Fluidic actuator device and methods for construction thereof

Abstract

A fluidic tactile device has a first substrate having a top surface and a bottom surface. The device also includes a pumping layer which has a first electrode layer with a first group of multiple electrodes, a pumping membrane including a fluid, and a second electrode layer, comprising a second group of multiple electrodes. The device also includes a reservoir layer that holds some of the fluid. The reservoir layer is in fluid communication with the pumping membrane. The device has a second substrate having a top surface and a bottom surface. A method of manufacturing the device includes applying an adhesive to portions of the fluidic device to assemble and seal the portions together.

Description

FLUIDIC ACTUATOR DEVICE AND METHODS FOR CONSTRUCTION THEREOFCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Application 63 / 598,387, filed on November 13, 2023, which is hereby incorporated by reference in its entirety.FIELD

[0002] The application relates generally to the haptic and feedback systems, and more specifically to a fluid actuator device and method for construction thereof. Furthermore, the application relates to the field of electroosmotic pumps and specifically to an improved design and construction that offers enhanced sealing, flexibility, and robustness.BACKGROUND

[0003] This disclosure describes a system and method for creating an electroosmotic based fluidic tactile actuator device that is both mechanically flexible and robust. Flexibility here means the ability of the entire device to contort its shape by bending (under internal or external load), for instance, to match the curvature of an appendage, such as a fingertip or curving touch sensitive surface (i.e. a touchscreen). Robustness here means the ability of the device to not wear out or break down, for instance, over a period of time, under bending, compression, changes in environment, or other normal or extreme operating conditions. These two characteristics are usually in direct conflict with one another, as enabling flexibility typically makes devices more fragile and prone to wear. Therefore, it is imperative that the two are considered and optimized together. An advantage of this approach is that the resulting devices that can be made using the techniques described herein are similarly imbued with robust qualities and making the entire actuation device flexible ensures maximum geometriccompatibility with the overall device structure as well as different parts of the human body. These qualities are important when considering the ergonomics, functionality, and reliability of the device, and they often are a deciding factor on whether or not a new technology is commercially viable.

[0004] To create such a device stackup, every layer of the construction of the electroosmotic fluidic actuator must be considered including the bonding layers. The bending stiffness of the overall multilayer structure is a function of the stiffness, thickness, and position of the individual layers, as well as the shear compliance between layers. This includes the output touch layer, the pumping membrane, the electrical routing and electrodes, system housing and substrate, any chambers and reservoirs, and all of the adhesive layers used to bring the components together. All of these components must be sufficiently thin, sufficiently elastic, or a combination of both, in order to ensure that the overall device can be bent without damage or delamination. A sufficient amount of bending for many human computer interaction applications includes a minimum radii of curvatures of approximately 4 mm, though smaller curvatures may also be possible or preferred. The methods of construction described can also result in system stackups under 1 mm in thickness.

[0005] Another aspect of this disclosure are ways of creating a device stackup that is overall chemically resistant to the organic solvents that are used as the working fluid in some contemporary non bubble producing electroosmotic pumps (also used in an embodiment). These liquids are crucial for the electrochemical and mechanical function of the device, but they introduce new issues of reliability and chemical compatibility when used, as the solvent will dissolve, absorb into, and plasticize many common materials used in flexible devices, such as acrylic or epoxy based adhesives, epoxy laminates, and a number other polymers such as polyethersulfone, polycarbonate, polyvinylidene fluoride, acrylonitrile butadiene styrene,nitrile rubber, or polyvinyl chloride, to name a few. Breakdown of these materials over time can lead to device failure, especially when the device is subjected to bending stress, therefore it is important that these issues are addressed and overcome.SUMMARY

[0006] This application teaches adhesive layer constructions that are compatible with flexible and robust actuator construction. In an embodiment, thermoplastic adhesives are utilized as the primary method of adhesion, offering a robust and durable material bond. These adhesives are particularly chosen for their ability to form a solid bond with the substrate, housing, pumping membrane, or other components they are applied to. For example, materials of the same class such as polyamides are chosen for both the substrate and the adhesive layer. Alternatively, materials that are known to adhere effectively in lamination processes are selected. This can include using a polyethylene terephthalate (PET) substrate and pairing it with a polyethylene (PE) adhesive layer, or a PTFE substrate paired with a FEP or ETFE adhesive layer. This approach ensures a strong bond and compatibility between the layers during the lamination process.

