Patent Application
20100251914
The present disclosure relates to an imaging member having a heat sensitive material whose surface compatibility to printing agents, such as toners and inks, can be substantially changed in response to a small variation in temperature. For example, a hydrophobic area of the surface of an imaging member can be quickly switched to a hydrophilic area upon exposure to a temperature shift. Similarly, an oleophilic area of the surface of the imaging member can be switched to an oleophobic surface. This disclosure also relates to apparatuses including such imaging members, and methods of using such imaging members, such as in lithographic printing applications.
Lithography is a method for printing using a generally smooth surface. The surface, such as the surface of a plate or of an imaging member, is comprised of (i) hydrophobic areas that repel solution (water) and attract ink; and (ii) hydrophilic areas that repel ink and attract solution. Fountain solution, which is typically a water-based solution, is then applied to the surface and adheres to the hydrophilic (i.e. oleophobic) areas while the ink adheres to the hydrophobic (i.e. oleophilic) areas to form the image.
In offset lithography, the image on the imaging member is generally then transferred to an intermediate transfer member which picks up the ink. The ink image on the intermediate transfer member is then transferred to the final substrate (e.g. paper).
Offset lithography offers consistent high image quality, large substrate latitude, and longer printing plate life compared to direct lithography processes. In addition, offset lithography generally offers lower costs for large-quantity duplicated printing because most of the cost in offset lithography is incurred upfront.
Conventional lithography techniques use an image plate with permanent hydrophobic areas and hydrophilic areas. However, such plates are costly and require considerable set-up time. This limits the attractiveness of lithography for short-run printings (i.e. low quantity) and variable-data printings (e.g. direct mail ads).
One approach has been to utilize heat-sensitive materials on the plate or imaging member to enable digital variable-data printing. However, such materials generally require high temperatures (e.g. greater than 100° C.) and/or are slow to reverse their state. It would be desirable to provide devices and/or methods for lithography where hydrophilic/hydrophobic states, etc., could be quickly changed by small temperature changes.
The present disclosure is directed to an imaging member useful for printing processes such as digital-direct or digital-offset lithography. The imaging member comprises a surface outer layer of a heat sensitive material whose surface compatibility to printing agents, such as toners and inks, can be substantially changed in response to variations in temperature. This heat sensitive material shifts between hydrophilic/hydrophobic states, oleophilic/oleophobic states, or other compatible/incompatible states, or vice versa, after being exposed to a small temperature change at a time scale compatible with typical offset press speeds. This system allows the imaging member to be quickly changed to print different images with only a small amount of heat added to or removed from the imaging member. Printing apparatuses containing the imaging member and methods of printing using such an imaging member are also disclosed.
More particularly, disclosed in certain embodiments is an imaging member having a surface layer comprising a heat sensitive material whose compatibility or non-compatibility to a printing agent can be quickly and substantially reversed in response to a temperature change.
In further embodiments, the imaging member comprises: a substrate; and a surface layer comprising a heat sensitive material permitting reversible switching between wettability states.
The imaging member may be in the form of an endless belt, a cylindrical sleeve, or a cylinder. The imaging member may also further comprise an absorption layer between the substrate and the surface layer. The absorption layer may comprise an addressable metamaterial, in forms such as individually addressable unit cells controlled by integrated circuitry.
In other embodiments, the imaging member comprises: a substrate; and a surface layer comprising a heat sensitive material permitting reversible switching between a printing agent compatible state and a printing agent non-compatible state. For example, the heat sensitive material may permit switching between hydrophilic and hydrophobic states, or between oleophilic and oleophobic states.
Also disclosed is a printing apparatus comprising a heat source; an ink source; and an imaging member comprising (i) a substrate and (ii) a surface layer that comprises a heat sensitive material whose compatibility with a printing agent can be substantially reversed in response to a temperature change.
In embodiments, the heat sensitive material can be an acrylamide polymer. The acrylamide polymer may be a copolymer that comprises an N-isopropylacrylamide monomer, or it may be an N-isopropylacrylamide homopolymer.
The heat sensitive material may switch states when exposed to a temperature of from about 10° C. to about 120° C., including a temperature greater than about 25° C. and less than about 90° C. or a temperature of about 25° C. to about 40° C.
