Patent ID: 12201980

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.

DETAILED DESCRIPTION

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 5 μm to about 10 μm. 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.

An example 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 example 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 example method also includes aligning the first substrate with a second substrate. The second substrate includes a second treated layer. In the example 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.

In some examples, the method 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 10 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 10 micrometers. Also, in some examples, a thickness of the conductive layer is less than about 120 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.1is a diagram of a first example system or assembly100for creating a base substrate of a droplet actuator. The first example assembly100includes a series or a plurality of rollers, including a first roller102, a second roller104, and a third roller106, which operate in synchronized rotation to drive a base substrate108through the first example assembly100. The first example assembly100can include rollers in addition to the first through third rollers102,104,106to move the base substrate108through 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 substrate108to produce individual droplet actuators, the base substrate108can be considered a substrate web that may be in a rolled, partially rolled, or unrolled configuration as the base substrate108moves through the first example assembly100.

In the first example assembly100, the first roller102rotates to unwind the base substrate108, which, in some examples, is a single sheet in a rolled configuration. The base substrate108includes a first layer110and a second layer112. In this example, the first layer110comprises a non-conductive flexible substrate, such as for example a plastic, and the second layer112includes a conductive material. The conductive material of the second layer112can 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 substrate108includes an adhesive layer113disposed between the non-conductive first layer110and the conductive second layer112. As an example, the adhesive layer113can comprise chrome, with a layer of gold disposed on top of the chrome adhesive layer113to form the conductive second layer112. Thus, in the base substrate108ofFIG.1, the non-conductive first layer110and the conductive second layer112are pre-adhered to form the base substrate108prior to being unwound by the first roller102.

In the example base substrate108ofFIG.1, the non-conductive first layer110has a thickness of less than about 500 nm. As will be described below, such a thickness allows for the base substrate108to move through the example first assembly100via the plurality of rollers. Also, in some examples, the thickness of the non-conductive first layer110is greater than a thickness of the conductive second layer112. As an example, the thickness of the conductive second layer112can be approximately 30 nm. In other examples, the thickness of the conductive second layer112is less than about 500 nm, and in some examples the thickness of the second layer112is less than about 120 nm. In some examples, the thickness of the non-conductive first layer110and/or the conductive second layer112is selected based on, for example, the materials of the first and/or second layers110,112and/or an operational purpose for which the droplet actuator formed from the base substrate108is to be used.

The first roller102drives the base substrate108to a laser ablation station114. The laser ablation station114includes a mask116containing a master pattern118that is to be projected onto the conductive second layer112of the base substrate108. The master pattern118associated with the mask116may be predefined based on characteristics such as resolution (e.g., number of electrodes per an area of the base substrate108to 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 pattern118are selected based on one or more operational uses of the droplet actuator with which the base substrate108is to be associated (e.g., for use with biological and/or chemical assays). Also, in some examples, the master pattern118is configurable or reconfigurable to enable the laser ablation station114to form different patterns on the base substrate108. Additionally or alternatively, in some examples the mask116is replaceable with one or more alternative masks.

The laser ablation station114includes a lens120. As the base substrate108encounters the laser ablation station114as result of the rotation of the rollers (e.g., the first roller102), a portion122of the base substrate108passes under or past the lens120. The portion122may be, for example, a rectangular or square section of the base substrate108having an area less than the area of the base substrate108and including the conductive second layer112. The lens120images or projects at least a portion of the master pattern118onto the conductive second layer112associated with the portion122. A laser beam124is directed onto the portion122via the mask116and the lens120such that the laser beam124selectively penetrates the conductive second layer112based on the projected master pattern118. In some examples, the non-conductive first layer110or a portion (e.g., a fraction of the thickness of the non-conductive first layer110) may also be penetrated by the laser beam124based on the projected master pattern118. The solid portions of the mask116block the laser beam124, and the open portions of the mask116allow the laser beam124to pass through the mask116and into contact with the base substrate108. The laser beam124can be associated with, for example, an excimer laser.

As a result of exposure to the laser beam124, the irradiated non-conductive first layer110of the portion122absorbs energy associated with the laser beam124. The irradiated non-conductive first layer110undergoes photochemical dissociation, resulting in a selective breaking up of the structural bonds of non-conductive first layer110and ejection of fragments of the non-conductive first layer110and portions of the conductive second layer112overlaying the irradiated non-conductive first layer110in accordance with the master pattern118to form an electrode array126on the conductive second layer112. Thus, the ejection of fragments of the non-conductive first layer110as a result of penetration of the laser beam124in the non-conductive first layer110during formation of the electrode array126can result in structural changes to the non-conductive first layer110. Such structural changes may alter the appearance of the non-conductive first layer110.

As disclosed above, the laser beam124selectively penetrates the non-conductive first layer110and the conductive second layer112in accordance with the master pattern118mask116. Thus, the portions or fragments of the non-conductive first layer110that are ejected are based on the master pattern118such that after the fragmentation of the non-conductive first layer110, the non-conductive first layer110includes a feature of the master pattern118corresponding to the electrode array126. The feature or marking in the non-conductive first layer110can include, for example, an outline or a substantial outline of at least a portion of the master pattern118. In some examples, the non-conductive first layer110includes a disturbance (e.g., a burn mark) formed as a result of the penetration of the laser beam124into the non-conductive first layer110. The disturbance can include, for example, a change in the thickness of at least some portion of the non-conductive first layer110, an indentation (e.g., a groove) in a portion of the non-conductive first layer110, or a projection in a surface of the non-conductive first layer110(e.g., as a result of the breaking up and fragmentation of the non-conductive first layer110). The indentations can include angled or sloped portions forming walls in the non-conductive first layer110. Thus, as result of the concurrent exposure of the non-conductive first layer110and the conductive second layer112to the laser beam124, the non-conductive first layer110can undergo one or more structural changes that may be reflected in grooves, projections, markings, discolorations, etc., as will be further disclosed below in connection withFIG.2E.