[0007] In some embodiments, a fluidic tactile actuator device is disclosed. The fluidic tactile device has a first substrate having a top surface and a bottom surface. The device also includes a pumping layer which has a first electrode layer with a first group of multiple electrodes, a pumping membrane including a fluid, and a second electrode layer, comprising a second group of multiple electrodes. The device also includes a reservoir layer that holds some of the fluid. The reservoir layer is in fluid communication with the pumping membrane. The device has a second substrate having a top surface and a bottom surface.

[0008] In some embodiments, a first layer of adhesive disposed between the bottom surface of the first substrate and the first electrode layer. A second layer of adhesive disposed between thefirst electrode layer and the pump membrane. A third layer of adhesive disposed between the second electrode layer and the second substrate. The multiple electrodes of the first group of multiple electrodes and the second group of multiple electrodes are porous.

[0009] In some embodiments, the pumping membrane is an electroosmotic pump that creates a liquid / solid interface and a flow path across which an electric field may be applied to induce electroosmotic flow of the fluid. The top surface of the first substrate is deformable at multiple areas by movement of the fluid from the pumping membrane through the first group of multiple electrodes, the deformable multiple areas forming individual actuator outputs in the top surface.

[0010] In some embodiments, the first group of multiple electrodes have a corresponding electrode from the second group of multiple electrodes, thereby forming an electrode pair, wherein each electrode pair is individually controllable via application of an electrical voltage to a respective electrode pair. The first layer of adhesive, the second layer of adhesive, the third layer of adhesive each comprise a thermoplastic adhesive, and wherein a melting point of the thermoplastic adhesive is lower than a melting point of the first substrate and the first electrode layer.

[0011] Furthermore, the appended claims may serve as a summary of this application.BRIEF DESCRIPTION OF FIGURES

[0012] FIG. 1A is a diagram illustrating a flexible tactile actuator device 100 in a flex configuration with inflated outputs.

[0013] FIG. IB is a diagram illustrating a flexible tactile actuator device 100 in an unbent flat configuration with inflated outputs.

[0014] FIG. 2 is a diagram illustrating a single inflated fluidic tactile actuator in bending.

[0015] FIG. 3 is a diagram depicting how a tactile device enabled by an example embodiment wraps around an appendage, such as the fingertip.

[0016] FIG. 4 is a diagram illustrating an example stackup of the pump, electrode, substrate, and adhesive layers.

[0017] FIG. 5 is a diagram illustrating a top-down view of a substrate with electrode and routing areas (one side).

[0018] FIG. 6 is a diagram illustrating an exemplary method of manufacturing a fluidic actuator device.DETAILED DESCRIPTION

[0019] Described in this disclosure are various methods used to create a flexible and robust fluidic actuator. Embodiments of device stackups which use these methods are also disclosed in order to illustrate the usefulness of the invention. A stackup is meant to describe the ordered stack of materials which are brought together during manufacture by use of adhesives or some other method of joining. In general, a fluidic actuator assembly consists of the housing, substrate, electrodes, electrical routing, pumping membrane, output contact layer, fluid reservoirs, fluid routing, and adhesives. This actuator assembly creates a fluidically closed electrohydraulic actuator system.

[0020] Output layers can be arrayed, with multiple connected to a single housing and substrate (for example in FIG.1A and FIG. IB), or they can be single individual actuators (e.g. FIG.2). Coming off of the fluidic actuator is a flexible electrical cable that is connected to an electrical power supply and control circuitry. This electrical cable can contain a plurality of control signals and can operate as both transmit or receive lines for an external system to electrically communicate with the various electrodes embedded in the flexibly fluidic actuator. In certainembodiments, all or parts of the control circuitry can be embedded into the flexible cable itself, or interior to the fluidic actuator itself, as is commonly done with chip-on-flex type configurations. As shown in FIG.1A, FIG. 2, and FIG. 3, the entire fluidic actuator can bend, including all of the components listed as part of the actuator assembly. Enabling this bending is, at the core, a flexible substrate, electrode, and pumping membrane sub-assembly. An example diagram of this actuator subassembly is seen in FIG.4.

[0021] The present invention describes a construction through the combination of multiple functional layers. Layered constructions are preferable for their ease of assembly and economical manufacturing methods. Each individual layer must be flexible, maintain a liquid seal both within the layer, and between layers, and be impervious to strong solvating agents (which are commonly used as the working fluid), while also performing its specific function for operation of the device.

