solvent to a tool having a first feature pattern and removing the solvent, e.g., by evaporation.
• the tool can be formed using any of a number of techniques known to those skilled in the art, selected depending in part upon the tool material and features of the desired topography.
• Illustrative techniques include etching (e.g., chemical etching, mechanical etching, or other ablative means such as laser ablation, electron beam, or reactive ion etching, etc., and combinations thereof), photolithography, stereolithography, micromachining, knurling (e.g., cutting knurling or acid enhanced knurling), scoring, cutting, etc., or combinations thereof.
• Alternative methods of forming an engineered surface include thermoplastic extrusion, pulsed electron beam ablation, curable fluid coating methods, and embossing thermoplastic layers, which can also be cured. Additional information regarding the substrate material and various processes for forming the engineered surface 110 can be found, for example, in Halverson et al., PCT Publication No. WO 2007/070310 and US Publication No. US 2007/0134784; US Publication No. US 2003/0235677 (Hanschen et al.); PCT Publication No. WO2004/000569 (Graham et al.); US Patent No. 6,386,699 (Ylitalo et al.); Johnston et al., US Publication No. US 2002/0128578 and US Patent Nos. US 6,420,622, US 6,867,342, US 7,223,364; and US Patent No. 7,309,519 (Scholz et al.).
• an aesthetic coating may be applied to an engineered surface of the present disclosure in order to further improve aesthetics.
• Suitable aesthetic coatings may be one of or mixture of at least two among silver (Ag), zinc (Zn), tin (Sn), indium (In), platinum (Pt), tungsten (W), nickel (Ni), chromium (Cr), aluminum (Al), palladium (Pd), gold (Au), and rhodium (Rh).
• a coating may be applied by any appropriate coating method, such as electroplating, sputtering, vapor deposition, spin coating, dip coating, roll-to-roll coating, or any other number of suitable methods.
• Suitable methods include those contemplated by International Publication No. WO2009/045036 (Kim), as well as the electroplating methods for aluminum discussed in Lemkuhl et al., The Principles and Techniques of Electrolytic Aluminum Deposition and Dissolution in Organoaluminum Electrolytes in Advances in Electrochemical Science and Engineering, 177-226 (3d. ed., Heinz Gerischer et al., 1994) and US Patent Nos. 4,101,386 and 4,948,475 (Dotzer et al.).
• electroplated aluminum deposited generally according to these methods may be provided in addition to or in lieu of engineered features on the orthodontic appliance or other article.
• Aesthetic metal coatings typically have a thickness in the range of about 0.1-50 microns, in some embodiments in the range of about 0.5-10 microns, and in yet other embodiments in the range of about 2- 3 microns.
• the aesthetic metal coating has a thickness of about 0.1 to 0.3 microns. Coatings having a nanoscale thickness may, in certain circumstances, more closely contour to the engineered features and result in less disruption of the desired optical effects.
• surface contaminants, such as oxides or nitrides, on the substrate are removed by a cleaning process before the aesthetic coating (e.g., noble metal) deposition process is initiated. Ion sputtering techniques may be used for the cleaning process.
• Oxides on the surface can be removed by reducing agents, such as solutions of strong acid salts or the acids themselves.
• Certain passive or non-platable surfaces such as stainless steel are rendered oxide free (activated) by hydrochloric acid.
• Shape memory alloys such as nickel-titanium alloys, can have their surfaces activated by reducing agents, e.g., ammonium bifluoride.
• the entire engineered surface can be plated by the techniques discussed above or specific areas of the engineered surface can be coated by a localized brush or small area plating device.
• the coating, once disposed on the engineered surface may be anodized, passivated, or protected by barrier film according to methods known in the art.
• Engineered surfaces of the present invention are suitable for use in myriad orthodontic and oral care applications.
• an orthodontic archwire is processed to include one or more engineered surfaces.
• An exemplary horizontal orthodontic archwire 1000 is shown in Figure 10 comprising a central curved portion 1020 and first and second end portions 1030, 1040 extending relative to opposing ends of central curved portion 1020.