In some examples, a depth (e.g., a radiation intensity) to which the laser beam124penetrates the base substrate108is predefined based on a depth (e.g., a thickness) of the non-conductive first layer110and/or the conductive second layer112. In some examples, the laser beam124penetration depth is adjustable to change the depth at which the laser beam124ablates the conductive second layer112as a result of the fragmentation of the underlying non-conductive first layer110. In some examples, this adjustment is dynamic as the example system100operates. Also, in some examples, the base substrate108undergoes cleaning after exposure to the laser beam124to remove particles and/or surface contaminants.

As illustrated inFIG.1, after exposure to the laser ablation station114, the portion122of the base substrate108includes the electrode array126. The electrode array126is made up of a plurality of electrodes formed into the conductive second layer112(FIG.2A). As a result of the exposure to the laser beam124and fragmentation of the non-conductive first layer110, portions of the conductive second layer112are removed from the base substrate108. The removed portions associated with the electrode array126are based on the master pattern118. In some examples, the removed portions match the open portions of the mask116.

For example,FIG.2Aillustrates a top view of the portion122of the base substrate108after exposure to the laser ablation station114of the first example assembly100ofFIG.1. As show inFIG.2A, exposure to the laser beam124results in the formation of a laser-ablated electrode pattern200on the conductive second layer112. The laser-ablated electrode pattern200includes lines202and spacings204, which correspond to the master pattern118projected onto the portion122via the lens120ofFIG.1.

In the example electrode pattern200, the lines202and the spacings204define one or more array electrodes206that form the electrode array126. The example electrode pattern200also includes one or more non-array electrodes208. The non-array electrodes208that are not a part of the electrode array126facilitate external electrical connections during operation of the droplet actuation. The array electrodes206and the non-array electrodes208of the electrode pattern200can vary in size and/or shape. For example, the non-array electrodes208can be substantially square-shaped whereas the array electrodes206can be in a configuration other than a square. The shapes and/or sizes of the electrodes206,208of the electrode pattern200are defined by the lines202and the spacings204in association with the master pattern118projected onto the base substrate108. As a result of formation via laser ablation, the lines202defining the electrodes206,208are substantially smooth and/or have substantially reduced roughness with respect to the definition of the edges of the electrodes206,208as compared to, for example, other methods for forming electrode arrays such as photolithography or printed circuit board methods.

In some examples, the lines202and/or the spacings204formed via laser ablation measure (e.g., have a width of) approximately 10 μm; in other examples, the lines202and/or the spacings204are greater or less than 10 μm (e.g., about 5 μm). The arrangement and sizes of the lines202and/or the spacings204define a resolution of the electrode array126. For example, minimal spacings204between the lines202allows for a greater number of array electrodes206in close proximity (e.g., inter-digitization of the array electrodes206) within the electrode array126and, 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 pattern200maximize a surface area of the portion122that 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 electrodes206facilitates an ease with which droplets are actuated on the base substrate108via manipulation of electrical potentials. Increased resolution of the electrode array126also improves a precision of droplet sizes that are actuated.

Laser ablation of the portion122of the base substrate or web108at the laser ablation station114may be achieved via broad field ablation or via rastering. Broad field ablation involves exposure of the laser beam124over substantially the entire portion122. The master pattern118is created on the portion122by removing material from the conductive second layer112with a substantially single instance of exposure of the non-conductive first layer110and the conductive second layer112to the laser beam124(e.g., a single flash of the laser beam124). In broad field laser ablation, the master pattern118is thus simultaneously created across the area of the conductive second layer112associated with the portion122to ablate the base substrate108at high speeds. FIG.2B is a top view of a portion209of the electrode pattern200ofFIG.2Acreated via broad field ablation based on the master pattern118. As shown inFIG.2B, the portion209includes the lines202and the spacings204defining the electrode pattern200. The lines202and/or spacings204can have widths of less than 10 μm. As also shown inFIG.2B, edges211of the lines202are substantially smooth and without substantial rough, sharp, pointed, or uneven portions. Such smooth and defined edges211result from the irradiation of the base substrate108by the laser beam124to create the master pattern118with a single exposure of the laser beam124on the portion122.

Alternatively, laser ablation can be achieved via rastering or scribing, in which the laser beam124iteratively etches the master pattern118into the portion122to form the electrode pattern200, including the electrode array126, in the conductive second layer112as the base substrate108and/or the laser beam124moves. In examples where rastering techniques are used, the electrode pattern200is determined digitally without the use of the mask116. For example, to iteratively etch the master pattern118into the portion122, the laser beam124moves along the base substrate108to inscribe the master pattern118into the conductive second layer112via a series of individual pulses in adjacency. The individual pulses result in lines202having widths between, for example, 30 and 200 μm. In examples where the rastering is used to form the electrode pattern200, the edges of the array electrodes206may be less smooth due to pulse markings formed by the individual laser pulses iteratively penetrating the conductive second layer112, as compared to broad field laser ablation.

FIG.2Cis a top view of a portion214of the electrode pattern200ofFIG.2Acreated using laser ablation rastering or scribing techniques. As a result of the indexing of pulses to etch the master pattern118into the base substrate108, edges216of the lines202defining the electrode pattern200differ from the edges211of the electrode pattern200created via broad field laser ablation shown inFIG.2B. For example, the edges216of the portion214created via rastering include curved, partially curved, or wave-like features corresponding to the iterative exposure of the portion214to individual pulses of the laser beam124. Also, because the individual pulses irradiate adjacent portions of the base substrate108, the curved or wave-like features of the edges216define a pattern or at least a partial pattern over the respective lines202in that in a first curved feature resulting from a first laser pulse of the laser beam124can resemble or partially resemble a second curved features resulting from a second laser pulse of the laser beam124. Thus, the edges216of the electrode pattern200created via rastering can be distinguished from electrode patterns created via techniques such as photolithography, which can result in lines having random, irregularly shaped edges.

