FOLDABLE DIGITAL MICROFLUIDIC (DMF) DEVICE USING FLEXIBLE ELECTRONIC PLATFORM AND METHODS OF MAKING SAME

A foldable digital microfluidic (DMF) device using a flexible electronic platform and methods of making same is disclosed. The foldable DMF device includes a flexible polyimide substrate with thin copper features that is foldable to provide opposing substrates. The foldable DMF device further includes a flexible polyimide dielectric layer also with thin copper features. In some embodiments, the structure for forming the presently disclosed foldable DMF device is based on the use of blind vias. In some embodiments, the foldable DMF device includes one droplet actuation layer. In other embodiments, the foldable DMF device includes multiple droplet actuation layers. Additionally, a method of making the foldable DMF device is provided.

TECHNICAL FIELD

The presently disclosed subject matter relates generally to microfluidic devices for performing assays and more particularly to a foldable digital microfluidic (DMF) device using a flexible electronic platform and methods of making same.

BACKGROUND

In digital microfluidics technology, the digital microfluidic (DMF) devices are often printed circuit board (PCB)-based DMF devices or cartridges (also called droplet actuators). For example, a PCB-based substrate is arranged opposite a glass or plastic substrate. The PCB-based substrate may include an arrangement of droplet operations electrodes (e.g., electrowetting electrodes). The glass or plastic substrate may include a ground reference electrode that is substantially optically transparent, such as an indium tin oxide (ITO) ground reference electrode. There is a gap between the PCB-based substrate and the glass or plastic substrate. The gap may be filled with filler fluid (e.g., silicone oil) or air and droplet operations can occur in the gap. Examples of droplet operations can include, but are not limited to, droplet transporting, droplet splitting, droplet merging, droplet mixing, droplet agitating, droplet diluting, and the like.

There are certain drawbacks with conventional DMF devices or cartridges or droplet actuators. For example, they can be complex and costly to fabricate. Namely, conventional DMF devices may include two substrates that must be precisely assembled together and also connected electrically. Further, a PCB-based substrate may have limitations with respect to dielectric uniformity and surface flatness. These limitations may result in performance problems such as limited droplet transport velocities, reduced droplet actuation reliability, and requiring higher electrowetting voltages.

SUMMARY

The present disclosure relates to flexible digital microfluidics (DMF) devices. The DMF devices described herein may utilize a flexible electronics platform or substrate, which may facilitate advantages in relation to the manufacture and/or operation of the DMF device.

In some embodiments, the presently disclosed subject matter provides a foldable digital microfluidic (DMF) device using a flexible electronic platform and methods of making same. Namely, the presently disclosed foldable DMF device may include a flexible substrate that is foldable to provide opposing substrates. In certain embodiments, the flexible substrate may comprise a flexible polyimide substrate. Accordingly, the “bottom” substrate (and its features) and the “top” substrate (and its features) of the DMF device may share a common substrate, which may be a flexible and foldable polyimide substrate. This enables simultaneous processing of either “top” or “bottom” aspects of the DMF device during manufacture. Further, the presently disclosed foldable DMF device may include the flexible polyimide substrate as well as a flexible polyimide dielectric layer. Additionally, either or both of the flexible polyimide substrate and the flexible polyimide dielectric layer may include thin copper features. Further, the presently disclosed foldable DMF device may include multiple flexible polyimide layers with copper to provide, for example, multiple routing, wiring, and/or shielding layers. In particular, droplet actuation electrodes and the necessary electrical connections for operation thereof may be formed in a conductive material (e.g., copper) to facilitate droplet operations once the DMF device has been folded into a desired configuration. Moreover, one or more ground plane electrodes, which may facilitate operation of the droplet actuation electrodes may be formed. In any regard, multiple copper layers are provided, separated by polyimide and adhesive.

In some embodiments, the presently disclosed foldable DMF device may be a U-shaped foldable DMF device that has one droplet actuation layer.

In some embodiments, the presently disclosed foldable DMF device may be a serpentine-shaped foldable DMF device that has multiple droplet actuation layers.

In some embodiments, the presently disclosed foldable DMF device may be a serpentine-shaped foldable DMF device that has multiple droplet actuation layers and that has substantially the same footprint as the single-chamber U-shaped foldable DMF device.

In some embodiments, the structure for forming the presently disclosed foldable DMF device may be based on the use of blind vias. In yet other embodiments, the structure for forming the presently disclosed foldable DMF device may be based on the use of through-hole vias.

