Patent Publication Number: US-2023158736-A1

Title: Texture embraced meniscus polymerization

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part application of U.S. application Ser. No. 17/535,540, filed Nov. 24, 2021. The entire disclosure of U.S. application Ser. No. 17/535,540 is hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     Field of the Invention 
     The present invention generally relates to a system and method of 3D printing. More specifically, the present invention relates to a 3D printing system and method including a tank having a textured surface through which light is configured to pass and a layer of an inert liquid disposed on the textured surface. 
     Background Information 
     3D (three-dimensional) printing is the construction of a three-dimensional object from a digital file, such as a CAD model or a digital 3D model. A conventional additive manufacturing process creates the object by successively adding layers one at a time until the object is complete. One type of additive manufacturing process is vat polymerization, which includes stereolithography (SLA) and digital light processing (DLP) processes. 
     As shown in step S 1  of  FIG.  1   , DLP 3D printing includes a tank, or vat,  10  having a transparent projection window  12 . The vat  10  contains a liquid polymer resin  14 . A build platform  16 , on which an object is to be printed, is lowered into the resin  14 . 
     A light projection system  18 , such as a laser, projector or LED/LCD panel, emits a light  20 , such as ultraviolet light, through the transparent projection window  12  in the vat  10 , as shown in Step S 2  of  FIG.  1   . The emitted light  20  causes a reaction within the resin  14  in which the molecules bond together, or cure, to form a first layer of a solid object  22  on the build platform  16 . The entire first layer is cured simultaneously. The build platform  16  is moved in a direction away from the transparent projection window  12  to form a second laver on the first layer. Layers are formed, one layer at a time, until the object is printed. 
     During the printing process, the polymerized resin can adhere to the transparent projection window  12  of the vat  10 , which can interfere with forming additional layers on the build platform  16 . Additionally, the gap between the build platform  16  and the transparent window  12 , or between the formed solid object  22  on the build platform  16  and the transparent window  12  for subsequent layers, is small (e.g., a distance substantially equal to a thickness of one formed layer on the build platform). As shown in step S 3  of  FIG.  1   , the build platform  16  is removed from the vat  10 . Any polymerized resin adhered to the transparent window  12  of the vat  10  can be removed, and additional liquid polymer resin  14  can be added to the vat  10 . 
     As shown in step S 4  of  FIG.  1   , the build platform  16  is lowered into the liquid polymer resin  14  in the vat  10  until the appropriate distance between the printed object  22  and the transparent window  12  is obtained. The separation step of the build platform  16  from the vat  10  in step S 3  and repositioning the build platform  16  in the vat  10  in step S 4  are time consuming steps that slow down the DLP 3D printing process. Removing any resin adhered to the transparent window  12  further slows down the printing process. 
     A conventional 3D printing system used in the DLP 3D printing process of  FIG.  1    is shown in  FIG.  2   . The light projection system  18  emits light, such as UV (ultraviolet) light, corresponding to a single image of the layer to be formed on the build platform  16 . The emitted light  20  passes through a projection lens  24  to adjust the resolution of the emitted light  20 . The projection lens  24  is selected based on the desired focal depth, such as 30 or 100 micrometers. The projected light  26  is transmitted to a mirror  28 . The reflected light  30  is transmitted into the vat  10  through a transparent window  12  ( FIG.  1   ) thereof. The reflected light  30  cures the resin in the vat  10  to form a first layer of the printed object  22 . A robotic arm  32  moves the build platform  16  such that successive layers can be formed to construct the printed object  22 . 
     SUMMARY 
     A need exists for a 3D printing system in which adhesion between the printed object and the window is substantially prevented. A need also exists for a 3D printing process in which resin flows in a timely manner toward a gap between a printed object and a window to form a successive resin layer to facilitate continuous photopolymerization. A further need exists for a 3D printing process facilitating resin flow. 
     In view of the state of the known technology, one aspect of the present disclosure is to provide a 3D printing system including a tank containing a liquid photopolymer resin. A textured surface is disposed in the tank. The textured surface is configured such that light passes through and into the liquid polymer resin. A layer of an inert material is disposed on the textured surface. 
     Another aspect of the present disclosure is to provide a 3D printing system including a tank containing a liquid photopolymer resin, and a rigid base on which an object is configured to be printed. A textured surface is disposed in the tank. The textured surface is configured such that light passes through and into the liquid polymer resin. A layer of an inert material disposed on the textured surface. The resin is disposed between the layer of the inert material and the rigid base. 
