Patent Publication Number: US-2012038705-A1

Title: Method and Apparatus for Delivering Ink Material from a Discharge Nozzle

Description:
The instant application claims priority to provisional application No. 61/453,098, filed Mar. 15, 2011 and to patent application Ser. No. 12/139,409, filed Jun. 13, 2008, which claims priority to provisional application No. 60/944,000, filed Jun. 14, 2007, the disclosure of the identified applications are incorporated herein in their entirety. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The disclosure relates to method and apparatus for efficiently depositing patterns of film on a substrate. More specifically, the disclosure relates to a method and apparatus for providing ink to a deposition apparatus for depositing an organic film on a substrate. 
     2. Description of Related Art 
     The manufacture of light emitting devices requires depositing one or more organic films on a substrate and coupling the top and bottom of the film stack to electrodes. The film thickness is a prime consideration and the deposition process must be optimized to deliver optimal thickness uniformity. The printing is typically accomplished by introducing liquid ink containing film material dissolved or suspended in a carrier fluid onto a discharge nozzle which then delivers all or part of the received film material onto the substrate. 
     The liquid ink is typically stored in a reservoir and is delivered to a discharge array. The discharge array comprises a multitude of interconnected discharge nozzles arranged in rows and columns. Each discharge nozzle prints a pixel on the substrate. The discharge nozzles typically comprise one or more micropores. The micropores receive liquid ink from the ink reservoir at a surface proximal thereto and dispense the ink material onto the substrate from their distal surface. The ink material can be dispensed in substantially vapor phase so as to allow formation of a film layer on the substrate in the absence of a carrier fluid. 
     Each discharge nozzle is spaced apart from its adjacent discharge nozzles. Although the liquid ink is intended to be delivered directly to the microarrays of each discharge nozzle, misalignment issues prevent complete delivery and only a fraction of the supplied ink makes its way to the micropores. The ratio of the quantity of liquid ink entering the pores compared to the quantity of liquid ink (including dissolved or suspended material) remaining or drying on the surface is called ink loading efficiency. When a large amount of liquid is supplied to the discharge array but only a small portion of the ink material makes its way into the micropores, the system is considered to have low loading efficiency. Moreover, when liquid ink material is finally delivered to the micropores, one or more solid particles can clog a micropore and thereby cause incomplete discharge. 
     Accordingly, there is a need for a method and apparatus that allows filling the micropores uniformly even if liquid ink is delivered some distance away from the region of interest with high loading efficiency. 
     SUMMARY 
     The disclosure relates to a method and apparatus for efficiently depositing a film on a substrate. More specifically, the disclosure relates to a method and apparatus for directing liquid ink containing dissolved or suspended OLED material to a printhead surface in order to form an OLED film on the substrate. The OLED film can be substantially-free from carrier fluid and the delivery system is optimized to increase the loading efficiency. 
     An exemplary implementation of the disclosure relates to a method for loading film material into a discharge array. The discharge array includes a surface and a plurality of micropores extending through the surface. The discharge array is interposed between a liquid ink delivery system and a substrate. The liquid ink delivery system may include a plurality of nozzles which correspond to, and are aligned, with the plurality of micropores. The nozzles deliver liquid ink comprising of a carrier fluid having suspended or dissolved film material therein. 
     After a quantity of liquid ink is delivered to the discharge array, only a portion of the delivered ink is received at the micropores and the balance is received at the surface of the array. A pressurized gas knife is then moved over the discharge array to drive the delivered ink material to the micropores. The carrier fluid is removed from the delivered ink to form a substantially carrier-free ink material at the micropores prior to dispensing the substantially carrier-free film material from the micropores. 
     In another embodiment of the disclosure, the non-discharge surfaces and the micropores are treated such that the non-discharge surfaces repel liquid ink while the micropores attract the liquid ink. The treatment can be one of chemical treatments (i.e., coating with a repellant or attracting chemical), a physical treatment (i.e., differential surface roughness etching or other forms of solid surface treatment), an electrochemical treatment (i.e., anodic treatment) or a combination of these treatments. 
