Patent Abstract:
The present invention is a method that (i) allows for creating micro and/or nanostructures on either planar or non-planar three-dimensional surfaces in a single molding step, and (ii) allows for the molded production of complex high-aspect ratio micro and/or nanostructures including but not limited to cylinders, conical structures, low aspect-ratio channels, bumps, or posts. An example of such a complex structure are high aspect ratio pillars with enlarged “mushroom-shaped” or undercut tips which demonstrate enhanced, repeatable adhesion and shear strength on a variety of substrates when compared with other micro and/or nanostructures and unstructured materials. The mold of such a material requires an “undercut” feature that cannot be produced using typical micro/nano-molding processing techniques.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a 35 U.S.C. 371 US national phase application of PCT international application s/n PCT/US2012/033583, filed on Apr. 13, 2012, and is herein incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention is related generally to the method steps of three dimensional molding, and in particular to a process of molding simple or complex micro and/or nanopatterned features on a wide array of molded objects and both planar and non-planar surfaces. It also relates to the molded objects and surfaces resulting from these method steps as well as the molded objects produced with micro and/or nanopatterned features. 
       BACKGROUND OF THE INVENTION 
       [0003]    There is a need in the current technology to incorporate simple or complex micro and/or nanoscale structures on surfaces of many different mass-produced molded parts. One example application of this invention is in the area of mass-production of solar panel clamping brackets with biologically-inspired adhesive microfibers on the glass-contacting surface to simplify the assembly of solar panel racking systems and improve their clamping ability with respect to non micropatterned alternative products. Incorporating biologically-inspired adhesive surfaces on molded parts may have a broader range of applications in the healthcare, defense, apparel, sporting good, and household good industries. For example, highly adhesive surfaces can be incorporated into the skin-contacting interfaces of sleep apnea masks or personal safety masks to improve the seal of the mask to the face and improve customer satisfaction or safety when using the products. Beyond the range of geometries of biologically-inspired fibrillar adhesives, this invention may be used to apply different micro and/or nanoscale structures to products which have applications in optics, fog resistance, pressure sensing, tissue engineering, microfluidics, and other applications known to those familiar in this field which could benefit from micro and/or nanoscale patterning. 
       SUMMARY OF THE INVENTION 
       [0004]    There are two primary advantages of the present invention when compared with present technology of molding simple or complex micro and/or nanopatterned features on both planar or non-planar molded objects and surfaces. The first is that it allows for creating micro and/or nanostructures on either planar or non-planar three-dimensional surfaces in a single molding step, eliminating the need for secondary manufacturing processes after the part is removed from the mold. The second advantage is that it allows for the molded production of complex high-aspect ratio micro and/or nanostructures, not merely cylinders, conical structures, low aspect-ratio channels, bumps, or posts. An example of such a complex structure are high aspect ratio pillars with enlarged “mushroom-shaped” tips which demonstrate enhanced, repeatable adhesion and shear strength on a variety of substrates when compared with other micro and/or nanostructures and unstructured materials. The mold of such a material requires an “undercut” feature that cannot be produced using existing mass production micro/nano-molding techniques. 
         [0005]    The present invention can be applied to fabricating micro and/or nanopatterned surfaces to enhance adhesion and friction for a variety of three dimensional injection molded products, including industrial clamps, skin contacting surfaces in the healthcare, personal safety, defense, and cosmetics industries, tissue contacting surfaces for medical device applications, materials to replace traditional “hook and loop” closures for clothing and sports apparel, athletic gloves for enhanced grip for activities like football, soccer, rock climbing, golf, and baseball. Future applications may extend beyond adhesive applications to the fabrication of micro- or nano-electronic devices, micro/nano sensors, tissue engineering scaffolds, etc. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    For the present invention to be easily understood and readily practiced, the invention will now be described, for the purposes of illustration and not limitation, in conjunction with the following figures, wherein: 
           [0007]      FIG. 1  are illustrations of the mold fabrication process of the present invention; and 
           [0008]      FIGS. 2A-G  are pictorial representations of embodiments of the present invention to fabricate a product with micro and/or nanopatterned features. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0009]    The present invention describes a process to incorporate simple or complex, three-dimensional, high aspect ratio micro and/or nanopatterned features onto surfaces of small batch or mass-produced molded parts, which includes: (1) a method for replicating micro and/or nanostructures fabricated through well-established micro/nanofabrication techniques onto thin, flexible, compliant backings; (2) a method to incorporate the patterned micro and/or nanostructures onto planar or non-planar surfaces of a molding tool with an additional surface modification molding step performed on the tool; (3) A molded part which incorporates micro and/or nanopatterned features produced using a tool modified through step (2) above. With the present invention, mass-production of injection molded parts with planar or non-planar surfaces patterned with either simple or complex, high-aspect ratio micro and/or nanostructures in a single step at extremely low cost becomes possible. Micro and/or Nanopatterned features means a cluster or grouping of multiple micro and/or nanoscale elements in a predetermined arrangement. Various patterned embodiments can be configured where adjacent sections of clustered groups can have different patterns of varying element characteristic lengths, element characteristic outer diameters, and characteristic recess or void depths and widths. The term “characteristic” refers to a representative length, diameter, depth or width where the feature may not have uniform dimensions. For example, an elliptical cross-section is non-circular but it can have a characteristic diameter determined by well known mathematical expressions. 