• FIG. 11 A cross-sectional view of the archwire 1000 is illustrated in Figure 11.
• the cross-sectional shape shown in FIG. 11 is typical of the cross-sectional shape of the archwire 1000 along its entire length.
• the archwire may, for example, have a generally rectangular cross-sectional shape, a circular cross-sectional shape, or an ovoid cross-sectional shape, though it will be appreciated that other cross-sectional configurations are possible.
• the cross-sectional shape of the archwire 1000 is typically substantially uniform along its entire length. However, other embodiments are possible, such as archwires wherein the cross-sectional shape of the archwire varies from one portion to the next along the length of the archwire.
• the occlusal side 1014 and the gingival side 1018 are generally flat and parallel to each other, and the buccolabial side 1012 and the lingual side 1016 are flat and parallel to each other.
• the distance between the sides 1014, 1018 is typically selected to matingly fit within an archwire slot or passage of an orthodontic appliance such as a bracket or buccal tube. It will be appreciated by those skilled in the art that the identification of the occlusal and gingival sides will depend on whether the archwire is installed on the upper or lower dental arch.
• all four sides are ablated or otherwise treated to include an engineered surface.
• only three sides include an aesthetic, engineered surface.
• only the buccolabial 1012, occlusal 1014, and gingival sides 1018 may include an engineered surface, with the lingual surface 1016 untreated.
• only the buccolabial surface 1012 is treated to include the engineered surfaces of the present disclosure,
• only the central portion 1020 includes the engineered surfaces of the present disclosure. In other embodiments, the central portion 1020 and one or both the end portions 1030, 1040 include engineered surfaces.
• an engineered surface may be created on myriad dental and orthodontic components, including but not limited to orthodontic brackets, buccal tubes, archwire slot liners, self- ligating clips and other latches, restoratives, replacements, inlays, onlays, veneers, full and partial crowns, bridges, implants, implant abutments, copings, anterior fillings, posterior fillings, and cavity liners, and bridge frameworks.
• dental and orthodontic components including but not limited to orthodontic brackets, buccal tubes, archwire slot liners, self- ligating clips and other latches, restoratives, replacements, inlays, onlays, veneers, full and partial crowns, bridges, implants, implant abutments, copings, anterior fillings, posterior fillings, and cavity liners, and bridge frameworks.
• An orthodontic appliance comprising:
• each recess of the plurality of recesses includes a base having a cross-sectional dimension, and wherein the dimension is at least 5 and no greater than 60 microns.
• the cross-sectional dimension includes a diameter, and wherein the diameter is at least 20 and no greater than 40 microns.
• each well includes a base at least partially defined by the surface, and wherein each base includes a greatest dimension of at least 20 microns and no greater than 50 microns.
• the appliance comprises a base and a body extending outwardly from the base, the body defining an elongated slot, and wherein the engineered surface is disposed on at least a portion of the body.
• An appliance comprising: a body having an exterior surface including metal; and a plurality of engineered features on the surface, the surface exhibiting a diffuse L* min70/maxl5 ratio of at least 0.2 at a Total CIE Chroma of less than 14, a minimum L* value of at least 20 at an incident angle of 0 degrees and a view angle of 70 degrees, as measured by the Diffuse Scattering Test.
• An appliance comprising; an exterior surface including a metal; a plurality of recesses defined in the surface, each recess having a depth from the surface of at least 0.5 microns, wherein the recesses are arranged in overlapping arrays such that a majority of the recesses overlap with adjacent recesses at boundary regions.
• a method for improving the aesthetic appearance of an article comprising: providing an article having an exterior surface, the surface including metal; ablating at least a portion of the surface to create a plurality of features thereon, such that the surface exhibits a diffuse L* min70/maxl5 ratio of at least 0.2, as measured by the Diffuse Scattering Test.
