Patent Description:
Droplet actuators are used in a variety of microfluidic operations for manipulating and analyzing discrete volumes of fluid. Droplet actuators include two plates separated by a gap, with at least one of the plates containing an array of electrodes coated with a hydrophobic and/or dielectric material. Fabricating drop actuators involves creating the electrode array, which can require high production costs in terms of time and pricing to define the electrode array without sacrificing technical performance qualities of the electrodes of the array.

<CIT> discloses a method for forming an inkjet print head which includes attaching a plurality of piezoelectric elements to a diaphragm of a jet stack subassembly, electrically attaching a flex circuit to the plurality of piezoelectric elements, then dispensing a dielectric underfill between the flex circuit and the jet stack subassembly.

The figures are not to scale. Instead, to clarify multiple layers and regions, the thickness of the layers may be enlarged in the drawings. Wherever possible, the same reference numbers will be used throughout the drawing(s) and accompanying written description to refer to the same or like parts. As used in this patent, stating that any part (e.g., a layer, film, area, or plate) is in any way positioned on (e.g., positioned on, located on, disposed on, or formed on, etc.) another part, means that the referenced part is either in contact with the other part, or that the referenced part is above the other part with one or more intermediate part(s) located therebetween. Stating that any part is in contact with another part means that there is no intermediate part between the two parts.

Methods, systems, and apparatus involving fabrication of droplet actuators are disclosed herein. Droplet actuators are used in microfluidic analysis, and, in particular, are used in the field of droplet-based, or digital, microfluidics. Droplet actuators include two surfaces separated by a gap. At least one of the surfaces includes an electrode array that is coated or insulated by a hydrophobic material or a dielectric. A droplet disposed in the gap can be manipulated on the surface of the hydrophobic and/or dielectric material by selectively applying electrical potentials to electrodes of the electrode array to affect the wetting properties of the hydrophobic and/or dielectric surface pursuant to, for example, electrowetting or dielectrophoresis processes. Droplets disposed in the gap can include biological fluid samples such as, for example, blood, plasma, serum, saliva, sweat, etc. Electrical potentials may be used to transfer droplets between adjacent electrodes of the array, and/or to merge or split droplets as part of a variety of analyses, including for example, DNA sequencing and protein analysis.

Fabricating the example droplet actuators disclosed herein includes creating an electrode pattern that includes an electrode array on a base surface and coating the surface with at least one layer of a material exhibiting hydrophobic and/or dielectric properties. Producing the example droplet actuators also includes creating a top substrate, which may include a conductive surface coated with a material having hydrophobic and/or dielectric qualities and joining (e.g., bonding) the top substrate and the bottom substrate at a spaced apart distance to accommodate a droplet. The pattern of the electrode array that is created on at least the base substrate is based on design qualities of the electrodes that affect performance of the droplet actuator, such as, for example, electrical conductivity and electrode spacing. Increasing the number of electrodes per an area of the substrate provides for accommodation of differently sized electrodes and greater inter-digitation of the electrodes in the array. Higher resolution of the electrode array results in increased precision of the sizes of the droplets that are actuated by the droplet actuator and facilitates ease of transfer of the droplets between electrodes.

Known methods and systems for fabricating droplet actuators require a compromise between production efficiencies and quality of the electrode array. For example, lithographic methods provide for high spatial resolution in defining electrode arrays, but involve slow production times and expensive methodology. For example, lithographic methods involve depositing a photoresist on a substrate to engrave patterns in the substrate via chemical treatments. Depositing the photoresist must be repeated across the substrate to form individual electrode arrays, which increases production times. Also, droplet actuators formed using lithographic methods require post-processing steps such as cleaning the droplet actuators to remove the photoresist from the substrate. However, traces of chemicals can remain on the substrate after rinsing and can result in water marks on the substrate. Further, although lithographic methods can provide for high spatial resolution of an electrode array, the quality of the lines and gaps of the resulting electrode array can be poor quality, including rough edges defining the electrode array and random (e.g., non-systematic) defects between droplet actuators due inconsistencies with respect to deposition of the photoresist on the substrate.

Attempts to improve production efficiencies include printing electrodes on printed circuit boards. However, although the use of printed circuit boards may provide for faster production of droplet actuators at reduced material costs as compared to lithographic methods, the spatial resolutions of the arrays are sacrificed, which affects the capabilities of the droplet actuator in generating and manipulating droplets. Droplet actuator fabrication methodologies involving printed circuit boards can also require multiple steps to join or adhere one or more of a supporting surface and/or a hydrophobic surface to the printed circuit board to form the base layer of the droplet actuator.

Disclosed herein are example methods and systems for fabricating droplet actuators using laser ablation as part of a roll-to-roll assembly. Laser ablation can define electrode arrays including a plurality of electrodes at fast production speeds without sacrificing electrode quality by removing materials from a solid substrate via laser beam in a controlled manner. Technical advantages of electrodes produced via laser ablation include increased electrical conductivity as compared to printed electrodes; a low degree of surface roughness; a low degree of roughness associated with the edges defining the electrode features, thereby improving inter-digitization of the electrodes of the array; and a low degree of variation between features of the respective electrodes of the array. Laser ablation can produce an electrode pattern including lines and gaps measuring from, for example, less than <NUM> to about <NUM>. Further, laser ablation does not require the use of solvents that might negatively interfere with the use of the resulting droplet actuators by leaving residues or chemicals that are harmful to the production environment.

The example methods and systems disclosed herein are implemented via a roll-to-roll assembly, which can operate to move a substrate through various stations at high speeds, including, for example, rates of meters per second. Roll-to-roll assemblies facilitate the unwinding of a rolled substrate, the advancement of the substrate through the stations, and the rewinding of the processed substrate into a roll. Thus, a base and/or top substrate of a droplet actuator may be processed through one or more of a laser ablation station, a hydrophobic and/or dielectric printer, and a curing station at a rapid, continuous pace without compromising the technical qualities of the resulting droplet actuator. Further, the disclosed example methods and systems produce a base substrate and/or top substrate that do not require further individual assembly with respect to, for example, the electrode array, the hydrophobic and/or dielectric layer, and/or a supporting structural base, thereby reducing operation time and costs. Thus, examples disclosed herein provide for efficient production of droplet actuators without sacrificing quality of the microfluidic device.

A method disclosed herein for making a droplet actuator includes ablating a first substrate with a laser to form an electrode array on the first substrate. The method includes applying at least one of a hydrophobic or a dielectric material to the electrode array to form a first treated layer on the first substrate. The method also includes aligning the first substrate with a second substrate. The second substrate includes a second treated layer. In the method, the alignment includes a gap between at least a portion of the first treated layer and at least a portion of the second treated layer.

The method also includes inserting one or more capillary tubes between the first substrate and the second substrate to create the gap.

In some examples, the method includes curing at least one of the hydrophobic material or the dielectric to form the first treated layer. In some examples, curing the hydrophobic material includes exposing the at least one of the hydrophobic or the dielectric material to at least one of heat or ultraviolet light.

In some examples, ablating the first substrate includes projecting a pattern onto a portion of the first substrate via a lens and focusing the laser on the portion. In such examples, the laser is to penetrate the portion to form the pattern on the portion. Also, in some such examples, the pattern comprises a plurality of lines and gaps, the lines having a width of about <NUM> micrometers.

Also, in some examples, ablating the first substrate includes exposing a plurality of portions of the first substrate to the laser in succession. In such examples, the laser is to form the electrode array onto each of the plurality of the portions.

In some examples, the method includes coating a first portion of the plurality of portions with the at least one of the hydrophobic or the dielectric material at substantially the same time a second portion of the plurality of portions is exposed to the laser.

In some examples, the first substrate includes at least a first portion and a second portion. Each of the first portion and the second portion comprises a respective electrode array. In such examples, the second substrate includes at least a third portion and a fourth portion. Also, in such examples, aligning the first substrate with the second substrate includes aligning the first portion and the third portion at a first spaced apart distance and the second portion and the fourth portion at a second spaced apart distance. The first spaced apart distance and the second spaced apart distance correspond to the gap. In some examples, the method includes dicing the aligned first substrate and the second substrate, wherein the dicing is based on the alignment of the first portion and the third portion and the second portion and the fourth portion. Also, in some examples, the method includes bonding the first portion the third portion and the second portion and the fourth portion, respectively, with an adhesive material.

Also disclosed herein is an example system including a plurality of rollers to drive a first substrate between a plurality of positions. The example system includes a laser to penetrate the first substrate when the first substrate is in a first position of the plurality of positions. The laser to form at least one electrode pattern on the first substrate. The example system includes a printer to apply at least one of a hydrophobic or a dielectric material to the at least one electrode pattern when the first substrate is in a second position of the plurality of positions. In the example system, the plurality of rollers are to drive the first substrate from the second position to a third position of the plurality of positions. In the third position, the first substrate is to align with a second substrate to form a droplet actuator.

In some examples, the laser is to substantially continuously pulse during operation of the plurality of rollers and the laser is to penetrate one or more portions of the first substrate during the operation of the plurality of rollers.

In some examples, the first substrate comprises a first layer and a second layer. The second layer comprises a conductive material. In some examples, the first substrate includes a third layer disposed between the first layer and the second layer. The third layer is to adhere the second layer to the first layer.

In some examples, the laser is to remove at least a portion of the second layer to form the electrode pattern.

In some examples, the second layer is disposed on the first layer in a first roll. The plurality of rollers are to unwind the first roll to drive the first substrate to the first position. The plurality of rollers are to drive the first substrate to the third position to form a second roll. In such examples, the second layer is disposed on the first layer in the third position.

Some of the disclosed examples include a splitter to cut the second roll to form at least one microfluidic chip.

Also, in some examples, the printer comprises one or more coating rollers to apply the at least one of the hydrophobic or the dielectric material to the at least one electrode pattern. In some examples, the coating rollers are to apply an anti-fouling material to the first substrate.

In some examples, the system further comprises a merger to align the first substrate with the second substrate in the third position. In some examples, the merger comprises two rollers. Also, some of the disclosed examples include a curing station to cure the at least one of the hydrophobic material or the dielectric material. Some of the disclosed examples also include a bonding station to bond at least a first portion of the first substrate with at least a first portion of the second substrate. The bonded portions include the at least one electrode pattern.

Also disclosed herein is an example method including patterning an electrode array on a first sheet using a laser. The example method includes applying at least one of a hydrophobic material or a dielectric to the first sheet to create a first treated layer. The example method includes applying the at least one of the hydrophobic material or the dielectric to a second sheet to create a second treated layer. The example method also includes associating the first sheet and the second sheet at a spaced apart distance. The first treated layer is an insulating layer relative to the electrode array and a droplet received between the first treated layer and the second treated layer.