[0022] Housing / Substrate Materials

[0023] Purpose of the housing / substrate is to contain the liquid and provide a mechanically robust platform for other layers to be built off of. In general, the housing portions are those that contain the liquid, and the substrate is what provides the strength and backbone of the device as well as support for electrical routing and electrodes, but in practice the two parts become intermingled. In an embodiment, common flex circuit materials are used, such as polyimide (PI) or polyethylene terephthalate (PET) film. These materials are preferred because they have broad chemical compatibility with solvents used as working fluids, and there are also standard ways of attaching conductors to them which are known in the art. This allows for robust yet inexpensive construction. Other suitable materials are polyamides (PA), polypropylene (PP), other polyethylenes (LDPE or HDPE), fluropolymers such as polytetrafluoroethylene (PTFE), perfluoroalkoxy (PF A), ethylene tetrafluoroethylene (ETFE) or fluorinated ethylene propylene(FEP), polyetherimide (PEI), or polyetheretherketone (PEEK). Some additional materials include woven or non-woven ceramic fabrics, and various rubbers, such as silicone, butyl, or neoprene. Rubbers such as butyl and neoprene are especially favored due to their enhanced durability and reduced gas permittivity. This reduces the effects of outside humidity on the device. In some embodiments, the substrate and housing materials may also act as adhesive tie layers, as some polymers are thermoplastics and are able to flow under elevated temperature. This additional aspect is detailed elsewhere in this disclosure. In general, it is the thinness of the materials that makes them able to withstand significant bending. Typical thickness of substrate layers are on the order of 12-50um, with 25um being a preferred thickness. The housing may contain spacer layers of more substantial thicknesses, lOOum or more, in order to accommodate larger enclosed fluidic volumes. Where the housing must enable protection of the fluid to the outside environment, for example, near the contact layer or reservoir layer, thicker layers may be used, such as 250um or more. The thicknesses given are only as an example.

[0024] Referring to FIG. 6, a method 600 of making a pumping device is described. In some embodiments, a device is formed that includes a pumping layer that includes a first electrode layer, with a first group of multiple electrodes, a pumping membrane where the pumping membrane is porous, and where the pumping membrane creates an interface along a flow path across which an electric field may be applied to induce electroosmotic flow of a fluid. The device may include a reservoir layer that holds some of the fluid. The reservoir layer is in fluid communication with the pumping membrane.

[0025] In step 610, a pumping layer is formed with a first electrode layer, a pumping membrane and a second electrode layer.

[0026] In step 620, a first layer of adhesive is applied to a first side of the pumping layer such that the layer of penetrates into the pumping membrane and forms a non-porous structure that surrounds porous areas about the one or more electrodes of the first group of multiple electrodes.

[0027] In step 630, a second layer of adhesive is applied to a second side of the pumping layer.

[0028] In step 640, an amount of heat is applied to the first layer of adhesive and / or the second layer of adhesive, such that the applied heat melts the first layer of adhesive and / or the second layer of adhesive, but not the pumping membrane.

[0029] In step 650, a top layer comprising a flexible material is added to the first side of the pumping layer.

[0030] In step 660, a bottomer layer comprising a flexible material is added to the second side of the pumping layer.

[0031] Further aspects and details of the method of making a fluidic tactile device are further described below.

[0032] The choice of adhesive systems is critical in developing a device stackup. The ease with which the adhesive systems join various layers together determines the manufacturability and much of the robustness of the device. Adhesives need to prevent separation of the layers they attach to due to shear and peel forces, and they also serve to encapsulate the fluid, preventing any leaks from occurring between layers. High peel strength, flexibility, excellent chemical compatibility, adhesive compatibility or stickiness with a broad range of materials, mechanical strength, and the ability to be patterned or masked are some of the key considerations when selecting an adhesive system for flexible fluidic actuators.

[0033] Prior art offers little to no guidance or teaching on what types of adhesive systems are used for joining system layers. Some systems use no adhesive, and only rely on clamping pressure from external bolts and plates. This method, however, is not compatible with thin and flexible form factors. Other prior systems use pressure sensitive adhesive sheets, which are easy to pattern and have wide adhesive compatibility, but offer low mechanical strength, and can be prone to solvent swelling. These sheets are composed of a soft, acrylic or silicone based adhesive attached to one or more liner materials. The liner and sheet adhesive can be 2D patterned, for instance, by laser, waterjet cutter, or a controlled knife edge, and then applied to a substrate. The liner is then removed and the other material is attached using pressure. Pressure sensitive adhesives can be used as pump adhesive layers, for example, in FIG.4, or to attach parts of the output layer or reservoir together with the housing and substrate.