Further, as compared with conventional DMF devices, the presently disclosed foldable DMF device that includes the blind via-based structure may include a thinner copper layer (e.g., about 2 μm vs 35+ μm for conventional), thinner dielectric (e.g., polyimide layer about 12.7 μm (0.5 mils) thick), only one dielectric layer, and/or flatter more uniform surfaces.

Further, as compared with conventional DMF devices, the presently disclosed foldable DMF device lends well to improved DMF droplet movement (higher velocities, more reliable actuation, lower electrowetting voltage) by facilitating a thinner, more uniform dielectric and flatter surfaces. Namely, a method of making the presently disclosed foldable DMF devices is provided, which may be a top-down process that may begin with a thin polyimide substrate (i.e., the dielectric) with no adhesive that results in flatter DMF devices with thinner dielectric and better performance as compared with conventional DMF devices.

Further, the presently disclosed foldable DMF device may include a folding mechanism that can reduce the part-count per device, simplify fabrication, and reduce device cost as compared with conventional DMF devices.

DETAILED DESCRIPTION

FIG. 1shows a side view of an example of a DMF structure100on which the presently disclosed foldable DMF device is based. In this example, DMF structure100is a structure based on the use of blind vias. For example, DMF structure100can be the basis for forming the presently disclosed foldable DMF devices200shown inFIG. 2throughFIG. 9.

DMF structure100may include a polyimide substrate110that may further include an arrangement of droplet operations electrodes112that may be formed using a blind-via technique. For example, the droplet operations electrodes112may include an actuation electrode114on one side of polyimide substrate110and an outer electrode116on the opposite side of polyimide substrate110. Then, respective ones of the actuation electrode114and outer electrode116may be electrically connected using a blind via118that passes through the thickness of polyimide substrate110. In one example, polyimide substrate110is about 12.7 μm (0.5 mils) thick. Actuation electrodes114and outer electrodes116may be, for example, copper electrodes that are about 2 μm thick. Likewise, blind vias118may be columns of copper having a diameter of, for example, about 100 μm. Droplet operations electrodes112are not limited to copper. Droplet operations electrodes112can be formed, for example, of copper, gold, silver, aluminum, and the like.

The use of blind vias118, as compared with through-hole vias (seeFIG. 11), allows the surfaces of actuation electrodes114and outer electrodes116to be highly flat, uniform, and planar. The mechanism that enables this is that blind-vias (e.g., blind vias118) mean the top electrodes (e.g., actuation electrodes114) do not get electroplated during the via plating process. Atop actuation electrodes114in DMF structure100is a polyimide dielectric layer120that is, for example, about 12.7 μm (0.5 mils) thick. The polyimide dielectric layer120may be flexible, and is therefore interchangeably referred to herein as the flexible polyimide dielectric layer120. The polyimide dielectric layer120that has an adhesive layer122may be laminated atop actuation electrodes114. Generally, the thickness of the polyimide substrate110and the polyimide dielectric layer120can be the same or can be different. In one example, both polyimide substrate110and polyimide dielectric layer120are about 12.7 μm thick. In another example, polyimide substrate110is thicker than polyimide dielectric layer120. For example, polyimide substrate110is about 25 μm thick and polyimide dielectric layer120is about 12.7 μm thick.

In the presently disclosed foldable DMF devices200, DMF structure100may facilitate (1) a highly uniform surface due to the presence of flat and thin electrodes, and (2) lower electrowetting voltages as compared with conventional DMF devices or cartridges or droplet actuators due to the thin dielectric layer. Because the force applied to a droplet in an electrowetting device is inversely proportional to the thickness of the dielectric and proportional to the square of the voltage, the presently disclosed foldable DMF devices200may use lower voltage to perform droplet operations as compared with conventional DMF devices. Further, the lower electrowetting voltage in the presently disclosed foldable DMF devices200reduces electrical complexity and increases DMF device and instrumentation electronics lifetime as compared with conventional DMF devices. More details of examples of the presently disclosed foldable DMF device using DMF structure100are shown and described hereinbelow with reference toFIG. 2throughFIG. 9.