In some examples, the method includes curing the first treated layer and the second treated layer.

In some examples, associating the first sheet and the second sheet includes orienting the second treated layer in a first orientation, the first orientation opposite a second orientation of the first treated layer and merging the first treated layer and the second treated layer in a substantially parallel configuration. In some examples, merging the first sheet and the second sheet includes applying an adhesive material to at least one of the first sheet or the second sheet and bonding the first sheet with the second sheet. In such examples, the bonding is to preserve the spaced apart distance between the first sheet and the second sheet.

In some examples, the second sheet comprises a substantially single electrode. The second treated layer is to insulate the electrode.

In some examples, the method includes patterning an electrode array on the second sheet. In some examples, the second sheet includes a non-conductive material.

In some examples, the method includes embossing the first sheet to create one or more projections on the first sheet. In such examples, the projections are to separate the first sheet and the second sheet at the spaced apart distance.

Also disclosed herein is an example apparatus including a non-conductive layer and a conductive layer. The conductive layer is adhered to the non-conductive layer. The example apparatus includes an electrode pattern disposed in the conductive layer. The electrode pattern is insulated by at least one of a hydrophobic or a dielectric material. In the example apparatus, at least a portion of the non-conductive layer includes a feature of the electrode pattern.

In some examples, the feature is an outline of at least a portion of the electrode pattern. In some examples, the electrode pattern comprises a line and the feature at least partially corresponds to a position of the line in the electrode pattern. Also, in some examples, the feature is at least one of an indentation or a projection in a surface of the portion of the non-conductive layer.

In some examples, the example apparatus includes an anti-fouling layer disposed on the electrode pattern.

Also disclosed herein is an example substrate web for forming a plurality of droplet actuators therefrom. The substrate web includes a non-conductive layer and a conductive layer coupled to the non-conductive layer. The conductive layer includes a first electrode pattern and a second electrode pattern. The second electrode pattern is spaced apart from the first electrode pattern. The first electrode pattern includes a first marking and the second electrode pattern includes a second marking. The first marking is substantially identical to the second marking. The substrate web also includes at least one of a hydrophobic layer or a dielectric layer disposed over a substantial entirety of the respective first and second electrode patterns.

In some examples, the first marking and the second marking are substantially identical based on at least one of a size or a position of the first and second markings on the respective first and second electrode patterns.

In some examples, the first electrode pattern includes a plurality of lines and gaps. The lines having a width of about <NUM> micrometers. Also, in some examples, a thickness of the conductive layer is less than about <NUM> nanometers.

In some examples, the non-conductive layer defines a groove therein. The groove is based on the first electrode pattern.

Some examples of the substrate web include an adhesive layer disposed between the conductive layer and the non-conductive layer to couple the conductive layer to the non-conductive layer.

In some examples, the first electrode pattern includes lines and spacings, and edges of the lines bordering the spacings are substantially smooth. Also, in some examples, the marking is an interruption to a line defining the electrode pattern.

Also disclosed herein is an example apparatus including a first substrate having a plastic layer and a metal layer. The example apparatus also includes an electrode pattern formed in the metal layer. The electrode pattern is insulated by at least one of a hydrophobic or a dielectric material. The electrode pattern includes lines having at least partially curved edges defining spacings between the lines.

In some examples, the example apparatus includes a second substrate aligned with the first substrate, wherein the alignment includes a gap between the first substrate and the second substrate. In some examples, one or more projections are disposed in the gap. In some examples, the projections are capillary tubes. Also, in some examples, the second substrate includes at least one of a hydrophobic or a dielectric material.

In some examples, the plastic layer includes a partially curved groove corresponding to the electrode pattern formed in the metal layer.

Turning now to the figures, <FIG> is a diagram of a first example system or assembly <NUM> for creating a base substrate of a droplet actuator. The first example assembly <NUM> includes a series or a plurality of rollers, including a first roller <NUM>, a second roller <NUM>, and a third roller <NUM>, which operate in synchronized rotation to drive a base substrate <NUM> through the first example assembly <NUM>. The first example assembly <NUM> can include rollers in addition to the first through third rollers <NUM>, <NUM>, <NUM> to move the base substrate <NUM> through the assembly using roll-to-roll techniques. Other examples may use conveyors, pulleys and/or any other suitable transport mechanism(s). Prior to cutting or sizing of the base substrate <NUM> to produce individual droplet actuators, the base substrate <NUM> can be considered a substrate web that may be in a rolled, partially rolled, or unrolled configuration as the base substrate <NUM> moves through the first example assembly <NUM>.

In the first example assembly <NUM>, the first roller <NUM> rotates to unwind the base substrate <NUM>, which, in some examples, is a single sheet in a rolled configuration. The base substrate <NUM> includes a first layer <NUM> and a second layer <NUM>. In this example, the first layer <NUM> comprises a non-conductive flexible substrate, such as for example a plastic, and the second layer <NUM> includes a conductive material. The conductive material of the second layer <NUM> can be, for example, a metal such as gold, silver, or copper, or a non-metallic conductor, such as a conductive polymer. In other examples different metal(s) or combination(s) of metal(s) and/or conductive polymer(s) may be used. In some examples, the base substrate <NUM> includes an adhesive layer <NUM> disposed between the non-conductive first layer <NUM> and the conductive second layer <NUM>. As an example, the adhesive layer <NUM> can comprise chrome, with a layer of gold disposed on top of the chrome adhesive layer <NUM> to form the conductive second layer <NUM>. Thus, in the base substrate <NUM> of <FIG>, the non-conductive first layer <NUM> and the conductive second layer <NUM> are pre-adhered to form the base substrate <NUM> prior to being unwound by the first roller <NUM>.

In the example base substrate <NUM> of <FIG>, the non-conductive first layer <NUM> has a thickness of less than about <NUM>. As will be described below, such a thickness allows for the base substrate <NUM> to move through the example first assembly <NUM> via the plurality of rollers. Also, in some examples, the thickness of the non-conductive first layer <NUM> is greater than a thickness of the conductive second layer <NUM>. As an example, the thickness of the conductive second layer <NUM> can be approximately <NUM>. In other examples, the thickness of the conductive second layer <NUM> is less than about <NUM>, and in some examples the thickness of the second layer <NUM> is less than about <NUM>. In some examples, the thickness of the non-conductive first layer <NUM> and/or the conductive second layer <NUM> is selected based on, for example, the materials of the first and/or second layers <NUM>, <NUM> and/or an operational purpose for which the droplet actuator formed from the base substrate <NUM> is to be used.

The first roller <NUM> drives the base substrate <NUM> to a laser ablation station <NUM>. The laser ablation station <NUM> includes a mask <NUM> containing a master pattern <NUM> that is to be projected onto the conductive second layer <NUM> of the base substrate <NUM>. The master pattern <NUM> associated with the mask <NUM> may be predefined based on characteristics such as resolution (e.g., number of electrodes per an area of the base substrate <NUM> to be ablated), electrode size, configuration of lines defining the electrode pattern, inter-digitation of the electrodes, and/or gaps or spacing between the electrodes. In some examples, the characteristics of the master pattern <NUM> are selected based on one or more operational uses of the droplet actuator with which the base substrate <NUM> is to be associated (e.g., for use with biological and/or chemical assays). Also, in some examples, the master pattern <NUM> is configurable or reconfigurable to enable the laser ablation station <NUM> to form different patterns on the base substrate <NUM>. Additionally or alternatively, in some examples the mask <NUM> is replaceable with one or more alternative masks.

The laser ablation station <NUM> includes a lens <NUM>. As the base substrate <NUM> encounters the laser ablation station <NUM> as result of the rotation of the rollers (e.g., the first roller <NUM>), a portion <NUM> of the base substrate <NUM> passes under or past the lens <NUM>. The portion <NUM> may be, for example, a rectangular or square section of the base substrate <NUM> having an area less than the area of the base substrate <NUM> and including the conductive second layer <NUM>. The lens <NUM> images or projects at least a portion of the master pattern <NUM> onto the conductive second layer <NUM> associated with the portion <NUM>. A laser beam <NUM> is directed onto the portion <NUM> via the mask <NUM> and the lens <NUM> such that the laser beam <NUM> selectively penetrates the conductive second layer <NUM> based on the projected master pattern <NUM>. In some examples, the non-conductive first layer <NUM> or a portion (e.g., a fraction of the thickness of the non-conductive first layer <NUM>) may also be penetrated by the laser beam <NUM> based on the projected master pattern <NUM>. The solid portions of the mask <NUM> block the laser beam <NUM>, and the open portions of the mask <NUM> allow the laser beam <NUM> to pass through the mask <NUM> and into contact with the base substrate <NUM>. The laser beam <NUM> can be associated with, for example, an excimer laser.

As a result of exposure to the laser beam <NUM>, the irradiated non-conductive first layer <NUM> of the portion <NUM> absorbs energy associated with the laser beam <NUM>. The irradiated non-conductive first layer <NUM> undergoes photochemical dissociation, resulting in a selective breaking up of the structural bonds of non-conductive first layer <NUM> and ejection of fragments of the non-conductive first layer <NUM> and portions of the conductive second layer <NUM> overlaying the irradiated non-conductive first layer <NUM> in accordance with the master pattern <NUM> to form an electrode array <NUM> on the conductive second layer <NUM>. Thus, the ejection of fragments of the non-conductive first layer <NUM> as a result of penetration of the laser beam <NUM> in the non-conductive first layer <NUM> during formation of the electrode array <NUM> can result in structural changes to the non-conductive first layer <NUM>. Such structural changes may alter the appearance of the non-conductive first layer <NUM>.

As disclosed above, the laser beam <NUM> selectively penetrates the non-conductive first layer <NUM> and the conductive second layer <NUM> in accordance with the master pattern <NUM> mask <NUM>. Thus, the portions or fragments of the non-conductive first layer <NUM> that are ejected are based on the master pattern <NUM> such that after the fragmentation of the non-conductive first layer <NUM>, the non-conductive first layer <NUM> includes a feature of the master <NUM> corresponding to the electrode array <NUM>. The feature or marking in the non-conductive first layer <NUM> can include, for example, an outline or a substantial outline of at least a portion of the master pattern <NUM>. In some examples, the non-conductive first layer <NUM> includes a disturbance (e.g., a burn mark) formed as a result of the penetration of the laser beam <NUM> into the non-conductive first layer <NUM>. The disturbance can include, for example, a change in the thickness of at least some portion of the non-conductive first layer <NUM>, an indentation (e.g., a groove) in a portion of the non-conductive first layer <NUM>, or a projection in a surface of the non-conductive first layer <NUM> (e.g., as a result of the breaking up and fragmentation of the non-conductive first layer <NUM>). The indentations can include angled or sloped portions forming walls in the non-conductive first layer <NUM>. Thus, as result of the concurrent exposure of the non-conductive first layer <NUM> and the conductive second layer <NUM> to the laser beam <NUM>, the non-conductive first layer <NUM> can undergo one or more structural changes that may be reflected in grooves, projections, markings, discolorations, etc., as will be further disclosed below in connection with <FIG>.