     In still another embodiment, the disclosure relates to an apparatus for loading ink material into discharge system. The apparatus comprises an ink discharge system defined by an array having a surface and at a first micropore extending through the surface; an ink supply for delivering liquid ink to the discharge system, the liquid ink can be defined by a carrier fluid containing dissolved or suspended film material therein; a gas knife for directing pressurized gas to the surface and the first micropore to distribute liquid ink across the surface and into the first micropore; and an energy source for evaporating the carrier fluid from the delivered liquid ink to thereby leave a substantially carrier-free film material in the first micropore. The energy source can comprise a heater. The micropore can be configured to receive the ink and the surrounding surfaces can be configured to repel the ink. The film that forms on the substrate can be a substantially carrier-free layer of an organic light emitting diode. 
     In yet another embodiment, the disclosure relates to a method for depositing a film material on a substrate by (1) supplying a quantity of liquid ink defined by a carrier fluid containing dissolved or suspended ink material to an array defined by a first surface having a plurality of blind micropores extending therethrough; (2) repelling the liquid ink from the first surface of the array toward a first of the plurality of blind micropores; (3) receiving the liquid ink at the first micropore; (4) flowing a pressurized gas over the surface to drive the liquid ink into the first micropore; (5) removing the carrier fluid from the delivered ink to form a substantially carrier-free ink material at the first micropore; and (6) dispensing the substantially carrier-free ink material from the at least one micropore to form the film on a substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other embodiments of the disclosure will be discussed with reference to the following exemplary and non-limiting illustrations, in which like elements are numbered similarly, and where: 
         FIG. 1A  provides a schematic representation of a thermal jet print-head which can be used with an embodiment of the disclosure; 
         FIG. 1B  is a schematic representation of an apparatus for depositing a film according to still another embodiment of the disclosure; 
         FIGS. 2A-2D  schematically illustrate the process of depositing a solvent-free material using a print-head apparatus according to an embodiment of the disclosure; 
         FIG. 3A-3C  schematically illustrate representative discharge arrays; 
         FIG. 4  is an exemplary embodiment of a gas knife according to one embodiment of the disclosure; 
         FIG. 5  is an exemplary embodiment of the surface of an exemplary discharge nozzle; 
         FIG. 6A  shows a pore array according to an embodiment of the disclosure; 
         FIGS. 6B and 6C  are schematic representations of an embodiment of the invention. 
         FIG. 7  shows a discharge nozzle having an interconnected channel structure; 
         FIGS. 8A-8D  schematically illustrate cross-sections of exemplary micropore structures; and 
         FIG. 9  schematically illustrates top views of exemplary micropores. 
     
    
    
     DETAILED DESCRIPTION 
     In one embodiment, the disclosure relates to a method and apparatus for depositing a film substantially free from carrier liquid on a substrate. In another embodiment, the disclosure relates to a method and apparatus for depositing a film of material in a substantially solid form on a substrate. In another embodiment, the disclosure relates to a method and apparatus for depositing a film of material substantially free of solvent onto a substrate. Such films can be used, for example, in the design and construction of OLEDs and large area transistor circuits. The materials that may be deposited by the apparatuses and methods described herein include organic materials, metal materials, and inorganic semiconductors and insulators, such as inorganic oxides, chalcogenides, Group IV semiconductors, Group III-V compound semiconductors, and Group II-VI semiconductors. 
       FIG. 1A  provides a schematic representation of a thermal jet print-head which can be used with implementation of the disclosure. Referring to  FIG. 1A , the exemplary apparatus for depositing a material on a substrate comprises reservoir  130 , orifice  170 , nozzle  180 , and micro-porous conduits  160  (interchangeably, micropores  160 ). Reservoir  130  receives ink in liquid form and communicates the ink from orifice  170  to discharge nozzle  180 . The exemplary ink can be defined by a carrier fluid containing dissolved or suspended film material therein. These dissolved or suspended film materials may comprise single molecules or atoms, or aggregations of molecules and/or atoms. The path between orifice  170  and discharge reservoir  180  defines a delivery path. In the embodiment of  FIG. 1A , discharge nozzle  180  comprises conduits  160  separated by partitions  165 . Conduits  160  may include micro-porous material therein. A surface of discharge nozzle  180  proximal to orifice  170  defines the inlet port to discharge nozzle  180  while the distal surface of discharge nozzle  180  defines the outlet port. A substrate (not shown) can be positioned proximal to the outlet port of discharge nozzle  180  for receiving ink deposited from the nozzle. 
     While reservoir  130  appears in alignment with discharge nozzle  180 , in practice the two may be misaligned. Consequently, the ink liquid ink is dropped over the exposed surface area adjacent discharge nozzle  180  and not into micropores  160 . This misalignment causes poor loading efficiency as significantly less ink or film material makes its way to the micropore and ultimately onto the substrate. 