FIGS.2A-Cillustrate features of the electrode pattern200that are visible from a top view of the base substrate108after exposure to the laser beam124at the laser ablation station114ofFIG.1.FIG.2Dis a cross-sectional view of the portion122of the base substrate108after exposure to the laser ablation station114of the first example assembly100ofFIG.1, taken along the1-1line ofFIG.2A. As shown inFIG.2D, the portion122includes the non-conductive first layer110and the conductive second layer112including replications of the electrode array126of the electrode pattern200formed across the base substrate108. Although the portion122of the base substrate108is shown having three electrode arrays126, the portion122can include less or additional electrode arrays126of the electrode pattern200ofFIG.2A. Also, the portion122is part of the base substrate or web108.

As disclosed above with respect toFIG.2A, the electrode arrays126include one or more arrays electrode206. The laser beam124penetrates a thickness t of the conductive second layer112as the laser beam124pulses or etches the lines202and corresponding spacings204into the conductive second layer112to define the array electrodes206. The depth of the penetration of the laser beam124into the conductive second layer112can be based on, for example, the thickness t1of the conductive second layer112and/or an intensity of the laser beam124. In some examples, the laser beam124penetrates a depth substantially equal to the thickness t1, less than the thickness t1, or greater than the thickness t1, such that the laser beam124penetrates a portion of the non-conductive layer110, as will be disclosed below in connection withFIG.2E. Also, the laser beam124defines features of the electrode array126with respect to a resolution or a number of electrodes206per an area of the base substrate108, the size of the array electrodes206, and the configuration of lines202and the spacings204therebetween, which define a degree of inter-digitation of the array electrodes206.

Although laser ablation results in a well-defined electrode pattern200including the electrode array126having increased resolution, in some examples, defects or imperfections in the mask116or the lens120can result corresponding defects in the based substrate108. Such defects can include debris on the mask116or the lens120, openings in the mask116that allow the laser beam124to irradiate the base substrate108where such exposure was not intended (e.g., an additional opening in the mask116or a wider than intended opening), and/or imperfections in the mask116that prevent the laser beam124from penetrating the base substrate108where the penetration was intended (e.g., incomplete openings in the mask116). Debris (e.g., hair, dust, etc.) or imperfections in the mask116can result in interruptions or inconsistencies in the resulting electrode pattern200, such as gaps or alterations to the shapes of the lines202and/or the spacings204defining the electrode pattern200). Another example of a defect includes inconsistencies in the spacings204in the master pattern118due to a defect in the master pattern118.

FIG.2Dillustrates the conductive second layer112of the base substrate108including defects or markings212. In the example portion122, the defects212are included in each of the iterations of the electrode array126of the electrode pattern200across the base substrate108. However, the defects212can be located elsewhere in the electrode pattern200, such as in connection with the non-array electrodes208. In examples where the electrode pattern200is formed using broad field laser ablation, the defects212are systematic, or substantially identical in each of the electrode arrays126of the portion122. In particular, the systematic occurrences of the defects212results from the exposure of the laser beam124over substantially the entire portion122to concurrently form multiple electrode patterns200. Thus, the defects212are substantially uniformly replicated in each of the electrode patterns200irradiated into the conductive second layer112as the base substrate108is exposed to the laser beam124at the laser ablation station114. For example, the defects212can be disposed at substantially the same position relative to the respective electrode patterns200. Also, the defects212can be the substantially the same size within the respective electrode patterns200. Therefore, the resulting substrate web, including the base substrate108and the electrode patterns200, includes substantially identical, systematically reproduced defects212in each of the electrode patterns200.

In some examples, markings such as the defects212, could be purposeful. For example, such markings may be included as a signature that appears across all electrodes patterns200to identify a particular manufacturer, manufacturing run, product, or manufacturing location.

FIG.2Eis a cross-sectional view of the portion122including the electrode pattern200taken along the2-2line ofFIG.2A. As an example,FIG.2Eillustrate a section of the electrode pattern200other than the electrode array126. For example,FIG.2Eillustrates the lines202and the spacings204defining one or more of the non-array electrodes208.

As disclosed above with respect to the exposure of the base substrate108to the laser beam124in connections withFIGS.1and2D, in some examples, the laser beam124selectively penetrates through the conductive second layer112and the non-conductive first layer110. In such examples, the laser beam124penetrates through the thickness t1of the conductive second layer112and a thickness t2of the non-conductive first layer110, which may be less or substantially less than a total thickness t3of the non-conductive first layer110. The non-conductive first layer110absorbs some of the energy of the laser beam124. As a result of the irradiation of the non-conductive first layer110, a portion of the non-conductive first layer110having the thickness t2is ejected from the non-conductive first layer110, which results in structural changes to the non-conductive first layer110. The ejection of the portion of the non-conductive first layer110can result in ejection of a portion of the conductive second layer112to define the electrode pattern200. As illustrated inFIG.2E, the non-conductive first layer110includes one or more disturbances210due to the penetration of the laser beam124. The portions or disturbances210includes indentations, spacings, openings, or grooves in the non-conductive first layer110resulting from the ejection of one or more portions of the irradiated non-conductive first layer110. The respective thicknesses of the disturbances210depend on the thickness of the non-conductive first layer110and a depth of the penetration of the laser beam124. Also, although the disturbances210are illustrated inFIG.2Eas rectangular in shape, the disturbances210can 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 layer110.

Although laser ablation of the base substrate108at the laser ablation station114has been described with respect to the portion122, it is to be understood that, as part of the continuous movement of the base substrate108through the first example assembly100via the first through third rollers102,104,106, the laser beam124penetrates more than one portion of the base substrate108during operation of the first example assembly100. In the first example assembly100, as the base substrate108passes under and/or by the lens120, successive portions n of the conductive second layer112are exposed to the laser beam124for repeatedly creating the master pattern118on each of the successive portions n. The size of the portions and the spacing between the portions as the base substrate108passes through the laser ablation station114may be predetermined based on, for example, the size and configuration of the master pattern118, the dimensions of the base substrate108, the thickness of the conductive second layer112, and/or the dimensions of the droplet actuator with which the base substrate108will be associated.