In some examples, a depth (e.g., a radiation intensity) to which the laser beam <NUM> penetrates the base substrate <NUM> is predefined based on a depth (e.g., a thickness) of the non-conductive first layer <NUM> and/or the conductive second layer <NUM>. In some examples, the laser beam <NUM> penetration depth is adjustable to change the depth at which the laser beam <NUM> ablates the conductive second layer <NUM> as a result of the fragmentation of the underlying non-conductive first layer <NUM>. In some examples, this adjustment is dynamic as the example system <NUM> operates. Also, in some examples, the base substrate <NUM> undergoes cleaning after exposure to the laser beam <NUM> to remove particles and/or surface contaminants.

As illustrated in <FIG>, after exposure to the laser ablation station <NUM>, the portion <NUM> of the base substrate <NUM> includes the electrode array <NUM>. The electrode array <NUM> is made up of a plurality of electrodes formed into the conductive second layer <NUM> (<FIG>). As a result of the exposure to the laser beam <NUM> and fragmentation of the non-conductive first layer <NUM>, portions of the conductive second layer <NUM> are removed from the base substrate <NUM>. The removed portions associated with the electrode array <NUM> are based on the master pattern <NUM>. In some examples, the removed portions match the open portions of the mask <NUM>.

For example, <FIG> illustrates a top view of the portion <NUM> of the base substrate <NUM> after exposure to the laser ablation station <NUM> of the first example assembly <NUM> of <FIG>. As show in <FIG>, exposure to the laser <NUM> results in the formation of a laser-ablated electrode pattern <NUM> on the conductive second layer <NUM>. The laser-ablated electrode pattern <NUM> includes lines <NUM> and spacings <NUM>, which correspond to the master pattern <NUM> projected onto the portion <NUM> via the lens <NUM> of <FIG>.

In the example electrode pattern <NUM>, the lines <NUM> and the spacings <NUM> define one or more array electrodes <NUM> that form the electrode array <NUM>. The example electrode pattern <NUM> also includes one or more non-array electrodes <NUM>. The non-array electrodes <NUM> that are not a part of the electrode array <NUM> facilitate external electrical connections during operation of the droplet actuation. The array electrodes <NUM> and the non-array electrodes <NUM> of the electrode pattern <NUM> can vary in size and/or shape. For example, the non-array electrodes <NUM> can be substantially square-shaped whereas the array electrodes <NUM> can be in a configuration other than a square. The shapes and/or sizes of the electrodes <NUM>, <NUM> of the electrode pattern <NUM> are defined by the lines <NUM> and the spacings <NUM> in association with the master pattern <NUM> projected onto the base substrate <NUM>. As a result of formation via laser ablation, the lines <NUM> defining the electrodes <NUM>, <NUM> are substantially smooth and/or have substantially reduced roughness with respect to the definition of the edges of the electrodes <NUM>, <NUM> as compared to, for example, other methods for forming electrode arrays such as photolithography or printed circuit board methods.

In some examples, the lines <NUM> and/or the spacings <NUM> formed via laser ablation measure (e.g., have a width of) approximately <NUM>; in other examples, the lines <NUM> and/or the spacings <NUM> are greater or less than <NUM> (e.g., about <NUM>). The arrangement and sizes of the lines <NUM> and/or the spacings <NUM> define a resolution of the electrode array <NUM>. For example, minimal spacings <NUM> between the lines <NUM> allows for a greater number of array electrodes <NUM> in close proximity (e.g., inter-digitization of the array electrodes <NUM>) within the electrode array <NUM> and, as will be disclosed below, reduces an amount of dielectric and/or hydrophobic material applied between adjacent electrodes. Thus, the features of the laser ablated electrode pattern <NUM> maximize a surface area of the portion <NUM> that contributes to operation of the resulting droplet actuator, thereby reducing an amount of materials necessary to form individual droplet actuators. Further, increased inter-digitation of the array electrodes <NUM> facilitates an ease with which droplets are actuated on the base substrate <NUM> via manipulation of electrical potentials. Increased resolution of the electrode array <NUM> also improves a precision of droplet sizes that are actuated.

Laser ablation of the portion <NUM> of the base substrate or web <NUM> at the laser ablation station <NUM> may be achieved via broad field ablation or via rastering. Broad field ablation involves exposure of the laser beam <NUM> over substantially the entire portion <NUM>. The master pattern <NUM> is created on the portion <NUM> by removing material from the conductive second layer <NUM> with a substantially single instance of exposure of the non-conductive first layer <NUM> and the conductive second layer <NUM> to the laser beam <NUM> (e.g., a single flash of the laser beam <NUM>). In broad field laser ablation, the master pattern <NUM> is thus simultaneously created across the area of the conductive second layer <NUM> associated with the portion <NUM> to ablate the base substrate <NUM> at high speeds. <FIG> is a top view of a portion <NUM> of the electrode pattern <NUM> of <FIG> created via broad field ablation based on the master pattern <NUM>. As shown in <FIG>, the portion <NUM> includes the lines <NUM> and the spacings <NUM> defining the electrode pattern <NUM>. The lines <NUM> and/or spacings <NUM> can have widths of less than <NUM>. As also shown in <FIG>, edges <NUM> of the lines <NUM> are substantially smooth and without substantial rough, sharp, pointed, or uneven portions. Such smooth and defined edges <NUM> result from the irradiation of the base substrate <NUM> by the laser beam <NUM> to create the master pattern <NUM> with a single exposure of the laser beam <NUM> on the portion <NUM>.

Alternatively, laser ablation can be achieved via rastering or scribing, in which the laser beam <NUM> iteratively etches the master pattern <NUM> into the portion <NUM> to form the electrode pattern <NUM>, including the electrode array <NUM>, in the conductive second layer <NUM> as the base substrate <NUM> and/or the laser beam <NUM> moves. In examples where rastering techniques are used, the electrode pattern <NUM> is determined digitally without the use of the mask <NUM>. For example, to iteratively etch the master pattern <NUM> into the portion <NUM>, the laser beam <NUM> moves along the base substrate <NUM> to inscribe the master pattern <NUM> into the conductive second layer <NUM> via a series of individual pulses in adjacency. The individual pulses result in lines <NUM> having widths between, for example, <NUM> and <NUM>. In examples where the rastering is used to form the electrode pattern <NUM>, the edges of the array electrodes <NUM> may be less smooth due to pulse markings formed by the individual laser pulses iteratively penetrating the conductive second layer <NUM>, as compared to broad field laser ablation.

<FIG> is a top view of a portion <NUM> of the electrode pattern <NUM> of <FIG> created using laser ablation rastering or scribing techniques. As a result of the indexing of pulses to etch the master pattern <NUM> into the base substrate <NUM>, edges <NUM> of the lines <NUM> defining the electrode pattern <NUM> differ from the edges <NUM> of the electrode pattern <NUM> created via broad field laser ablation shown in <FIG>. For example, the edges <NUM> of the portion <NUM> created via rastering include curved, partially curved, or wave-like features corresponding to the iterative exposure of the portion <NUM> to individual pulses of the laser beam <NUM>. Also, because the individual pulses irradiate adjacent portions of the base substrate <NUM>, the curved or wave-like features of the edges <NUM> define a pattern or at least a partial pattern over the respective lines <NUM> in that in a first curved feature resulting from a first laser pulse of the laser beam <NUM> can resemble or partially resemble a second curved features resulting from a second laser pulse of the laser beam <NUM>. Thus, the edges <NUM> of the electrode pattern <NUM> created via rastering can be distinguished from electrode patterns created via techniques such as photolithography, which can result in lines having random, irregularly shaped edges.

<FIG> illustrate features of the electrode pattern <NUM> that are visible from a top view of the base substrate <NUM> after exposure to the laser beam <NUM> at the laser ablation station <NUM> of <FIG>. <FIG> is a cross-sectional view of the portion <NUM> of the base substrate <NUM> after exposure to the laser ablation station <NUM> of the first example assembly <NUM> of <FIG>, taken along the <NUM>-<NUM> line of <FIG>. As shown in <FIG>, the portion <NUM> includes the non-conductive first layer <NUM> and the conductive second layer <NUM> including replications of the electrode array <NUM> of the electrode pattern <NUM> formed across the base substrate <NUM>. Although the portion <NUM> of the base substrate <NUM> is shown having three electrode arrays <NUM>, the portion <NUM> can include less or additional electrode arrays <NUM> of the electrode pattern <NUM> of <FIG>. Also, the portion <NUM> is part of the base substrate or web <NUM>.

As disclosed above with respect to <FIG>, the electrode arrays <NUM> include one or more arrays electrode <NUM>. The laser beam <NUM> penetrates a thickness t of the conductive second layer <NUM> as the laser beam <NUM> pulses or etches the lines <NUM> and corresponding spacings <NUM> into the conductive second layer <NUM> to define the array electrodes <NUM>. The depth of the penetration of the laser beam <NUM> into the conductive second layer <NUM> can be based on, for example, the thickness t<NUM> of the conductive second layer <NUM> and/or an intensity of the laser beam <NUM>. In some examples, the laser beam <NUM> penetrates a depth substantially equal to the thickness t<NUM>, less than the thickness t<NUM>, or greater than the thickness t<NUM>, such that the laser beam <NUM> penetrates a portion of the non-conductive layer <NUM>, as will be disclosed below in connection with <FIG>. Also, the laser beam <NUM> defines features of the the electrode array <NUM> with respect to a resolution or a number of electrodes <NUM> per an area of the base substrate <NUM>, the size of the array electrodes <NUM>, and the configuration of lines <NUM> and the spacings <NUM> therebetween, which define a degree of inter-digitation of the array electrodes <NUM>.