     Also other objects, features, aspects and advantages of a 3D printing system and method will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the 3D printing system and method. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the attached drawings which form a part of this original disclosure: 
         FIG.  1    is a schematic representation of a conventional 3D printing system and method; 
         FIG.  2    is a perspective view of a conventional 3D printing system of  FIG.  1   ; 
         FIG.  3    is a side elevational view of a 3D printing system in accordance with an exemplary embodiment; 
         FIG.  4    is a side elevational view of a 3D printing system in accordance with another exemplary embodiment; 
         FIG.  5    is an elevational view of the 3D printing system of  FIG.  3    illustrating a resin flow path generated by a transducer: 
         FIG.  6    is a perspective view of a tank of the 3D printing system of  FIG.  3   ; 
         FIG.  7    is an elevational view of the tank of  FIG.  6   ; 
         FIG.  8    is an elevational view of a tank of a 3D printing system in accordance with another exemplary embodiment in which a transducer is connected to an upper portion of a tank; 
         FIG.  9    is a side elevational view of the tank of  FIG.  8   ; 
         FIG.  10    is a perspective view of a 3D printing system in accordance with yet another exemplary embodiment in which a plurality of transducers are mounted to a tank; 
         FIG.  11    is a top plan view of the tank of  FIG.  10   ; 
         FIG.  12    is a schematic representation of an inert layer disposed on a textured surface of the tank of  FIG.  3   ; 
         FIG.  13    is a schematic representation of speeds at which acoustic waves generated by a transducer travel through the inert layer and the resin of  FIG.  12   ; 
         FIG.  14    is a side elevational view of the textured surface of the tank of  FIG.  3    having a hydrophobic coating; 
         FIG.  15    is a top plan view of the textured surface of the tank of  FIG.  3   ; 
         FIG.  16    is side elevational view of the textured surface of  FIG.  15   ; 
         FIG.  17    is a side elevational view of the textured surface of  FIG.  15    having hydrophobic nanostructures: 
         FIG.  18    is a side elevational view of a textured surface in accordance with another exemplary embodiment; 
         FIG.  19    is a side elevational view of the textured surface of  FIG.  18    having hydrophobic nanostructures; and 
         FIG.  20    is a side elevational view of a 3D printing system in accordance with another exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Selected exemplary embodiments will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the exemplary embodiments are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. 
     Referring initially to  FIG.  3   , a 3D printing system  110  in accordance with an exemplary embodiment includes a tank  112 , a textured surface  114  connected to the tank  112 , and a first transducer  116  configured to emit an acoustic wave  118  toward the textured surface  114 . The 3D printing system  110  further includes a rigid base  120  on which an object  122  is to be printed and a control arm  124  connected to the rigid base  120 . 
     The rigid base  120  has a print surface  120 A on which the object  122  is configured to be printed, as shown in  FIG.  3   . The control arm  124  is connected to the rigid base  120  to move the rigid base  120  relative to the tank  112 . The first transducer  116  is connected to the tank  112  and is configured to emit the first acoustic wave  118  toward the textured surface  114 . A light source  126  is configured to emit light  128  to the tank  112  to form the printed object  122  on the rigid base  120 . 
     The tank  112  contains a liquid photopolymer resin  130 , as shown in  FIGS.  3  and  6 - 8   . The tank  112  can be any suitable shape to hold the liquid polymer resin  130  therein, such as rectangular or circular. The tank  112  has a base  132  and a side wall  134  extending upwardly from the base  130 . The base  132  is preferably transparent such that the light  128  emitted from the light source  126  can pass through the base  132 . The entirety of the base  132  can be transparent, or a portion of the base  132  can be transparent. The transparent portion of the base  132  constitutes an optically transparent window  132 A through which the emitted light  128  can pass. 
     The rigid base, or build platform, build plate or print bed,  120  provides the surface  120 A on which the object  122  is printed. The print surface  120 A is preferably a planar surface, as shown in  FIG.  3   . The rigid base  120  can be made of any suitable material, such as plastic, such as polylactic acid (PLA), or glass. 
     The control arm  124  is connected to the rigid base  120  to control movement and positioning of the rigid base  120  during the printing process. The control arm  124  is connected to the rigid base  120  to move the rigid base  120  relative to the tank  112 . The control arm  124  preferably has six degrees of freedom, such that the rigid base  120  can move through a curvilinear path to more accurately print the object  122 . The control arm  124  is preferably a robotic arm having six degrees of freedom. The six degrees of freedom are movements along the three axes (i.e., the X, Y and Z axes), and rotation about each of the three axes (i.e., pitch, roll and yaw). Providing the control arm  124  with multiple degrees of freedom, such as six degrees of freedom, allows the control arm  124  to move the rigid base  120  through a curvilinear path, including moving the rigid base  124  to a plurality of positions, thereby allowing a more accurate object  122  to be printed. 
     The liquid polymer resin  130  is selectively cured by light-activated polymerization, such as by photopolymerization, which preferably uses visible or UV light, although light having any suitable wavelength can be used, to form in situ cross-linked polymer structures. The liquid polymer resin  130  preferably includes monomer and oligomer molecules that are converted to solid polymers during photopolymerization when the light  128  emitted by the light source  126  is guided through the transparent portion, or the optically transparent window  132 A, of the base  132  of the tank  112 . 
     The light source  126  emits light  128  to cure the liquid polymer resin  130  in the tank  112 , as shown in  FIG.  3   . The light source  126  preferably emits UV light  128  having a wavelength between approximately 10 and 400 nanometers, inclusive. Preferably, the emitted UV light  128  has a wavelength between approximately 380 and 400 nanometers, inclusive. Light having any suitable wavelength can be used, such as, but not limited to, UV, visible and infrared light. 