         [0010]    The application refers to the following terms, words, and phrases that have particular meaning with regards to the present invention. A geometric feature being micro or microscale means that at least one of the characteristic lengths of the feature in any 3D direction should be between 0.5-500 micrometers in length. Micropatterned surfaces are surfaces which have at least one microscale feature on them. A geometric feature being nano or nanoscale means that at least one of the characteristic lengths of the feature in any 3D direction should be between 0.2-500 nanometers in length. Nanopatterned surfaces are surfaces which have at least one nanoscale feature on them. Micro and nanopatterned surfaces refer to surfaces with any combination and quantity of microscale (0.5-500 micrometers in length) and nanoscale (0.2-500 nanometers in length) features on them. The characteristic diameters of the micro and nanopatterned features can range from 0.2-500 micrometers and 0.2-500 nanometers for microscale and nanoscale features, respectively. Therefore, surfaces of the present invention can contain only microscale features, only nanoscale features, or both microscale and nanoscale features. 
         [0011]    Though injection molding is described herein as one possible approach to manufacturing the molded part, other molding approaches include, but are not limited to, compression molding, blow molding, vacuum molding, extrusion molding, injection compression molding, extrusion compression molding, rotational molding, thermoforming, casting, pultruding, stamping, forging, or any combination thereof. 
         [0012]      FIG. 1  shows the steps to replicate micro and/or nanostructures onto a rigid  12 A or compliant  12 B backing material. The first step in the process is to start with the base material  10  with actual micro and/or nanoscale features that are to be produced on molded parts  14 A (on a planar molded surface),  14 B (on a non-planar molded surface) using one of the molding processes described below, but not limited to: 
         [0013]    A. Injection molding: Injection over molding, Co-injection molding, Gas assist injection molding, Tandem injection molding, Ram injection molding, Micro-injection molding, Vibration assisted molding, Multiline molding, Counter flow molding, Gas counter flow molding, Melt counter flow molding, Structural foam molding, Injection-compression molding, Oscillatory molding of optical compact disks, Continuous injection molding, Reaction injection molding (Liquid injection molding, Soluble core molding, Insert molding), and Vacuum Molding; 
         [0014]    B. Compression molding: Transfer molding, and Insert molding; 
         [0015]    C. Thermoforming: Pressure forming, Laminated sheet forming, Twin sheet thermoforming, and Interdigitation; 
         [0016]    D. Casting: Encapsulation, Potting, and impregnation; 
         [0017]    E. Coating Processes: Spray coating, Powder coatings, Vacuum coatings, Microencapsulation coatings, Electrode position coatings, Floc coatings, and Dip coating; 
         [0018]    F. Blow molding: Injection blow molding, Stretch blow molding, and Extrusion blow molding; 
         [0019]    F. Vinyl Dispersions: Dip molding, Dip coatings, Slush molding, Spray coatings, Screened inks, and Hot melts; and 
         [0020]    G. Composite manufacturing techniques involving molds: Autoclave processing, Bag molding, Hand lay up, and Matched metal compression. 
         [0021]    The second step is to attach bottom surface  11  of starting material  10  described in step 1 onto a rigid planar backing  12 A or flexible backing  12 B to form product  18 A,  18 B, such that the actual micro and/or nanoscale features  10 A are facing outward opposing the backing  12 A,  12 B. 
         [0022]    The third step is to prepare planar  16 A or non-planar  16 B tool surface of tooling  17 A,  17 B using one of the methods described below, but not limited to: 
         [0023]    A. Plasma treatment; 
         [0024]    B. Silane adhesion promoters and coupling agents; 
         [0025]    C. Acid etching; 
         [0026]    D. Mechanical abrasion; 
         [0027]    E. Chlorinated polypropylene treatment, and 
         [0028]    F. No treatment necessary 
         [0029]    Another embodiment of the present invention includes a tool surface that is partially planar and partially non-planar (not shown). 