Although laser ablation results in a well-defined electrode pattern <NUM> including the electrode array <NUM> having increased resolution, in some examples, defects or imperfections in the mask <NUM> or the lens <NUM> can result corresponding defects in the based substrate <NUM>. Such defects can include debris on the mask <NUM> or the lens <NUM>, openings in the mask <NUM> that allow the laser beam <NUM> to irradiate the base substrate <NUM> where such exposure was not intended (e.g., an additional opening in the mask <NUM> or a wider than intended opening), and/or imperfections in the mask <NUM> that prevent the laser beam <NUM> from penetrating the base substrate <NUM> where the penetration was intended (e.g., incomplete openings in the mask <NUM>). Debris (e.g., hair, dust, etc.) or imperfections in the mask <NUM> can result in interruptions or inconsistencies in the resulting electrode pattern <NUM>, such as gaps or alterations to the shapes of the lines <NUM> and/or the spacings <NUM> defining the electrode pattern <NUM>). Another example of a defect includes inconsistencies in the spacings <NUM> in the master pattern <NUM> due to a defect in the master pattern <NUM>.

<FIG> illustrates the conductive second layer <NUM> of the base substrate <NUM> including defects or markings <NUM>. In the example portion <NUM>, the defects <NUM> are included in each of the iterations of the electrode array <NUM> of the electrode pattern <NUM> across the base substrate <NUM>. However, the defects <NUM> can be located elsewhere in the electrode pattern <NUM>, such as in connection with the non-array electrodes <NUM>. In examples where the electrode pattern <NUM> is formed using broad field laser ablation, the defects <NUM> are systematic, or substantially identical in each of the electrode arrays <NUM> of the portion <NUM>. In particular, the systematic occurrences of the defects <NUM> results from the exposure of the laser beam <NUM> over substantially the entire portion <NUM> to concurrently form multiple electrode patterns <NUM>. Thus, the defects <NUM> are substantially uniformly replicated in each of the electrode patterns <NUM> irradiated into the conductive second layer <NUM> as the base substrate <NUM> is exposed to the laser beam <NUM> at the laser ablation station <NUM>. For example, the defects <NUM> can be disposed at substantially the same position relative to the respective electrode patterns <NUM>. Also, the defects <NUM> can be the substantially the same size within the respective electrode patterns <NUM>. Therefore, the resulting substrate web, including the base substrate <NUM> and the electrode patterns <NUM>, includes substantially identical, systematically reproduced defects <NUM> in each of the electrode patterns <NUM>.

In some examples, markings such as the defects <NUM>, could be purposeful. For example, such markings may be included as a signature that appears across all electrodes patterns <NUM> to identify a particular manufacturer, manufacturing run, product, or manufacturing location.

<FIG> is a cross-sectional view of the portion <NUM> including the electrode pattern <NUM> taken along the <NUM>-<NUM> line of <FIG>. As an example, <FIG> illustrate a section of the electrode pattern <NUM> other than the electrode array <NUM>. For example, <FIG> illustrates the lines <NUM> and the spacings <NUM> defining one or more of the non-array electrodes <NUM>.

As disclosed above with respect to the exposure of the base substrate <NUM> to the laser beam <NUM> in connections with <FIG> and <FIG>, in some examples, the laser beam <NUM> selectively penetrates through the conductive second layer <NUM> and the non-conductive first layer <NUM>. In such examples, the laser beam <NUM> penetrates through the thickness t<NUM> of the conductive second layer <NUM> and a thickness t<NUM> of the non-conductive first layer <NUM>, which may be less or substantially less than a total thickness t<NUM> of the non-conductive first layer <NUM>. The non-conductive first layer <NUM> absorbs some of the energy of the laser beam <NUM>. As a result of the irradiation of the non-conductive first layer <NUM>, a portion of the non-conductive first layer <NUM> having the thickness t<NUM> is ejected from the non-conductive first layer <NUM>, which results in structural changes to the non-conductive first layer <NUM>. The ejection of the portion of the non-conductive first layer <NUM> can result in ejection of a portion of the conductive second layer <NUM> to define the electrode pattern <NUM>. As illustrated in <FIG>, the non-conductive first layer <NUM> includes one or more disturbances <NUM> due to the penetration of the laser beam <NUM>. The portions or disturbances <NUM> includes indentations, spacings, openings, or grooves in the non-conductive first layer <NUM> resulting from the ejection of one or more portions of the irradiated non-conductive first layer <NUM>. The respective thicknesses of the disturbances <NUM> depend on the thickness of the non-conductive first layer <NUM> and a depth of the penetration of the laser beam <NUM>. Also, although the disturbances <NUM> are illustrated in <FIG> as rectangular in shape, the disturbances <NUM> can be substantially any shape including irregularly shaped, curved, or angled grooves or indentations corresponding to the shape of the fragments ejected from the non-conductive first layer <NUM>.

Although laser ablation of the base substrate <NUM> at the laser ablation station <NUM> has been described with respect to the portion <NUM>, it is to be understood that, as part of the continuous movement of the base substrate <NUM> through the first example assembly <NUM> via the first through third rollers <NUM>, <NUM>, <NUM>, the laser beam <NUM> penetrates more than one portion of the base substrate <NUM> during operation of the first example assembly <NUM>. In the first example assembly <NUM>, as the base substrate <NUM> passes under and/or by the lens <NUM>, successive portions n of the conductive second layer <NUM> are exposed to the laser beam <NUM> for repeatedly creating the master pattern <NUM> on each of the successive portions n. The size of the portions and the spacing between the portions as the base substrate <NUM> passes through the laser ablation station <NUM> may be predetermined based on, for example, the size and configuration of the master pattern <NUM>, the dimensions of the base substrate <NUM>, the thickness of the conductive second layer <NUM>, and/or the dimensions of the droplet actuator with which the base substrate <NUM> will be associated.

Returning to <FIG>, after the portion <NUM> undergoes laser ablation at the laser ablation station <NUM> to form the electrode array <NUM> (e.g., as part of the electrode pattern <NUM> of <FIG>), the portion <NUM> is moved, via rotation of the first through third rollers <NUM>, <NUM>, <NUM>, to a printer <NUM>. In the first example assembly <NUM>, the printer <NUM> includes an apparatus or an instrument capable of applying at least one layer of material <NUM> having a hydrophobic and/or a dielectric property to the electrode array <NUM>. In the first example assembly <NUM>, the printer <NUM> can deposit the hydrophobic and/or dielectric material <NUM> via deposition techniques including, but not limited to, web-based coating (e.g., via rollers associated with the printer <NUM>), slot-die coating, spin coating, chemical vapor deposition, physical vapor deposition, and/or atomic layer deposition. The printer <NUM> can also apply other materials in addition to the hydrophobic and/or dielectric material <NUM> (e.g., anti-fouling coatings, anti-coagulants). Also, the printer <NUM> can apply one or more layers of the material(s) with different thicknesses and/or covering different portions of the base substrate <NUM>.

As described above, in the first example assembly <NUM>, at least one of the first through third rollers <NUM>, <NUM>, <NUM> advance the base substrate or web <NUM> to the printer <NUM> for application of the hydrophobic and/or dielectric material <NUM> to the electrode array <NUM>. In some examples, the printer <NUM> includes a plurality of registration rollers <NUM> to facilitate accuracy in feeding and registration of the base substrate <NUM> as part of operation of the printer <NUM> in applying the hydrophobic and/or dielectric material <NUM>, for example, via roller coating methods.

In the first example assembly <NUM>, the hydrophobic and/or dielectric material <NUM> is applied to the electrode array <NUM> to completely or substantially completely insulate the electrode array <NUM>. For example, referring again to <FIG>, the printer <NUM> selectively applies the hydrophobic and/or dielectric material <NUM> to the electrodes <NUM> of the electrode array <NUM>, however, the printer <NUM> does not apply the hydrophobic and/or dielectric material <NUM> to the other electrodes <NUM> of the electrode pattern <NUM>. The selective application of the hydrophobic and/or the dielectric material <NUM> to the electrode pattern <NUM> provides for electrodes that are capable of making electrical contact with other electrodes (e.g., the non-array electrodes <NUM> that are not covered with the hydrophobic and/or dielectric material <NUM>) as well as electrodes that are covered or coated as part of the electrode array <NUM> (e.g., the array electrodes <NUM>). As a result of the hydrophobic and/or the dielectric material <NUM>, a droplet placed proximate to the electrode array <NUM> is in a beaded configuration forming a contact angle with respect to the portion <NUM>. In operation, the electrodes <NUM> of the coated electrode array <NUM> control the contact angle (e.g., a degree of the contact angle) via electric forces.

In some examples, the hydrophobic and/or dielectric material <NUM> is a polytetrafluoroethylene material (e.g., Teflon®) or a fluorosurfactant (e.g., FluoroPel™) applied to the conductive second layer <NUM> to substantially cover the electrode array <NUM>. In other examples, the hydrophobic and/or dielectric material <NUM> is a dielectric such as a porcelain (e.g., a ceramic) or a plastic. In some examples, a dielectric is applied in combination with the hydrophobic material, such that the electrode array <NUM> is coated with a first layer of the dielectric and a second layer of, for example, Teflon® disposed on to the dielectric layer. In such examples, the first layer of dielectric may have a greater thickness than the second layer of the treated layer. Also, in some examples, an anti-fouling coating is applied to the electrode array <NUM> (e.g., as an additional layer or in connection with the hydrophobic and/or dielectric material <NUM>) to reduce surface fouling that can result from accumulation of proteins other biological species during clinical use of the resulting droplet actuator and that may result in contamination of the microfluidic device. Other materials can be applied based on operational use of the droplet actuator. For example, an anti-coagulant material can be applied to prevent clotting of a biological specimen before an assay is completed.

In some examples, the hydrophobic and/or dielectric material <NUM> is deposited via the printer <NUM> in substantially liquid form. To create a structural, or treated layer <NUM> on the base substrate <NUM> to support a droplet, the portion <NUM> is moved via the rollers (e.g., the first through third rollers <NUM>, <NUM>, <NUM>) through a curing station <NUM>. At the curing station <NUM>, the hydrophobic and/or dielectric material is treated and/or modified to form the first treated layer <NUM>. Treating and/or modifying the hydrophobic and/or dielectric material can include curing the material. For example, at the curing station <NUM>, heat is applied to facilitate the hardening of the hydrophobic and/or dielectric material <NUM>. In some examples, the portion <NUM> is exposed to an ultraviolet light to cure the hydrophobic and/or dielectric material <NUM> and form the treated layer <NUM> to insulate the electrode array <NUM>. In other examples, the curing and/or modification of the hydrophobic and/or dielectric material is accomplished without heat and/or a photon source. In some examples, the treated layer <NUM> supports a droplet as an electric field is applied (e.g., in connection with electrode array <NUM>) to manipulate the droplet. For example, during an electrowetting process, a contact angle of the droplet with respect to the treated layer <NUM> changes as a result of an applied voltage, which affects the surface tension of the droplet on the treated surface <NUM>.

