Patent Publication Number: US-2023151492-A1

Title: Direct Printing of Catalyst Inks

Description:
GOVERNMENT LICENSE RIGHTS 
     This invention was made with Government support under Contract No. N00178-04-D-4119-FC46 awarded by the United States Navy. The Government has certain rights in this invention. 
    
    
     BACKGROUND 
     Known lithographic approaches for manufacturing integrated circuits having high precision may be costly. As the scale of features decreases, optical lithography may require increasingly expensive masks for patterning along with complex exposure tools including high powered excimer lasers and stacks of precision ground lens elements to achieve desired resolution. For metallization processes, optical lithography may require eight processing steps (substrate metallization, photoresist deposition, photoresist cure, mask alignment, extreme ultraviolet exposure, photoresist development, metal etch, and photoresist removal) and associated manufacturing equipment. Nanoimprint lithography is a competing technology for creating smaller scale integrated circuits. But with metallization processes, nanoimprint lithography may require six process steps (substrate metallization, photoresist deposition, photoresist cure, stamp positioning/impression transfer, metal etch, and photoresist removal). 
     SUMMARY 
     This Summary is provided to introduce a selection of some concepts in a simplified form as a prelude to the Detailed Description. This Summary is not intended to identify key or essential features. 
     Catalyst ink may be directly printed onto a substrate using a stamp. The printed catalyst ink may then be converted, by plating, to a pattern of one or more metal traces. The pattern may comprise micrometer scale features. The steps may be repeated an arbitrary number of times to replicate the pattern in different locations and/or on different substrates. To promote transfer of catalyst ink from the stamp to the substrate, materials for a stamp and/or a substrate, and/or components of a catalyst ink, may be selected so that attraction of one or more of components of the catalyst ink to one or more print surfaces of the substrate is greater than attraction of those one or more ink components to one or more write surfaces of the stamp. Metal traces and/or patterns may be formed by such steps in connection with fabrication of integrated circuits, system-on-chip assemblies, printed circuit boards, conformal patterns (e.g., for antenna arrays), and/or other articles. 
     These and other features are described in more detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some features are shown by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements. 
         FIG.  1    is a flow chart showing steps of an example method of direct stamp printing of a catalyst ink pattern and plating that pattern. 
         FIGS.  2 A and  2 B  are respective plan and area cross-sectional views of an example stamp that may be used in the method of  FIG.  1   . 
         FIGS.  3 A,  3 B, and  3 C  are partially schematic area cross-sectional views showing an example of applying a catalyst ink to write surfaces of the stamp of  FIGS.  2 A and  2 B . 
         FIGS.  4 A,  4 B, and  4 C  are partially schematic area cross-sectional views showing an example of transferring catalyst ink  40  to a print surface of a substrate. 
         FIG.  5 A  is a partially schematic plan view of a substrate print surface after transfer of catalyst ink. 
         FIG.  5 B  is a partially schematic plan view of the substrate print surface of  FIG.  5 A  after plating of catalyst ink. 
         FIGS.  6 A and  6 B  are partially schematic area cross-sectional views showing examples of substrate print surfaces. 
         FIG.  7    shows an example configuration of a stamp to provide laser or UV light treatment of catalyst ink. 
         FIG.  8    shows an example configuration of a stamp to provide sonification of catalyst ink. 
     
    
    