     The thermal jet print-head of  FIG. 1A  further includes bottom structure  140 , which receives discharge nozzle  180 . Discharge nozzle  180  can be fabricated as part of the bottom structure  140 . Alternatively, discharge nozzle  180  can be manufactured separately and later combined with bottom structure  140  to form an integrated structure. Top structure  142  receives reservoir  130 . Top structure  142  can be formed with appropriate cavities and conduits to form reservoir  130 . Top structure  142  and bottom structure  140  are coupled through bonds  120  to form a housing. A heater  110  can be optionally added to reservoir  130  for heating and/or dispensing the ink. In  FIG. 1A , heater  110  is positioned inside reservoir  130 . 
     Discharge nozzle  180  includes partitions (or rigid portions)  165  separated by micropores  160 . Micropores  160  and rigid portions  165  can collectively define a micro porous environment. The micro-porous environment can be composed of a variety of materials, including, micro-porous alumina or solid membranes of silicon or silicon carbide and having micro-fabricated pores. Micropores  160  prevent the material dissolved or suspended in the liquid from escaping through discharge nozzle  180  until the medium is appropriately activated. When the discharged droplet of liquid encounters discharge nozzle  180 , the liquid is drawn into micropores  160  with assistance from capillary action. The carrier fluid in the quantity of ink may evaporate prior to activation of discharge nozzle  180 , leaving behind a coating of the dissolved or suspended film material on the micropore walls. The carrier fluid may comprise one or more solvents with a relatively low vapor pressure. The carrier fluid may also comprise one or move solvents with a relatively high vapor pressure. 
     The evaporation of the carrier fluid may be accelerated by heating the discharge nozzle. The evaporated carrier fluid can be removed from the reservoir and subsequently collected (not shown), for instance, by flowing gas over one or more of the discharge nozzle faces. Depending on the desired application, micropores  160  can provide conduits (or passages) having a maximum linear cross sectional distance W of a few nanometers to hundreds of micrometers. The microporous region comprising discharge nozzle  180  will take a different a shape and cover a different area depending on the desired application, with a typical maximum linear cross-sectional dimension D ranging from a few hundred nanometers to tens of millimeters. In one embodiment, the ratio of W/D is in a range of about 1/10 to about 1/1000. 
     In the exemplary apparatus of  FIG. 1A , discharge nozzle  180  is energized by nozzle heater  150 . Nozzle heater  150  can be positioned proximal to discharge nozzle  180 . Nozzle heater  150  may comprise a thin metal film. The thin metal film can comprise, for example, platinum. When activated, nozzle heater  150  provides pulsating thermal energy to discharge nozzle  180 , which acts to dislodge the material contained within micropores or conduits  160 , which can subsequently flow out from the discharge nozzle. In one embodiment, the pulsations can be variable on a time scale of one minute or less. 
     Dislodging the dissolved or suspended film material may include vaporization, either through sublimation or melting and subsequent boiling. It should be noted again that the term dissolved or suspended film material is used generally, and includes anything from a single molecule or atom to a cluster of molecules or atoms. In general, one can employ any energy source coupled to the discharge nozzle that is capable of energizing discharge nozzle  180  and thereby discharging the film material from micropores  160 ; for instance, mechanical (e.g., vibrational). 
       FIG. 1B  is a schematic representation of an apparatus for depositing a film according to still another embodiment of the disclosure. In the exemplary apparatus of  FIG. 1B , optional confining well  145  is introduced. This structure mechanically confines the quantity of liquid ink, or any other material, supplied to discharge nozzle  180  from ink reservoir  130  through reservoir orifice  170 . This structure can enhance the uniformity of the loading of ink into micropores  160  and can correct for positioning errors in the placement of ink material supplied to discharge nozzle  180  from ink reservoir  130 .  FIG. 1B  also shows connective regions  155  and gaps  120 , which separate two parts of the housing. Connective regions  155  are used to connect discharge nozzle  180  to bottom structure  140 .  FIG. 1B  also shows heater  150  extending beneath brackets  155  to reach discharge nozzle  180 . 
       FIGS. 2A-2D  schematically show the process of depositing film on a substrate according to one embodiment of the disclosure. In  FIG. 2A , liquid ink  101  is commissioned to reservoir  130 . Ink  101  can have a conventional composition. In one embodiment, ink  101  is a liquid ink defined by a carrier fluid containing dissolved or suspended particles therein. 