         [0030]    If initial material described in step 1 is rigid and patterning is being performed on a non-planar surface, it will be necessary to first replicate it using one or more molding steps to reproduce the material with micro and/or nanoscale features from a compliant material listed below; as well as binding materials from Step 2 will also need to be compliant: 
       A. Thermosets: 
       [0031]    i. Formaldehyde Resins (PF, RF, CF, XF, FF, MF, UF, MUF); 
         [0032]    ii. Polyurethanes (PU); 
         [0033]    iii. Unsaturated Polyester Resins (UP); 
         [0034]    iv. Vinylester Resins (VE), Phenacrylate Resins, Vinylester Urethanes (VU); 
         [0035]    v. Epoxy Resins (EP); 
         [0036]    vi. Diallyl Phthalate Resins, Allyl Esters (PDAP); 
         [0037]    vii. Silicone Resins (Si); and 
         [0038]    viii. Rubbers: R-Rubbers (NR, IR, BR, CR, SBR, NBR, NCR, IIR, PNR, SIR, TOR, HNBR), M-Rubbers (EPM, EPDM, AECM, EAM, CSM, CM, ACM, ABM, ANM, FKM, FPM, FFKM), O-Rubbers (CO, ECO, ETER, PO), Q-(Silicone) Rubber (MQ, MPQ, MVQ, PVMQ, MFQ, MVFQ), T-Rubber (TM, ET, TCF), U-Rubbers (AFMU, EU, AU) Text, and Polyphosphazenes (PNF, FZ, PZ) 
       B. Thermoplastics 
       [0039]    i. Polyolefins (PO), Polyolefin Derivates, and Copoplymers: Standard Polyethylene Homo- and Copolymers (PE-LD, PE-HD, PE-HD-HMW, PE-HD-UHMW, PE-LLD); Polyethylene Derivates (PE-X, PE+PSAC); Chlorinated and Chloro-Sulfonated PE (PE-C, CSM); Ethylene Copolymers (ULDPE, EVAC, EVAL, EEAK, EB, EBA, EMA, EAA, E/P, EIM, COC, ECB, ETFE; Polypropylene Homopolymers (PP, H-PP) 
         [0040]    ii. Polypropylene Copoplymers and -Derivates, Blends (PP-C, PP-B, EPDM, PP+EPDM) 
         [0041]    iii. Polybutene (PB, PIB) 
         [0042]    iv. Higher Poly-α-Olefins (PMP, PDCPD) 
         [0043]    v. Styrene Polymers: Polystyrene, Homopolymers (PS, PMS); Polystyrene, Copoplymers, Blends; Polystyrene Foams (PS-E, XPS) 
         [0044]    vi. Vinyl Polymers: Rigid Polyvinylchloride Homopolymers (PVC-U); Plasticized (Soft) Polyvinylchloride (PVC-P); Polyvinylchloride: Copolymers and Blends; Polyvinylchloride: Pastes, Plastisols, Organosols; Vinyl Polymers, other Homo- and Copolymers (PVDC, PVAC, PVAL, PVME, PVB, PVK, PVP) 
         [0045]    vii. Fluoropolymers: FluoroHomopolymers (PTFE, PVDF, PVF, PCTFE); Fluoro Copolymers and Elastomers (ECTFE, ETFE, FEP, TFEP, PFA, PTFEAF, TFEHFPVDF (THV), [FKM, FPM, FFKM]) 
         [0046]    viii. Polyacryl- and Methacryl Copolymers 
         [0047]    ix. Polyacrylate, Homo- and Copolymers (PAA, PAN, PMA, ANBA, ANMA) 
         [0048]    x. Polymethacrylates, Homo- and Copolymers (PMMA, AMMA, MABS, MBS) 
         [0049]    xi. Polymethacrylate, Modifications and Blends (PMMI, PMMA-HI, MMA-EML Copolymers, PMMA+ABS Blends 
         [0050]    xii. Polyoxymethylene, Polyacetal Resins, Polyformaldehyde (POM): Polyoxymethylene Homo- and Copolymers (POM-H, POM-Cop.); Polyoxymethylene, Modifications and Blends (POM+PUR) 
         [0051]    xiii. Polyamides (PA): Polyamide Homopolymers (AB and AA/BB Polymers) (PA6, 11, 12, 46, 66, 69, 610, 612, PA 7, 8, 9, 1313, 613); Polyamide Copolymers, PA 66/6, PA 6/12, PA 66/6/610 Blends (PA+: ABS, EPDM, EVA, PPS, PPE, Rubber); Polyamides, Special Polymers (PA NDT/INDT [PA 6-3-t], PAPACM 12, PA 6-I, PA MXD6 [PARA], PA 6-T, PA PDA-T, PA 6-6-T, PA 6-G, PA 12-G, TPA-EE); Cast Polyamides (PA 6-C, PA 12-C); Polyamide for Reaction Injection Molding (PA-RIM); Aromatic Polyamides, Aramides (PMPI, PPTA) 