     DETAILED DESCRIPTION 
     A patterned stamp may be used to replicate patterns of catalyst ink on a substrate. One or more write surfaces of the stamp may be coated with a layer of catalyst ink. The catalyst ink coating the stamp write surface(s) may be brought into contact with one or more print surfaces of a substrate. When in contact, the catalyst ink may transfer from the stamp write surface(s) to the substrate print surface(s), thereby creating a reverse version of the stamp pattern on a surface of the substrate. Attraction of one or more components of the catalyst ink (e.g., catalyst nanoparticles, one or more ink additives) to the substrate print surface(s) may be greater than attraction of the catalyst ink component(s) to the stamp write surface(s). The stamping process may be repeated an arbitrary number of times on a substrate (and/or on multiple substrates) for replicating the pattern in different locations. Subsequent electroless plating of the catalyst ink patterns on the substrate(s) may transform those catalyst ink patterns into metal traces. Direct printing using a stamp allows creation of catalyst ink patterns, and corresponding conductive regions after plating, having features at micrometer (μm) or nanometer (nm) scales. 
       FIG.  1    is a flow chart showing steps of an example method of direct stamp printing of a catalyst ink pattern and plating that pattern. One or more of the steps shown in  FIG.  1    may be modified and/or repeated, and/or other steps may be added. In step  11 , a catalyst ink may be applied to one or more write surfaces of a stamp. 
       FIG.  2 A  is a partially schematic plan view of a working face  31  of an example stamp  30  which may be used in the method of  FIG.  1   . The working face  31  comprises write surfaces  32   a  and  32   b.    FIG.  2 B  is a partially schematic area cross-sectional view of the stamp  30  taken from the plane A-A indicated in  FIG.  2 A . The write surfaces  32   a  and  32   b  may be collectively referred to herein as “the write surfaces  32 ,” and an arbitrary one of the write surfaces  32   a  and  32   b  may be generically referred herein to as “a write surface  32 .” The write surfaces  32  are part of a relatively simple and confined pattern selected to facilitate description of one or more example methods. The write surfaces  32  and other structures and/or characteristics of the stamp  30  are merely examples. Stamps having one or more write surfaces with different configurations may also or alternatively be used in methods described herein. Such different configurations may include parts of patterns that are much more complex and/or expansive (e.g., that extend over a much larger stamp face). 
     The write surfaces  32  may be part of a pattern  35 , an approximate boundary of which is indicated in  FIG.  2 A  with large broken lines. The pattern  35  may comprise raised regions that form the write surfaces  32  and valleys that form spaces surrounding and/or separating the write surfaces  32 . The pattern  35  may comprise one or more features. A feature may have a shape and/or one or more dimensions. A feature of the pattern  35  may comprise a region corresponding to a write surface or a portion thereof. For example, the pattern  35  may comprise a rectangular feature  35   a,  corresponding to a portion  32   a   1  of the write surface  32   a,  having a dimension (e.g., an edge-to-edge width) d 1 . A feature of the pattern  35  may comprise a region corresponding to a space between and/or otherwise defined by one or more edges of one or more write surfaces. For example, the pattern  35  may comprise a feature  35   b,  corresponding to a space between portions  32   b   1  and  32   b   2  of write surface  32   b,  having a dimension d 2 . Dimensions d 1 , d 2 , and/or other dimensions of pattern  35  features may be micrometer (μm) or nanometer (nm) scale values. For example, dimensions d 1 , d 2 , and/or other dimensions of pattern  35  features may be less than 100 μm, less than 50 μm, less than 20 μm, less than 10 μm, or smaller. With appropriate stamp patterning and use of sufficiently small nanoparticles, smaller feature dimensions may be achieved (e.g., hundreds of nm scale, tens of nm scale, less than 10 nm scale). 
     The stamp  30  may comprise a main body formed from one or more parent materials, examples of which are described below. The write surfaces  32  may comprise a parent material of the main body, and/or may comprise one or more surface treatments and/or coatings, examples of which are also described below. The pattern  35  and/or other patterns may, for example, be formed using electron beam lithography, nanoimprint lithography, or other fabrication methods. 