Returning toFIG.1, after the portion122undergoes laser ablation at the laser ablation station114to form the electrode array126(e.g., as part of the electrode pattern200ofFIG.2A), the portion122is moved, via rotation of the first through third rollers102,104,106, to a printer128. In the first example assembly100, the printer128includes an apparatus or an instrument capable of applying at least one layer of material130having a hydrophobic and/or a dielectric property to the electrode array126. In the first example assembly100, the printer128can deposit the hydrophobic and/or dielectric material130via deposition techniques including, but not limited to, web-based coating (e.g., via rollers associated with the printer128), slot-die coating, spin coating, chemical vapor deposition, physical vapor deposition, and/or atomic layer deposition. The printer128can also apply other materials in addition to the hydrophobic and/or dielectric material130(e.g., anti-fouling coatings, anti-coagulants). Also, the printer128can apply one or more layers of the material(s) with different thicknesses and/or covering different portions of the base substrate108.

As described above, in the first example assembly100, at least one of the first through third rollers102,104,106advance the base substrate or web108to the printer128for application of the hydrophobic and/or dielectric material130to the electrode array126. In some examples, the printer128includes a plurality of registration rollers131to facilitate accuracy in feeding and registration of the base substrate108as part of operation of the printer128in applying the hydrophobic and/or dielectric material130, for example, via roller coating methods.

In the first example assembly100, the hydrophobic and/or dielectric material130is applied to the electrode array126to completely or substantially completely insulate the electrode array126. For example, referring again toFIG.2A, the printer128selectively applies the hydrophobic and/or dielectric material130to the electrodes206of the electrode array126, however, the printer128does not apply the hydrophobic and/or dielectric material130to the other electrodes208of the electrode pattern200. The selective application of the hydrophobic and/or the dielectric material130to the electrode pattern200provides for electrodes that are capable of making electrical contact with other electrodes (e.g., the non-array electrodes208that are not covered with the hydrophobic and/or dielectric material130) as well as electrodes that are covered or coated as part of the electrode array126(e.g., the array electrodes206). As a result of the hydrophobic and/or the dielectric material130, a droplet placed proximate to the electrode array126is in a beaded configuration forming a contact angle with respect to the portion122. In operation, the electrodes206of the coated electrode array126control the contact angle (e.g., a degree of the contact angle) via electric forces.

In some examples, the hydrophobic and/or dielectric material130is a polytetrafluoroethylene material (e.g., Teflon®) or a fluorosurfactant (e.g., FluoroPel™) applied to the conductive second layer112to substantially cover the electrode array126. In other examples, the hydrophobic and/or dielectric material130is 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 array126is 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 array126(e.g., as an additional layer or in connection with the hydrophobic and/or dielectric material130) 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 material130is deposited via the printer128in substantially liquid form. To create a structural, or treated layer132on the base substrate108to support a droplet, the portion122is moved via the rollers (e.g., the first through third rollers102,104,106) through a curing station134. At the curing station134, the hydrophobic and/or dielectric material is treated and/or modified to form the first treated layer132. Treating and/or modifying the hydrophobic and/or dielectric material can include curing the material. For example, at the curing station134, heat is applied to facilitate the hardening of the hydrophobic and/or dielectric material130. In some examples, the portion122is exposed to an ultraviolet light to cure the hydrophobic and/or dielectric material130and form the treated layer132to insulate the electrode array126. 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 layer132supports a droplet as an electric field is applied (e.g., in connection with electrode array126) to manipulate the droplet. For example, during an electrowetting process, a contact angle of the droplet with respect to the treated layer132changes as a result of an applied voltage, which affects the surface tension of the droplet on the treated surface132.

After passing through the curing station134, the portion122is prepared to serve as a bottom substrate of a droplet actuator and/or as a digital microfluidic chip. Because the base substrate108includes the non-conductive first layer110bonded with the conductive second layer112, as disclosed above, additional adhesion of, for example, the electrode array126to the non-conductive first layer110is not required. Such a pre-adhered configuration increases the efficiency of the preparation of the base substrate108for the droplet actuator by reducing processing steps. Also, as described above, when the portion122is at any one of the laser ablation station114, the printer128, or the curing station134, other portions n of the base substrate108are concurrently moving through the others of the respective stations114,128,134of the first example assembly100. For example, when the portion122is at the curing station134, the first through third rollers102,104,106are continuously, periodically, or aperidiocally advancing one or more other portions n of the base substrate108through, for example, the laser ablation station114and/or the printer128. In such a manner, preparation of the base substrate108for the droplet actuator is achieved via a substantially continuous, high-speed, automated process.

Although the base substrate108may be considered as including successive portions, during some example operations of the first example assembly100, the base substrate108remains as a single sheet or web as the successive portions undergo processing to create the electrode arrays126(e.g., via the electrode pattern200ofFIG.2A) and receive the coating of hydrophobic and/or dielectric material130. Thus, to create one or more droplet actuators using the processed base substrate108, the base substrate or web108, in some examples, is cut (e.g., diced) to form individual units comprising the electrode arrays126, as will be further disclosed below (e.g.,FIGS.4,6). In some examples, prior to dicing, the base substrate108, including the portion122, is rewound in a rolled configuration similar to the initial rolled configuration of the base substrate108prior to being unwound by the first roller102. Such rewinding may be accomplished via one or more rollers as part of the roll-to-roll processing. In such examples, the base substrate108may be diced or otherwise separated at a later time. In other examples, the rollers (e.g., the second and third rollers104,106), advance the base substrate108for merging with a top substrate, as will be further disclosed below (e.g.,FIGS.4,6).