         [0052]    xiv. Aromatic (Saturated) Polyesters: Polycarbonate (PC); Polyesters of Therephthalic Acids, Blends, Block Copolymers; Polyesters of Aromatic Diols and Carboxylic Acids (PAR, PBN, PEN) 
         [0053]    xv. Aromatic Polysulfides and Polysulfones (PPS, PSU, PES, PPSU, PSU+ABS): Polyphenylene Sulfide (PPS); Polyarylsulfone (PSU, PSU+ABS, PES, PPSU) 
         [0054]    xvi. Aromatic Polyether, Polyphenylene Ether, and Blends (PPE): Polyphenylene Ether (PPE); Polyphenylene Ether Blends 
         [0055]    xvii. Aliphatic Polyester (Polyglycols) (PEOX, PPDX, PTHF) 
         [0056]    xviii. Aromatic Polyimide (PI): Thermosetting Polyimide (PI, PBMI, PBI, PBO, and others); Thermoplastic Polyimides (PAI, PEI, PISO, PMI, PMMI, PESI, PARI); 
         [0057]    xix. Liquid Crystalline Polymers (LCP) 
         [0058]    xx. Ladder Polymers: Two-Dimensional Polyaromates and—Heterocyclenes: Linear Polyarylenes; Poly-p-Xylylenes (Parylenes); Poly-p-Hydroxybenzoate (Ekonol); Polyimidazopyrrolone, Pyrone; Polycyclone 
         [0059]    xxi. Biopolymers, Naturally Occurring Polymers and Derivates: Cellulose- and Starch Derivates (CA, CTA, CAP, CAB, CN, EC, MC, CMC, CH, VF, PSAC); 2 Casein Polymers, Casein Formaldehyde, Artificial Horn (CS, CSF); 
         [0060]    Polylactide, Polylactic Acid (PLA); Polytriglyceride Resins (PTP®); xix. Photodegradable, Biodegradable, and Water Soluble Polymers; 
         [0061]    xxii. Conductive/Luminescent Polymers; 
         [0062]    xxiii. Aliphatic Polyketones (PK); 
         [0063]    xxiv. Polymer Ceramics, Polysilicooxoaluminate (PSIOA); 
         [0064]    xxv. Thermoplastic Elastomers (TPE): Copolyamides (TPA), Copolyester (TPC), Polyolefin Elastomers (TPO), Polystyrene Thermoplastic Elastomers (TPS), Polyurethane Elastomers (TPU), Polyolefin Blends with Crosslinked Rubber (TPV), and Other TPE, TPZ; and 
         [0065]    xxvi. Other materials known to those familiar with the art 
         [0066]    The fourth step is to add liquid tool insert material  20 A,  20 B (see possible materials in listed above for step 3 to planar  16 A or non-planar  16 B tool surface. 
         [0067]    The fifth step is to press the product  18 A,  18 B of Step 2 into tool insert material  20 A,  20 B of Step 4 and allow to cure. 
         [0068]    The sixth step is to remove product  18 A,  18 B of Step 2 from tool insert material  20 A,  20 B for final tooling  17 A,  17 B which now has a mold surface  22 A,  22 B with the negative micro and/or nanoscale features  19 A,  19 B of the micro/nanoscale features  10 A. Herein, a negative feature is a defined as an opposite of an actual feature, such as a recess, cavity or void in a negative mold is a negative feature of a structure that projects from a surface of an actual part or product. Whereas, a structure that projects from a surface of a negative mold is a negative feature of a recess, cavity or void in an actual part or product. 
         [0069]    The seventh step is to mold tool  17 A,  17 B produced by step 6 with a moldable part material (see above materials list for step 3). The product  14 A,  14 B of this step is a molded part with micro and/or nanoscale features  24  on one or more planar surfaces or non-planar surfaces. 