• ablating at least a portion of the surface includes creating a first pattern of recesses, the first pattern having a pitch between adjacent recesses in the array of at least 10 microns and no greater than 100 microns.
• ablating a portion of the surface further includes creating a series of recesses according to a second pattern, wherein the second pattern is substantially similar to the first pattern.
• ablating the surface comprises periodically exposing the surface to the beam of a laser.
• ablating the surface includes selecting a focal point for a laser relative to the surface, and wherein the focal point is above or below the surface of the article.
• ablating the surface includes creating a first pattern of features in a first array over at least a portion of the surface, and disrupting a portion of the first pattern, such that the geometric dimension of at least two recesses of the first pattern is changed.
• disrupting a portion of the first pattern comprises creating a second pattern of features in a second array, wherein the second pattern of features is offset from the first pattern and wherein the features of the second array at least partially overlap with features of the first array.
• ablating the surface comprises periodically exposing the surface to laser energy at a first pattern orientation; modifying the laser path of travel relative to the surface to define a second pattern orientation; and periodically exposing the surface to laser energy at the second pattern orientation.
• the metal includes at least one of stainless steel, aluminum, titanium, beta-titanium, nickel titanium, and alloys thereof.
• the surface exhibits a diffuse L* min70/maxl5 ratio of at least 0.2, and a minimum L* value of at least 20 an incident angle of 0 degrees and a view angle of 70 degrees, as measured by the Diffuse Scattering Test.
• An orthodontic appliance comprising:
• the orthodontic appliance of embodiment 73 wherein the appliance is an orthodontic archwire.
• the electroplated metal coating comprises at least one of aluminum and rhodium.
• the laser beam was directed to a commercially available 2D galvo laser scanner head (hurrySCAN® 20, available from ScanLab America, Inc., Naperville, IL) equipped with a 100 mm telecentric f-theta focusing lens.
• the scanner was mounted to a 3D gantry system (available from Aerotech, Inc., Pittsburg, PA) to enable positioning in the X, Y, and Z directions in the laser patterning process further described below.
• An exhaust system (FA-2, available from Fumex, Inc., Kennesaw, GA) was used to minimize contamination of the work area with local debris.
• a local assist gas of compressed nitrogen (volumetric flow rate of -140 L/min) was used to prevent oxidation of the laser patterned surface (particularly at higher laser powers) as well as to keep local debris from entering the work area.
• the beam was expanded with a 7x beam expander enlarging the beam diameter from approximately 1.1 mm to approximately 7.7 mm before entering the scanner.
• Images of the processed substrates were recorded with a microscope (VHX-2000, available from Keyence Corp., Itasca, IL) capable of high magnification and microscopic measurements.
• a block diagram of the fiber laser system is shown in Figure 7. Substrates
• Rectangular, metal shim stock coupons ( ⁇ 0.33-0.39 mm x -12.7 mm x -50.8 mm) of 304 and 316 stainless steel ("304SS” and "316SS", available from Xylem Co., Inc., Chanhassen, MN) or nitinol ("NiTi", Nitinol Devices & Components, Inc., Fremont, CA) were used as substrates in the laser patterning experiments.
• the substrates were clamped to the process platform via a magnetic chuck prior to laser patterning.
• a small square portion (-10 mm X 10 mm) of the coupon was patterned according to parameters outlined below. After patterning, the substrates were cleaned in an ultrasonic acid bath.
• Examples SI, S3-S7, S10 and S12 employed NiTi or 304SS coupons as substrates.
• the substrates were laser patterned with a series of approximately parallel "lines” using LaserDESK software (ScanLab AG) to design the pattern, with each "line” being composed of a linear series of concave- shaped features on the patterned surface.
• An illustration of such "lines” extending in the transverse direction on an article surface is shown in Figure 8 A.
• the distance between adjacent features within a given "line” was a function of both the scan speed and the repetition rate of the laser.
• the relationship between the scan speed of the laser beam, repetition rate, and the distance between adjacent features is shown in Equation 5, where v is the scan speed, d is the feature-to-feature distance, and/is the laser repetition rate.