     Referring again to  FIG. 2A , reservoir heater  110  comprises the ink dispensing mechanism and pulsatingly imparts thermal energy into liquid ink  101 . The thermal energy drives at least a portion of liquid ink  101  through orifice  170  to form ink droplet  102 . Ink droplet  102  can define all of, or a portion of liquid ink  101 . The pulsating impartment of energy from an energy source (e.g., heater  110 ) determines the quantity of liquid ink to be metered out from reservoir  130 . Once droplet  102  is metered out of reservoir  130 , it is directed to discharge nozzle  180 . 
     In another exemplary embodiment, piezoelectric elements (not shown) can be positioned at or near reservoir  130  to meter out the desired quantity of ink  101  through orifice  170 , thereby forming droplet  102 . In yet another exemplary embodiment, liquid can be streamed out of reservoir  130  through orifice  170  (by, for instance, maintaining a positive ink pressure) and this stream can be pulsatingly interrupted by a mechanical or electrostatic force such that metered droplets created from this stream and further directed onto discharge nozzle  180 . If mechanical force is utilized, it can be provided by introducing a paddle (not shown) that pulsatingly intersects the stream. If electrostatic force is utilized, it can be provided by introducing a capacitor (not shown) around the stream that pulsatingly applies an electromagnetic field across the stream. Thus, any pulsating energy source that activates a dispensing mechanism and thereby meters liquid ink  101  delivered from reservoir  130  through orifice  170  and to discharge nozzle  180  can be utilized. The intensity and the duration of each energy pulse can be defined by a controller (not shown) which is discussed below. Furthermore, as noted above, this metering can occur primarily when the ink is ejected from reservoir  130  through orifice  170 ; alternatively, this metering can occur primarily while the ink is traveling from orifice  170  to discharge nozzle  180 . 
     As discussed in the exemplary embodiments of  FIGS. 1A and 1B , discharge nozzle  180  includes micropores for receiving and transporting metered liquid ink  102  to the substrate. Discharge nozzle heater  150  is placed proximal to discharge nozzle  180  to heat the discharge nozzle. A heater can also be integrated with the discharge nozzle such that partitions  165  define the heating elements. 
     Discharge nozzle  180  has a proximal surface (alternatively, inlet port)  181  and a distal surface (alternatively, outlet port)  182 . Proximal surface  181  and distal surface  182  are separated by a plurality of partitions  160  and micropores  165 . Proximal surface  181  faces reservoir  130  and distal surface  182  faces substrate  190 . Nozzle heater  150  can be activated such that the temperature of discharge nozzle  180  exceeds the ambient temperature which enables rapid evaporation of the carrier liquid from droplet  102  which is now lodged in conduits  160 . Nozzle heater  150  may also be activated prior to energizing the ink dispenser (and metering ink droplet  102  as it travels from reservoir  130  through orifice  170  to discharge nozzle  180 ) or after droplet  102  lands on discharge nozzle  180 . In other words, reservoir heater  110  and discharge heater  150  can be choreographed to pulsate simultaneously or sequentially. 
     In the next step of the process, liquid ink  103  (previously liquid ink droplet  102 ) is directed to inlet port  181  of discharge nozzle  180  between confining walls  145 . Liquid ink  103  is then drawn through conduits  160  toward outlet port  182 . The carrier fluid in liquid ink  103 , which may fill conduits  160  extends onto the surrounding surface, with the extent of this extension controlled in part by the engineering of confining walls  145 , may evaporate prior to activation of discharge nozzle  180 , leaving behind on the micropore walls the dissolved or suspended film material (herein, solid ink material)  104  ( FIG. 2C ) that are substantially solid and which can be deposited onto substrate  190 . Alternatively, the carrier fluid ( FIG. 2B ) may evaporate during activation of nozzle heater  150 . 