[0034] The present invention teaches adhesive layer constructions that are compatible with flexible and robust actuator construction. In an embodiment, thermoplastic adhesives are utilized as the primary method of adhesion, offering a robust and durable material bond. These adhesives are particularly chosen for their ability to form a solid bond with the substrate, housing, pumping membrane, or other components they are applied to. For example, materials of the same class such as polyamides are chosen for both the substrate and the adhesive layer. Alternatively, materials that are known to adhere effectively in lamination processes are selected. This can include using a polyethylene terephthalate (PET) substrate and pairing it with a polyethylene (PE) adhesive layer, or a PTFE substrate paired with a FEP or ETFE adhesive layer. This approach ensures a strong bond and compatibility between the layers during the lamination process.

[0035] A critical aspect of selecting the appropriate thermoplastic adhesive is ensuring that its melting point is lower than that of the materials it is bonding to. This may be achieved bychoosing different, but compatible material classes, or through different formulations of materials in the same class.

[0036] Suitable thermoplastics for this purpose include Nylon or other polyamides, PEI (polyetherimide), thermoplastic PI (polyimide), FEP (fluorinated ethylene propylene), ETFE (ethylene tetrafluoroethylene), and PFA (perfluoroalkoxy alkane), among other lower temperature polymers. Moreover, certain polymers, such as PTFE (polytetrafluoroethylene), have the unique capability to directly fuse together, further enhancing the bonding strength. This bonding approach is carefully designed to ensure optimal adhesion while maintaining the integrity and functionality of the components involved.

[0037] Adhesive layers may be separate integral sheets that are positioned and registered within the stackup. In an embodiment, the sheets are pre-formed to a specific thickness (around 25um) and then they are patterned in 2D, for example, by laser machining or CNC milling. Following patterning they are further aligned with the rest of the stackup. In an alternative embodiment, a sheet of adhesive is tack bonded to the substrate or pumping membrane, patterned in 2D, and then it is set during a separate heat process. This has the advantage of registering the 2D pattern while the adhesive is already directly attached to the stackup. In another embodiment, adhesive layers are coated onto or otherwise bonded to other layers such as the substrate or pumping membrane prior to attachment. This approach simplifies the assembly process.

[0038] In an alternative embodiment, the methodology diverges from the use of a separate adhesive layer. Instead, direct fusion of the non-adhesive layers through plastic welding techniques is used. This process results in the creation of a cohesive, intermingled material structure, where the layers are seamlessly integrated to form a unified bond.

[0039] In an alternative embodiment, a rivet-like construction is used. Holes are introduced to an interior layer such as the substrate layer or the pumping membrane layer, which allow adhesive to pass through the adjacent layer and bond to the layer beyond. This construction introduces additional shear and peel strength due to the mechanical interlocking between the adhesive layer and interior layer.

[0040] In an alternative embodiment, setting or curing adhesive materials are utilized. These may include drying adhesives, anaerobic adhesives, reactive adhesives, UV-curing adhesives, catalyst-curing adhesives, and thermosetting adhesives.

[0041] Silicone materials exhibit effective solvent resistance and are flexible, making them desirable for a setting or curing adhesive construction. Furthermore, silicone materials may be processed in a partially cured state (B staged), such that they are solid and may be more easily handled and positioned than a liquid, yet still form an effective bond when cured completely. In order to increase adhesive peel and shear strength, silicone adhesives are used in combination with a rivet-like construction.

[0042] In another embodiment, the contact surface and the reservoir are formed from the same material and form a co-mingled bonded solid through rivet-like connections and / or connection past the edge of the interior layers. The adhesive layer may additionally be of the same material and additionally form a co-mingled bond to the contract surface and / or reservoir layers.

[0043] In some embodiments, the reservoir is geometrically designed or shaped to change volume with minimal pressure. For example, a center area of the reservoir may have a volumetric capacity for a particular area that is greater than an area that is closer to a boundary or edge of the reservoir. The fluidic device may have a more flexible area in a center area than an area that is closer to a boundary or edge of the fluidic device.

[0044] Epoxy materials exhibit solvent resistance and may be used. Resin-like epoxies may be used despite being relatively stiff, because they can be applied in very thin layers, resulting in overall low bending stiffness. Certain acrylic and polyurethane formulations exhibit solvent resistance, but are less preferred for portions of the system directly exposed to the liquid due to the potential to swell and / or delaminate over time.