     The liquid polymer resin  130  includes a photoinitiator that initiates photopolymerization in the tank  112  when the light  128  emitted by the light source  126  passes through the optically transparent window  132 A of the base  132  of the tank  112 . The photoinitiator absorbs light energy having a predetermined wavelength from the light  128  emitted by the light source  126  to the tank  112 . The photoinitiator is preferably selected based on the wavelength of the light  128  emitted by the light source  126 . 
     As shown in  FIG.  3   , the printed object  122  is formed on the surface  120 A of the rigid base  120 . The printed object  122  is based on a model supplied to a computer (now shown) that controls the 3D printing process. The light  128  emitted from the light source  126  is guided to the tank  112  to cure the liquid polymer resin  130  on the surface  120 A of the rigid base  120  to form a first layer of the printed object  122 . The control arm  124  is connected to the rigid base  120  to move the rigid base  120  relative to the tank  112  in a direction away from the optically transparent window  132 A of the base  132 . The rigid base  120  is moved a distance approximately equal to a thickness of the formed layer. The light  128  is emitted from the light source  126  to cure the liquid polymer resin  130  in the tank  112  to form a second layer on the first layer. This process is repeated until the entire object is printed. When the printing is complete, the printed object  122  can be removed from the print surface  120 A of the rigid base  120 . 
     As shown in  FIG.  3   , the textured surface  114  is connected to the tank  112 . The textured surface  114  is preferably at least disposed on the optically transparent window  132 A of the base  132 . The textured surface  114  is configured such that the light  128  emitted by the light source  126  passes through the textured surface  114  to the liquid polymer resin  130  in the tank  112 . The base  132  has an outer surface  132 B that faces the light source  126  and an inner surface  132 C that faces the liquid polymer resin  130  and the build plate  120 . The textured surface  114  is formed on the inner surface  132 C of the optically transparent window  132 A facing the liquid polymer resin  130 . 
     Referring to  FIG.  3   , the textured surface  114  is formed integrally with the base  132  of the tank  112 . In other words, the textured surface  114  is the surface of the optically transparent window facing the liquid polymer resin  130 . The textured surface  114  includes a plurality of protrusions  136  extending upwardly from the inner surface  132 C of the base  132 . The plurality of protrusions  136  form a plurality of rows extending in a length direction L of the base  132 , and a plurality of columns extending in the width direction W of the base  132 , as shown in  FIGS.  6  and  15   . Each protrusion  136  is preferably equally spaced from adjacent protrusions  136  in the row by a distance L 1 . Each protrusion  136  is preferably equally spaced from adjacent protrusions  136  in the column by a distance W 1 . Preferably, the distances L 1  and W 1  are substantially equal. The projections  136  are enlarged for visualization in the drawing figures. Preferably, the projections  136  measure a few microns or sub-microns in the x, y and z directions. For example, the textured surface  114  can include projections  136  measuring 10×10×10 microns. 
     As shown in  FIGS.  3  and  5 - 7   , the protrusions have a substantially rectangular shape. The protrusions  136  increase the surface area of the inner surface  132 C of the base  132  to increase heat dissipation of the heat generated during light radiation and resin polymerization. In other words, the protrusions  136  act like a heat sink to facilitate heat dissipation. As shown in  FIG.  5   , heat  152  generated during the light radiation and resin polymerization is dissipated from tank  112  through the textured surface  114 . 
     The textured surface  114  can be fabricated in any suitable manner, such as by photolithography, laser texturing, molding, or any other suitable patterning technique. The textured surface  114  can be further treated with a hydrophobic layer  180  to produce a hydrophobic or superhydrophobic surface, as shown in  FIG.  14   . The treated hydrophobic or superhydrophobic surface provides a thermodynamically favorable condition for impregnation by a layer of an inert liquid  146 . For example, the textured surface  114  is formed of fused silica, which is treated with the hydrophobic layer  180  of silane to provide a hydrophobic textured surface. The textured surface  114  can be formed of any suitable optically transparent material. The hydrophobic layer  180  can be any suitable material to provide a hydrophobic or superhydrophobic surface to the textured surface  114 . 
     As shown in  FIGS.  3 ,  6  and  7   , the first transducer  116  is mounted on an interior surface of the tank  112 . Preferably, the first transducer  116  is mounted on the inner surface  132 C of the base  132 . Alternatively, the first transducer  116  can be mounted on an inner surface  134 A of the wall  134 . As shown in  FIG.  3   , the first transducer  116  is mounted on the inner surface  132 C of the base  112  and on the inner surface  134 A of the wall  134  of the tank  112 . The first transducer  116  is mounted at a height of the textured surface  114 . The tank  112  is substantially rectangular as shown in  FIG.  6   , such that the first transducer  116  is disposed on a first wall  134 B that is oppositely disposed a second wall  134 C on which the second transducer  138  is disposed. 
     As shown in  FIGS.  3 ,  6  and  7   , a second transducer  138  is connected to the tank  112  and is configured to emit a second acoustic wave  140  toward the textured surface  114 . The second transducer  138  is disposed opposite the first transducer  116 . The second transducer  138  is preferably disposed at approximately the same height relative to the base  132  of the tank  112  as the first transducer  116 . 