     Activating nozzle heater  150  in  FIG. 2C , provides pulsating energy to discharge nozzle  180  and dislodges solid ink material  104  from conduits  160 . The result is shown in  FIG. 2D . The intensity and the duration of each energy pulse can be defined by a controller (not shown.) The activating energy can be thermal energy. Alternatively, any energy source directed to discharge nozzle  180  which is capable of energizing discharge nozzle  180  to thereby discharge material  104  from conduits  160  (e.g., mechanical, vibrational, ultrasonic, etc.) can be used. Deposited film  105  is thus deposited in solid form substantially free of the carrier fluid present in liquid ink  101  (see  FIG. 2A ). That is, substantially all of the carrier fluid is evaporated from ink  103  while it travels through discharge nozzle  180 . The evaporated carrier fluid, which typically comprises a mixture of one or more solvents, can be transported away from the housing by one or more gas conduits (not shown). 
     In an exemplary embodiment, ink material  104  is heated so as to evaporate the solid ink material and direct a vapor stream containing ink material  104  onto substrate  190 . Substrate  190  is positioned proximal to discharge nozzle  180  for receiving the vaporized ink material to form thin film  105 . Simultaneously, reservoir  130  is provided with a new quantity of liquid ink  101  for the next deposition cycle. 
       FIG. 3A  a schematic representation of a discharge array. In  FIG. 3 , discharge array  330  includes a plurality of discharge nozzles  332  which appear in rows and columns for dispensing ink material onto a substrate. An exploded view of an exemplary discharge nozzle  332  is also provided showing a plurality of micropores  336 . Micropores  336  can define conduits or any other forms suitable for receiving and transferring ink material. 
     Micropores can extend through the discharge nozzle or they can define blind micropores.  FIGS. 3B and 3C  illustrate these embodiments. Specifically,  FIG. 3B  shows micropores  338  extending from distal side  339  to the proximal side  342  of discharge nozzle  332 . In contrast,  FIG. 3C  shows an embodiment in which micropores  340  are blind micropores extending partially through discharge nozzle  334 . The blind micropores extend from proximal surface  342 . 
     In an exemplary printing process each discharge nozzle receives liquid ink from one or more reservoirs (not shown). The discharge nozzles are preferably aligned with a corresponding liquid ink reservoir (see, for example,  FIG. 1A ). A controller meters liquid ink from each reservoir to a corresponding discharge nozzle. In practice, however, a portion of the supplied ink is received at the surface area separating adjacent discharge nozzles. This quantity of liquid ink fails to make its way into the micropores and often dries on the proximal surface of discharge array  300 , causing gumming and other problems. Another continuing problem with the deposition material is the clogging of the pores and/or incomplete dispensing of material from the nozzle. 
     To address these and other problems, an embodiment of the disclosure is directed to a gas knife for providing a continuous gas stream over the proximal surface of the discharge array. The proximal surface of the discharge array receives ink from one or more reservoirs. Once a quantity of the liquid ink is delivered to the discharge nozzle, pressurized gas (or air) in the form of a gas knife is directed over a surface of the discharge nozzle. The gas knife distributes pressurized gas (or air) across a surface of the discharge nozzle driving the liquid ink into the micropores and away from the surfaces between adjacent micropores. 
     In the embodiment of  FIG. 3B , discharge nozzle  332  is inked on distal surface  339 . A gas knife provides pressurized gas to distal surface  339  to thereby drive the ink material into micropores  338 . Ink material is deposited from proximal surface  342  onto the substrate (not shown). The gas knife helps drive ink material through micropores  332 . In the embodiment of  FIG. 3C , discharge nozzle  334  receives ink material on proximal surface  342 . A gas knife is then used on proximal surface  342  to drive ink material into micropores  340 . Thereafter, a substrate (not shown) can be positioned adjacent to proximal surface  342  to receive ink material therefrom. 
       FIG. 4  is an exemplary embodiment of a gas knife according to one embodiment of the disclosure. Specifically,  FIG. 4  shows exemplary gas knife apparatus  400  having discharge  410  and lips  420 . Gas knife  400  can be coupled to a gas source, a compressor or any other device capable of producing high pressure gas. Gas knife  400  may provide compressed air or a noble gas at ambient temperature or at elevated temperature. Lips  420  can form a slit opening to supply pressurized gas to the underlying structure. Apparatus  400  can be stationary with respect to the micropores or it can be move relative thereto. 
     After liquid ink is deposited on the micropores and the array surface ( 300   FIG. 3 ), pressurized gas is supplied by apparatus  400  and is targeted to the proximal surface of the discharge array  440 . The flow of pressurized gas is shown by arrows  430 . In an exemplary embodiment, apparatus  400  is moved over the array in order to distribute the delivered ink across the surface, and into each micropore. As stated, the pressurized gas can be at an elevated temperature to help evaporate the carrier fluid contained in the liquid ink. 