The surface layer can be a rough, i.e. non-smooth, surface. The roughness may be caused by ordered structures and/or random structures being present on the top surface. The surface layer may have a roughness of from about 10 nanometers to about 100 microns in the lateral direction (along the surface) and from about 10 nanometers to about 10 microns in the vertical direction (i.e. perpendicular to the surface). Such structures could be naturally formed during the fabrication/synthesis process, or be artificially created as an additional manufacturing step. The structures may be on the micron or nanometer scale, or multiscale (hierarchical) structures. The structures causing the roughness can be in the shape of, for example, grooves, bumps, pillars, etc. For example, the surface layer may comprise orderly structured grooves. The grooves may have a width of about 10 nm to about 10 microns, a depth of about 10 nm to about 10 microns, and/or a spacing of about 10 nm to about 100 microns between adjacent grooves.
The imaging member may further comprise an absorption layer between the substrate and the surface layer. The absorption layer may be a radiation absorption layer, and may also be addressable.
The heat sensitive material may permit reversible switching (i) between hydrophilic and hydrophobic states; (ii) between oleophilic and oleophobic states; or (iii) between a printing agent compatible state and a printing agent non-compatible state.
The heat source may be an electromagnetic heating device (e.g. optical or microwave), an acoustic heating device, a thermal print head, a resistive heating finger, or a microheater array. The heat source can be located within the imaging member between the substrate and the surface layer. The heat source may also be located separately from the imaging member.
The printing apparatus may optionally comprise an intermediate transfer member that forms a transfer nip with the imaging member, along with a secondary heat source adapted to provide heat in or near the transfer nip, and/or a cleaning unit to clean the intermediate transfer member.
Disclosed in still other embodiments is a method of printing comprising: coating a substrate with a heat sensitive material whose compatibility with a printing agent can be rapidly and substantially reversed in response to a temperature change to form an imaging member having a surface layer; selectively exposing the surface layer to a thermal stimulus to form an image area and a non-image area; filling the image area with a printing agent to form a printed image; and transferring the printed image to a recording medium. Also included is the printed image produced by this process.
The printed image may first be transferred to an intermediate transfer member. This transfer may be aided by exposing the image area to a thermal stimulus which transforms or converts the image area to a printing agent incompatible state. The printing agent is then repelled by the image area on the surface layer of the imaging member and more readily moves to the intermediate transfer member.
These and other non-limiting aspects and/or objects of the disclosure are more particularly described below.
The following is a brief description of the drawings, which are presented for the purposes of illustrating the disclosure set forth herein and not for the purposes of limiting the same.
A more complete understanding of the processes and apparatuses disclosed herein can be obtained by reference to the accompanying drawings. These figures are merely schematic representations based on convenience and the ease of demonstrating the existing art and/or the present development, and are, therefore, not intended to indicate relative size and dimensions of the assemblies or components thereof.
Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings, and are not intended to define or limit the scope of the disclosure. In the drawings and the following description below, it is to be understood that like numeric designations refer to components of like function.
The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (for example, it includes at least the degree of error associated with the measurement of the particular quantity). When used with a specific value, it should also be considered as disclosing that value. For example, the term “about 2” also discloses the value “2” and the range “from about 2 to about 4” also discloses the range “from 2 to 4.”
The present disclosure relates to an imaging member comprising a surface layer of a heat sensitive material (i.e. a reversible surface energy material). The compatibility of the heat sensitive material with a printing agent (such as a toner or ink) can be substantially reversed in response to a temperature change. The heat sensitive material can also be considered as permitting reversible switching between compatible and non-compatible states.
In a compatible state, the printing agent is attracted to the surface while in a non-compatible state, the printing agent is repelled. Examples of switching between compatible and non-compatible states include switching from either a hydrophilic state to a hydrophobic state or from an oleophilic state to an oleophobic state, or vice versa, when exposed to a small change in temperature. In a hydrophilic state, the material is relatively attracted to water or other aqueous solution, while in a hydrophobic state the material tends to repel water or other aqueous solution. In a oleophilic state, the material is relatively attracted to oils, while in a oleophobic state the material tends to repel oils.