     A first heat exchanger  142  is connected to the tank  112 , as shown in  FIGS.  3 ,  6  and  7   . The first heat exchanger  142  is configured to cool the liquid polymer resin  130 . The first heat exchanger  142  is preferably mounted on an outer surface  134 D of the wall  134  of the tank  112 . The first heat exchanger  142  is preferably mounted to the same wall  134  to which the first transducer  116  is mounted. The first heat exchanger  142  is preferably mounted proximate the first transducer  116 . The first heat exchanger  142  is preferably mounted higher than the first transducer  116  relative to the base  132  of the tank  112 . In other words, the first heat exchanger  142  is preferably mounted higher than the first transducer  116  relative to the transparent window  132 A of the tank  112 . The first transducer  116  is preferably disposed such that at least a portion of the first transducer  116  is lower than an upper surface  130 A of the liquid polymer resin  130  in the tank  112 , as shown in  FIGS.  3  and  7   . 
     As shown in  FIGS.  3 ,  6  and  7   , a second heat exchanger  144  is connected to the tank  112 . The second heat exchanger  144  is configured to cool the liquid polymer resin  130 . The second heat exchanger  144  is preferably mounted on an outer surface  134 D of the wall  134  of the tank  112 . The second heat exchanger  144  is preferably mounted to the same wall  134  to which the second transducer  138  is mounted. The second heat exchanger  144  is preferably mounted proximate the second transducer  138 . The second heat exchanger  144  is preferably mounted higher than the second transducer  138  relative to the base  132  of the tank  112 . In other words, the second heat exchanger  144  is preferably mounted higher than the second transducer  138  relative to the transparent window  132 A of the tank  112 . 
     The first and second heat exchangers  142  and  144  can be any suitable heat exchangers. The first and second heat exchangers  142  and  144  can be passive or active heat exchangers that facilitate extracting and removing heat from the liquid polymer resin  130  in the tank  112  generated by the emitted light  128  and the photopolymerization process of printing the printed object  122 . The first and second heat exchangers  142  and  144  can include a peltier module to facilitate removing heat from the liquid polymer resin  130 . Alternatively, the first and second heat exchangers  142  and  144  can be mounted on an inner surface  134 A of the wall  134  of the tank  112 . Alternatively, the heat exchangers can be implemented into the textured surface  114  to provide direct cooling of the printing region in an active or passive manner. Alternatively, the heat exchangers can be passively or actively circulated by a cooling radiator to facilitate transferring cooler resin from an upper end of the tank  112  to a lower end of the tank  112 . A temperature sensor (not shown) can be disposed in the liquid polymer resin  130  in the tank  112  to monitor the temperature of the resin  130  such that he first and second heat exchangers  142  and  144  can be controlled to maintain the liquid polymer resin  130  at a predetermined temperature. 
     A layer of an inert liquid  146  is disposed on the textured surface  114 , as shown in  FIGS.  3  and  5 - 7   . The inert liquid  146  facilitates preventing adhesion between the liquid polymer resin  130  and the textured surface  114 . The inert liquid  146  is preferably disposed above upper surfaces  136 A of the projections  136  of the textured surface  114 . A refractive index of the inert liquid  146  is approximately equal to a refractive index of the textured surface  114 . Referring to  FIG.  12   , substantially matching the refractive indices of the inert liquid  146  and the textured surface  114  minimizes diffraction of the light  128  emitted by the light source  126  ( FIG.  3   ) to facilitate maintaining printing resolution. The inert liquid  146  is preferably immiscible and non-reactive with the liquid polymer resin  130 . Preferably, the inert liquid  146  has a higher density than the liquid polymer resin  130  to facilitate the inert liquid  146  being disposed between the textured surface  114  and the liquid polymer resin  130 . The inert liquid  146  can be any suitable liquid, such as perfluoropolyether copolymers, fluorosilicone polymers, perfluorocarbon liquid, gallicin or garlic oils, Chemours Krytox GPL oil, and Solvay Fomblin Y oil. 
     The emitted light  128  ( FIG.  3   ) passing through the layer of the inert liquid  146  exhibits minimal attenuation, such that the transmitted power of the emitted light is substantially not reduced. The resulting 3D printing process is energy efficient such that high-speed fabrication of parts is possible with the 3D printing process in accordance with the exemplary embodiments. Existing methods to prevent resin adhesion during the printing process, such as forming a resin dead zone between the transparent window and the printed part, results in problematic light attenuation, which reduces the transmitted power of the emitted light and greatly reduces the obtainable printing speed of the existing 3D printing systems. 
     Referring to  FIGS.  3 ,  5 ,  6  and  7   , the first and second transducers  116  and  138  are mounted to the inner surface  134 A of the wall  134  of the tank  112  and the first and second heat exchangers  142  and  144  are mounted to the outer surface  134 D of the wall  134  of the tank  134 . The first and second transducers  116  and  138  are oppositely disposed. The first and second heat exchangers  142  and  144  are oppositely disposed. The first and second heat exchangers  142  and  144  are disposed above the first and second transducers  116  and  138  relative to the optically transparent window  132 A of the base  132 . 