FIG. 2shows a side view of an example of a flexible structure105prior to folding for forming the presently disclosed foldable DMF device200. Flexible structure105may include the flexible polyimide substrate110, which is, for example, a polyimide sheet that may be about 12.7 μm (0.5 mils) thick. An arrangement of droplet operations electrodes112may be provided at one portion (e.g., at one end) of flexible structure105. Further, polyimide dielectric layer120may be laminated atop droplet operations electrodes112using adhesive layer122. A ground reference electrode (or plane)124may be provided at another portion (e.g., at the other end and/or in non-overlapping relation with the droplet operation electrodes112in the unfolded configuration depicted inFIG. 2) of flexible structure105and atop polyimide dielectric layer120. A ground contactor126may be provided for electrical connection to ground reference electrode124. A hydrophobic layer128may be provided atop ground reference electrode124and any exposed portion of polyimide dielectric layer120. Hydrophobic layer128may be, for example, a single hydrophobic spray coat that can be used for forming the presently disclosed foldable DMF device200.

Flexible structure105may have a folding region138between the arrangement of droplet operations electrodes112and ground reference electrode124. For example, to form foldable DMF device200, the flexible polyimide substrate110may be folded with droplet operations electrodes112and ground reference electrode124folding toward one another. Accordingly, when flexible structure105is folded at folding region138, the arrangement of droplet operations electrodes112may be opposite ground reference electrode124as shown inFIG. 3.

FIG. 3shows a top view and a side view of the flexible structure105shown inFIG. 2after folding and forming a U-shaped foldable DMF device200having one droplet actuation layer. For example, in foldable DMF device200, droplet operations electrodes112may be arranged substantially opposite the ground reference electrode124. Further, the plane of droplet operations electrodes112may be substantially parallel to the plane of ground reference electrode124. In one example, a lower portion140of foldable DMF device200may include droplet operations electrodes112whereas an upper portion142of foldable DMF device200may include ground reference electrode124. Lower portion140and upper portion142of foldable DMF device200may be separated by a droplet operations gap130to form a droplet actuation layer154. The height of droplet operations gap130may be set by the bend in folding region138and/or a spacer132between the now opposing ends of flexible structure105. In one example, spacer132can be one or more conventional pillars formed of, for example, additional layers of polyimide or as a template of plastic. In another example, spacer132can be a precision solder spacer disk, such as the TrueHeight® Spacer Blocks available from Alpha Assembly Solutions (Somerset, N.J.). In foldable DMF device200, the gap height can be from about 10s of microns to 100s of microns.

The sides of foldable DMF device200may be sealed, for example, by an adhesive compound or by mechanical force that holds the lower portion140and upper portion142together. In one example, this adhesive is an ultraviolet (UV)-cured adhesive and foldable DMF device200is sealed on three sides. For example, an adhesive layer144may be “wrapped” around foldable DMF device200starting at a first side, then the non-folded end opposite the folding region, and then a second side opposite the first side as shown, for example, in the top view ofFIG. 3.

The terms “top,” “bottom,” “upper,” “lower,” “over,” “under,” “in,” and “on” are used throughout the description with reference to the relative positions of components of the presently disclosed foldable DMF devices, such as the relative positions of lower portion140and upper portion142of foldable DMF device200. It will be appreciated that the foldable DMF device is functional regardless of its orientation in space.

FIG. 4shows a side view of the foldable DMF device200shown inFIG. 3when in use. In this example, droplet actuation layer154may be filled with a filler fluid134. Filler fluid134may, for example, be or include a low-viscosity oil, such as silicone oil or hexadecane filler fluid. One or more droplets136may be in droplet operations gap130in droplet actuation layer154. Droplets136may, for example, be aqueous or non-aqueous or may be mixtures or emulsions including aqueous and non-aqueous components. Droplet operations may be conducted atop droplet operations electrodes112on a droplet operations surface. In this example, droplet operations are conducted in filler fluid134. In another example, droplet actuation layer154may be filled with air instead of filler fluid134and droplet operations are conducted in air. Further still, droplets136may be provided in an “oil-shell” in the actuation layer154. That is, a filler fluid134such as an oil may be provided in a coating about at least a portion, if not substantially surrounding, the droplet136.