After passing through the curing station <NUM>, the portion <NUM> is prepared to serve as a bottom substrate of a droplet actuator and/or as a digital microfluidic chip. Because the base substrate <NUM> includes the non-conductive first layer <NUM> bonded with the conductive second layer <NUM>, as disclosed above, additional adhesion of, for example, the electrode array <NUM> to the non-conductive first layer <NUM> is not required. Such a pre-adhered configuration increases the efficiency of the preparation of the base substrate <NUM> for the droplet actuator by reducing processing steps. Also, as described above, when the portion <NUM> is at any one of the laser ablation station <NUM>, the printer <NUM>, or the curing station <NUM>, other portions n of the base substrate <NUM> are concurrently moving through the others of the respective stations <NUM>, <NUM>, <NUM> of the first example assembly <NUM>. For example, when the portion <NUM> is at the curing station <NUM>, the first through third rollers <NUM>, <NUM>, <NUM> are continuously, periodically, or aperidiocally advancing one or more other portions n of the base substrate <NUM> through, for example, the laser ablation station <NUM> and/or the printer <NUM>. In such a manner, preparation of the base substrate <NUM> for the droplet actuator is achieved via a substantially continuous, high-speed, automated process.

Although the base substrate <NUM> may be considered as including successive portions, during some example operations of the first example assembly <NUM>, the base substrate <NUM> remains as a single sheet or web as the successive portions undergo processing to create the electrode arrays <NUM> (e.g., via the electrode pattern <NUM> of <FIG>) and receive the coating of hydrophobic and/or dielectric material <NUM>. Thus, to create one or more droplet actuators using the processed base substrate <NUM>, the base substrate or web <NUM>, in some examples, is cut (e.g., diced) to form individual units comprising the electrode arrays <NUM>, as will be further disclosed below (e.g., <FIG>, <FIG>). In some examples, prior to dicing, the base substrate <NUM>, including the portion <NUM>, is rewound in a rolled configuration similar to the initial rolled configuration of the base substrate <NUM> prior to being unwound by the first roller <NUM>. Such rewinding may be accomplished via one or more rollers as part of the roll-to-roll processing. In such examples, the base substrate <NUM> may be diced or otherwise separated at a later time. In other examples, the rollers (e.g., the second and third rollers <NUM>, <NUM>), advance the base substrate <NUM> for merging with a top substrate, as will be further disclosed below (e.g., <FIG>, <FIG>).

As described above, an example droplet actuator includes a base substrate, such as the base substrate <NUM> including the electrode array <NUM> (<FIG> and <FIG>) and a top substrate. The top substrate may include for example, an electrode pattern and associated electrode array created via laser ablation in substantially the same manner as the electrode pattern <NUM> and electrode array <NUM> of <FIG> and <FIG>, a single electrode (e.g., a layer of a conductive metal), or a non-conductive substrate (e.g., a dielectric). Alternatively, in some examples, the droplet actuator does not include a top substrate. In preparing the top substrate and/or a configuration of the top substrate, consideration is given to, for example, intended applications of the droplet actuator.

<FIG> illustrates a second example assembly <NUM> for creating an example top substrate of a droplet actuator having a single electrode. The second example assembly <NUM> includes a series or a plurality of rollers, including a first roller <NUM>, a second roller <NUM>, and a third roller <NUM>, which operate in synchronized rotation to drive a top substrate <NUM> through the second example assembly <NUM>. The second example assembly <NUM> can include rollers in addition to the first through third rollers <NUM>, <NUM>, <NUM> to move the top substrate <NUM> through the assembly <NUM>. Prior to cutting or sizing of the top substrate <NUM>, the top substrate <NUM> can be considered a substrate web that may be in a rolled, partially rolled, or unrolled configuration as the top substrate <NUM> moves through the second example assembly <NUM>.

In the second example assembly <NUM>, the first roller <NUM> rotates to unwind the top substrate <NUM>, which, in some examples, is a sheet in a rolled configuration. The example top substrate <NUM> of <FIG> includes a first layer <NUM> and a second layer <NUM>. As with the example base substrate <NUM>, in this example, the example first layer <NUM> of the top substrate <NUM> comprises a non-conductive material such as, for example, a plastic, and the example second layer <NUM> includes a conductive material, such as a metal including, for example, one or more of gold, chrome, silver, or copper and/or any other suitable metal(s), conductive polymer(s), or combination(s) of metal(s) and/or conductive polymer(s). In some examples, the conductive second layer <NUM> is adhered to the non-conductive first layer <NUM> via an adhesive layer (e.g., chrome).

In the second example assembly <NUM>, the first through third rollers <NUM>, <NUM>, <NUM> rotate to advance the top substrate <NUM> to a printer <NUM>. The printer <NUM> coats the conductive second layer <NUM> with a hydrophobic and/or dielectric material <NUM> (e.g., Teflon® or a dielectric such as a ceramic). The printer <NUM> is substantially similar to the printer <NUM> of the first example assembly <NUM> of <FIG>. For example, the printer <NUM> can apply the hydrophobic and/or dielectric material <NUM> to the top substrate <NUM> via web-based coating, slot-die coating, spin coating, chemical vapor deposition, physical vapor deposition, atomic layer deposition, and/or other deposition techniques. The printer <NUM> can include registration rollers <NUM> to facilitate alignment of the top substrate <NUM> with respect to the printer <NUM> during application of the hydrophobic and/or dielectric material <NUM> and/or other coating materials.

After receiving the coating of the hydrophobic and/or dielectric material <NUM>, the second roller <NUM> and the third roller <NUM> advance the portion <NUM> to a curing station <NUM>. As disclosed in connection with the curing station <NUM> of <FIG>, the curing station <NUM> of the second example assembly <NUM> facilitates the modification (e.g., curing) of the hydrophobic material via heat to form a treated layer <NUM>. The treated layer <NUM> insulates the conductive second layer <NUM>, which serves as the single electrode of the top substrate <NUM>, by completely or substantially completely covering the conductive second layer <NUM>. Thus, in coating the second layer <NUM> of the portion <NUM>, electrical potential conducting portion of the top substrate <NUM> is insulated from a droplet that may be applied to a droplet actuator that includes the portion <NUM>.

After passing through the curing station <NUM>, the portion <NUM> is prepared to serve as a top substrate of a droplet actuator. Because the top substrate <NUM> includes the non-conductive first layer <NUM> pre-adhered to the conductive second layer <NUM> prior to processing of the top substrate via the second example assembly <NUM>, additional adhesion of, for example, an electrode to the non-conductive first layer <NUM> is not required, thereby increasing the efficiency of the preparation of the top substrate <NUM> for the droplet actuator.

Also, and as disclosed in connection with the first example assembly <NUM> of <FIG>, in the second example assembly <NUM>, the first through third rollers <NUM>, <NUM>, <NUM> rotate to advance the top substrate <NUM> such that portions of the top substrate pass through one of the printer <NUM> or the curing station <NUM> in substantially continuous, periodic and/or aperiodic succession as part of the roll-to-roll operation of the second example assembly <NUM>. Thus, although the second example assembly <NUM> is described in association with the portion <NUM>, it is to be understood that successive portions of the top substrate <NUM> are prepared in substantially the manner as the portion <NUM> as a result of rotation of the first through third rollers <NUM>, <NUM>, <NUM>. In such as manner, the top substrate <NUM> is provided with a treated layer <NUM> along the length of the top substrate <NUM>.

In the example top substrate <NUM>, the conductive second layer <NUM> serves an electrode. However, in some examples, the conductive second layer <NUM> undergoes laser ablation to form one or more electrode arrays. In such examples, the second example assembly <NUM> includes a laser ablation station substantially similar to the laser ablation station <NUM> of the first example assembly <NUM> of <FIG>. Thus, prior to receiving the hydrophobic material <NUM>, the top substrate <NUM> is exposed to a laser beam, which creates an electrode pattern in the irradiated conductive second layer <NUM>. The electrode pattern formed on the top substrate <NUM> can be the same or different from the electrode pattern formed on the base substrate <NUM> of <FIG>. In examples where the top substrate <NUM> is ablated via a laser, the second example assembly <NUM> is substantially similar to the first example assembly <NUM>. Also, in some examples, the electrode array is not formed on/in the base substrate <NUM> but only on/in the top substrate <NUM>.

During operation of the second example assembly <NUM>, the top substrate remains single sheet as successive portions of the top substrate <NUM> are coated with the hydrophobic material <NUM>. As part of the fabrication of one or more droplet actuators, the top substrate <NUM> is aligned with the base substrate (e.g., the base substrate <NUM> of <FIG>). In some examples, after passing through the curing station <NUM>, the top substrate is rewound into a rolled configuration via one or more rollers. In such examples, the finished roll may be diced or otherwise cut and/or separated into individual units that are aligned at a space apart distance and bonded with individual diced units of the base substrate <NUM> of <FIG> to create a droplet actuator.

In other examples, after passing through the curing station <NUM>, the rollers (e.g., the first through third rollers <NUM>, <NUM>, <NUM>) continue to advance the top substrate <NUM> to merge the top substrate <NUM> with the base substrate <NUM> of <FIG> via automated roll-to-roll processing, as will be discussed below in connection with <FIG>. In such examples, to prepare the top substrate <NUM> for alignment with the base substrate <NUM>, the rollers of the second example assembly <NUM> (e.g., the first through third rollers <NUM>, <NUM>, <NUM>) rotate so as to reverse the orientation of the top substrate <NUM> relative to the base substrate <NUM> of <FIG> such that the treated layer <NUM> of the base substrate <NUM> faces the treated layer <NUM> of the top substrate <NUM> when the base substrate <NUM> and the top substrate <NUM> are aligned in parallel configuration (see, e.g., <FIG>).

<FIG> is a diagram of a third example assembly <NUM> for processing the substrate webs. The example assembly <NUM> operates to merge a base substrate with a top substrate to fabricate a droplet actuator via roll-to-roll processing. The third example assembly <NUM> can be implemented in connection with the first example assembly <NUM> of <FIG> and the second example assembly <NUM> of <FIG> to fabricate a droplet actuator from the base substrate <NUM> of <FIG> and the top substrate <NUM> of <FIG>. For example, as shown in <FIG>, after passing through the curing station <NUM> associated with the second example assembly <NUM>, the top substrate <NUM> is advanced by a first roller <NUM> of the third example assembly <NUM>. Similarly, after passing through the curing station <NUM> associated with the first example assembly <NUM>, the base substrate <NUM> is advanced by a second roller <NUM> of the third example assembly <NUM> to facilitate alignment of the substrates <NUM>, <NUM>.