     As shown in  FIGS.  3  and  5   , the first and second heat exchangers  142  and  144  extract heat  154  from the resin  130 . Removing the heat cools the liquid polymer resin  130 , which increases the density of the resin  130 . As indicated by the flow arrows  150  and  151 , the increased density of the liquid polymer resin  130  proximal the first and second heat exchangers  142  and  144  imparts a downward flow of the resin  130 . The first and second heat exchangers  142  and  144  are configured to cool the liquid polymer resin  130  in the tank  112  to facilitate flow of the liquid polymer resin  30  toward the first and second transducers  116  and  138 , respectively. The wall  134  of the tank  112  is heat dissipative to facilitate removing the heat  154  from the liquid polymer resin  130 . The thermal conductivity of the heat dissipative wall  134  of the tank further facilitates dissipating heat from the resin  130  as the resin flows downwardly proximal the inner surface  134 A of the wall  134 , as indicated by the resin flow arrows  150  and  151 . 
     The first and second transducers  116  and  138  emit first and second acoustic waves  118  and  140 , as shown in  FIGS.  3  and  5   . Preferably, as shown in  FIG.  3   , a first direction of the first acoustic wave  118  is substantially parallel to a second direction of the second acoustic wave  140 . The first and second acoustic waves  118  and  140  facilitate guiding the resin  130  toward the printed object  122 . 
     As shown in  FIGS.  3  and  5   , the flow  150  and  151  of the cooled resin flows toward the textured surface  114 , and the first and second transducers  116  and  138  facilitate guiding the cooled resin toward the printed object  122 . As shown in  FIG.  5   , a circular flow  156  is imparted to the resin  130  by the combination of the first and second heat exchangers  142  and  144  and the first and second transducers  116  and  138  to facilitate guiding resin to a build area of the printed object  122 . The first and second heat exchangers  142  and  144  cool the resin as it flows downwardly proximal the inner surface  134 A of the wall  134 , and the textured surface  114  further facilitates cooling the resin  130  as it flows substantially horizontally across the textured surface  114 , as indicated by the flow arrows  150  and  151  in  FIG.  3   . 
     Referring to  FIG.  13   , the first and second acoustic waves  118  and  140  travel through the resin  130  and the inert liquid  146 . The portion  174  of the acoustic wave generated by the first transducer  116  traveling through the inert liquid  146  travels faster than the portion  172  of the acoustic wave generated by the first transducer  116  through the resin  130 . The faster moving acoustic waves  174  in the inert liquid relative to the slower moving acoustic waves  172  in the resin  130  generates a shearing effect at the interface between the inert liquid  146  and the liquid polymer resin  130 . The generated shearing effect substantially prevents adhesion of the liquid polymer resin  130  to the textured surface  114  of the optically transparent window  132 A. 
     Further, the first and second transducers  116  and  138  are mounted on an interior surface  132 C of the tank  112  such that the emitted the first and second acoustic waves  118  and  140  travel through the inert liquid layer  146  and the liquid polymer resin  130 , which generates a shear vibration at the interface between the inert liquid layer  146  and the liquid polymer resin  130  to further facilitate resin flow. The shear vibration further reduces the interfacial friction force at the interface between the inert liquid layer  146  and the liquid polymer resin  130  to facilitate resin flow. 
     The layer of the inert liquid  146  is inert to the photopolymerization reaction occurring during the 3D printing process. The textured surface  114  stabilizes the layer of the inert liquid  146  to reduce the shear resistance of the resin flow and to substantially prevent resin adhesion, such that the speed of the 3D printing process is improved. The first and second transducers  116  and  138  control the acoustic energy flow to guide the direction flow of the liquid polymer resin  130 , as indicated by the resin flow arrows  150  and  151  in  FIGS.  3  and  156    in  FIG.  5   . The first and second transducers  116  and  138  further facilitate controlling the resin flow to improve the speed of the 3D printing process. The first and second heat exchangers  142  and  144 , in addition to the textured surface  114 , further improve controlling the resin flow by removing heat from the resin. The textured surface  114  scatters the incident acoustic waves to further facilitate resin flow toward the rigid base  120 . 
     As shown in  FIG.  4   , a 3D printing system and method  210  in accordance with another illustrated exemplary embodiment is substantially similar to the 3D printing system and method  110  of the exemplary embodiment illustrated in  FIGS.  3  and  5 - 7    except for the differences described below. Similar parts are identified with similar reference numerals, except increased by 100 (i.e., 2xx, accordingly). 
     The 3D printing system  210  illustrated in  FIG.  4    includes a textured surface  214  that is an insert  219  in the tank  212 . The textured surface  214  is made of an optically transparent material that overlies the optically transparent window  232 A of the base  232  such that the light  228  emitted by the light source  226  passes through the window  232 A and the textured surface  214  into the liquid polymer resin  230  to form a printed object  222  on the rigid base  220 . The insert  219  is disposed adjacent the optically transparent window  232 A. The textured surface  214  is the surface of the insert  219  facing the liquid polymer resin  230 . The insert  219  can be easily replaced when the textured surface  214  deteriorates with time and use. 