FIG. 5shows a side view of an example of the presently disclosed foldable DMF device200with stiffeners installed. To assist with holding flatness and/or rigidity, disclosed foldable DMF device200may include a stiffener150against one or both sides. For example, one stiffener150may be provided against lower portion140of foldable DMF device200and another stiffener150may be provided against the upper portion142of foldable DMF device200. Stiffeners150may be formed, for example, of glass or plastic. In another example, stiffeners150may be a standard rigid PCB material, such as FR4. Further to the example,FIG. 6shows a method of accessing electrically any electrode of foldable DMF device200when a stiffener150is present. For example and showing again the DMF structure100, a portion of outer electrode116of droplet operations electrode112may extend beyond the edge of or into an opening of stiffener150. Accordingly, an electrode access 152-portion of outer electrode116is provided.

FIG. 7shows a side view of another example of a flexible structure105prior to folding for forming the presently disclosed foldable DMF device200. In this example, flexible structure105may include a plurality of segments that comprise repeating pattern160and multiple folding regions138between adjacent instances of the segments comprising the repeating pattern160for forming the serpentine-shaped foldable DMF device200shown inFIG. 8. Namely,FIG. 8shows a side view of a serpentine-shaped foldable DMF device200having three droplet actuation layers154(e.g., droplet actuation layers154a,154b,154b). The serpentine-shaped foldable DMF device200may further include one or more flow channels158for providing fluid connection between the three droplet actuation layers154. That is, one or more droplet actuation layers may be connected by a flow channel for establishing fluid communication therebetween. For example, a flow channel158amay fluidly connect droplet actuation layer154ato droplet actuation layer154b. Additionally, a flow channel158bfluidly connects droplet actuation layer154bto droplet actuation layer154b. Multiple spacers132may be provided for setting the gaps of and defining the boundaries of the reaction (or assay) chambers of the various droplet actuation layers.

A serpentine-shaped foldable DMF device200may facilitate certain beneficial features. In one example, the flow channels158may allow fluid to be transported between tiers (e.g., droplet actuation layers154a,154b,154b). Accordingly, serpentine-shaped foldable DMF device200can be used to effectively double or triple the amount of active area as, for example, the single tier U-shaped foldable DMF device200shown inFIG. 3,FIG. 4, andFIG. 5while maintaining the same footprint. In another example, the mirrored droplet operations electrodes112that are shared between droplet actuation layer154aand droplet actuation layer154ballow multiplexing of the experiment (e.g., for alternative investigations and/or for use of reference sensors). In yet another example, sensor spots (not shown) can overlap so that one detection location can serve multiple analyses.

FIG. 9shows a side view of another example of a serpentine-shaped foldable DMF device200having multiple droplet actuation layers154. The serpentine-shaped foldable DMF device200can include any number of droplet actuation layers154that are fluidly connected by flow channels158.

In the presently disclosed foldable DMF devices200described hereinabove with reference toFIG. 1throughFIG. 9, the polyimide layers and copper layers may not be optically transparent. Accordingly, optical detection methods may not lend well to foldable DMF devices200. However, other detection methods are possible with foldable DMF devices200. In this regard, a sensor may be provided that is positioned relative to the foldable DMF device such that the sensor is disposed for measurement of the foldable DMF device. In one example, detection can be accomplished using a sensor comprising an infrared (IR) camera capable of imaging through the polyimide layers and/or copper layers. In another example, a sensor may comprise capacitive feedback can be used that is operative to monitor droplet movements. Another method of detection may be to interface a sensor with the fluid from the side or edge of the device. For example, a sensor comprising an optical fiber with a chemical sensor on the tip may be introduced from the side of edge into the fluid to perform analyses. such as surface plasmon resonance.

Conventional DMF devices are typically made using a bottom-up process (i.e., bottom substrate to top substrate) in which the dielectric layer (e.g., polyimide) is laminated at the end of the process. However, this process requires a thick adhesive layer to perform the lamination of the dielectric layer. The thick dielectric/adhesive layer results in a certain amount of dielectric nonuniformity and surface roughness that adversely effects performance. By contrast, a method of making the presently disclosed foldable DMF devices is provided, which may be a top-down process that begins with a thin polyimide substrate (i.e., the dielectric) with no adhesive that facilitates a flatter DMF devices with thinner dielectric and better performance as compared with conventional DMF devices. By way of example,FIG. 10shows a flow diagram of an example of a method300of making the presently disclosed foldable DMF devices200. A main benefit of method300is that it enables simultaneous processing of either or both “top” and/or “bottom” aspects of the presently disclosed foldable DMF devices200. Method300may include, but is not limited to, the following steps.