The imaging member of the present disclosure can be useful in a printing apparatus for digital-direct lithography or digital-offset lithography. The present disclosure is also related to a printing apparatus comprising a heat source, an ink source, and an imaging member as described herein. The heat source may be located within (i.e. integral to) the imaging member or a separate unit or component of the printing apparatus.
In the depicted embodiment the imaging member 110 rotates counterclockwise. The apparatus includes a fountain solution source 120 and an ink source 130. Here, the ink is similar to commercial offset inks (i.e. an oil-based ink). A primary heat source 140 is located so that heat can be generated on and/or applied to the surface layer 114 prior to the application of the fountain solution and the ink. For example, as shown here, the primary heat source 140 is located so heat is applied at a nip region 122 between the imaging member 110 and the fountain solution source 120. The primary heat source 140 selectively heats portions of the surface layer 114 to create image areas 142 and non-image areas 144 on the surface layer. Fountain solution is then applied to the non-image areas and ink is applied to the image areas to form an ink image. Generally, when fountain solution is applied, it is applied prior to application of the ink.
An impression cylinder 150 feeds a recording medium or printing substrate 160, such as paper, to a nip region 152 between the impression cylinder 150 and the imaging member 110. The ink image is then transferred to the printing substrate. A cleaning unit 170 cleans the imaging member of any residual ink or fountain solution. The cleaning unit may also cool down the surface layer from an elevated temperature in selected areas to an initial state where the temperature of the surface layer is relatively constant over its entirety.
In this embodiment, any of the principal types of ink (oil-based, water-based, ultraviolet-curable) can be used. Application of heat to the surface layer 214 would create ink compatible areas 242 and non-compatible areas 244. For example, an oil-based ink would be applied to oleophilic areas 242, while a water-based ink would be applied to hydrophilic areas 244. The oleophobic or hydrophobic area would not be inked respectively.
In addition, a secondary heat source 280 is located near a nip region 252 between the impression cylinder 250 and the imaging member 210. The secondary heat source could be used to increase the efficiency of the transfer of ink from the imaging member 210 to the printing substrate 260. For example, the surface layer 214 becomes oleophobic after being heated. After the surface layer is selectively heated, an oil-based ink would be applied to the oleophilic areas. Then, as the oil-based ink is being transferred to the printing substrate, the secondary heat source 280 could heat the oleophilic areas, switching them to oleophobic areas and causing complete release of the ink from the imaging member 210.
The heat sensitive material used in the surface layer can comprise an acrylamide polymer. The acrylamide polymer may be a homopolymer or a copolymer comprising an acrylamide monomer. The acrylamide polymer will contain an acrylamide unit of Formula (I):
wherein R is hydrogen or alkyl having from 1 to about 10 carbon atoms, including from about 1 to about 6 carbon atoms.
In particular embodiments, R is isopropyl, so that the acrylamide polymer is poly(N-isopropylacrylamide) (i.e. the homopolymer) or an N-isopropylacrylamide copolymer, particularly a dipolymer having only two monomers. When the acrylamide polymer is an N-isopropylacrylamide (NIPAM) copolymer, the acrylamide monomer should comprise from 50 to 100 percent of the repeating units of the copolymer or from 50 to 100 mole percent of the copolymer. The other comonomer of the copolymer may be, for example, styrene; bisphenol-A; acrylic acid; 4-vinylphenylboronic acid (VPBA); ethylmethacrylate; methylmethacrylate (MMA); butylmethacrylate (BMA); N,N-diethylaminoethyl methacrylate (DEAEMA); or methacrylic acid (MAA). The other comonomer could also be a fluorinated alkyl acrylate or fluorinated alkyl methacrylate, such as hexafluoroisopropylmethacrylate (HFIPMA) or 2,2,3,3,4,4-hexafluorobutylmethacrylate (HFBMA). The other comonomer could also be another acrylamide monomer, such as N-ethylacrylamide (NEAM); N-methylacrylamide (NMAM); N-n-propylacrylamide (NNPAM); N-t-butylacrylamide (NtBA); or N,N-dimethylacrylamide (DMAM).
Poly(N-isopropylacrylamide) (PNIPAM) is an exemplary heat sensitive material that exhibits a large change in surface energy in response to a small change in temperature. PNIPAM has a lower critical solution temperature (LCST) of about 32° C. to about 33° C. The contact angle of a water drop on a surface modified by PNIPAM changes dramatically above and below the LCST. In one experiment, an imaging member was modified with PNIPAM, and a water drop was applied. The contact angle was 63.5° at 25° C., but 93.2° at 40° C.