         [0070]    Another embodiment of the present invention includes a tool surface of the molding tool having a plurality of sections (not shown). Each section of the plurality of sections includes negative micro and/or nanopatterned features having different characteristics than an adjacent section of the plurality of sections. The different characteristics include but are not limited to a recess depth, a recess inner diameter, a projection length, and a projection outer diameter. 
         [0071]    Another embodiment of the present invention includes a removable tool insert of the molding tool having one or more planar or non-planar surfaces where at least one of these planar or non-planar surfaces includes negative micro and/or nanopatterned features produced using steps 1-6 above. This removable tool insert can be interchanged with different tool inserts with different negative micro and/or nanopatterned features should a production run require quantities of parts with various micro and/or nanopatterned features. Alternatively, these inserts may be transferred to different production sites, or to different partners or customers without transferring or being responsible for the entire molding tool. 
         [0072]    Now turning to  FIGS. 2A-C  illustrating the incorporation of the micro and/or nanopatterned negative mold surface  114  into an injection molding tool. An injection molding tool with the desired part geometry, such as mold part  120 , can be fabricated from any existing tool manufacturing process such as but not limited to machining, rapid prototyping, or clamshell molding.  FIG. 2A  illustrates an injection molding tool using clamshell molding halves  116 ,  118  to produce molded part  120 . Next, the micro and/or nanopatterned geometry  108  of master template  110  are incorporated into the micro and/or nanopatterned negative mold surface  114  using the process illustrated in  FIG. 2B . The micro and/or nanopatterned negative mold surface  114  starts as a curable molding liquid such as (but not limited to) a silicone rubber or epoxy used to coat the bottom surface  124  of the bottom half of the injection molding tool  116 . Additives such as (but not limited to) primers, silanes, etc., may be used to treat the coated surface  124  to improve the binding of the curable molding liquid to the bottom half of the injection molding tool  116 . Next, the bottom surface  122  of master template  110  containing micro and/or nanopatterned geometry  108  is pressed into the curable molding liquid and a rigid backing holds the entire system in place as it cures. After curing, the rigid backing and bottom surface  122  are peeled from the bottom half injection molding  116  resulting in the final mold illustrated in  FIG. 2C . Here, the molded surface of flexible negative mold  114  is patterned with the negative (female) micro and/or nanopatterned geometry. During molding with top half mold  118  in place, a molding liquid (not shown) is injected into cavity  115  to flow over and into flexible negative mold  114  to produce molded part  120  (see  FIG. 2D ). This injection molding process is able to be incorporated into large scale geometry of the tool to mass produce molded part  120  with micro and/or nanopatterned geometry  126 . 
         [0073]    Now turning to  FIGS. 2E-G  that illustrate uniform and non-uniform cross-sectional areas over predetermined lengths of a replicated micro and/or nanopatterned feature  128  of replicated micro and/or nanopatterned geometry  126 . Each replicated micro and/or nanoscale feature of the plurality of replicated micro and/or nanoscale features  126  comprise a predetermined length L having (i) a replicated tip  130  at a distal end  136  of the replicated feature  128 , (ii) a replicated base  132  at a proximal end  138  of the replicated feature  128 , and (iii) a plurality of replicated cross-sectional areas (see below) along the replicated feature predetermined length L.  FIG. 2E  illustrates one embodiment of the replicated feature  128  of replicated micro and/or nanopatterned geometry  126  having a uniform (only one) cross-sectional area A along the entire length L having a replicated flat tip  130  and a replicated base  132 , wherein replicated base  132  is attached to backing layer  134 .  FIG. 2F  illustrates another replicated feature stem  128  of replicated micro and/or nanopatterned geometry  126  has a substantially uniform (only one) cross-sectional area A 1  over replicated feature mid-section length L 1 , and substantially non-uniform cross-sectional Areas A 2  and A 3  over replicated fiber end lengths L 2  (tip transition) and L 3  (base transition), respectively. The present invention is not to be limited to three distinction sections (tip transition, mid-section, and base transition), but as illustrations of one possible embodiment.  FIG. 2G  illustrates another embodiment of the present invention can include varying cross-sectional areas (A 4 , A 5 , A 6 , A 7 ) within length L 1  (corresponding to segment lengths L 4 , L 5 , L 6 , L 7 , L 8 ). The number of segments, segment lengths, and varying cross-sectional areas can be any dimension desired by the user whether the dimensions are structured based on mathematical formulas (e.g., aspect ratios) or arbitrary selections. The present invention is not to be limited to any particular numbers of sections (e.g., tip transition, mid-section, and base transition) or any particular number of varying cross-sectional areas (e.g., A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , A 7 ), but as illustrations of possible embodiments. It should be noted that the varying cross-sectional areas can alternate between increasing and decreasing (reducing) and increasing again along length L, as shown in  FIG. 2G . Another embodiment can be conically-shaped fiber with decreasing diameters from the fiber base  132  to tip  130  (not shown) or with increasing diameters from the fiber base  132  to tip  130  (not shown). Also, while the illustrations of  FIGS. 2E-G  illustrate replicated projecting micro and/or nanopatterned features  128 , one skilled in the art will appreciate that the replicated micro and/or nanopatterned features  128  can be represented as substantially equivalent replicated recesses micro and/or nanopatterned features of negative mold  114 . For example, a projected micro and/or nanopatterned feature characteristic that represents a fiber length is substantially equivalent to a recess depth for a recessed micro and/or nanopatterned feature characteristic. Another example is an outer diameter of the fiber is a replicated projected micro and/or nanopatterned feature characteristic that is substantially equivalent to an inner diameter of a replicated recess micro and/or nanopatterned feature characteristic. 