At a step310, a sheet may be provided that can be used with the top-down process described in method300. The sheet may include a substrate layer and a conductive material layer. For instance, the substrate layer may comprise a flexible substrate layer, which may be a polyimide sheet. The conductive material layer may comprise a thin copper layer on at least one side of the polyimide sheet. For example, polyimide sheets are available from Panasonic Corporation, DowDuPont Incorporated and many other suppliers. In one example, a 12.7 μm (0.5 mils)-thick polyimide sheet that has a 5 μm-thick copper layer on one side is provided. In another example, a 12.7 μm (0.5 mils)-thick polyimide sheet that has a 2 μm-thick copper layer on both sides is provided. In this example, one of the 2 μm-copper layers may be removed. For example, an etching process can be used to remove this copper layer. In so doing, a polyimide sheet is provided that has a 2 μm-thick copper layer on one side only. The polyimide portion of the resulting sheet is the flexible polyimide dielectric layer120of foldable DMF devices200.

At a step315, electrodes and/or any other features are patterned in the thin copper layer on one side of the polyimide sheet provided in step310. For example, using standard photolithography and/or etching processes, actuation electrodes114of droplet operations electrodes112are patterned in the 2 μm-thick or 5 μm-thick copper layer on one side of this polyimide sheet, which is flexible polyimide dielectric layer120.

At a step320, another sheet may be provided. This sheet may also comprise a substrate layer comprising a polyimide sheet that has a conductive material layer (e.g., a thin copper layer) on at least one side is provided. Again, polyimide sheets are available from Panasonic Corporation and DowDuPont Incorporated among other suppliers. In one example, a 12.7 μm (0.5 mils)-thick polyimide sheet that has a 5 μm-thick copper layer on one side is provided. In another example, a 12.7 μm (0.5 mils)-thick polyimide sheet that has a 2 μm-thick copper layer on both sides is provided. In this example, one of the 2 μm-copper layers may be removed. For example, an etching process can be used to remove this copper layer. In so doing, a polyimide sheet is provided that has a 2 μm-thick copper layer on one side only. In another example, this polyimide sheet that is about 25 μm thick. The polyimide portion of the resulting sheet is the flexible polyimide substrate110of foldable DMF devices200. In foldable DMF devices200, the exposed side (non-copper side) of this polyimide sheet (i.e., polyimide substrate110) is facing the patterned side (copper side) of the first polyimide sheet (i.e., polyimide dielectric layer120) provided in step310.

At a step325, electrodes and/or any other features are patterned in the thin copper layer on one side of the polyimide sheet provided in step320. For example, using standard photolithography and/or etching processes, outer electrodes116of droplet operations electrodes112are patterned in the 2 μm-thick or 5 μm-thick copper layer on one side of this polyimide sheet, which is flexible polyimide substrate110.

At a step330, the polyimide sheet (i.e., polyimide substrate110) provided in steps320and325is laminated to any previously provided polyimide sheets, such as the polyimide sheet (i.e., polyimide dielectric layer120) provided in steps310and315. For example, the exposed side (i.e., the non-copper side) of polyimide substrate110has an adhesive layer122that is laminated to the side of polyimide dielectric layer120that has and actuation electrodes114.

Additionally, steps320,325, and330may be repeated multiple times to form any stack of multiple copper layers for, for example, routing, wiring, and/or shielding purposes, and wherein the layers are laminated via corresponding adhesive layers (e.g., adhesive layer122).

At a step335, the blind vias are formed in droplet operations electrodes112. For example, openings or columns that correlate to the positions of the blind vias118are patterned in the stack of outer electrodes116, polyimide substrate110, and actuation electrodes114(seeFIG. 1) but not through the polyimide dielectric layer120. Further, the openings or columns may reach but not penetrate actuation electrodes114. For example, using standard photolithography, etching, and/or drilling processes using conventional or laser drills, openings or columns that correlate with the positions of blind vias118are patterned in the stack of outer electrodes116, polyimide substrate110, and actuation electrodes114. Then, using standard PCB processes, copper may be deposited, electroplated, or otherwise provided in the openings to form blind vias118and thereby electorally connect respective ones of the outer electrode116to a corresponding actuation electrode114to form the droplet operations electrode112.

At a step340, a hydrophobic layer is provided atop the polyimide dielectric layer and atop any features thereof. For example, hydrophobic layer128is provided atop ground reference electrode124and any exposed portion of polyimide dielectric layer120. Namely, hydrophobic layer128can be applied via a hydrophobic spray coating. A benefit of the presently disclosed foldable DMF devices200is that only one spray coating may be used for both the “bottom” and “top” substrates of the finished foldable DMF devices200. At the completion of this step, flexible structure105, such as shown inFIG. 2andFIG. 7, is formed.