[0045] Various surface treatments and primers to improve adhesion are known to practitioners skilled in the art. Non-adhesive layers may be treated to improve adhesion prior to assembly.

[0046] Pumping Membrane

[0047] The pumping membrane in an electroosmotic pump serves the primary function of creating a liquid / solid interface and flow path across which an electric field can be applied to induce electroosmotic flow. For the present invention, the pumping membrane is required to perform several functions that are both competing and contradictory in nature. Firstly, it must induce a zeta potential at the fluid / solid boundary, which is essential for its operation as an electroosmotic pump. Higher magnitude potentials, and higher amounts of surface charge (of either positive or negative polarity) are more beneficial for operation. In addition to this, the membrane needs to be flexible and robust, allowing it to adapt and conform to varying shapes and pressures that it may encounter without damage. While being robust it must also be porous (with effective pore sizes generally on the order of 400nm, to lum), allowing liquid to flow through and offering large amounts of surface area. Lastly, the membrane must provide effective sealing, preventing flow around the edges of the membrane. Each of these requirements poses unique challenges, as choosing high zeta potential materials may influence the flexibility and sealing capability. Furthermore, the porous nature of the membrane is fundamentally at odds with the desire to provide effective sealing, making the engineering ofsuch a membrane a complex task. In some embodiments, the porosity is 25% to 75% about the area of the electrodes. In some embodiments, porous holes are less than 150 microns.

[0048] The conventional construction of pumping membranes involves the utilization of one or more discrete membranes. These membranes are interspersed and held apart by a spacer layer. However, this configuration presents significant challenges, particularly in the accurate placement of discrete pump membranes, in the prevention of internal leaks due to gaps between the membrane and spacer layer edges, and in the handling of discrete, often small and delicate component parts. Prior art lacks sufficient guidance on the arrangement and sealing methods for these components.

[0049] Porous glass materials have been used as readily available materials that induce a relatively high zeta potential as a result of deprotonated silanol groups on the surface of the glass. Sintered glass beads or other porous solids like open cell glass foams may be used and they are robust, but they are not flexible. Binderless glass fiber filters may be used and they are flexible, but they are not robust while flexing, and they loosen or break apart with mechanical strain and fluid flow.

[0050] The present invention introduces alternative pumping membrane material types together with constructions suitable for flexible and robust fluidic actuators. In one embodiment, a glass and polymer composite material is used. The use of glass serves to retain a high zeta potential, while the polymer serves as a binder that adds robustness. Care must be taken that the binder is chemically compatible with the working fluid and does not overly influence the surface charge characteristics of the glass. A preferred composite material is a non-woven glass fiber matrix which is then lightly bonded using PTFE. Another method is to introduce small glass beads or fibers into a polymer mixture (such as polyamide), and then create a porous polymer membrane using techniques known in the art, such as a phase inversionmethod. In this way, the PA membrane, which has excellent chemical and mechanical properties, can have various amounts of glass incorporated into the matrix. The glass primarily serves to boost the zeta potential.

[0051] It should be appreciated that other forms of glass, and other types of polymers can also be used in composite construction, and these embodiments were only explained as example systems. Base porous polymers can also be used with or without modification. Without modification the zeta potentials are quite small, therefore, it is also desirable to surface modify these membranes with various charged polymer species. For instance, a polymer membrane may be formed using a phase inversion process, and then it can be post-treated with a highly charged polymer surface layer through a coating and crosslinking process. The same process could be used with a so-called track etched membrane as well. In this method, the polymer is formed as a solid sheet, then exposed to charged particles from a nuclear reactor. These particles form “tracks” in the polymer which are then subsequently preferentially etched in a post process, leaving highly regular pores in the membrane, which can then be coated with surface coatings to modify their zeta potential. As the coating layers, any suitable polymer which contains high amounts of charge and can be crosslinked with the base polymer is suitable.

[0052] Forming of the Pumping Membrane

[0053] The pumping membrane is a porous structure, and therefore must be sealed to prevent the liquid from leaking from the system, or to another location within the device. The present invention introduces an innovative approach where the pumping membrane, or an array of membranes, is constructed as an integral sheet layer. The invention contemplates two sections in the integral sheet layer: the porous pumping area and the non-porous sealing area, these can be seen in FIG.5. The porous pumping area contains one or more pumping membranes. Thenon-porous sealing area surrounds the porous pumping area for sealing, and may additionally contain registration features, handling locations, voids, or routing.