Poly(N-n-propylacrylamide) (PNNPAM) is another exemplary heat sensitive material that exhibits a large change in surface energy in response to a small change in temperature. PNNPAM has a lower critical solution temperature (LCST) of about 24° C.
Without being bound by theory, it is believed that at a temperature below LCST, the PNIPAM chains form expanded structures caused by intermolecular hydrogen bonding occurring predominantly between the PNIPAM chains and water molecules present in the applied solution. This intermolecular bonding contributes to the hydrophilicity of the PNIPAM-modified surface. However, at temperatures above the LCST, hydrogen bonding occurs predominantly between PNIPAM chains themselves, with the carbonyl oxygen atom of one PNIPAM chain bonding to the hydrogen atom on the nitrogen atom of an adjacent PNIPAM chain. This intramolecular hydrogen bonding between the C═O and N—H groups of adjacent PNIPAM chains results in a compact conformation that results in hydrophobicity at temperatures above the LCST. This interaction is shown in
The heat sensitive material can be considered heat sensitive in at least three different ways. The heat sensitive material can be considered as switching states (e.g. between hydrophilic and hydrophobic) when exposed to a temperature change of from about 10° C. to about 80° C. (i.e., a relative temperature difference), particularly a temperature change of from about 10° C. to about 20° C. Alternatively, the heat sensitive material can switch states when exposed to a temperature of greater than about 20° C. and less than about 120° C. (i.e. an absolute temperature). In some embodiments, the heat sensitive material switches states when exposed to a temperature of greater than about 25° C. and less than about 90° C. or from about 30° C. and less than about 55° C. Finally, the heat sensitive material may switch states at a temperature of from about 25° C. to about 40° C., including about 32° C.
The direction in which the heat sensitive material switches when heat is applied may vary. In some embodiments, the material is ink compatible at a relatively lower temperature and ink non-compatible at a relatively higher temperature. In some other embodiments, it is ink compatible at a relatively higher temperature and ink non-compatible at a relatively lower temperature. In some embodiments, the material is hydrophilic at room temperature (i.e. from about 23° C. to about 25° C.) and hydrophobic at an elevated temperature. In other embodiments, the material is oleophilic at room temperature and oleophobic at an elevated temperature.
The acrylamide polymer may be combined with other materials to form the surface layer of the imaging member, or may form the entire surface layer, or may modify a surface of the substrate to form a surface layer. In some embodiments, the surface layer is a self-assembled monolayer of the acrylamide polymer. In other embodiments, the surface layer is a composite of the acrylamide polymer with another material. For example, a silicon substrate might be modified with both the acrylamide polymer and octadecylsilane to form a surface layer. Alternatively, strong radiation-absorbing particles, such as carbon black or carbon nanotubes, could be dispersed within a polyacrylamide polymer-based network to form a composite surface layer. As seen in
The properties of the surface layer can be modified by adding different components. For example, the LCST of a homopolymer (i.e. 100 mole %) of NIPAM is about 32° C. However, the LCST of a copolymer of 70 mole % NIPAM and 30 mole % NtBA is about 20° C. Similarly, the LCST of a copolymer of 70 mole % NIPAM and 30 mole % NEAM is about 43° C. The LCST of a copolymer of 70 mole % NIPAM and 30 mole % NMAM is about 40° C. In some embodiments, the LCST of the acrylamide polymer used in the surface layer is from about 25° C. to about 45° C. As another example, the hydrophobicity of the surface layer could be modified by including a NIPAM polymer and hydrophobic octadecylsilane.
The response time of the surface layer (i.e, the time it takes for the heat sensitive material to switch states) affects the maximum print speed of the printing apparatus. There are two factors that contribute to the total response time: (1) the thermal response time; and (2) the conformation response time. The thermal response time indicates how quickly the imaging member can switch between two operating temperatures, and depends on the power used to heat a given area on the surface layer. For a given heating power, the thermal response time of a NIPAM-modified surface is very short due to the small temperature difference that needs to be provided to switch between the hydrophilic and hydrophobic states. The conformation response time indicates how quickly the acrylamide polymer chains can change their conformation in response to the temperature change. In experiments, PNIPAM polymers became insoluble in water within 300 milliseconds. Thus, the conformation response time of a surface layer of PNIPAM chains on a two-dimensional surface should be in the order of milliseconds as well. In embodiments, the surface layer can switch between the two states within one second (i.e. 1000 milliseconds). In other embodiments, the surface layer can switch states within 500 milliseconds.