The third example assembly <NUM> includes a third roller <NUM> and a fourth roller <NUM> that form a pair of merging rollers to which the base substrate <NUM> and the top substrate <NUM> are fed via the respective first roller <NUM> and the second roller <NUM> of the third example assembly <NUM>. As each of the merging rollers <NUM>, <NUM> rotates, the base substrate <NUM> and the top substrate <NUM> are aligned in a parallel configuration at a predetermined spaced apart distance, or gap.

For example, <FIG> illustrates a merged portion <NUM> including the base substrate <NUM> and the top substrate <NUM> in parallel alignment and including a gap <NUM> separating the treated layer <NUM> of the base substrate <NUM> and the treated layer <NUM> of the top substrate <NUM>. The gap <NUM> is a predetermined spaced apart distance between the treated layers <NUM>, <NUM>. The gap <NUM> can be created using one more gap formation techniques. Such techniques can include, for example, inserting one or more capillary tubes and/or microbeads between the base and top substrates <NUM>, <NUM> to serve as spacers to separate the respective treated layers <NUM>, <NUM>. Additionally or alternatively, other examples for forming and/or maintaining the gap include embossing or molding pillars into, for example, the non-conductive first layer <NUM> of the base substrate <NUM> to provide a frame to separate the base substrate <NUM> and the top substrate <NUM>. Further still, other additional or alternative examples for forming and/or maintaining the gap include laminating one or more of the treated layers <NUM>, <NUM> of the respective base substrate <NUM> and the top substrate <NUM> to create a film to separate the substrates or spraying a filler fluid (e.g., a fluid immiscible with the droplet fluid) on at least a portion of the substrates <NUM>, <NUM>. In some examples, the gap formation techniques may be implemented via roll-to-roll processing. For example, as one or more the base substrate <NUM> or the top substrate <NUM> passes proximate to one or more rollers of the first through third example assemblies <NUM>, <NUM>, <NUM>, one or more of the rollers may provide for embossing and/or lamination of the base substrate <NUM> and/or the top substrate <NUM>.

Similarly, in examples where the base substrate <NUM> and the top substrate <NUM> are rewound as individual rolls (e.g., as part of the first example assembly <NUM> of <FIG> and the second example assembly <NUM> of <FIG>), diced separately, and then aligned, the base substrate <NUM> and the top substrate <NUM> are also arranged so that a gap exists between treated layers <NUM>, <NUM> of the respective base substrate <NUM> and the top substrate <NUM>.

As show in <FIG>, the example third assembly <NUM> includes a bonding station <NUM>. The bonding station <NUM> joins, or bonds, the base substrate <NUM> and the top substrate <NUM> as part of fabricating the droplet actuator. For example, at the bonding station <NUM>, one or more adhesives may be selectively applied to a predefined portion of the base substrate <NUM> and/or the top substrate <NUM> (e.g., a portion of the base substrate <NUM> and/or the top substrate <NUM> defining a perimeter of the resulting droplet actuator) to create a bond between the base substrate <NUM> and the top substrate <NUM> while preserving the gap <NUM>. In some examples, bonding the substrates <NUM>, <NUM> at the bonding station <NUM> including forming the gap <NUM> (e.g., in advance of applying the adhesive).

Examples of adhesive(s) that may be used at the bonding station <NUM> include epoxies, foils, tapes, and/or ultraviolet curable adhesives. In some examples, layers of polymers such as SU-<NUM> and/or polydimethylsiloxane (PDMS) are applied to the base substrate <NUM> and/or the top substrate <NUM> to bond the substrates. Also, in some examples, the bonding station <NUM> provides for curing of the adhesive(s) via, for example, ultraviolet light. The bonding station <NUM> may apply one more methods involving, for example, heat (e.g. thermal bonding), pressure, curing, etc. to bond the base substrate <NUM> and the top substrate <NUM>.

In the example third assembly <NUM>, the merged portion <NUM> can be selectively cut, diced or otherwise separated to form one or more droplet actuators, as substantially represented in <FIG> by the merged portion <NUM>. The example third assembly <NUM> includes a dicing station <NUM>. The dicing station <NUM> can be, for example, a cutting device, a splitter, or more generally, an instrument to divide the continuous merged portion <NUM> into discrete units corresponding to individual droplet actuators. The merged portion <NUM> may be cut into individual droplet actuators based on, for example, the electrode pattern <NUM> of <FIG> such that each droplet actuator includes a footprint of the electrode array <NUM> and the other electrodes that are formed via the electrode pattern <NUM> (e.g., the non-array electrodes <NUM>). During operation of the resulting droplet actuator, the gap <NUM> can receive a droplet that can be manipulated using electrical potentials via the insulated electrodes <NUM> of the electrode array <NUM> of the base substrate <NUM> (e.g., the conductive second layer <NUM>) and/or the insulated electrode of the top substrate <NUM> (e.g., the conductive second layer <NUM>). The insulated nature of the conductive surfaces of the base substrate <NUM> and the top substrate <NUM> prevents unintended chemical reactions or changes to the droplet fluid due to exposure to the electrodes, thereby protecting the integrity of the droplet manipulation and analysis.

<FIG> is a block diagram of an example processing system <NUM> for use with a droplet actuator fabrication assembly such as, for example, the first, second, and/or third example assemblies <NUM>, <NUM>, <NUM> of <FIG>, <FIG> and <FIG> for processing one or more substrate webs. The example processing system <NUM> includes a controller <NUM>, which controls operation the first, second, and/or third example assembles <NUM>, <NUM>, <NUM> via selected driver components.

For example, the example processing system <NUM> includes a roller driver <NUM>, which controls one or more of the rollers of the first, second, and/or third example assembles <NUM>, <NUM>, <NUM>. In some examples, the example processing system <NUM> includes one or more roller drivers <NUM>. In the example shown, the roller driver(s) <NUM> are communicatively coupled to rollers 506a-n. The rollers 506a-n may correspond, for example, to the first through third rollers <NUM>, <NUM>, <NUM> of the first example assembly <NUM>; the first through third rollers <NUM>, <NUM>, <NUM> of the second example assembly <NUM>; and/or the first through fourth rollers <NUM>, <NUM>, <NUM>, <NUM> of the third example assembly <NUM>. The roller driver(s) <NUM> control rotation of the rollers 506a-n using, for example, a motor, to regulate one or more operational characteristics of the rollers. Such operational characteristics may include speed of rotation, duration of rotation, direction of rotation, acceleration, etc. of the rollers 506a-n. One or more of the operational characteristics controlled by the roller driver(s) <NUM> at least partially determine a position of a portion of the one or more substrates fed through the first, second, and third example assemblies <NUM>, <NUM>, <NUM> (e.g., the portion <NUM> of the base substrate <NUM>, the portion <NUM> of the top substrate <NUM>, and/or the merged portion <NUM>) at any time during the operation of the rollers 506a-n. Further, one or more of the operational characteristics controlled by the roller driver(s) <NUM>, such as speed of rotation, at least partially determine a duration for which a portion of the substrates is exposed to one or more stations of the first, second, and third example assemblies <NUM>, <NUM>, <NUM> (e.g., the laser ablation station <NUM> of the first example assembly <NUM>). Thus, the roller driver(s) <NUM> control rate at which the one or more substrates are processed. Also, an example processor <NUM> operates the roller driver(s) <NUM> and, thus, the first, second, and third example assemblies <NUM>, <NUM>, <NUM> in accordance with a droplet actuator fabrication protocol.

The example processing system <NUM> also includes a laser driver <NUM>. In some examples, the example processing system <NUM> includes one or more laser drivers <NUM>. In the example shown, the one or more laser driver(s) <NUM> are communicatively coupled to one or more lasers <NUM> to control the laser(s) <NUM>. The laser(s) <NUM> may correspond to, for example, the laser beam <NUM> of the laser ablation station <NUM> of the first example assembly <NUM>. In some examples, the second example assembly <NUM> includes a laser ablation station having a laser beam. In such examples, the laser driver(s) <NUM> also control the laser associated with the second example assembly <NUM>. The laser driver(s) <NUM> control, for example, the intensity of the laser(s) <NUM>, a size of surface area of irradiation with respect to the substrate(s), the depth to which the laser(s) <NUM> penetrate a substrate (e.g., the conductive second layer <NUM> and the non-conductive first layer <NUM> of the base substrate <NUM>), and/or a duration for which the laser(s) <NUM> do or do not penetrate the substrate. The laser driver(s) <NUM> also control a manner in which the laser(s) <NUM> are exposed on the substrate(s), including whether the laser(s) <NUM> iteratively irradiate the substrate(s) as part of laser ablation rastering techniques or whether the laser(s) <NUM> are exposed over an predetermined surface area of the substrate(s) for inscribing an electrode pattern in the substrate(s) via a single exposure of the laser via broad field laser ablation. In examples where the laser(s) <NUM> iteratively etch the pattern into the subtrate(s), the laser driver(s) <NUM> control the movement (e.g., direction and speed) of the laser(s) <NUM> across the substrate(s). Also, the example processor <NUM> operates the laser driver(s) <NUM> and, thus, the laser(s) <NUM> in accordance with a laser ablation protocol.

The example processing system <NUM> also includes a printer driver <NUM> which controls one or more of the printers of the first and/or second example assemblies <NUM>, <NUM>. In some examples, the example processing system <NUM> includes one or more printer drivers <NUM>. In the example shown, the printer driver(s) <NUM> are communicatively coupled to a first printer <NUM> and a second printer <NUM>. The first printer <NUM> may correspond, for example, to the printer <NUM> of the first example assembly <NUM>. The second printer <NUM> may correspond, for example, to the printer <NUM> of the second example assembly <NUM>. The printer driver(s) <NUM> control, for example, the thickness, width, and/or pattern of the hydrophobic and/or dielectric material applied to the substrates by the first printer <NUM> and the second printer <NUM>. In examples where the hydrophobic and/or dielectric material is applied via web-based printing, the printer driver(s) <NUM> can control a pressure with which rollers associated with the first printer <NUM> and/or the second printer <NUM> contact the substrates and thus, affect the quality of the hydrophobic and/or dielectric layer of material applied to the electrode array. In some examples, the first printer <NUM> and the second printer <NUM> operate in connection with the rollers 506a-n. In such examples, the printer driver(s) <NUM> work in association with the roller driver(s) <NUM> to define, for example, a rate at which the hydrophobic and/or dielectric material is deposited on the substrates. Also, the example processor <NUM> operates the printer driver(s) <NUM> and, thus, the first printer <NUM> and the second printer <NUM> in accordance with a hydrophobic and/or dielectric material application protocol.