[0054] This integral sheet layer can be formed by melt sealing select areas of a continuous porous sheet material, allowing efficient manufacturing and allowing the use of batch sheet or continuous roll construction processes. The advantage of using an integral sheet over discrete pump membranes increases as the number of discrete actuators within an array or within a manufacturing batch increases. This is to say that this process scales very well, and is therefore highly beneficial for large numbers of actuators to be manufactured at high volume and low cost.

[0055] To form the integral sheet layer, the invention utilizes thermoformable membrane materials. This process involves melting the porous material to effectively seal the pores around the pumping membrane. The formation of the integral sheet layer can be achieved through a variety of heating methods. These include heat pressing techniques, which encompass methods like hot bar, heat staking, thermode, and impulse sealing. Additionally, laser-based methods are also viable, specifically laser melting or laser welding. Furthermore, the process can be carried out using ultrasonic and Radio Frequency (RF) melting processes, which offer alternative means of achieving the desired outcome.

[0056] In an embodiment, the non-porous sealing area extends beyond the edges of the porous pumping area. In this way, the non-porous sealing area can be sealed to the flat surface of the substrate. Because the porous pumping area and non-porous sealing area are formed together, there is no gap between them, and there is a reduced requirement for tight tolerances, and matching dimensions.

[0057] The integral sheet layer may be formed as a component part and bonded to the substrate using an adhesive layer. In an method, a hot press is used to melt the membrane materialdirectly to the substrate in the non-porous seal areas. In another embodiment, a hot press is used to simultaneously form the integral sheet and attach an interposing meltable adhesive layer to the substrate.

[0058] In another embodiment, the integral sheet layer is formed using a liquid, paste, gel, adhesive or other solidifying material selectively applied to the continuous porous sheet material to penetrate the pores, and then solidify, forming the non-porous sealing area. This embodiment has the additional advantage of being compatible with porous sheet materials that are not melt formable. The solidifying material may have the additional advantage of forming the adhesive layer to the substrate. This embodiment may have additional advantages of robustness imbued from the solidifying material.

[0059] In another embodiment, the continuous sheet material is anisotropically porous, such that pores primarily extend through the normal direction to the sheet and substantially less in the planar directions. In this embodiment, the non-porous sealing area may be formed through melt forming, a solidifying material, and additionally through a cap layer. The cap layer is a layer that covers the continuous sheet material selectively at the non-porous sealing area, blocking the pores in that area. The cap layer may be bonded or not bonded, and may form the adhesive layer.

[0060] Electrical Routing and Electrodes

[0061] The electrical components in this method are created to also be thin and flexible. They are made of conductive material which serves the purpose of both routing and transmitting or receiving electrical fields from the pumping membrane. An embodiment for a flexible stack up is to use thin copper deposited on top of polymer substrate. Rolled annealed copper is preferred as opposed to electrodeposited due to its increased bending reliance, however both are acceptable. The copper is etched using standard photolithography techniques known in the art.Typically, the copper can be adhered to the polymer substrate by means of an adhesive. This adhesive should be capable of withstanding contact with solvents without delamination. A preferred adhesive system is to use thermoplastic or liquid polyimide (sometimes called an “adhesiveless” system), which can bond to a polyimide substrate and the copper. Other substrates for copper include PTFE, PET, or composite materials. Another embodiment of the electrode and routing layers may be a PEDOT:PSS conductive polymer, layer formulations using silver or carbon nanowires or powder, or any composite material dispensed on polymer substrate, for instance, in the form of conductive ink, which is common in printed electronics systems. Thin film aluminum on PET (trade name Mylar) is another option. These patterned conductor systems have the advantage of being able to be mass produced via roll-to-roll processing techniques known in the art, and therefore it is very advantageous that the rest of the system stack-up is made to be compatible with them.

[0062] Additional systems for providing electrodes include deposition of conductor directly onto the top surface of the pumping membrane, or depositing on a porous mesh which is then pressed directly up against the pumping membrane. This mesh fills the small gap left between the membrane and flexible routing layer. Once deposited, this material can be etched, ablated, chemically deactivated, or otherwise patterned using techniques known in the art to create a plurality of discrete electrodes. The routing layer can additionally be integrated onto the top of the pumping membrane, especially in the case of low numbers of actuators, where the routing of the electrodes is not as tightly packed. This conductor method is especially useful insofar as it can eliminate the substrate layers seen in FIG.4, thus reducing the thickness of the device while not sacrificing the output performance of the actuator. In this case, however, the pumping membrane must also serve as the mechanical core of the device, and thus not all membrane types are suitable.