If desired, the mechanical strength of the surface layer comprising a heat-sensitive material can be improved. For example, composite materials, such as nanofillers, can be included. As another example, the surface layer could include other polymers that crosslink with the acrylamide polymer. It is also contemplated that the surface layer comprising a heat-sensitive material could be constructed separately from the substrate of the imaging member. The surface layer could be made in the form of a sleeve which could be easily removed and replaced.
The roughness of the surface layer may be manipulated to amplify the ink compatibility/non-compatibility (hydrophilicity/hydrophobicity) of the heat sensitive material. In other words, the surface layer can be non-smooth. Put in other ways, the upper surface of the surface layer does not maintain a constant distance from the substrate upon which it rests, or the surface layer can vary in thickness from its lowest point to its highest point. This surface roughness can be accomplished by several means. For example, material can be added or removed from the top of the surface layer to form structures that prevent the surface layer from being smooth. As another example, if the surface layer is coated onto the substrate, the surface layer may be slightly roughened during the application and/or prevented from being smoothed out. Generally speaking, the surface roughness may be created by the addition, subtraction, or creation of orderly structures and/or randomly arranged structures on the micron or nanometer scale, or by multiscale (hierarchical) structures. In some embodiments, as shown in
Any suitable temperature source may be used as the primary heat source to cause the temperature change in the surface layer. Exemplary heat sources include an optical heating device such as a laser or an LED bar, a thermal print head, resistive heating fingers, or a microheater array. A resistive heating finger is an array of finger-like micro-electrodes that result in resistive heating when the fingers are in contact with the surface that is to be heated. In all cases, the heat source may be used to selectively heat the surface layer for pixel addressability.
The primary heat source and the optional secondary heat source may be located anywhere within the printing apparatus where their function can be accomplished. For example, as shown in
In other embodiments depicted in
In yet another system, the absorption layer 630 is made with a pixel-wise addressable material. For example, the absorption layer could be made from a metamaterial. A metamaterial is a macroscopic composite material having a manmade, three-dimensional, periodic cellular architecture designed to produce a combination, not available in nature, of two or more responses to a specific excitation. For example, the absorption layer could comprise a metamaterial that is divided into absorption-tunable cells to act as an addressable layer. An electrical signal to a cell of the metamaterial would control the absorption coefficient of that cell, particularly for an active metamaterial which has a tunable element such as a capacitor. Broad uniform light illumination could then be used with such an absorption layer, rather than requiring the heat source to be addressable.
In another system, if an acoustic heat source was used instead of a radiation heat source, the absorption layer 630 could be an acoustic energy absorber relative to the other layers. To obtain the spatial resolution, the acoustic source could be an array of electrically addressable acoustic sources.
The fountain solution source and ink source may also be temperature controlled to optimize temperature contrast in the nip region where they are applied to the imaging member.
The imaging members of the present disclosure allow for digital lithography “on the fly”. Because the surface layer can switch states after application of a small temperature change (as low as about 15° C.), energy requirements are modest compared to metallic oxide-based surfaces that do not switch states until the imaging members reach a temperature of above 200° C.
The substrate of the imaging member may be opaque or substantially transparent and may comprise any suitable material having the required mechanical properties. For example, the substrate may comprise a layer of an electrically non-conductive, semiconductive, or conductive material such as an inorganic or an organic composition. Various resins may be employed as non-conductive materials including polyimides, polyesters, polycarbonates, polyamides, polyurethanes, and the like, which are flexible as thin webs. An electrically conducting substrate may be any metal, for example, aluminum, nickel, steel, copper, and the like or a polymeric material, as described above, filled with an electrically conducting substance, such as carbon, metallic powder, and the like or an organic electrically conducting material. The electrically insulating, semiconductive, or conductive substrate may be in the form of an endless flexible belt, a web, a cylindrical sleeve that is placed on a cylinder, a cylinder, a sheet, and the like. In particular embodiments, the imaging member (and the substrate) are in the form of a flexible belt, a cylindrical sleeve, or a cylinder.