       FIGS.  3 A through  3 C  are partially schematic area cross-sectional views showing an example of applying a catalyst ink to the write surfaces  32 . For simplicity, the stamp  30  is shown in  FIGS.  3 A through  3 C  using the area cross-sectional view from  FIG.  2 B . Also shown in area cross-sectional view in  FIGS.  3 A through  3 C  is a portion of a bath  42  of a catalyst ink  40 . The bath  42  may comprise a surface  41  having an area large enough to engage the entirety of the write surfaces  32  in one contact. To apply the catalyst ink  40 , and as shown in  FIG.  3 A , the working face  31  of the stamp  30  may be moved toward the surface  41 . That movement may continue until the write surfaces  32  contact the surface  41 , as shown in  FIG.  3 B . The working face  31  may then be moved away from the surface  41 , as shown in  FIG.  3 C . As shown in  FIG.  3 C , a portion of the catalyst ink  40  from the bath  42  remains on the write surfaces  32 . Instead of, or in addition to, a bath as shown in  FIGS.  3 A- 3 C , one or more droplets of catalyst ink may be dispensed in a staging area on a substrate, and a stamp dipped into the one or more droplets. Multiple write steps may be performed from a single set of such staging area droplet(s). Also or alternatively, catalyst ink may be applied to write surfaces from a source other than an open bath or staging area droplet(s). For example, the surface  41  may alternatively comprise a surface of a plate or roller to which the catalyst ink  40  has been applied, a surface of a mat or other porous material impregnated with the catalyst ink  40 , or a portion of some other structure that holds the catalyst ink  40 . Also or alternatively, a stamp may comprise an internal catalyst ink dispense mechanism that comprises an array of one or more channels through which a conformal coat of catalyst ink may flow onto a stamp write surface. Also or alternatively, atomic layer deposition or other thin film material deposition processes (e.g., sputtering, molecular beam epitaxy (MBE), chemical vapor deposition (CVD)) may be used to apply the catalyst ink to the stamp. 
     The catalyst ink  40  may comprise a catalyst ink such as one or more of the catalyst inks described in U.S. Pat. No. 10,619,059, which patent is incorporated by reference herein. The catalyst ink  40  may be a colloidal solution. Components of the catalyst ink  40  may, for example, comprise catalyst nanoparticles and/or catalyst molecules, one or more solvents, and one or more binders and/or other additives. The catalyst nanoparticles may be palladium (Pd) nanoparticles and/or nanoparticles of one or more other catalyst materials. Examples of other catalyst materials comprise platinum (Pt) and rhodium (Rh). Sizes of the catalyst nanoparticles may, for example, range from 15 nm to 500 nm. A size of a catalyst nanoparticle may, for example, be a largest linear dimension of that nanoparticle (e.g., a diameter of a spherical nanoparticle). A size range of catalyst nanoparticles for a particular catalyst ink may be selected based on resolution of features of a pattern to be printed with that catalyst ink. In general, nanoparticles for a catalyst ink should be smaller than the smallest feature dimension of a pattern to be printed. Although smaller nanoparticle sizes allow for printing of smaller features, larger-sized nanoparticles may be less costly to process and/or handle. Example ranges of catalyst nanoparticle sizes may comprise 5 nm to 100 nm, 5 nm to 50 nm, 5 nm to 10 nm, 15 nm to 500 nm, 15 nm to 400 nm, 15 nm to 300 nm, 15 nm to 200 nm, 15 nm to 100 nm, 15 nm to 50 nm, 50 nm to 500 nm, 50 nm to 400 nm, 50 nm to 300 nm, 50 nm to 200 nm, 50 nm to 100 nm, 100 nm to 500 nm, 100 nm to 400 nm, 100 nm to 300 nm, 100 nm to 200 nm, 200 nm to 500 nm, 200 nm to 400 nm, 200 nm to 300 nm, 300 nm to 500 nm, 300 nm to 400 nm, and 400 nm to 500 nm. 
     The concentration of catalyst nanoparticles in a catalyst ink may be selected based on a desired viscosity, thickness, and/or other characteristics of a catalyst ink. A catalyst ink formulated for printing may have a higher concentration of catalyst nanoparticles (e.g., to increase reaction rate during electroless plating) than a catalyst ink formulated for application via aerosol jet. A catalyst ink may, for example, contain from 0.1 weight percent (wt %) to 5.0 wt % catalyst nanoparticles. Example ranges of catalyst nanoparticle concentration for a catalyst ink may comprise 0.1 wt % to 5.0 wt %, 0.1 wt % to 4.0 wt %, 0.1 wt % to 3.0 wt %, 0.1 wt % to 2.2 wt %, 0.1 wt % to 1.5 wt %, 0.1 wt % to 0.5 wt %, 0.5 wt % to 5.0 wt %, 0.5 wt % to 4.0 wt %, 0.5 wt % to 3.0 wt %, 0.5 wt % to 2.2 wt %, 0.5 wt % to 1.5 wt %, 1.5 wt % to 5.0 wt %, 1.5 wt % to 4.0 wt %, 1.5 wt % to 3.0 wt %, 1.5 wt % to 2.2 wt %, 2.2 wt % to 5.0 wt %, 2.2 wt % to 4.0 wt %, 2.2 wt % to 3.0 wt %, 3.0 wt % to 5.0 wt %, 3.0 wt % to 4.0 wt %, and 4.0 wt % to 5.0 wt %. 