         [0074]    The relationships between backing layer  134 , replicated feature  128 , and replicated tip  130  that can vary in different embodiments of the present invention. In the illustrated embodiment, replicated feature  128  can form angles  1  and  2  relative to a plane P parallel to backing layer  134 . Similarly, replicated flat surface  136  of replicated tip  130  can form angle β 1  or β 2  relative to a plane P parallel to backing layer  134 . Angles  and β singularly or in combination can be defined during the fabrication process. Typically, angles  and β can range between 0 and 180. 
         [0075]    One skilled in the art understand that the description of the replicated micro and/or nanopatterned geometry  126  of the mass produce molded part  120  in  FIGS. 2E-F  are the same for the description of the actual micro and/or nanopatterned geometry  108  of the master template  110  illustrated in  FIG. 2B , and actual micro and/or nanoscale features  10 A of material  10  and actual micro and/or nanoscale features  24  of molded parts  14 A,  14 B illustrated in  FIG. 1 . Therefore, disclosures pertaining to micro and/or nanopatterned features or geometries apply to both actual and replicated micro and/or nanopatterned features or geometries, such that the actual micro and/or nanopatterned features of the material and the replicated micro and/or nanopatterned features of the product are substantially equivalent. 
         [0076]    The present invention is capable of replicating the following microscale and/or nanoscale feature geometries: 
         [0000]    A. Features which Protrude from the Part Surface: 
         [0077]    i. Low aspect ratio protrusions (Feature height is approximately the same or less than the feature characteristic diameter): Bumps; Pyramids; Treads (Straight treads, Curved treads, Parallel treads, Intersecting treads, Random treads); Treads with non-uniform width (Straight, curved, parallel, intersecting or random treads with one or more enlarged areas with respect to the average tread width; Straight, curved, parallel, intersecting or random treads with one or more narrowed areas with respect to the average tread width); Solid prismatic shapes with uniform cross section (Cylindrical prisms, Elliptical prisms, Rectangular prisms, Hexagonal prisms, Pentagonal prisms, Etc. (any-sided prism shape)); Solid prismatic shapes with hollow cross section; Prismatic shapes with non-uniform cross section (Enlarged prism tip shape (Spherical tip shape, Pyramidal tip shape, Spatula tip shape, Mushroom tip shape, Conical tip shape, Convex tip shape, Concave tip shape); Modified prism base shape (Narrowed base with respect to average prism diameter, Enlarged base with respect to average prism diameter); Prismatic shapes that are either enlarged or narrowed at areas that are neither the tip nor the base); 
         [0078]    ii. High aspect ratio protrusions (Feature height is greater than the feature characteristic diameter): Treads (Straight treads, Curved treads, Parallel treads, Intersecting treads, Random treads), Treads with non-uniform width (Straight, curved, parallel, intersecting or random treads with one or more enlarged areas with respect to the average tread width; Straight, curved, parallel, intersecting or random treads with one or more narrowed areas with respect to the average tread width); Solid prismatic shapes with uniform cross section (Cylindrical prisms, Elliptical prisms, Rectangular prisms, Hexagonal prisms, Pentagonal prisms, Etc. (any-sided prism shape)); Solid prismatic shapes with hollow cross section; Prismatic shapes with non-uniform cross section (Enlarged prism tip shape (Spherical tip shape, Pyramidal tip shape, Spatula tip shape, Mushroom tip shape, Conical tip shape, Convex tip shape, Concave tip shape, Modified prism base shape (Narrowed base with respect to average prism diameter, Enlarged base with respect to average prism diameter), Prismatic shapes that are either enlarged or narrowed at areas that are neither the tip nor the base); 
         [0079]    iii. Parts with randomly formed protrusions; 
         [0080]    iv. Parts with other geometrical protrusions produced using micro/nanofabrication processes; 
         [0081]    v. Parts with geometries produced using mechanical or chemical etching or abrasion processes; 
         [0082]    vi. Parts with more than one type of micro and/or nanofeature that protrudes from the part surface: Multiple micro and/or nanofeatures at the same length scale; Multiple micro and/or nanofeatures at different length scales. 