At a step345, the flexible structure is folded and spacers are installed. For example and referring again toFIG. 2andFIG. 7, flexible structure105is folded over on itself at any one or more of the folding regions138. Namely, any fold occurs by folding the arrangement of droplet operations electrodes112toward its corresponding ground reference electrode124such that, once folded, the arrangement of droplet operations electrodes112is opposite its corresponding ground reference electrode124as shown, for example, inFIG. 3andFIG. 8. Next, one or more spacers132are installed to set the gaps of and define the boundaries of the reaction (or assay) chambers of the various droplet actuation layers (e.g., one or more droplet actuation layers154).

At a step350, the sides of the foldable DMF device are sealed. For example, the sides of the foldable DMF device200shown inFIG. 3orFIG. 8are sealed using an adhesive compound or by mechanical means that holds the lower portion140and upper portion142together. In one example, this adhesive is a UV-cured adhesive and foldable DMF device200is sealed on three sides. For example and referring again to the top view ofFIG. 3, adhesive layer144is “wrapped” around foldable DMF device200starting at one side, then the non-folded end, and then the other side. An example of UV-cured epoxy suitable for adhesive layer144is EPO-TEK® OG675 available from Epoxy Technology, Inc (Billerica, Mass.). The thickness of adhesive layer144can be, for example, about 300 μm.

FIG. 11shows a side view of another example of a DMF structure400for forming the presently disclosed foldable DMF device200. In this example, DMF structure400may be a structure based on the use of through-hole vias. For example, DMF structure400can be the basis for forming the presently disclosed foldable DMF devices. DMF structure400may include a polyimide substrate110as described with reference to DMF structure100ofFIG. 1. In DMF structure400, polyimide substrate110may include an arrangement of droplet operations electrodes412that may be formed using through-hole vias. The polyimide substrate110may be referred to herein interchangeably as the flexible polyimide substrate110. For example, the droplet operations electrode412may include an actuation electrode414on one side of polyimide substrate110and an outer electrode416on the opposite side of polyimide substrate110. Then, actuation electrode414and outer electrode416are electrically connected using a through-hole via418that passes through the thickness of polyimide substrate110. Droplet operations electrodes412may be formed, for example, of copper.

The method for forming DMF structure400may include laminating layers of polyimide with copper, drilling the through-holes, and then plating the electrodes and through-holes. Finally, a thin polyimide dielectric layer120may be laminated atop actuation electrode414using adhesive layer122. Namely, DMF structure400may formed using the conventional bottom-up process (i.e., bottom substrate to top substrate) in which polyimide dielectric layer120is laminated at the end of the process. However, this process requires a thick adhesive layer122to perform the lamination of polyimide dielectric layer120.

While the presently disclosed foldable DMF devices, such as the foldable DMF devices200shown inFIG. 2throughFIG. 9, can be formed using DMF structure400, there are certain differences as compared with DMF structure100ofFIG. 1. For example, the actuation electrodes414of DMF structure400are much larger and/or thicker than the actuation electrodes114of DMF structure100. This adds surface roughness and/or surface nonuniformity as compared with the surface of DMF structure100. This may further result in the adhesive layer122of DMF structure400being significantly thicker than the adhesive layer122of DMF structure100. This, in turn, affects the electrowetting behavior. For example, DMF structure400may use a higher electrowetting voltage as compared with DMF structure100.

In summary and referring now again toFIG. 1throughFIG. 11, foldable DMF devices200are provided that are formed according to method300ofFIG. 10using a flexible electronic platform, such as flexible polyimide substrate110in combination with flexible polyimide dielectric layer120. In the presently foldable DMF devices200, flexible polyimide substrate110and flexible polyimide dielectric layer120are foldable to provide opposing substrates. Namely, the lower portion140(or “bottom” substrate) and the upper portion142(or “top” substrate) of the DMF device200share a common substrate, which is flexible polyimide substrate110. Namely, method300enables simultaneous processing of either or both “top” and/or “bottom” aspects of the presently disclosed foldable DMF devices200. Additionally, either or both flexible polyimide substrate110and flexible polyimide dielectric layer120may include thin copper features.