• Figure 8 A shows a lOOOx magnified image of a 304SS surface patterned with a single line (i.e., series) of recesses created using the 40 W fiber laser at 2.25 W, with a line scan speed of 1 m/s a repetition rate of 30 kHz, and a waveform of 0 (pulse duration -250 ns). From the experimentally determined feature size, various feature-to-feature distances were evaluated for their effect on the optical characteristics of the patterned surface.
• Two pass patterns were created on the 304SS and NiTi coupons of Examples S2, S8, S9, SI 1, and S13 as follows.
• a -10 mm X 10 mm portion of each Example substrate was patterned with as series of parallel lines, the laser pattern rotated by 90°, and the patterning process repeated over the same -10 mm X 10 mm portion.
• Figure 9 illustrates a two pass patterning sequence, with a 90° rotation of the laser pattern between passes (only the engineered portion of the substrate is illustrated).
• the initial "lines" 920 of the first feature pattern 910 extend in the longitudinal direction on an article surface 900 prior to rotation.
• the series of "lines" 940 of the second pattern 930 extend in the transverse direction.
• a spacing ratio was selected and the corresponding feature-to-feature distance was calculated depending on the desired pitch and a scan speed arrived at by multiplying by the repetition rate of the laser shown in Equation 5.
• a spacing ratio of 1.1 and pitch of 30 ⁇ are used in the calculations shown below:
• the LaserDESK software used to control the scanner included pertinent parameters such as scan speed, pitch, laser delays, and jump speeds between scanning, with the pitch and derived scan speed as the variable inputs.
• Feature size e.g., diameter, ECD, and depth
• Feature size can be varied according to the power of the laser.
• neighboring features are so closely packed, that noticeable interference (i.e., overlapping feature boundary regions) is evident, shrinking the effective feature diameter or ECD.
• Table 3 shows a summary of the samples S1-S21 tested during the course of experiments. All patterned samples included a spacing ratio of 1.1 : 1. Pitch in the x-direction of the first pattern is reported first in Table 3. Table 3: Samples SI -SI 8
• the patterned substrates were further subjected to a metal coating process (after ultrasonic cleaning) to further enhance optical and other qualities.
• Aluminum (Al) coatings (-75 nm or -150 nm thickness) were applied to selected patterned substrates (S10-S17) using an e- beam/thermal evaporator (K. J. Lesker Co., Jefferson Hills, PA). Aluminum was deposited at a rate of 15 angstroms per second in the absence of an external gas at a chamber pressure of approximately 3 x 10 ⁇ 5 Torr.
• Aluminum (AL) coatings (-5-20 ⁇ thickness) were applied to unpatterned substrates (S19-S21) using electroplating methods generally described in Lemkuhl et al., The Principles and Techniques of Electrolytic Aluminum Deposition and Dissolution in Organoaluminum Electrolytes in Advances in Electrochemical Science and Engineering, 111, 204-211 (3d. ed., Heinz Gerischer et al., 1994), as well as US Patent Nos. 4,101,386 and 4,948,475 (Dotzer et al.). Rhodium (Rh) coatings (-0.4-2.0 ⁇ thickness) were also applied via conventional electroplating (Prodigy Surface Tech., Santa Clara, CA). Optical Measurements
• Gloss is the ability of a surface to reflect visible light in specular directions. Gloss measurements were made using a Novo-Curve Gloss Meter (Rhopoint Instruments, East Canal, UK) at an incident angle of 60 degrees and conformed to standard test methods (ASTM D523, ISO 2813, DIN 67530, and JIS Z 8741). Reported results are an average of two measurements for given sample, with the sample being rotated 90 degrees between measurements. Diffuse Scattering Test
• BRDF Color bidirectional scattering distribution function
• BRDFs were measured for each sample at an incidence angle of 0° with specular light excluded. Color measurements were made based on the Commission Internationale de l'Eclairage L*a*b* scoring system. The CIE L* and total CIE chroma were calculated along the vertical and horizontal cross sections of the 0° incidence BRDFs. The total CIE chroma is equal to the root mean square of the total CIE a* and total CIE b* and is the distance in color space from the L* axis. It represents the color saturation; a zero chroma has no color. A perfect Lambertian reflector was chosen to be the reference white which has a BRDF equal to l/ ⁇ for all incidence and scattered (i.e., view) angles.