         [0000]    B. Features which Recess into the Part Surface: 
         [0083]    i. Low aspect ratio recessions (Pores, Pyramidal projections, Grooves or channels with uniform width (Straight grooves or channels, Curved grooves or channels, Parallel grooves or channels, Intersecting grooves or channels, Random grooves or channels), Grooves or channels with non-uniform width (Straight, curved, parallel, intersecting or random grooves or channels with one or more enlarged areas with respect to the average groove or channel width; Straight, curved, parallel, intersecting or random grooves or channels with one or more narrowed areas with respect to the average groove or channel width), Prismatic holes with uniform cross section (Cylindrical holes, Elliptical holes, Rectangular holes, Hexagonal holes, Pentagonal holes, Etc. (any-sided holes shape)), Hole shapes with non-uniform cross section (Enlarged hole base shape (Spherical base shape, Pyramidal base shape, Spatula base shape, Mushroom base shape, Conical base shape, Convex base shape, Concave base shape), Modified hole intersection with part surface (Narrowed base with respect to average prism diameter, Enlarged base with respect to average prism diameter), Holes that are either enlarged or narrowed at areas that are neither the tip nor the base); 
         [0084]    ii. High aspect ratio recessions: Grooves or channels with uniform width (Straight grooves, Curved grooves, Parallel grooves, Intersecting grooves, Random grooves); Grooves or channels with non-uniform width (Straight, curved, parallel, intersecting or random grooves with one or more enlarged areas with respect to the average groove or channel width; Straight, curved, parallel, intersecting or random grooves with one or more narrowed areas with respect to the average groove or channel width); Prismatic holes with uniform cross section (Cylindrical holes, Elliptical holes, Rectangular holes, Hexagonal holes, Pentagonal holes, Etc. (any-sided holes shape)); Hole shapes with non-uniform cross section (Enlarged hole base shape (Spherical base shape, Pyramidal base shape, Spatula base shape, Mushroom base shape, Conical base shape, Convex base shape, Concave base shape); Modified hole intersection with part surface (Narrowed base with respect to average prism diameter, Enlarged base with respect to average prism diameter); Holes that are either enlarged or narrowed at areas that are neither the tip nor the base); 
         [0085]    iii. Parts with randomly formed projections; 
         [0086]    iv. Parts with other geometrical projections using micro and/or nanofabrication processes; 
         [0087]    v. Parts with geometries produced using mechanical or chemical etching or abrasion processes; 
         [0088]    vi. Parts with more than one type of micro and/or nanofeature that projects into the part surface (Multiple micro and/or nanofeatures at the same length scale, Multiple micro and/or nanofeatures at different length scales). 
         [0000]    C. Parts with a Combination of Features that Recess into the Part Surface and Protrude from the Part Surface: 
         [0089]    i. Multiple micro and/or nanofeatures at the same length scale; 
         [0090]    ii. Multiple micro and/or nanofeatures at different length scales. 