The example processing system <NUM> also includes a curing station driver <NUM> that controls one or more of the curing stations of the first and/or second example assembles <NUM>, <NUM>. In some examples, the example processing system <NUM> includes one or more curing station drivers <NUM>. In the example shown, the curing station driver(s) <NUM> are communicatively coupled to a first curing station <NUM> and a second curing station <NUM>. The first curing station <NUM> may correspond, for example, to the first curing station <NUM> of the first example assembly <NUM>. The second curing station <NUM> may correspond, for example, to the second curing station <NUM> of the second example assembly <NUM>. The curing station driver(s) <NUM> control, for example, the intensity of heat and/or ultraviolet light applied to the substrates, the size of an area of the substrates exposed to the heat and/or ultraviolet light, a duration of exposure of the heat and/or ultraviolet light, etc. Also, the example processor <NUM> operates the curing station driver(s) <NUM> and, thus, the first curing station <NUM> and the second curing station <NUM> in accordance with a hydrophobic and/or dielectric material curing protocol.

The example processing system <NUM> also includes a bonding station driver <NUM> that controls the bonding station of the third example assembly <NUM>. In some examples, the example processing system <NUM> includes one or more bonding station drivers <NUM>. In the example shown, the bonding station driver(s) <NUM> are communicatively coupled to a bonding station <NUM>. The bonding station <NUM> may correspond, for example, to the bonding station <NUM> of the third example assembly <NUM>. The bonding station driver(s) <NUM> control, for example, a thickness with which the adhesive is applied, a configuration or layout in which the adhesive is applied, a duration and/or intensity of heat applied to facilitate curing or thermal bonding, a pressure applied to bond the substrates, etc. In some examples, the bonding station driver(s) also control formation of a gap between the substrates (e.g., via lamination). Also, the example processor <NUM> operates the bonding station driver(s) <NUM> and, thus, the first bonding station <NUM> in accordance with a substrate bonding protocol.

The example processing system <NUM> also includes a dicing station driver <NUM> that controls the dicing station of the third example assembly <NUM>. In some examples, the example processing system <NUM> includes one or more dicing station drivers <NUM>. In the example shown, the dicing station driver(s) <NUM> are communicatively coupled to a dicing station <NUM>. The dicing station <NUM> may correspond, for example, to the dicing station <NUM> of the third example assembly <NUM>. The dicing station driver(s) <NUM> control, for example, the cutting or splitting of the substrate webs (e.g., the bonded substrates or, in some examples, the substrates as individual layers), a size of the discrete units into which the substrates are cut, a spacing between discrete units formed from the continuous substrates, an operational speed of a cutting instrument, retraction of the cutting instrument, etc. Also, the example processor <NUM> operates the dicing station driver(s) <NUM> and, thus, the dicing station <NUM> in accordance with a substrate web dicing protocol.

The example processing system <NUM> also includes a database <NUM> that may store information related to the operation of the example system <NUM>. The information may include, for example, information about the length and dimensions of the substrates to be fed through the first, second, and/or third example assemblies <NUM>, <NUM>, <NUM>; the materials comprising the substrates (e.g., type of metal of the conductive second layer <NUM> of the base substrate <NUM>), rotational characteristics of the rollers, such as a speed and/or diameter; the electrode pattern(s) to be ablated on the substrate(s) via the laser(s); properties of the hydrophobic, dielectric, adhesive, and/or other material(s) to be applied to the substrates, etc..

The example processing system <NUM> also includes a user interface such as, for example, a graphical user interface (GUI) <NUM>. An operator or technician interacts with the processing system <NUM>, and thus, the first, second, and/or third example assemblies <NUM>, <NUM>, <NUM> via the interface <NUM> to provide, for example, commands related to operation of the rollers 506a-n such as speed, duration of rotation, etc. of the rollers; the pattern(s) to be ablated on the substrates via the laser(s) <NUM>; the intensity of the laser(s) <NUM>; the type of hydrophobic and/or dielectric material(s) to be applied to the substrates by the printers; the intensity of the curing stations <NUM>, <NUM>; the size of the gap in aligning the base substrate and top substrate via the rollers 506a-n, the adhesives applied to bond the substrates at the bonding station <NUM>; the size of the discrete units into which the substrates are cut via the dicing station <NUM>; etc. The interface <NUM> may also be used by the operator to obtain information related to the status of any substrate processing completed and/or in progress, check parameters such as speed and alignment, and/or to perform calibrations.

In the example shown, the processing system components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are communicatively coupled to other components of the example processing system <NUM> via communication links <NUM>. The communication links <NUM> may be any type of wired connection (e.g., a databus, a USB connection, etc.) and/or any type of wireless communication (e.g., radio frequency, infrared, etc.) using any past, present or future communication protocol (e.g., Bluetooth, USB <NUM>, USB <NUM>, etc.). Also, the components of the example system <NUM> may be integrated in one device or distributed over two or more devices.

While an example manner of implementing the first, second, and/or third example assemblies <NUM>, <NUM>, <NUM> of <FIG>, <FIG>, and <FIG> is illustrated in <FIG>, one or more of the elements, processes and/or devices illustrated in <FIG> may be combined, divided, re-arranged, omitted, eliminated and/or implemented in any other way. Further, the example controller <NUM>, the example roller driver(s) <NUM>, the example processor <NUM>, the example laser driver(s) <NUM>, the example printer driver(s) <NUM>, the example curing station driver(s) <NUM>, the example bonding station driver(s) <NUM>, the example dicing station driver(s) <NUM>, the example database <NUM> and/or, more generally, the example processing system <NUM> of <FIG> may be implemented by hardware, software, firmware and/or any combination of hardware, software and/or firmware. Thus, for example, any of the example controller <NUM>, the example roller driver(s) <NUM>, the example processor <NUM>, the example laser driver(s) <NUM>, the example printer driver(s) <NUM>, the example curing station driver(s) <NUM>, the example bonding station driver(s) <NUM>, the example dicing station driver(s) <NUM>, the example database <NUM> and/or, more generally, the example processing system <NUM> of <FIG> could be implemented by one or more analog or digital circuit(s), logic circuits, programmable processor(s), application specific integrated circuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)) and/or field programmable logic device(s) (FPLD(s)). When reading any of the apparatus or system claims of this patent to cover a purely software and/or firmware implementation, at least one of the example controller <NUM>, the example roller driver(s) <NUM>, the example processor <NUM>, the example laser driver(s) <NUM>, the example printer driver(s) <NUM>, the example curing station driver(s) <NUM>, the example bonding station driver(s) <NUM>, the example dicing station driver(s) <NUM>, and/or the example database <NUM> is/are hereby expressly defined to include a tangible computer readable storage device or storage disk such as a memory, a digital versatile disk (DVD), a compact disk (CD), a Blu-ray disk, etc. storing the software and/or firmware. Further still, the example processing system <NUM> of <FIG> may include one or more elements, processes and/or devices in addition to, or instead of, those illustrated in <FIG>, and/or may include more than one of any or all of the illustrated elements, processes and devices.

A flowchart representative of example machine readable instructions for implementing the first, second, and third example assemblies <NUM>, <NUM>, <NUM> and/or the example processing system <NUM> of <FIG>, and <FIG> is shown in <FIG>. In this example, the machine readable instructions comprise a program for execution by a processor such as the processor <NUM> shown in the example processor platform <NUM> discussed below in connection with <FIG>. The program may be embodied in software stored on a tangible computer readable storage medium such as a CD-ROM, a floppy disk, a hard drive, a digital versatile disk (DVD), a Blu-ray disk, or a memory associated with the processor <NUM>, but the entire program and/or parts thereof could alternatively be executed by a device other than the processor <NUM> and/or embodied in firmware or dedicated hardware. Further, although the example program is described with reference to the flowchart illustrated in <FIG>, many other methods of implementing the example first, second, and third example assemblies <NUM>, <NUM>, <NUM> and/or the example processing system <NUM> may alternatively be used. For example, the order of execution of the blocks may be changed, and/or some of the blocks described may be changed, eliminated, or combined.

As mentioned above, the example process of <FIG> may be implemented using coded instructions (e.g., computer and/or machine readable instructions) stored on a tangible computer readable storage medium such as a hard disk drive, a flash memory, a read-only memory (ROM), a compact disk (CD), a digital versatile disk (DVD), a cache, a random-access memory (RAM) and/or any other storage device or storage disk in which information is stored for any duration (e.g., for extended time periods, permanently, for brief instances, for temporarily buffering, and/or for caching of the information). As used herein, the term tangible computer readable storage medium is expressly defined to include any type of computer readable storage device and/or storage disk and to exclude propagating signals and to exclude transmission media. As used herein, "tangible computer readable storage medium" and "tangible machine readable storage medium" are used interchangeably. Additionally or alternatively, the example process of <FIG> may be implemented using coded instructions (e.g., computer and/or machine readable instructions) stored on a non-transitory computer and/or machine readable medium such as a hard disk drive, a flash memory, a read-only memory, a compact disk, a digital versatile disk, a cache, a random-access memory and/or any other storage device or storage disk in which information is stored for any duration (e.g., for extended time periods, permanently, for brief instances, for temporarily buffering, and/or for caching of the information). As used herein, the term non-transitory computer readable medium is expressly defined to include any type of computer readable storage device and/or storage disk and to exclude propagating signals and to exclude transmission media. As used herein, when the phrase "at least" is used as the transition term in a preamble of a claim, it is open-ended in the same manner as the term "comprising" is open ended.

<FIG> depicts an example flow diagram representative of an example method <NUM> that may be implemented to fabricate a droplet actuator via operation of the first, second, and third example assemblies <NUM>, <NUM>, <NUM>. The example method <NUM> may be implemented by advancing a web of a base substrate via rollers (block <NUM>). For example, the first, second, and third rollers <NUM>, <NUM>, <NUM> may unwind and drive the base substrate or web <NUM> of <FIG> through the rollers. In some examples, the rollers <NUM>, <NUM>, <NUM> are controlled by the roller drivers(s) <NUM> of <FIG>. The example method <NUM> also includes ablating an electrode array on the base substrate (block <NUM>). For example, the base substrate <NUM> may pass, via the rollers, to the laser ablation station <NUM> of <FIG>. The laser beam <NUM> penetrates the base substrate <NUM> (e.g., the conductive second layer <NUM>) to selectively remove, or ablate, material from the base substrate <NUM> to form an electrode array <NUM>. The laser beam <NUM> may be controlled by the laser driver(s) <NUM> of <FIG>.