     A solvent used for a catalyst ink may comprise any suitable solvent (or combination of solvents) that yields, when mixed with other ingredients, a colloidal solution of the catalyst nanoparticles that is suitable for application to write surface(s) of a stamp and transfer to substrate print surface(s) from the write surface(s). Such solvents include, without limitation, toluene, dimethylformamide, tetrahydrofuran, xylenes, and combinations thereof. Also or alternatively, water may be used as a solvent in some catalyst inks. 
     One or more binders and/or other additives may be included in a catalyst ink to affect interaction between the catalyst ink and stamp write surfaces and/or between the catalyst ink and substrate print surfaces, to increase viscosity, to minimize wetting, and/or to affect other properties of the catalyst ink. Examples of additives comprise polyvinyl alcohols, cellulose acetate, carboxymethyl cellulose, polyvinylidene fluoride (PVDF), and polyvinyl acetate (PVA). Additives may, for example, have molecular weights in ranges of 10K to 180K. 
     The components of a catalyst ink may be mixed just prior to application to write surfaces and/or periodically remixed. The mixing and/or remixing may, for example, comprise sonification to disperse catalyst nanoparticles in the solution and/or prevent aggregation and/or settling. For example, sonification may be applied to the bath  42  prior to placement of the write surfaces  32  into contact with the surface  41 , after the write surfaces  32  are removed from contact with the surface  41  and prior to a subsequent placement of the write surfaces  32  into contact with the surface  41 , etc. Also or alternatively, sonification may be applied continuously to the bath  42 . 
     In step  12  ( FIG.  1   ), the catalyst ink  40  applied to the write surfaces  32  may be transferred to a print surface of a substrate.  FIGS.  4 A through  4 C  are partially schematic area cross-sectional views showing an example of transferring the catalyst ink  40  to a print surface  51  of a substrate  50 . As in  FIGS.  3 A through  3 C , the stamp  30  is shown in  FIGS.  4 A through  4 C  using the area cross-sectional view from  FIG.  2 B . The substrate  50  is shown in  FIGS.  4 A through  4 C  in an area cross-sectional view from the plane C-C indicated in  FIG.  5 A . As shown in  FIGS.  4 A and  4 B , the catalyst ink  40  may be transferred by moving the stamp  30  to place the catalyst ink  40 , applied to the write surfaces  32 , into contact with the print surface  51 . Subsequently, and as shown in  FIG.  4 C , the stamp  30  may be moved away from the substrate  50 . As the stamp  30  is moved away, some or all of the catalyst ink  40  previously on the write surfaces  32  adheres to and remains on the print surface  51 . As described below, the print surface  51  may be coated with and/or otherwise formed from one more materials to promote adhesion and/or to minimize wetting. 
     To achieve the relative motions shown in  FIGS.  3 A through  4 C , the stamp  30  and/or the substrate  50  may be manipulated using automated handling equipment (e.g., a movable stage for shifting the position of the substrate  50  relative to the stamp  30  and/or a stamp manipulator such as a robotic arm). Existing handling equipment (e.g., such as is used in nanoimprint lithography processes) may be adapted for such manipulation. Although the example of  FIGS.  3 A through  4 C  shows transfer of catalyst ink from multiple write surfaces to a single print surface, the method of  FIG.  1    may comprise transfer of ink from one or more write surfaces to one or more print surfaces. For example, the stamp  30  could be used to simultaneously print a first portion of a pattern  36  ( FIG.  5 A ) corresponding to the write surface  32   a  on a print surface of a first substrate and print a second portion of the pattern  36  corresponding to the write surface  32   b  on a print surface of a second substrate positioned alongside the first substrate. 
       FIG.  5 A  is a partially schematic plan view, from the plane B-B indicated in  FIG.  4 C , of the substrate  50  print surface  51  after transfer of the catalyst ink  40 . As shown in  FIG.  5 A , the transferred catalyst ink  40  forms the printed pattern  36  that corresponds to (e.g., is a reverse of) the pattern  35 . In step  13  ( FIG.  1   ), the catalyst ink  40  transferred to the print surface  51  may be dried and/or otherwise cured. Step  13  may comprise allowing the catalyst ink  40  to air dry, and/or may comprise applying heat, light, ultraviolet (UV) light (e.g., if the catalyst ink  40  comprises a UV curing agent), dry air, and/or other processing to the catalyst ink  40 . 