As described above, an example droplet actuator includes a base substrate, such as the base substrate108including the electrode array126(FIGS.1and2) 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 pattern200and electrode array126ofFIGS.1and2, 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.3illustrates a second example assembly300for creating an example top substrate of a droplet actuator having a single electrode. The second example assembly300includes a series or a plurality of rollers, including a first roller302, a second roller304, and a third roller306, which operate in synchronized rotation to drive a top substrate308through the second example assembly300. The second example assembly300can include rollers in addition to the first through third rollers302,304,306to move the top substrate308through the assembly300. Prior to cutting or sizing of the top substrate308, the top substrate308can be considered a substrate web that may be in a rolled, partially rolled, or unrolled configuration as the top substrate308moves through the second example assembly300.

In the second example assembly300, the first roller302rotates to unwind the top substrate308, which, in some examples, is a sheet in a rolled configuration. The example top substrate308ofFIG.3includes a first layer310and a second layer312. As with the example base substrate108, in this example, the example first layer310of the top substrate308comprises a non-conductive material such as, for example, a plastic, and the example second layer312includes 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 layer312is adhered to the non-conductive first layer310via an adhesive layer (e.g., chrome).

In the second example assembly300, the first through third rollers302,304,306rotate to advance the top substrate312to a printer314. The printer314coats the conductive second layer312with a hydrophobic and/or dielectric material316(e.g., Teflon® or a dielectric such as a ceramic). The printer314is substantially similar to the printer128of the first example assembly100ofFIG.1. For example, the printer314can apply the hydrophobic and/or dielectric material316to the top substrate308via web-based coating, slot-die coating, spin coating, chemical vapor deposition, physical vapor deposition, atomic layer deposition, and/or other deposition techniques. The printer314can include registration rollers317to facilitate alignment of the top substrate308with respect to the printer314during application of the hydrophobic and/or dielectric material316and/or other coating materials.

After receiving the coating of the hydrophobic and/or dielectric material316, the second roller104and the third roller106advance the portion318to a curing station320. As disclosed in connection with the curing station134ofFIG.1, the curing station320of the second example assembly300facilitates the modification (e.g., curing) of the hydrophobic material via heat to form a treated layer322. The treated layer322insulates the conductive second layer312, which serves as the single electrode of the top substrate308, by completely or substantially completely covering the conductive second layer312. Thus, in coating the second layer312of the portion318, electrical potential conducting portion of the top substrate308is insulated from a droplet that may be applied to a droplet actuator that includes the portion318.

After passing through the curing station320, the portion318is prepared to serve as a top substrate of a droplet actuator. Because the top substrate308includes the non-conductive first layer310pre-adhered to the conductive second layer312prior to processing of the top substrate via the second example assembly300, additional adhesion of, for example, an electrode to the non-conductive first layer310is not required, thereby increasing the efficiency of the preparation of the top substrate308for the droplet actuator.

Also, and as disclosed in connection with the first example assembly100ofFIG.1, in the second example assembly300, the first through third rollers302,304,306rotate to advance the top substrate308such that portions of the top substrate pass through one of the printer314or the curing station320in substantially continuous, periodic and/or aperiodic succession as part of the roll-to-roll operation of the second example assembly300. Thus, although the second example assembly300is described in association with the portion318, it is to be understood that successive portions of the top substrate308are prepared in substantially the manner as the portion318as a result of rotation of the first through third rollers302,304,306. In such as manner, the top substrate308is provided with a treated layer322along the length of the top substrate308.

In the example top substrate308, the conductive second layer312serves an electrode. However, in some examples, the conductive second layer312undergoes laser ablation to form one or more electrode arrays. In such examples, the second example assembly300includes a laser ablation station substantially similar to the laser ablation station114of the first example assembly100ofFIG.1. Thus, prior to receiving the hydrophobic material316, the top substrate308is exposed to a laser beam, which creates an electrode pattern in the irradiated conductive second layer312. The electrode pattern formed on the top substrate308can be the same or different from the electrode pattern formed on the base substrate108ofFIG.1. In examples where the top substrate308is ablated via a laser, the second example assembly300is substantially similar to the first example assembly100. Also, in some examples, the electrode array is not formed on/in the base substrate108but only on/in the top substrate308.

During operation of the second example assembly300, the top substrate remains single sheet as successive portions of the top substrate308are coated with the hydrophobic material316. As part of the fabrication of one or more droplet actuators, the top substrate308is aligned with the base substrate (e.g., the base substrate108ofFIG.1). In some examples, after passing through the curing station320, 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 substrate108ofFIG.1to create a droplet actuator.

In other examples, after passing through the curing station320, the rollers (e.g., the first through third rollers302,304,306) continue to advance the top substrate308to merge the top substrate308with the base substrate108ofFIG.1via automated roll-to-roll processing, as will be discussed below in connection withFIG.4. In such examples, to prepare the top substrate308for alignment with the base substrate108, the rollers of the second example assembly300(e.g., the first through third rollers302,304,306) rotate so as to reverse the orientation of the top substrate308relative to the base substrate108ofFIG.1such that the treated layer132of the base substrate108faces the treated layer322of the top substrate308when the base substrate108and the top substrate308are aligned in parallel configuration (see, e.g.,FIG.4).

FIG.4is a diagram of a third example assembly400for processing the substrate webs. The example assembly400operates to merge a base substrate with a top substrate to fabricate a droplet actuator via roll-to-roll processing. The third example assembly400can be implemented in connection with the first example assembly100ofFIG.1and the second example assembly300ofFIG.3to fabricate a droplet actuator from the base substrate108ofFIG.1and the top substrate308ofFIG.3. For example, as shown inFIG.4, after passing through the curing station320associated with the second example assembly300, the top substrate308is advanced by a first roller402of the third example assembly400. Similarly, after passing through the curing station134associated with the first example assembly100, the base substrate108is advanced by a second roller402of the third example assembly400to facilitate alignment of the substrates108,308.

The third example assembly400includes a third roller406and a fourth roller408that form a pair of merging rollers to which the base substrate108and the top substrate308are fed via the respective first roller402and the second roller404of the third example assembly400. As each of the merging rollers406,408rotates, the base substrate108and the top substrate308are aligned in a parallel configuration at a predetermined spaced apart distance, or gap.