The example method <NUM> also includes applying a hydrophobic and/or dielectric material to the electrode array (block <NUM>). In the example method <NUM>, the hydrophobic and/or dielectric material can be a hydrophobic material such as Teflon®, a dielectric, or a combination thereof. In some examples of the example method <NUM>, the printer <NUM> of <FIG> applies the hydrophobic and/or dielectric material to the electrode array <NUM> of the base substrate <NUM>. In the example method <NUM>, the hydrophobic and/or dielectric material substantially completely covers, or insulates, the electrode array <NUM>. In some examples, the printer <NUM> is controlled by the printer driver(s) <NUM> of <FIG>.

In the example method <NUM>, the hydrophobic and/or dielectric material is treated (e.g., cured or otherwise modified), to form a treated layer on the base substrate (block <NUM>). For example, heat and/or an ultraviolet light is applied to the base substrate to harden the hydrophobic material. The heat and/or the ultraviolet light can be applied via the curing station <NUM> of <FIG>. In some examples, curing station driver(s) <NUM> of <FIG> control the curing station <NUM>.

After treating the hydrophobic and/or dielectric material, the base substrate is ready for implementation as a bottom substrate of a droplet actuator. In the example method <NUM>, a top substrate (e.g. a substrate web) is concurrently processed for implementation as a top substrate of the droplet actuator. In other examples of the example method <NUM>, the top substrate is processed at a different time than the bottom substrate.

To prepare the top substrate for implementation as part of a droplet actuator in association with the base substrate, the example method <NUM> includes advancing the top substrate via rollers (block <NUM>). In some examples, the first, second, and third rollers <NUM>, <NUM>, <NUM> of <FIG> unwind and drive the top substrate <NUM> through the second example assembly <NUM>. Also, in some examples, the rollers <NUM>, <NUM>, <NUM> are controlled by the roller driver(s) <NUM>.

The example method <NUM> includes a decision whether to create an electrode array on the top substrate (block <NUM>). The top substrate can include a single electrode (e.g., a continuous layer of conductive material), an electrode array (e.g., a pattern including a plurality of electrodes), or a non-conductive material. If a decision is made at block <NUM> to create an electrode array on the top substrate, the example method <NUM> proceeds to block <NUM>, where an electrode array is created on the top substrate (e.g., the conductive second layer <NUM> of the top substrate <NUM>) via laser ablation. The laser ablation of the top substrate is performed in the substantially the same manner as the ablation of the base substrate at block <NUM> (e.g., via a laser to selectively remove conductive material in accordance with an electrode pattern).

If a decision is made not to create an electrode array on the top substrate (block <NUM>), the example method <NUM> continues where a hydrophobic and/or dielectric material is applied to the top substrate (block <NUM>). Also, in examples where an electrode array is formed on the top substrate (block <NUM>), the example method <NUM> proceeds to block <NUM>. In both instances, at least a portion of the top substrate is coated with the hydrophobic and/or dielectric material to, for example, insulate a single electrode or the electrode array associated with the top substrate. For example, the hydrophobic printer <NUM> of <FIG> may deposit a hydrophobic and/or dielectric material on the top substrate. In some examples, the printer <NUM> is controlled via the printer drivers of <FIG>.

In the example method <NUM>, the hydrophobic and/or dielectric material applied to the top substrate is treated (block <NUM>). Treating the hydrophobic and/or dielectric material on the top substrate may be performed substantially as described in connection with respect to treating the hydrophobic and/or dielectric material of the base substrate at block <NUM> (e.g., via heat and/or ultraviolet light applied via the curing station <NUM> of <FIG> and controlled by the curing station driver(s) <NUM> of <FIG>).

In the example method <NUM>, the top substrate is processed for implementation as part of a droplet actuator in connection with the base substrate. To form the droplet actuator, the example method <NUM> includes aligning the base substrate and the top substrate (block <NUM>). In some examples, the base substrate and the top substrate are configured as individual rolls (e.g., via the respective rollers of the first and second example assemblies <NUM>, <NUM> after the curing at blocks <NUM> and <NUM>). In such examples, aligning the base substrate and the top substrate includes aligning the individual rolls or aligning discrete portions of the base substrate and the top substrate if, for example, the individual rolls have been diced into discrete portions corresponding to predetermined dimensions of the droplet actuator (see block <NUM>). In other examples, aligning the base substrate and the top substrate is accomplished as part of continued advancement of the base substrate and top substrate via rollers such that the base substrate and the top substrate are merged and bonded prior to dicing (e.g., as described in connection with the third example process <NUM> of <FIG>). The base substrate and the top substrate may be bonded via an adhesive applied at the bonding station <NUM> of <FIG>.

Whether the alignment of the base substrate and the top substrate (e.g., the base substrate web and the top substrate web) occurs via alignment of discrete rolls and/or portions or as part of a roll-to-roll process (block <NUM>), the example method <NUM> includes forming a gap between the base substrate and the top substrate (block <NUM>). In the example method <NUM>, the gap can be formed by, for example, the insertion of capillary tubes between the substrates, embossing, and/or lamination of the hydrophobic and/or dielectric surfaces of the substrates.

The example method <NUM> includes dicing the substrate webs into individual units (block <NUM>). In some examples, the dicing occurs as part of the roll-to-roll process such that the bonded base substrate and top substrate are cut into an individual unit including the base substrate, the top substrate, and the gap. In examples where the base substrate and the top substrate are rolled into individual rolls (e.g., after the respective first and second example processes <NUM>, <NUM>), the substrates are cut into discrete units separately to form the droplet actuator and to subsequently undergo bonding and gap formation (e.g., blocks <NUM>, <NUM>). In the example method <NUM>, the substrate(s) may cut via a cutting or splitting instrument at the dicing station <NUM> of <FIG>. At the end of the example method <NUM> (block <NUM>), the droplet actuator can receive a droplet on the hydrophobic and/or dielectric surfaces of the substrates via the gap for manipulation by electrical potentials delivered via the base substrate and/or the top substrate.

<FIG> is a block diagram of an example processor platform <NUM> capable of executing the instructions of <FIG> to implement the apparatus and/or system of <FIG> and <FIG>. The processor platform <NUM> can be, for example, a server, a personal computer, a mobile device (e.g., a cell phone, a smart phone, a tablet such as an iPad™), a personal digital assistant (PDA), an Internet appliance, or any other type of computing device.

The input device(s) <NUM> permit(s) a user to enter data and commands into the processor <NUM>.

The output devices <NUM> can be implemented, for example, by display devices (e.g., a light emitting diode (LED), an organic light emitting diode (OLED), a liquid crystal display, a cathode ray tube display (CRT), a touchscreen, a tactile output device, a light emitting diode (LED), a printer and/or speakers). The interface circuit <NUM> of the illustrated example, thus, typically includes a graphics driver card, a graphics driver chip or a graphics driver processor.

The coded instructions <NUM> of <FIG> may be stored in the mass storage device <NUM>, in the volatile memory <NUM>, in the non-volatile memory <NUM>, and/or on a removable tangible computer readable storage medium such as a CD or DVD.

From the foregoing, it will be appreciated that the above disclosed methods, systems, and apparatus provide for fabrication of droplet actuators via laser ablation and roll-to-roll processing to efficiently produce substrates that form the droplet actuators without comprising technical superiority of the electrodes associated with the droplet actuators. A base substrate is efficiently moved through stations via rollers without interruption to create electrode arrays, coat the arrays with a hydrophobic material, and cure the hydrophobic material to create a substrate that can serve as a structural support for a droplet disposed on the droplet actuator. Further, processing of the top substrate of the droplet actuator can be achieved using substantially the same roll-to-roll techniques, with additional customization as to whether, for example, the top substrate includes an electrode array. The roll-to-roll processing provides for individually wound rolls of the processed base substrate and top substrate that can be further diced and aligned to create individual droplet actuators. Alternatively, roll-to-roll processing may be further used to merge the base substrate and the top substrate to create a single roll that can be diced.

The examples disclosed herein utilize laser ablation to define electrode arrays on the substrates as the substrates are driven by the rollers. Laser ablation provides for electrode arrays having high performance qualities without impacting production speeds. By exposing successive portions of the substrates to a laser, the electrode patterns are created on the substrates in accordance with the rate at which the rollers advance the substrates. Low operational costs are achieved as a result of the thin layers of pre-adhered conductive and non-conductive materials to form the base substrate. Such a configuration reduces (<NUM>) material costs as compared to thick-film printing methods, and (<NUM>) the number of processing steps due to the pre-adhesion of the substrates prior to formation of the electrode patterns. The electrical conductivity, electrode inter-digitization, low surface and edge roughness, and high resolution, and small footprint of the electrode arrays achieved via laser ablation improves the precision of the droplet manipulation performed via resulting droplet actuator. Further, in substantially completely insulating the electrodes of the substrates, the example methods disclosed herein prevent unintended chemical changes or reactions to the droplet placed on the hydrophobic materials during manipulation of the droplet via electrical potentials.

Thus, the substrates are processed through the stations in a substantially implementation-ready state such that the processed substrates can be diced into discrete portions after the curing of the hydrophobic materials to create one or more droplet actuators. Such a reduction in processing the substrates improves production time and lowers costs without compromising the quality of the resulting droplet actuators.

Claim 1:
A method for making a droplet actuator, the method comprising:
ablating (<NUM>) a first substrate (<NUM>, <NUM>) with a laser (<NUM>) to form an electrode array (<NUM>, <NUM>) on the first substrate (<NUM>, <NUM>);
applying (<NUM>) at least one of a hydrophobic material or a dielectric material (<NUM>, <NUM>) to at least a portion of the electrode array to form a first treated layer (<NUM>) on the first substrate; and
characterized in that the method further comprises:
aligning the first substrate (<NUM>, <NUM>) with a second substrate (<NUM>), the second substrate (<NUM>) including a second treated layer (<NUM>), wherein the alignment includes a gap (<NUM>) between at least a portion of the first treated layer (<NUM>) and at least a portion of the second treated layer (<NUM>); and
inserting one or more projections at least partially in the gap (<NUM>), the one or more projections including capillaries.