     In step  14 , electroless plating may be performed to plate the catalyst ink  40  of the printed pattern  36 . During the plating of step  14 , the catalyst ink  40  may be metallized with a plating metal (e.g., with copper (Cu), gold (Au), silver (Ag), Aluminum (Al), Nickel (Ni), or Iron (Fe)). The plating of step  14  may comprise immersing the print surface  51  in an electroless plating bath containing an electroless plating solution. Also or alternatively, microdroplets of an electroless plating solution may be applied to the catalyst ink  40  in the printed pattern  36 . Electroless plating solutions to plate copper to a Pd catalyst, as well as to plate any of a variety of other plating metals to Pd or to other catalysts, are known. After a plating time has elapsed, which time may be determined based on plating solution chosen, the print surface  51  may be removed from the electroless plating bath and/or the electroless plating solution otherwise removed (e.g., with compressed air or other drying process).  FIG.  5 B  is a partially schematic plan view of the print surface  51  after step  14 . As shown in  FIG.  5 B , the catalyst ink  40  has been transformed into metal traces  53   a  and  53   b.    
     In step  15  one or more additional processes may be performed. The one or more additional processes may, for example, comprise washing (e.g., with water, with acid, etc.), application of anti-tarnish compounds, application of other materials, etc. Also or alternatively, step  15  may comprise repeating one or more of steps  11  through  14 . For example, additional catalyst ink may be printed (e.g., using the stamp  30  or another stamp) on some or all of the metal trace  53   a  and/or the metal trace  53   b.  Electroless plating may subsequently be performed on the additional catalyst ink. Multiple printing and plating steps may be performed, for example, to obtain a thicker layer of plating metal in one or more regions. 
     Also or alternatively, one or more other materials (e.g., a layer of non-conductive material) may be applied onto some or all of the metal trace  53   a  and/or the metal trace  53   b.  Additional catalyst ink may then be printed onto those one or more other materials, and electroless plating subsequently performed on that additional catalyst ink. The resulting article may comprise layers of metal traces separated by an insulating material. 
     Stamps and/or substrates may comprise any of a variety of materials. Those materials, and/or components of a catalyst ink, may be selected to improve adherence of catalyst ink to a write surface, release of catalyst ink from a write surface, transfer of catalyst ink from a write surface to a print surface, adherence of catalyst ink to a print surface, wettability of a print surface by a catalyst ink (e.g., to inhibit a catalyst ink from spreading beyond desired regions of a printed pattern), and/or other interactions between the catalyst ink and the write surface and/or print surface. Although several specific examples are described below, other materials, combinations of materials, and/or surface treatments may also or alternatively be used. 
     A print surface of a substrate may comprise a surface of a parent material forming some or all of the remaining structure of the substrate. Also or alternatively, a substrate print surface may comprise a material (e.g., a coating) applied to the substrate parent material and/or to another material (e.g., an intermediate coating) fixed to the substrate parent material. For example,  FIG.  6 A  is an enlarged, partially schematic, area cross-sectional view of a portion of a substrate  50   a.  The substrate  50   a  is formed from a parent material  52   a.  A print surface  51   a  comprises a region of a surface of the parent material  51   a.  As another example,  FIG.  6 B  is an enlarged, partially schematic, area cross-sectional view of a portion of a substrate  50   b.  The substrate  50   b  is formed from a parent material  52   b.  A print surface  51   b  comprises a surface of a material  53   b  applied to a region of the surface of the parent material  52   b.  Similarly, a write surface of a stamp may comprise a surface of a parent material forming some or all of the remaining structure of the stamp. Also or alternatively, a stamp write surface may comprise a material (e.g., a coating) applied to the stamp parent material and/or to another material (e.g., an intermediate coating) fixed to the stamp parent material. 