• the minimum and maximum CIE L* were also calculated as a function of view angle.
• CIE L* can vary as a function of azimuthal angle.
• the minimum and maximum CIE L* were accordingly calculated over all the azimuthal angles for each given view angle. Note that because the measured CIE L* is only for a specific view angle, it is possible for it to be greater than 100. Due to asymmetry in the scatter pattern, it was instructive to look at the minimum and maximum CIE L* as a function of view angle instead of a total integrated value.
• samples were characterized using confocal scanning laser microscopy (50X objective).
• a Keyence VK-9710 (available from Keyence Corporation of America, Itasca, IL) was used for samples SI -SI 7 with the following settings: Real Peak Detection (RPD): on Mode: surface profile; Area: plane; Quality: super fine; Objective: 50X and 150X ;Optical Zoom: 1.0 X; Tiling: 2x2.
• RPD Real Peak Detection
• a Keyence VK-X200 was used with the same setting for samples S19-S21.Two height profiles were obtained for each sample. Whenever possible, fields of view were chosen to give a good sampling of the topography. Slope analyses were applied to the surface height profiles. MATLAB software (Math Works, Natick, MA) was used to calculate the slope distribution.
• Average x-slope and y-slope were evaluated in a 1.65 micron interval about each pixel.
• Gradient magnitude was determined from x and y slope data, andevaluated in a 1.65 ⁇ x 1.65 ⁇ box centered at each pixel.
• Gradient magnitude distribution, as well as x-slope and y-slope distribution were generated within a bin size of 0.5 degrees.
• Table 4 shows the Total CIE Chroma, as well as the minimum L* for scatter angle of 70° (Lmin70) and ratio of the minimum L* for scatter angle of 70° to maximum L* for Scatter Angle of 15° (Lmin70/Lmaxl5), each at incidence angle of 0°, for samples S1-S21.
• Table 6 shows gloss measurements for Samples S1-S9 & S12-S18.
• Laser patterned 304SS and NiTi orthodontic archwire prototypes were prepared as follows. Similar lengths of straight rectangular wires (304SS or NiTi, 0.46 mm x 0.64 mm x -180-250 mm) were ganged together and attached to a flat substrate, such that the sidewalls of adjacent wires were in contact. The rectangular wires were oriented such that each surface to be patterned for each wire was at the same height relative to the focal spot position of the laser beam (stated another way, the collective surface of the ganged rectangular wires to be patterned was substantially flat).
• a -10 mm X 10 mm portion of the surface the ganged wired assembly was laser patterned with 2 passes, at 30 um pitch, and 3.25 W (rotating the patternby 90° between passes), in a similar fashion as previously described.
• the ganged wire assembly was then moved (translated) and the laser patterning repeated over an adjacent unpatterned region, such that adjacent -10 mm X 10 mmpatterns overlapped by -40 ⁇ . Additional surfaces of the rectangular archwires were patterned simply by removing the wires from the flat substrate, rotating the wires by 90° to expose a new surface, re -ganging the wires, reattaching the ganged wires to the flat substrate, and repeating the patterning.
• Patterned, rectangular 304SS wires were hand- shaped to a suitable arch form for an orthodontic archwire.
• Patterned, rectangular NiTi wires may be shape set to an arch form at elevated temperatures, using conventional methods.
• fully 360° patterned, NiTi round wires (0.46 mm) were prepared in a similar fashion as described for NiTi rectangular wires, except that the wires were rotated by -120° to expose a new, unpatterned surface (and repeating the patterning).

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