For example,FIG.4illustrates a merged portion410including the base substrate108and the top substrate308in parallel alignment and including a gap412separating the treated layer132of the base substrate108and the treated layer322of the top substrate108. The gap412is a predetermined spaced apart distance between the treated layers132,322. The gap412can 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 substrates108,308to serve as spacers to separate the respective treated layers132,322. Additionally or alternatively, other examples for forming and/or maintaining the gap include embossing or molding pillars into, for example, the non-conductive first layer110of the base substrate108to provide a frame to separate the base substrate108and the top substrate308. Further still, other additional or alternative examples for forming and/or maintaining the gap include laminating one or more of the treated layers132,322of the respective base substrate108and the top substrate308to 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 substrates108,308. In some examples, the gap formation techniques may be implemented via roll-to-roll processing. For example, as one or more the base substrate108or the top substrate308passes proximate to one or more rollers of the first through third example assemblies100,300,400, one or more of the rollers may provide for embossing and/or lamination of the base substrate108and/or the top substrate308.

Similarly, in examples where the base substrate108and the top substrate308are rewound as individual rolls (e.g., as part of the first example assembly100ofFIG.1and the second example assembly300ofFIG.3), diced separately, and then aligned, the base substrate108and the top substrate308are also arranged so that a gap exists between treated layers132,322of the respective base substrate108and the top substrate308.

As show inFIG.4, the example third assembly400includes a bonding station414. The bonding station414joins, or bonds, the base substrate108and the top substrate308as part of fabricating the droplet actuator. For example, at the bonding station414, one or more adhesives may be selectively applied to a predefined portion of the base substrate108and/or the top substrate308(e.g., a portion of the base substrate108and/or the top substrate308defining a perimeter of the resulting droplet actuator) to create a bond between the base substrate108and the top substrate308while preserving the gap412. In some examples, bonding the substrates108,308at the bonding station414including forming the gap412(e.g., in advance of applying the adhesive).

Examples of adhesive(s) that may be used at the bonding station414include epoxies, foils, tapes, and/or ultraviolet curable adhesives. In some examples, layers of polymers such as SU-8 and/or polydimethylsiloxane (PDMS) are applied to the base substrate108and/or the top substrate308to bond the substrates. Also, in some examples, the bonding station414provides for curing of the adhesive(s) via, for example, ultraviolet light. The bonding station414may apply one more methods involving, for example, heat (e.g. thermal bonding), pressure, curing, etc. to bond the base substrate108and the top substrate308.

In the example third assembly400, the merged portion410can be selectively cut, diced or otherwise separated to form one or more droplet actuators, as substantially represented inFIG.4by the merged portion410. The example third assembly400includes a dicing station416. The dicing station416can be, for example, a cutting device, a splitter, or more generally, an instrument to divide the continuous merged portion410into discrete units corresponding to individual droplet actuators. The merged portion410may be cut into individual droplet actuators based on, for example, the electrode pattern200ofFIG.2Asuch that each droplet actuator includes a footprint of the electrode array126and the other electrodes that are formed via the electrode pattern200(e.g., the non-array electrodes208). During operation of the resulting droplet actuator, the gap412can receive a droplet that can be manipulated using electrical potentials via the insulated electrodes206of the electrode array126of the base substrate108(e.g., the conductive second layer112) and/or the insulated electrode of the top substrate312(e.g., the conductive second layer312). The insulated nature of the conductive surfaces of the base substrate108and the top substrate108prevents 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.5is a block diagram of an example processing system500for use with a droplet actuator fabrication assembly such as, for example, the first, second, and/or third example assemblies100,300,400ofFIGS.1,3and4for processing one or more substrate webs. The example processing system500includes a controller502, which controls operation the first, second, and/or third example assembles100,300,400via selected driver components.

For example, the example processing system500includes a roller driver504, which controls one or more of the rollers of the first, second, and/or third example assembles100,300,400. In some examples, the example processing system500includes one or more roller drivers504. In the example shown, the roller driver(s)504are communicatively coupled to rollers506a-n. The rollers506a-nmay correspond, for example, to the first through third rollers102,104,106of the first example assembly100; the first through third rollers302,304,306of the second example assembly300; and/or the first through fourth rollers402,404,406,408of the third example assembly400. The roller driver(s)504control rotation of the rollers506a-nusing, 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 rollers506a-n. One or more of the operational characteristics controlled by the roller driver(s)504at least partially determine a position of a portion of the one or more substrates fed through the first, second, and third example assemblies100,300,400(e.g., the portion122of the base substrate108, the portion318of the top substrate308, and/or the merged portion410) at any time during the operation of the rollers506a-n. Further, one or more of the operational characteristics controlled by the roller driver(s)504, 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 assemblies100,300,400(e.g., the laser ablation station114of the first example assembly100). Thus, the roller driver(s)504control rate at which the one or more substrates are processed. Also, an example processor508operates the roller driver(s)604and, thus, the first, second, and third example assemblies100,300,400in accordance with a droplet actuator fabrication protocol.

The example processing system500also includes a laser driver510. In some examples, the example processing system500includes one or more laser drivers510. In the example shown, the one or more laser driver(s)510are communicatively coupled to one or more lasers512to control the laser(s)512. The laser(s)512may correspond to, for example, the laser beam124of the laser ablation station114of the first example assembly100. In some examples, the second example assembly400includes a laser ablation station having a laser beam. In such examples, the laser driver(s)510also control the laser associated with the second example assembly400. The laser driver(s)510control, for example, the intensity of the laser(s)512, a size of surface area of irradiation with respect to the substrate(s), the depth to which the laser(s)512penetrate a substrate (e.g., the conductive second layer112and the non-conductive first layer110of the base substrate108), and/or a duration for which the laser(s)512do or do not penetrate the substrate. The laser driver(s)510also control a manner in which the laser(s)512are exposed on the substrate(s), including whether the laser(s)512iteratively irradiate the substrate(s) as part of laser ablation rastering techniques or whether the laser(s)512are 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)512iteratively etch the pattern into the substrate(s), the laser driver(s)510control the movement (e.g., direction and speed) of the laser(s)512across the substrate(s). Also, the example processor508operates the laser driver(s)510and, thus, the laser(s)512in accordance with a laser ablation protocol.