     A stamp may be formed from metallic, ceramic, or organic parent materials. For example, a stamp parent material may comprise steel or other metal or metal alloy, a metallic and/or inorganic silicate, a ceramic (e.g., (ZnMg)TiO 3 ), a dielectric such as a polyimide-based polymer (e.g., such as is found in KAPTON film), and/or other materials. To promote capture of catalyst ink by a write surface, the write surface may comprise a coating or a monolayer with chemical properties selected to enhance temporary catalyst ink bonding. Examples of materials for such coatings and monolayers comprise surface modifying compounds such as those described below. 
     Substrates may also be formed from any of a variety of parent materials. Examples of substrate parent materials comprise ceramic dielectric materials, organic dielectric materials, metals or metal alloys, polymers, and/or other materials. A substrate print surface may comprise a coating or monolayer of one more materials that are different from a parent material of the substrate. For example, print surfaces of substrates formed from more rigid parent materials may comprise a coating of a more flexible material. Such flexible materials may, for example, comprise a polyimide material (e.g., KAPTON film), PVA, cellulose acetate, PVDF, and/or another polymer material. A flexible print surface material may promote more complete catalyst ink transfer from write surface(s) of a stamp by, for example, facilitating embedding of catalyst nanoparticles in the print surface and/or compensating for minute imperfections in stamp write surface(s). Also or alternatively, a substrate print surface may comprise a coating or a monolayer with chemical properties selected to enhance temporary catalyst attraction to the print surface. 
     To promote and/or enhance transfer of catalyst ink from a stamp write surface to a substrate print surface, one or more stamp write surface materials, one or more substrate print surface materials, and/or one or more catalyst ink components may be selected so that attraction of one or more components of the catalyst ink to the substrate print surface is greater than attraction of the catalyst ink component(s) to the stamp write surface. For example, a substrate print surface may comprise a coating and/or monolayer (e.g., a self-assembled monolayer (SAM)) formed from one or more surface modifying compounds applied to a parent material of the substrate. A surface modifying compound may comprise a chemical having a terminating functional group that binds to the substrate parent material and a tail functional group that attracts a component of the catalyst ink more strongly than such catalyst ink component is attracted by material of a stamp write surface. 
     A surface modifying compound may be selected so that a tail functional group of that compound attracts the catalyst nanoparticles of the catalyst ink. For example, Pd nanoparticles are attracted by tail functional groups that comprise amines. Tail functional groups that comprise sulfur and/or phosphorous may also be used to attract a variety of metals, including Pd and Pt. Phosphorus- and/or phosphine-based tail functional groups may be used to attract Rh. Attraction of Pd, Pt, and/or Rh nanoparticles to such tails would be greater than attraction to steel, other metals and metal alloys, and inorganic silicates that may be used as substrate or stamp parent materials. 
     Selection of a surface modifying compound may also be based on a substrate parent material to which the compound will be applied. For example, amine and sulfur functional groups bond to iron- and copper-based materials. As another example, carboxylate functional groups bond to zinc-based materials. 
     A surface modifying compound may, for example, comprise a silane-based surface modifying compound. Silane surface modifying compounds known to bond to a large variety of materials, having known chemical structures, and/or having other properties (e.g., hydrophobicity, hydrophilicity) are commercially available. A surface modifying compound need not be a silane. For example, a surface modifying compound may comprise graphene oxide. Table 1 comprises a non-exhaustive list of example surface modifying compounds for various combinations of parent materials (to which a surface modifying compound may be applied) and catalyst nanoparticle materials. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Example Surface Modifying Compounds 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Catalyst 
                 Example 
               