     Alternatively, the insert  219  can include the base  232  of the tank  212 . In other words, the insert  219  is connected in an opening defined by the wall  234  of the tank  212 . 
     As shown in  FIGS.  8  and  9   , a 3D printing system and method  310  in accordance with another illustrated exemplary embodiment is substantially similar to the 3D printing system and method  110  of the exemplary embodiment illustrated in  FIGS.  3  and  5 - 7    except for the differences described below. Similar parts are identified with similar reference numerals, except increased by 200 (i.e., 3xx, accordingly). 
     The first and second transducers  316  and  338  and are mounted on an outer surface of the wall  334  of the tank  312 . The first and second heat exchangers  342  and  344  are mounted on the outer surface  334 D of the wall  334  of the tank  312 . The first transducer  316  is disposed above the first heat exchanger  342 . The second transducer  338  is disposed above the second heat exchanger  344 . In other words the first heat exchanger  342  is mounted lower than the first transducer  316  relative to the transparent window of the tank  312 , and the second heat exchanger  344  is mounted lower than the second transducer  344  relative to the transparent window of the tank  312 . The first and second transducers  316  and  338  are disposed above an upper surface of the liquid polymer resin  330  in the tank  330 . 
     The first transducer  316  emits a first acoustic wave  318  toward the textured surface  314 . The second transducer  338  emits a second acoustic wave  340  toward the textured surface  314 . A non-zero angle α is formed between the first direction of the first acoustic wave  318  and a second direction of the second acoustic wave  340 , as shown in  FIG.  8   . The first and second directions of the first and second acoustic waves  318  and  340  are not parallel. 
     The first and second transducers  316  and  338  are disposed above the protrusions  336  of the textured surface  314  and above the layer of the inert liquid  346 . The first and second transducers  316  and  338  are preferably disposed above an upper surface  330 A of the resin  330  in the tank  312 . 
     As shown in  FIGS.  10  and  11   , a 3D printing system and method  410  in accordance with another illustrated exemplary embodiment is substantially similar to the 3D printing system and method  110  of the exemplary embodiment illustrated in  FIGS.  3  and  5 - 7    except for the differences described below. Similar parts are identified with similar reference numerals, except increased by 300 (i.e., 4xx, accordingly). 
     Referring to  FIGS.  10  and  11   , the tank  412  is substantially rectangular. A transducer  416  and a heat exchanger  442  are mounted on an outer surface  434 D of each of the wall  434 . A first transducer  416  is mounted above a first heat exchanger  442  on a first wall  434 B. A second transducer  438  is mounted above a second heat exchanger  444  on a second wall  434 C. The second wall  434 C is disposed opposite the first wall  434 B. A third transducer  460  is mounted above a third heat exchanger  464  on a third wall  434 E. A fourth transducer  462  is mounted above a fourth heat exchanger  466  on a fourth wall  434 F. The fourth wall  434 F is disposed opposite the third wall  434 E. The third transducer is configured to emit a third acoustic wave, and the fourth transducer  462  is configured to emit a fourth acoustic wave. The third transducer  460  is disposed opposite the fourth transducer  462 . 
     The transducers  416 ,  438 ,  46 A) and  462  emit acoustic waves similarly to the acoustic waves of the transducers illustrated in  FIG.  8   . In other words, the acoustic waves emitted by the oppositely disposed transducers form non-zero angles. The transducers emit acoustic waves toward the textured surface  414 . 
     The first to fourth transducers  416 ,  438 ,  460  and  462  are disposed above the protrusions  436  of the textured surface  414  and above the layer of the inert liquid. The first to fourth transducers  416 ,  438 ,  460  and  462  are preferably disposed above an upper surface of the resin  430  in the tank  412 . 
     As shown in  FIGS.  16  and  17   , a textured surface  514  in accordance with another illustrated exemplary embodiment is substantially similar to the textured surface  114  of the 3D printing system and method  110  of the exemplary embodiment illustrated in  FIGS.  3  and  5 - 7    except for the differences described below. Similar parts are identified with similar reference numerals, except increased by 400 (i.e., 5xx, accordingly). 
     Each of the protrusions  536  extends from the inner surface  532 C, as shown in  FIGS.  16  and  17   . Each protrusion  536  has a substantially planar upper surface  536 A. A connecting portion  536 B connects an upper portion  536 C of the protrusion  536  to the inner surface  532 C. The connecting portion  536 B tapers inwardly to a lower surface  536 D of the upper portion  536 C of the protrusion  536 . The upper portion  536 C has a substantially rectangular cross section. 
     As shown in  FIG.  17   , the inner surface  532 C and the protrusions  536  can include nanostructures  582 . The nanostructures  582  are preferably hydrophobic, thereby further enhancing the hydrophobicity of the textured surface  514 . 