     Once the ink material is drawn into the micropores, pressurized gas can help further evaporate the carrier fluid and drive down the carrier-free ink material deeper into each micropore. Upon evaporation of the carrier fluid, substantially carrier-free ink material can be collected at each micropore and can be discharged onto the substrate in solid or vapor form. In one embodiment, substantially solid ink material is vaporized at the micropore and allowed to condense on the substrate surface as a substantially liquid-free film material. This process can be aided by a local heater proximal to, or integrated with, each discharge nozzle (see, for example,  FIGS. 1A and 1B ). 
     In an exemplary embodiment, the gas knife further includes a width and a length, which the sweeps along the longitude of the discharge nozzle. In one embodiment, the length of the gas knife is less than one third to total sweep distance, and the width is long enough to ensure complete coverage of the surface throughout the sweep. 
     In another embodiment, the liquid ink is delivered to and discharged from the proximal face of the micropores. The gas knife drives the delivered liquid ink into the micropores while simultaneously helping in evaporating and removing the carrier fluid from the proximal surface. It should be noted that the quantity of delivered ink can exceed the sum total of all of the available micropores&#39; volume. Once the delivered ink material is received by the micropores, additional carrier fluid is evaporated, leaving behind a substantially solid ink material within each micropore. The gas knife will then help drive the substantially solid ink material through the micropores toward the distal face of the micropore. The substantially dry ink material is then vaporized and or ejected from the distal end onto a substrate, forming a substantially solid film thereon. 
     For blind pores, the ink can also be delivered in larger volume to the surface and spread using a flow of nitrogen or other gases through the gas knife. The gas used in the gas knife can be air, one or more noble gases or any combination thereof. The ink can then flow into the pores as it is passing above them but will not stay on the surface and will drain into the pores. This provides improved uniformity versus inkjet loading of the pores and removes leftover ink from the surfaces spanning between adjacent discharge nozzles (non-discharge surfaces). It also provides an alternative ink distribution structure to the orifice  170  while still allowing control over the amount of ink that is loaded in the pores. Alternatively, the flow of gas can be used in conjunction with inkjet printing or other methods to deliver a small volume of ink. Here, the purpose would be to remove leftover ink from the non-discharge surfaces. 
     In another embodiment, the non-discharge surfaces are modified to further aid micropore ink loading. Particularly, the non-discharge surfaces and the micropores can be treated such that non-discharge surfaces repel liquid ink while the micropores attract the liquid ink. The treatment can be one of chemical treatments (i.e., chemical coating to increase/decrease surface tension or surface energy), a physical treatment (i.e., etching or other forms of solid surface treatment to improve flow), an electrochemical treatment (i.e., anodic treatment) or a combination of these treatments. In still another embodiment, the non-discharge surfaces can be modified geometrically by changing the roughness of the material or creating steps, recesses or other structures with different height (e.g., fabricating ink wells). Super-wetting structures such as a multitude of pillars (i.e., a pillar forest to enhance flow of liquid ink) can be utilized on top of a pattern of pores or instead of a pattern pores. 
     Containment structures can also be used to prevent liquid ink from spreading onto the non-discharge surfaces. This is useful for open micropores on the sides opposite to the ink delivery mechanism to limit the effect of ink leaking through the micropores. A containment structure can be formed by creating a discontinuity in the surface wetting properties, such as with an abrupt change in surface material or topography. One containment structure is an oxide containment ring. For exemplary micropores etched in a silicon surface, an oxide ring is realized by etching silicon dioxide around the micropores down to bare silicon, and simultaneously patterning a 2-5 μm wide silicon dioxide ring around the pores. The size of the silicon dioxide ring is a function of the area to be contained and is not limited to the range provided herein. 
       FIG. 5  is an exemplary embodiment of the surface of an exemplary discharge nozzle. More specifically, the embodiment of  FIG. 5  depicts the surface of the discharge nozzle facing a substrate (the distal surface). Discharge surface  500  includes micropores  530  which are formed in silicon layer  520 . Conventional MEMS processing can be used to form micropores  530 . Although micropores  530  are shown as circular, the disclosure is not limited to this configuration. Other forms of micropores are discussed in greater detail below. Oxide ring  510  separates the outer portion of discharge surface  500  from micropores  530 . Oxide ring  510  can be formed as a containment area. Alternatively, oxide ring  510  can have a composition configured to drive ink material towards micropores  530 . A localized heater or a piezoelectric element may also be integrated with the discharge surface  500 . 