               
                   
                 Parent 
                 Nanoparticle 
                 Surface Modifying 
               
               
                   
                 Material 
                 Material 
                 Compound 
               
               
                   
                   
               
               
                   
                 iron and/or 
                 Pd 
                 Amine terminated with  
               
               
                   
                 steel 
                   
                 linkage to sulfur or 
               
               
                   
                   
                   
                 phosphine 
               
               
                   
                 copper and/or 
                 Pd 
                 Amine terminated with  
               
               
                   
                 copper alloys 
                   
                 linkage to sulfur or 
               
               
                   
                   
                   
                 phosphine 
               
               
                   
                 zinc and/or 
                 Pd 
                 Amine or carboxylate  
               
               
                   
                 zinc alloys 
                   
                 terminated with linkage  
               
               
                   
                   
                   
                 to sulfur or phosphine 
               
               
                   
                 titanium and 
                 Pd 
                 Epoxy or hydride  
               
               
                   
                 or titanium 
                   
                 terminated with linkage  
               
               
                   
                 alloys 
                   
                 to sulfur or phosphine 
               
               
                   
                 tin and/or tin 
                 Pd 
                 Amine terminated with  
               
               
                   
                 alloys 
                   
                 linkage to sulfur or 
               
               
                   
                   
                   
                 phosphine 
               
               
                   
                 Silica oxide 
                 Pd 
                 Silicon chloride  
               
               
                   
                   
                   
                 terminated with linkage  
               
               
                   
                   
                   
                 to sulfur or phosphine 
               
               
                   
                   
               
            
           
         
       