[0063] Electrodes must be porous so that liquid can flow through them and preferably introduce minimal flow resistance. Computer numerically controlled (CNC) drilling of holes through the conductor and underlying substrate is one method of creating porosity. Another preferred method is to use a laser to ablate patterns in the conductor / substrate stack, as seen in the drawing of FIG. 5. As mentioned prior, a porous substrate that has been made of or coated with an conductive material may also serve as an effective electrode, given that it is electrically connected to or serves as the rest of the electrical routing to bring signals out of or into the actuator.

[0064] Liquid properties

[0065] The working liquid should have a moderately high dielectric constant, and remain liquid over a wide range of temperatures. A range of organic solvents fit this description, as does water. It should also have a low electrical conductivity, in order to maximize mechanical output for a given electrical power input. An organic solvent based liquid is preferable, however this introduces many chemical compatibility issues, as described in this disclosure. Various additives can be added to the liquid in order to lessen the burden of chemical compatibility and power draw. For instance, ion and water scavenging additives can reduce the electrical conductivity of the fluid over time, and help prevent unwanted faradaic reactions from occurring in the solvent. Additives which raise the dielectric constant of the overall liquid can be used, such as large zwitterionic species. Mixtures of liquids of various dielectric constants are also possible. For example, a low viscosity liquid can be added for better flow, while a high dielectric constant liquid is added for maximum dielectric effect. Certain additives could also be used to introduce self sealing qualities to the materials.

[0066] Filling with Liquid

[0067] A preferred method of filling a device with working fluid is described here. This method includes creating part of the housing which is able to be penetrated by a filling needle, and then self seal once the needle is removed. Various self-sealing methods are applicable, and one effective method is to use an elastomer attached to a solvent resistance thin polymer, such as polyamide. In this configuration, the PA serves as the primarily gas barrier and high mechanical strength layer, while the elastomer rubber layer, for example silicone, provides the self-sealing function. The durometer and thickness of silicone can be adjusted to improve the characteristics of the seal. Additionally, a heat seal of the punctured area can be applied post filling, to provide better robustness. Indeed, any post process which covers the filling port with an additional layer is beneficial. Gas bubbles may also be evacuated from the device via the same filling port.

[0068] Small Pores for Low Power

[0069] In certain use cases, it may be desirable to trade off actuation speed for applied electrical power. One way to perform this trade off is to use a pumping membrane that has extra high fluidic resistance through the membrane. This is achieved by using very small pore sizes (in general closer to lOOnm). This reduction in pore size has the effect of reducing the ohmic conductivity of the liquid through the membrane, and thus the applied electrical power. Electroosmotic flow can still occur, however, and the output pressures can be high enough to create substantial deformation in the device for tactile purposes. This technique can be useful, for instance, in creating a slowly inflating keyboard on a flat touchscreen surface, where small tactile features can pop up and remain inflated for long periods of time. The same effects of increasing zeta potential still apply, and flow can be increased by alternative means if necessary for the application. For instance, larger surface area pumps can be used to increase flow.

[0070] Stack up examples

[0071] Stack-up 1 Example

[0072] In one embodiment, the substrate and electrical routing and electrode layers are created using a polyimide and copper construction. Copper is adhered to a PI layer using a liquid PI, and then it is processed using a laser for drilling and photolithography for 2D features. The Cu is coated in a nickel and gold coating. The pumping membrane is a glass fiber and PTFE composite, which is formed using a heat press. A thermoplastic PI layer is used to bond the pumping membrane to the PI substrate. The rest of the housing is constructed using thermoplastic PI and regular PI layers, with silicone rubber being used over the filling port. The device is filled with an organic solvent.

[0073] Stack-up 2 Example

[0074] In another embodiment, the same composite membrane is used, and its method of forming, however a PTFE substrate is used, with copper and nickel / gold being used for the electrical routing. In this case FEP film is used as a bonding layer.

[0075] Stack-up 3 Example

[0076] In another embodiment, a PET substrate with PEDOT:PSS based electrodes and routing is used. A glass fiber filled nylon membrane serves as the pumping membrane, and it is attached to the PET through a lower temperature PE hot melt adhesive.

[0077] These examples are not exhaustive, and showcase only a few example ways in which materials can be brought together. In general, the methods disclosed here can be mixed, unless explicitly stated otherwise.

[0078] Use cases

[0079] XR accessories for the fingertip, finger, wrist, hand or face. Flexible displays which have haptic button portions. Curved automotive displays with pop up buttons. Laptops with pop up buttons. Flexible cell phones which have visible creases “filled-in” with liquid.