     As shown in  FIGS.  18  and  19   , a 3D printing system and method  210  in accordance with another illustrated exemplary embodiment is substantially similar to the 3D printing system and method  110  of the exemplary embodiment illustrated in  FIGS.  3  and  5 - 7    except for the differences described below. Similar parts are identified with similar reference numerals, except increased by 500 (i.e., 6xx, accordingly). 
     Each of the protrusions  636  extends from the inner surface  632 C, as shown in  FIGS.  17  and  18   . Each protrusion  636  has a substantially planar upper surface  636 A. A connecting portion  636 B connects an upper portion  636 C of the protrusion  636  to the inner surface  632 C. The connecting portion  636 B has a first portion that tapers inwardly moving away from the inner surface  632 C, and a second portion that tapers outwardly toward the upper portion  636 C. The connecting portion  636 B has a substantially concave outer surface. The upper portion  636 C has a substantially rectangular cross section. 
     As shown in  FIG.  18   , the inner surface  632 C and the protrusions  636  can include nanostructures  682 . The nanostructures  582  are preferably hydrophobic, thereby further enhancing the hydrophobicity of the textured surface  614 . 
     As shown in  FIG.  20   , a 3D printing system and method  710  in accordance with another illustrated exemplary embodiment is substantially similar to the 3D printing system and method  110  of the exemplary embodiment illustrated in  FIGS.  3  and  5 - 7    except for the differences described below. Similar parts are identified with similar reference numerals, except increased by 600 (i.e., 7xx, accordingly). The 3D printing system and method of  FIG.  20    can be used with the system and can use any of the features of any of  FIGS.  3 - 19   . 
     The 3D printing system  710  illustrated in  FIG.  20    includes a tank  112  containing a liquid photopolymer resin  730 . The tank  712  can be any suitable shape to hold the liquid polymer resin  730  therein, such as rectangular or circular. The tank  712  has a base  732  and a side wall ( 134 ,  FIG.  5   ) extending upwardly from the base  732 . The base  732  is preferably transparent such that light  728  emitted from a light source  726  passes through the base  732 . An outer surface  732 B of the base  732  faces the light source  726  The entirety of the base  732  can be transparent, or a portion of the base  732  can be transparent. The transparent portion of the base  732  constitutes an optically transparent window  732 A through which the light  728  emitted by the light source  726  passes. 
     The 3D printing system  710  illustrated in  FIG.  20    further includes a textured surface  714  disposed in a tank  712 . The textured surface  714  is made of an optically transparent material that overlies the optically transparent window  732 A of the base  732  such that the light  728  emitted by a light source  726  passes through the window  732 A and the textured surface  714  into the liquid polymer resin  730  to form a printed object  722  on a rigid base  720 . The textured surface can be hydrophobic or omniphobic. 
     The textured surface  714  can be an insert  719  disposed adjacent the optically transparent window  732 A, as shown in  FIG.  20   . The textured surface  714  is the surface of the insert  719  facing the liquid polymer resin  730 . The insert  719  can be easily replaced when the textured surface  714  deteriorates with time and use. The insert  719  can be made of any suitable material, such as polydimethylsiloxane (PDMS). 
     Alternatively, the insert  719  can include the base  732  of the tank  712 . In other words, the insert  719  is connected in an opening defined by a wall of the tank  712 . 
     Alternatively, the textured surface  714  can be etched onto a surface of the optically transparent window facing the liquid polymer resin  730 , as shown in  FIG.  3   . 
     A layer of an inert material  746  is disposed on the textured surface  714 , as shown in  FIG.  20   . The inert material  746  facilitates preventing adhesion between the liquid polymer resin  730  and the textured surface  714 . The inert material  746  is preferably disposed above upper surfaces  736 A of the projections  736  of the textured surface  714 . The resin  730  is disposed between the layer of the inert material  746  and the rigid base  720 . The layer of the inert material  746  is inert to the photopolymerization reaction occurring during the 3D printing process. The inert material  746  is preferably a liquid, a semi-liquid, or a semi-solid, including gels. 
     The layer of the inert material  746  forms a meniscus between the textured surface  714  and the resin  730 , as shown in  FIG.  20   . The inert material  746  provides a slippery surface to facilitate resin flow, including the recoating process, and facilitates smoothing out the cured surface of the printed object  722  to provide high speed printing and surface smoothness of the printed object  722 . The inert material  746  has an interfacial energy to strongly adhere to the textures surface  714  and has a surface tension and interfacial energy with the resin  730  to support and hold the resin  730  with minimal interruption in the inert material layer  746 . The meniscus formed by the layer of the inert material  746  substantially prevents penetration of the resin  730  into the inert material layer  746 , even when a density of the resin  730  is greater than a density of the inert material  730 . The inert material  746  separates and supports the resin  730  from the textured surface  714 . The inert material  746  is substantially uniform across the entire plane, as shown in  FIG.  20   , such that the surface  722 A of the printed object  722  can be smoothly formed. The light  728  emitted by the light source  726  cures the resin  730  substantially immediately after passing through the inert material layer  746 , such that the attenuation of the emitted light  728  is minimized to provide a sharper image to the resin  730  and improving the printing resolution. 