     
     Also or alternatively, materials may be selected so that attraction of one or more other catalyst ink components to a substrate print surface is greater than attraction of the other catalyst ink component(s) to a stamp write surface. For example, and for catalyst inks comprising organic solvents, PVDF and/or PVA may be added. PVDF and/or PVA will promote adhesion to organic substrate print surface materials, and may lessen adhesion to metallic and inorganic stamp write surface materials. 
     Also or alternatively, write surface materials, print surface materials, and/or catalyst ink components may be selected so that attraction of one or more catalyst ink components to a write surface is enhanced and/or greater than attraction of such catalyst ink component(s) to a print surface. For example, materials such as those described above for a print surface may be used for a write surface, and/or materials such as those described above for a write surface may be used for a print surface. Moreover, write surface materials, print surface materials, and/or catalyst ink components may also or alternatively be selected based on wettability of a print surface and/or write surface by a catalyst ink. Increased hydrophobicity/reduced wettability may reduce the tendency of printed catalyst ink to spread beyond print surface regions where that catalyst ink is initially deposited by a stamp write surface. 
     Also or alternatively, metallic stamp write surfaces and/or metallic substrate print surfaces may be laser or plasma treated. Laser surface treatment may, for example, create microscopic pitting and/or other surface features that increase retention of catalyst ink. Plasma surface treatment may, for example, activate a surface by ionizing atoms of the surface material, thereby increasing the tendency of the surface to retain catalyst ink. 
     As indicated above, catalyst ink may be treated with laser or UV light to cure that catalyst ink. Such curing may increase the adhesion of the catalyst ink to a print surface and/or accelerate evaporation of solvent from the catalyst ink. Such laser or UV treatment may be performed after catalyst ink has been applied to stamp write surface(s) and before transfer to substrate print surface(s), and/or may be performed as catalyst ink is being transferred from a stamp to a substrate.  FIG.  7    shows an example configuration of a stamp  130  to provide such treatment. In  FIG.  7   , the stamp  130  is shown using an area cross-sectional view from a plane similar to the plane A-A of  FIG.  2 A  and the substrate  50  is shown using an area cross-sectional view from the plane C-C  FIG.  5 A . The stamp  130  may similar to the stamp  30  in size and general configuration and may have working face pattern similar to the pattern  35 . However, the stamp  130  is formed from a transparent material. A laser or UV emitter  101  (shown schematically) may be coupled to the stamp  130  by a lens/light guide  102  (also shown schematically). As the catalyst ink  40  on write surfaces of the stamp  130  contacts the print surface  51  of the substrate  50 , laser or UV light from the emitter  101  may be transmitted via the lens/light guide  102  and the stamp  130  into the catalyst ink  40 . Also or alternatively, laser and/or UV light may be transmitted to the catalyst ink  40  via light guide(s) formed in space(s) surrounding some or all write surfaces and/or from a source not coupled to the stamp  130 . The catalyst ink  40  may comprise one or more curing agents that are activated by laser or UV light. 
     As indicated above, sonification may be used to promote transfer of catalyst ink from stamp write surface(s) to substrate print surface(s).  FIG.  8    shows an example configuration of the stamp  30  to provide such treatment. In  FIG.  8   , the stamp  30  is shown using an area cross-sectional view from the plane A-A of  FIG.  2 A  and the substrate  50  is shown using an area cross-sectional view from the plane C-C  FIG.  5 A . A sonic transducer  103  (shown schematically) may be coupled to the stamp  30 . As the catalyst ink  40  on write surfaces of the stamp  30  contacts the print surface  51  of the substrate  50 , the transducer  103  may be activated to generate ultrasonic energy that is transmitted via the stamp  30  into the catalyst ink  40 . 
     The configurations of  FIG.  7    and  FIG.  8    may be combined. Moreover, the configurations of  FIG.  7    and/or  FIG.  8    may be used in connection with stamps having write surface coatings or treatments and/or with substrates having print surface coatings or treatments. 
     A stamp may also be used to transfer catalyst ink from and/or to surfaces that are not flat. For example, one or more stamp write surfaces be portions of a complex surface, which surface also corresponds to one or substrate print surfaces. Catalyst ink may be applied to non-flat write surfaces using, e.g., a roller or porous body that conforms to the non-flat write surfaces. Also or alternatively, a stamp may be flexible and, after application of catalyst ink to write surfaces of that stamp in a flat configuration, able to conform to a non-flat substrate print surface. 
     Write surfaces of a stamp need not be fixed. For example, a stamp working face may comprise one or more pins or other structures that can be extended or retracted to create a desired pattern. 
     The foregoing has been presented for purposes of example. The foregoing is not intended to be exhaustive or to limit features to the precise form disclosed. The examples discussed herein were chosen and described in order to explain principles and the nature of various examples and their practical application to enable one skilled in the art to use these and other implementations with various modifications as are suited to the particular use and/or uses contemplated. The scope of this disclosure encompasses, but is not limited to, any and all combinations, subcombinations, and permutations of structure, operations, materials, and/or other features described herein and in the accompanying drawing figures.