         [0091]    The present invention is capable of replicating the following undercut microscale and/or nanoscale feature geometries; 
         [0000]    A. Features which Protrude from the Part Surface: 
         [0092]    i. Low aspect ratio protrusions (Feature height is approximately the same or less than the feature characteristic diameter): Treads with non-uniform width (Straight, curved, parallel, intersecting or random treads with one or more enlarged areas with respect to the average tread width; Straight, curved, parallel, intersecting or random treads with one or more narrowed areas with respect to the average tread width), Prismatic shapes with non-uniform cross section (Enlarged prism tip shape (Spherical tip shape, Pyramidal tip shape, Spatula tip shape, Mushroom tip shape (see tip  130  in  FIG. 2F  for illustration of a mushroom tip), Conical tip shape, Convex tip shape, Concave tip shape), Modified prism base shape (Narrowed base with respect to average prism diameter, Enlarged base with respect to average prism diameter), Prismatic shapes that are either enlarged or narrowed at areas that are neither the tip nor the base; 
         [0093]    ii. High aspect ratio protrusions (Feature height is greater than the feature characteristic diameter): Treads with non-uniform width (Straight, curved, parallel, intersecting or random treads with one or more enlarged areas with respect to the average tread width; Straight, curved, parallel, intersecting or random treads with one or more narrowed areas with respect to the average tread width), Prismatic shapes with non-uniform cross section (Enlarged prism tip shape (Spherical tip shape, Pyramidal tip shape, Spatula tip shape, Mushroom tip shape, Conical tip shape, Convex tip shape, Concave tip shape), Modified prism base shape (Narrowed base with respect to average prism diameter, Enlarged base with respect to average prism diameter), Prismatic shapes that are either enlarged or narrowed at areas that are neither the tip nor the base); 
         [0094]    iii. Parts with randomly formed protrusions containing undercut features; 
         [0095]    iv. Parts with other geometrical protrusions containing undercut features produced using micro/nanofabrication processes; 
         [0096]    v. Parts with geometries containing undercut features produced using mechanical or chemical etching or abrasion processes; 
         [0097]    vi. Parts with more than one type of micro and/or nanofeature that protrudes from the part surface (at least one containing an undercut feature (Multiple micro and nanofeatures at the same length scale, Multiple micro and nanofeatures at different length scales). 
         [0098]    See tip  130  in  FIG. 2F  for illustration of an undercut tip, where radius  138  illustrates an undercut of the tip cross-sectional area A 2  to stem cross-sectional area A 1 . Cross-sectional area can also be represented by a characteristic diameter. In other words, one embodiment of the present invention includes the step of fabricating a radius  138  between the actual feature tip characteristic diameter D 2  and the at least one actual stem characteristic diameter D 1  of the plurality of actual stem characteristic diameters associated with cross-sectional areas A 4 , A 5 , A 6 , A 7  of  FIG. 2G  to form an undercut feature. 
         [0000]    B. Features which Recess into the Part Surface: 
         [0099]    i. Low aspect ratio projections: Grooves or channels with non-uniform width (Straight, curved, parallel, intersecting or random grooves or channels with one or more enlarged areas with respect to the average groove or channel width; Straight, curved, parallel, intersecting or random grooves or channels with one or more narrowed areas with respect to the average groove or channel width), Hole shapes with non-uniform cross section (Enlarged hole base shape (Spherical base shape, Pyramidal base shape, Spatula base shape, Mushroom base shape, Conical base shape, Convex base shape, Concave base shape), Modified hole intersection with part surface (Narrowed base with respect to average prism diameter, Enlarged base with respect to average prism diameter), Holes that are either enlarged or narrowed at areas that are neither the tip nor the base); 
         [0100]    ii. High aspect ratio projections: Grooves or channels with non-uniform width (Straight, curved, parallel, intersecting or random grooves with one or more enlarged areas with respect to the average groove or channel width; Straight, curved, parallel, intersecting or random grooves with one or more narrowed areas with respect to the average groove or channel width), Hole shapes with non-uniform cross section (Enlarged hole base shape (Spherical base shape, Pyramidal base shape, Spatula base shape, Mushroom base shape, Conical base shape, Convex base shape, Concave base shape, Modified hole intersection with part surface, Narrowed base with respect to average prism diameter, Enlarged base with respect to average prism diameter), Holes that are either enlarged or narrowed at areas that are neither the tip nor the base); 
         [0101]    iii. Parts with randomly formed projections containing undercut features; 
         [0102]    iv. Parts with other geometrical projections containing undercut features fabricated using micro/nanofabrication processes; 
         [0103]    v. Parts with geometries containing undercut features produced using mechanical or chemical etching or abrasion processes; 
         [0104]    vi. Parts with more than one type of micro and/or nanofeature that recesses into the part surface, at least one of which is undercut (Multiple micro and/or nanofeatures at the same length scale, Multiple micro and/or nanofeatures at different length scales). 
         [0000]    C. Parts with a Combination of Features that Recess into the Part Surface and Protrude from the Part Surface, at least One of which is Undercut: 
         [0105]    i. Multiple micro and/or nanofeatures at the same length scale; 
         [0106]    ii. Multiple micro and/or nanofeatures at different length scales. 
         [0107]    While the disclosure has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the embodiments. Thus, it is intended that the present disclosure cover the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.

Technology Classification (CPC): 8