The example processing system500also includes a printer driver514which controls one or more of the printers of the first and/or second example assemblies100,300. In some examples, the example processing system500includes one or more printer drivers514. In the example shown, the printer driver(s)514are communicatively coupled to a first printer516and a second printer518. The first printer516may correspond, for example, to the printer128of the first example assembly100. The second printer518may correspond, for example, to the printer314of the second example assembly300. The printer driver(s)514control, for example, the thickness, width, and/or pattern of the hydrophobic and/or dielectric material applied to the substrates by the first printer516and the second printer518. In examples where the hydrophobic and/or dielectric material is applied via web-based printing, the printer driver(s)514can control a pressure with which rollers associated with the first printer516and/or the second printer518contact 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 printer516and the second printer518operate in connection with the rollers506a-n. In such examples, the printer driver(s)514work in association with the roller driver(s)504to define, for example, a rate at which the hydrophobic and/or dielectric material is deposited on the substrates. Also, the example processor508operates the printer driver(s)514and, thus, the first printer516and the second printer518in accordance with a hydrophobic and/or dielectric material application protocol.

The example processing system500also includes a curing station driver520that controls one or more of the curing stations of the first and/or second example assembles100,300. In some examples, the example processing system500includes one or more curing station drivers520. In the example shown, the curing station driver(s)520are communicatively coupled to a first curing station522and a second curing station524. The first curing station522may correspond, for example, to the first curing station134of the first example assembly100. The second curing station524may correspond, for example, to the second curing station320of the second example assembly300. The curing station driver(s)520control, 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 processor508operates the curing station driver(s)520and, thus, the first curing station522and the second curing station524in accordance with a hydrophobic and/or dielectric material curing protocol.

The example processing system500also includes a bonding station driver526that controls the bonding station of the third example assembly400. In some examples, the example processing system500includes one or more bonding station drivers526. In the example shown, the bonding station driver(s)526are communicatively coupled to a bonding station528. The bonding station528may correspond, for example, to the bonding station414of the third example assembly400. The bonding station driver(s)526control, 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 processor508operates the bonding station driver(s)526and, thus, the first bonding station528in accordance with a substrate bonding protocol.

The example processing system500also includes a dicing station driver530that controls the dicing station of the third example assembly400. In some examples, the example processing system500includes one or more dicing station drivers526. In the example shown, the dicing station driver(s)530are communicatively coupled to a dicing station532. The dicing station532may correspond, for example, to the dicing station416of the third example assembly400. The dicing station driver(s)530control, 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 processor508operates the dicing station driver(s)530and, thus, the dicing station532in accordance with a substrate web dicing protocol.

The example processing system500also includes a database534that may store information related to the operation of the example system500. 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 assemblies100,300,400; the materials comprising the substrates (e.g., type of metal of the conductive second layer112of the base substrate108), 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 system500also includes a user interface such as, for example, a graphical user interface (GUI)536. An operator or technician interacts with the processing system500, and thus, the first, second, and/or third example assemblies100,300,400via the interface536to provide, for example, commands related to operation of the rollers506a-nsuch as speed, duration of rotation, etc. of the rollers; the pattern(s) to be ablated on the substrates via the laser(s)512; the intensity of the laser(s)512; the type of hydrophobic and/or dielectric material(s) to be applied to the substrates by the printers; the intensity of the curing stations522,524; the size of the gap in aligning the base substrate and top substrate via the rollers506a-n, the adhesives applied to bond the substrates at the bonding station528; the size of the discrete units into which the substrates are cut via the dicing station532; etc. The interface536may 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 components502,504,508,510,514,520,526,530,534are communicatively coupled to other components of the example processing system500via communication links538. The communication links538may 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 2.0, USB 3.0, etc.). Also, the components of the example system500may 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 assemblies100,300,400ofFIGS.1,3, and4is illustrated inFIG.5, one or more of the elements, processes and/or devices illustrated inFIG.5may be combined, divided, re-arranged, omitted, eliminated and/or implemented in any other way. Further, the example controller502, the example roller driver(s)504, the example processor508, the example laser driver(s)510, the example printer driver(s)514, the example curing station driver(s)520, the example bonding station driver(s)526, the example dicing station driver(s)530, the example database534and/or, more generally, the example processing system500ofFIG.5may be implemented by hardware, software, firmware and/or any combination of hardware, software and/or firmware. Thus, for example, any of the example controller502, the example roller driver(s)504, the example processor508, the example laser driver(s)510, the example printer driver(s)514, the example curing station driver(s)520, the example bonding station driver(s)526, the example dicing station driver(s)530, the example database534and/or, more generally, the example processing system500ofFIG.5could 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 controller502, the example roller driver(s)504, the example processor508, the example laser driver(s)510, the example printer driver(s)514, the example curing station driver(s)520, the example bonding station driver(s)526, the example dicing station driver(s)530, and/or the example database534is/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 system500ofFIG.5may include one or more elements, processes and/or devices in addition to, or instead of, those illustrated inFIG.5, 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 assemblies100,300,400and/or the example processing system500ofFIGS.1, and3-5is shown inFIG.6. In this example, the machine readable instructions comprise a program for execution by a processor such as the processor712shown in the example processor platform700discussed below in connection withFIG.7. 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 processor712, but the entire program and/or parts thereof could alternatively be executed by a device other than the processor712and/or embodied in firmware or dedicated hardware. Further, although the example program is described with reference to the flowchart illustrated inFIG.6, many other methods of implementing the example first, second, and third example assemblies100,300,400and/or the example processing system500may 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 ofFIG.6may 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 ofFIG.6may 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.6depicts an example flow diagram representative of an example method600that may be implemented to fabricate a droplet actuator via operation of the first, second, and third example assemblies100,300,400. The example method600may be implemented by advancing a web of a base substrate via rollers (block602). For example, the first, second, and third rollers102,104,106may unwind and drive the base substrate or web108ofFIG.1through the rollers. In some examples, the rollers102,104,106are controlled by the roller drivers(s)504ofFIG.5. The example method600also includes ablating an electrode array on the base substrate (block604). For example, the base substrate108may pass, via the rollers, to the laser ablation station114ofFIG.1. The laser beam124penetrates the base substrate108(e.g., the conductive second layer112) to selectively remove, or ablate, material from the base substrate108to form an electrode array126. The laser beam124may be controlled by the laser driver(s)510ofFIG.5.