The thickness of the substrate depends on numerous factors, including strength and desired and economical considerations. A flexible belt may be of substantial thickness, for example, about 250 microns, or of minimum thickness, e.g., less than 50 microns, provided there are no adverse effects on the final device.
In embodiments where the substrate is not conductive, the surface thereof may be rendered electrically conductive by an electrically conductive coating. The conductive coating may vary in thickness over substantially wide ranges depending upon the optical transparency, degree of flexibility desired, and economic factors. Accordingly, for a flexible imaging member, the thickness of the conductive coating may be from about 1 nanometer to about 10 microns, and more preferably from about 10 nanometers to about 500 nanometers, for an optimum combination of electrical conductivity, flexibility, and light transmission. The flexible conductive coating may be an electrically conductive layer formed, for example, on the substrate by any suitable coating technique, such as a vacuum depositing technique or electrodeposition. The coating could use any typical coating metal or non-metal material, including ITO, tin, gold, aluminum, zirconium, niobium, tantalum, vanadium and hafnium, titanium, chromium, tungsten, molybdenum, and the like.
The radiation absorption layer 630 may be made from, for example, a high temperature resin having radiation-absorbing particles dispersed therein. This type of layer may have high light absorption efficiency and good thermal conductivity. Radiation-absorbing particles may include carbon black particles and carbon nanotubes. The radiation-absorbing particles may be from about 1.0 weight percent to about 50 weight percent of the radiation absorption layer. Exemplary high temperature resins include polyimide, mono/bis-maleimides, poly(amide-imide), polyetherimide, and polyetheretherketone. Additional materials, such as silver powder, may be added to the layer to improve material properties. The radiation absorption layer may also include dyes or pigments that have strong absorption at wavelengths (UV to IR) matching the wavelength of the radiation source. The thickness of the radiation absorption layer may be from about 20 nanometers to about 5,000 nanometers.
The thermal insulation layer may be made from low thermal conductivity materials, such as polyimide, polyurethane, and polystyrene. The thickness of the thermal insulation layer may be from about 50 microns to about 1 centimeter.
In other embodiments, a conformable layer 650 may be present to enable good contact to be made between the imaging member and other parts of a printing apparatus, for example when the imaging member is in the form of a cylindrical surface for mounting onto a cylinder. A typical conformable layer could be made from materials such as silicone, VITON®, a combination of both, etc., with fillers such as carbon and other nanofillers.
Aspects of the present disclosure may be further understood by referring to the following examples. The examples are merely for further describing various aspects of the imaging members and printing apparatuses of the present disclosure and are not intended to be limiting embodiments thereof.
Several devices were made to determine the effect of surface roughness on the hydrophilicity/hydrophobicity of the resulting surface layer. The devices consisted of a silicon substrate which was modified with PNIPAM to form a surface layer. Microgrooves were then formed in the surface layer in a checkerboard pattern. Each groove was 6 microns wide and 5 microns deep. The spacing between adjacent grooves varied. The devices were made with four different spacings: 6 microns, 8 microns, 18 microns, and 31 microns. In addition, measurements were also made on devices that did not have any microgrooves at all (i.e., a spacing of infinity).
The water contact angle was measured on the devices at both 25° C. and at 40° C. and the resulting graph is shown in
The water contact angle was measured over a range of temperatures on two devices, one with a surface layer having a groove spacing of 6 microns (Device A) and the other having a flat surface layer (Device B). The graph is shown in
The device with a surface layer having a groove spacing of 6 microns was cycled 20 times between 20° C. and 50° C. to determine whether switching between states would affect the performance of the surface layer. The graph is shown in
The imaging members, printing apparatuses, and methods of the present disclosure have been described with reference to exemplary embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiments be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
This application is related to U.S. patent application Ser. No. 12/060,427, filed on Apr. 1, 2008. This application is also related to [20070169-US-NP] and to [20070169Q-US-NP] and [20090067/20090068-US-NP]. These four patent applications are hereby fully incorporated by reference herein.