     An upper surface  746 A of the inert material  746  is spaced a predetermined distance D 1  above an uppermost surface  736 A of the projections  736  of the textured surface  736 . The predetermined distance D 1  is preferably between approximately one to ten microns, inclusive. A predetermined distance D 2  from the surface  714 A of the textured surface  714  to a lower surface  722 A of the printed object  722  (the surface  720 A of the rigid base  720  prior to initiating the printing process) is preferably between 1 to 500 microns, inclusive. 
     A refractive index of the inert material  746  is approximately equal to a refractive index of the textured surface  714 . Substantially matching the refractive indices of the inert material  746  and the textured surface  714  minimizes diffraction of the light  728  emitted by the light source  726  to facilitate maintaining printing resolution, as shown in  FIG.  12   . The inert material  746  is preferably immiscible and non-reactive with the liquid polymer resin  730 . Preferably, the inert material  746  has a higher density than the liquid polymer resin  730  to facilitate the inert material  746  being disposed between the textured surface  714  and the liquid polymer resin  730 , although the inert material  746  can have a density lower than a density of the resin  730 . The inert material  746  can be any suitable liquid, such as silicone/polydimethylsiloxane polymer oils, perfluoropolyether copolymers, fluorosilicone polymers, perfluorocarbon liquid, gallicin or garlic oils, Chemours Krytox GPL oil, and Solvay Fomblin Y oil, or any suitable semi-liquid, or semi-solid, including gels. 
     The inert material  746  preferably does not mix with the resin  730 . The inert material  746  preferably is any suitable material having a low viscosity, a low surface tension, and high density. The inert material  746  has any suitable viscosity, preferably between approximately 5 cps (centipoise) and 131 cps, inclusive. The inert material  746  can have any suitable surface tension, preferably between approximately 19 dynes/cm (centimeter) and 19.7 dynes/cm, inclusive. The inert material  746  can have any suitable density, preferably between approximately 0.913 grams/square centimeter and 1.9 grams/square centimeter, inclusive. 
     A control arm  724  is connected to the rigid base  720  to control movement and positioning of the rigid base  720  during the printing process. The control arm  724  is connected to the rigid base  720  to move the rigid base  720  relative to the tank  712 . The control arm  724  preferably has six degrees of freedom, such that the rigid base  720  can move through a curvilinear path to more accurately print the object  722 . The control arm  124  is preferably a robotic arm having six degrees of freedom along the three axes (i.e., the X, Y and Z axes), and rotation about each of the three axes (i.e., pitch, roll and yaw). 
     The projections  736  can have any suitable size and shape. As shown in  FIGS.  15  and  20   , the projections  736  are substantially rectangular and have a dimension A 1  of approximately 10 micros in the x-direction, a dimension A 2  of approximately 10 microns in the y-direction, and a dimension of approximately 10 microns in the z-direction. A distance A 3  between each of the projections  736  is approximately 10 micros. 
     The layer of the inert material  746  minimizes power loss of the light  728  emitted by the light source  726  by minimizing light diffraction through the textured surface  714 . The 3D printing system  710  does not include an unpolymerized resin area, or dead zone, such that the emitted light  728  substantially immediately cures the resin  730  after passing through the layer of the inert material  746  to provide a continuous, high-speed printing process. As the control arm  724  continuously moves the rigid base in the y-direction indicated by arrow  722 B, as shown in  FIG.  20   , the resin  730  flows from a first area  730 A to a second area  730 B and into a curing area  730 C. The layer of the inert material  746  provides a slippery liquid interface to facilitate the flow of resin  730  from the first area  730 A to the second area  730 B and into the curing area  730 C, further facilitating a continuous, high-speed printing process. The printing process in accordance with the embodiments of the present invention can obtain a linear printing speed of 667 microns/second or 2.4 m/hr. 
     The layer of the inert material in addition to the acoustic wave emitted by the transducer in accordance with the disclosure substantially prevents resin adhesion during the 3D printing process to eliminate the up and down motion of the rigid base performed in existing 3D printing processes. The acoustic waves emitted by the transducer in addition to the resin cooling provided by the heat exchanger in accordance with the disclosure facilitates resin flow to improve 3D printing speed. The layer of the inert material between the textured surface and the resin in accordance with the disclosure further facilitates continuous, high-speed printing. The provided resin cooling allows continuous, large volumetric 3D printing by minimizing the effects associated with thermal curing caused by over-heated resin. 
     General Interpretation of Terms 
     In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. 
     The term “detect” as used herein to describe an operation or function carried out by a component, a section, a device or the like includes a component, a section, a device or the like that does not require physical detection, but rather includes determining, measuring, modeling, predicting or computing or the like to carry out the operation or function. 
     The term “configured” as used herein to describe a component, section or part of a device includes hardware and/or software that is constructed and/or programmed to carry out the desired function. 
     The terms of degree such as “substantially”. “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. 
     While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, the size, shape, location or orientation of the various components can be changed as needed and/or desired. Components that are shown directly connected or contacting each other can have intermediate structures disposed between them. The functions of one element can be performed by two, and vice versa. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.