The example method600also includes applying a hydrophobic and/or dielectric material to the electrode array (block606). In the example method600, 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 method600, the printer128ofFIG.1applies the hydrophobic and/or dielectric material to the electrode array126of the base substrate108. In the example method600, the hydrophobic and/or dielectric material substantially completely covers, or insulates, the electrode array126. In some examples, the printer128is controlled by the printer driver(s)514ofFIG.5.

In the example method600, the hydrophobic and/or dielectric material is treated (e.g., cured or otherwise modified), to form a treated layer on the base substrate (block608). 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 station134ofFIG.1. In some examples, curing station driver(s)520ofFIG.5control the curing station134.

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 method600, 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 method600, 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 method600includes advancing the top substrate via rollers (block610). In some examples, the first, second, and third rollers302,304,306ofFIG.3unwind and drive the top substrate308through the second example assembly300. Also, in some examples, the rollers302,304,306are controlled by the roller driver(s)504.

The example method600includes a decision whether to create an electrode array on the top substrate (block612). 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 block612to create an electrode array on the top substrate, the example method600proceeds to block614, where an electrode array is created on the top substrate (e.g., the conductive second layer312of the top substrate308) 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 block604(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 (block612), the example method600continues where a hydrophobic and/or dielectric material is applied to the top substrate (block616). Also, in examples where an electrode array is formed on the top substrate (block614), the example method600proceeds to block616. 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 printer314ofFIG.3may deposit a hydrophobic and/or dielectric material on the top substrate. In some examples, the printer314is controlled via the printer drivers ofFIG.5.

In the example method600, the hydrophobic and/or dielectric material applied to the top substrate is treated (block618). 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 block608(e.g., via heat and/or ultraviolet light applied via the curing station320ofFIG.3and controlled by the curing station driver(s)520ofFIG.5).

In the example method600, 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 method600includes aligning the base substrate and the top substrate (block620). 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 assemblies100,300after the curing at blocks608and618). 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 block624). 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 process400ofFIG.4). The base substrate and the top substrate may be bonded via an adhesive applied at the bonding station414ofFIG.4.

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 (block620), the example method600includes forming a gap between the base substrate and the top substrate (block622). In the example method600, 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 method600includes dicing the substrate webs into individual units (block624). 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 processes100,300), the substrates are cut into discrete units separately to form the droplet actuator and to subsequently undergo bonding and gap formation (e.g., blocks620,622). In the example method600, the substrate(s) may cut via a cutting or splitting instrument at the dicing station416ofFIG.4. At the end of the example method600(block626), 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.7is a block diagram of an example processor platform700capable of executing the instructions ofFIG.6to implement the apparatus and/or system ofFIGS.1and3-5. The processor platform700can 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 processor platform700of the illustrated example includes a processor712. The processor712of the illustrated example is hardware. For example, the processor712can be implemented by one or more integrated circuits, logic circuits, microprocessors or controllers from any desired family or manufacturer.

The processor712of the illustrated example includes a local memory713(e.g., a cache). The processor712of the illustrated example is in communication with a main memory including a volatile memory714and a non-volatile memory716via a bus718. The volatile memory714may be implemented by Synchronous Dynamic Random Access Memory (SDRAM), Dynamic Random Access Memory (DRAM), RAMBUS Dynamic Random Access Memory (RDRAM) and/or any other type of random access memory device. The non-volatile memory716may be implemented by flash memory and/or any other desired type of memory device. Access to the main memory714,716is controlled by a memory controller.

The processor platform700of the illustrated example also includes an interface circuit720. The interface circuit720may be implemented by any type of interface standard, such as an Ethernet interface, a universal serial bus (USB), and/or a PCI express interface.

In the illustrated example, one or more input devices722are connected to the interface circuit720. The input device(s)722permit(s) a user to enter data and commands into the processor712. The input device(s) can be implemented by, for example, an audio sensor, a microphone, a camera (still or video), a keyboard, a button, a mouse, a touchscreen, a track-pad, a trackball, isopoint and/or a voice recognition system.

One or more output devices724are also connected to the interface circuit720of the illustrated example. The output devices724can 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 circuit720of the illustrated example, thus, typically includes a graphics driver card, a graphics driver chip or a graphics driver processor.

The interface circuit720of the illustrated example also includes a communication device such as a transmitter, a receiver, a transceiver, a modem and/or network interface card to facilitate exchange of data with external machines (e.g., computing devices of any kind) via a network726(e.g., an Ethernet connection, a digital subscriber line (DSL), a telephone line, coaxial cable, a cellular telephone system, etc.).

The processor platform700of the illustrated example also includes one or more mass storage devices728for storing software and/or data. Examples of such mass storage devices728include floppy disk drives, hard drive disks, compact disk drives, Blu-ray disk drives, RAID systems, and digital versatile disk (DVD) drives.

The coded instructions732ofFIG.7may be stored in the mass storage device728, in the volatile memory714, in the non-volatile memory716, 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 (1) material costs as compared to thick-film printing methods, and (2) 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.

Although certain example methods, apparatus and articles of manufacture have been disclosed herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the claims of this patent.