     When liquid ink reaches the oxide ring, which is more hydrophilic as compared to silicon, the ink is prevented from further spreading due to the abrupt increase in contact angle and surface energy at the outer oxide-silicon interface of the ring. Ink spreading is therefore blocked by the ring. Liquid Ink can then retract back into the pores as it dries. A small volume of ink may remain on the ring. 
       FIG. 6A  shows a micropore array according to an embodiment of the disclosure. Micropore array  600  includes a multitude of pores  610  arranged in rows and columns. Each pore is rectangular in shape. Pore array  600  may also include heating apparatus  620  at periphery  630 . The interior surface of pores  610  may be treated so as to attract the deposited liquid film material while surrounding area  630  can be treated to repel the same. The treatment may include, among others, physical treatment, chemical treatment and electrochemical treatment. By way of example, if the ink material contains water, the interior surfaces can be hydrophilic while the exterior and the periphery may be hydrophobic to thereby drive in the ink material into the micropores. 
       FIGS. 6B and 6C  schematically show an embodiment of the invention in which a portion of the pore array is treated to repel liquid film material. Namely, surface areas  642  are coated with a material configured to repel the liquid film material. Coated surface  642  are on top of pore array  640 . When liquid film material  642  is received on pore array  640 , it is immediately drawn by top surfaces of pore array and by the micropores. Coated surfaces  642  repel the liquid film material  642 . The molecular and capillary forces then draw in the liquid film material as shown in  FIG. 6C . In an optional embodiment of the disclosure, external pressure can be provided, for example with a gas knife, to further draw the film material into the micropores. 
     It should be noted that the illustrated embodiments of  FIGS. 6B and 6C  apply equally to blind micropores. Here, the top surfaces of the micropores are coated with liquid film material. The film material is drawn to the micropores and repelled by the surrounding areas. An optional gas knife can assist driving the film material into the micropores. Micropore array  640  can then be used to dispense or deposit the film material onto a substrate. 
     To increase uniformity for the liquid ink loading into the micropores, the pattern of micropores as well as the pitch and relative positions of the pores can be modified. The micropores may also be replaced by interconnected channels so that the ink will spread uniformly inside the channels. This can also help with robustness to misalignment, and loading efficiency, as the channels will be more effective at drawing in liquid from the neighboring surface areas than pores. 
       FIGS. 6B and 6C  also illustrate another embodiment of the disclosure in which the micropores are formed at a bottom of a shallow well defined by surfaces  642 . According to this embodiment, the well forms containment for the liquid ink material. 
       FIG. 7  shows a discharge nozzle having an interconnected channel structure. While the channel structure  700  of  FIG. 7  contains a single channel  710 , other pore structures can be devised within the scope of the disclosure whereby the pores are defined by discrete channels. As described in relation to  FIGS. 6A-6C , the interior surfaces of the channel may be treated so as to attract the received ink material while the periphery surfaces may repel the ink material. Additionally, heating elements (not shown) can be integrated with the discharge nozzle to assist in evaporating the carrier fluid prior to deposition. 
     To get the ink to preferentially wet the micropores compared to the non-discharge surfaces, the micropore sidewall surface and profile can be modified. For example the sidewalls can be smooth or rough, with different microstructures. The sidewall profile may be straight, slanted, or curved. The contour of the pore can also be modified; a pore with corners (such as a square for example) will be easier to fill than a round one. 
       FIGS. 8A-8D  schematically illustrate cross-sections of exemplary modified micropore structures. In particular,  FIG. 8A  shows a micropore having smooth, straight, sidewalls.  FIG. 8B  shows a micropore having tapered sidewalls. Depending on the application, the tapered end may be facing the substrate. Finally,  FIG. 8C  shows a micropore having curved sidewalls.  FIG. 8D  shows two micropores, each having a different interior portion. Here, the micropores are structured to have a contour which enables or enhances flow of ink material therethrough. The interior regions may further be chemically treated to be more attractive to the ink material.  FIG. 9  schematically illustrates plan-view sections of exemplary micropores, which include round, square and star-shaped profiles. 
     While the principles of the disclosure have been illustrated in relation to the exemplary embodiments shown herein, the principles of the disclosure are not limited thereto and include any modification, variation or permutation thereof.