[0080] In some embodiments, the fluidic tactile actuator device has reduced gas permeability in housing materials, especially butyl based elastomers, provides humidity resistance.

[0081] In some embodiments, the fluidic tactile actuator device includes Fluoropolymer based housings, substrates, and barrier layers.

[0082] In some embodiments, the fluidic tactile actuator device includes thermoplastic adhesive layers as the main adhesive system, including FEP, Nylon (polyamide), thermoplastic PI, ETFE.

[0083] In some embodiments, plastic welding techniques, such as ultrasonic welding, radio frequency welding or laser welding may be used to seal layers or substrates of the fluidic tactile actuator device together. The sealing process may use a plasma treatment.

[0084] In some embodiments, composite pumping membranes, in general, composed of a high zeta material with polymer binder may be used. For example, this may include polymer (PTFE) and glass.

[0085] In some embodiments, a coating of a polymer membrane with a separate polymer for high zeta may be applied (e.g., a track etched membrane.)

[0086] In some embodiments, the pump membrane may be formed into a porous pumping area and non-porous sealed area. For example, a single sheet of membrane may be taken and multiple areas defined by thermoplastic melting of a patterned thermoplastic polymer into the membrane. Additionally, porous and non-porous areas may be formed which also may attachthe membrane to interposing polymers. Additionally, porous and non-porous areas may be formed which include a liquid, paste, gel, or other adhesive fillers to form the non-porous areas. Additionally, porous and non-porous areas may be formed which include a cap layer, that is, a thin layer to seal off the very top of the membrane.

[0087] In some embodiments, a chemically durable bonding method may be used between the copper and substrate, for example thermoplastic polyimide or FEP.

[0088] In some embodiments, a method where the adhesive used to bond the copper is also used to bond to the membrane, specifically a thermoplastic such as FEP.

[0089] In some embodiments, electrodes may be formed by depositing porous, flexible conductors, such as PEDOT:PSS or silver nano-wires on top of the pumping membrane, and then patterning it by ablation, etching, or chemical deactivation.

[0090] In some embodiments, laser ablation of holes through the conductor layer in order to create controlled porosity (porosity generally above 25%) may be performed.

[0091] In some embodiments, water scavenging additives may be used in a solvent.

[0092] In some embodiments, exceptionally small pores to create electrical and hydraulic resistance which lowers overall power consumption may be created in the substrates.

[0093] In this specification, reference is made in detail to specific embodiments of the invention. Some of the embodiments or their aspects are illustrated in the drawings. For clarity in explanation, the invention has been described with reference to specific embodiments, however it should be understood that the invention is not limited to the described embodiments. On the contrary, the invention covers alternatives, modifications, and equivalents as may be included within its scope as defined by any patent claims. The following embodiments of theinvention are set forth without any loss of generality to, and without imposing limitations on, the claimed invention. In the following description, specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be practiced without some or all of these specific details. In addition, well known features may not have been described in detail to avoid unnecessarily obscuring the invention.

[0094] In addition, it should be understood that steps of the exemplary methods set forth in this exemplary patent can be performed in different orders than the order presented in this specification. Furthermore, some steps of the exemplary methods may be performed in parallel rather than being performed sequentially.

[0095] In the foregoing disclosure, implementations of the disclosure have been described with reference to specific example implementations thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope of implementations of the disclosure as set forth in the following claims. The disclosure and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.

[0096] It will be appreciated that the present disclosure may include any one and up to all of the following examples.

[0097] Example 1 : A device comprising: a pumping layer comprising: a first electrode layer, comprising a first group of multiple electrodes; a pumping membrane, wherein the pumping membrane is porous, and wherein the pumping membrane creates an interface along a flow path across which an electric field may be applied to induce electroosmotic flow of a fluid; a first layer of adhesive that penetrates into the pumping membrane and forms a non-porous structure that surrounds porous areas about the one or more electrodes of the first group of multiple electrodes; and a second electrode layer, comprising a second group of multiple electrodes.

[0098] Example 2. The device of Example 1, further comprising: a top layer comprising a flexible material positioned as external top layer of the device; and a bottom layer comprising a flexible material positioned as an external bottom layer of the device.

[0099] Example 3. The device of any one of Examples 1-2, wherein a top surface of the top layer is deformable at multiple areas by movement of the fluid from the pumping membrane through the first group of multiple electrodes, the deformable multiple areas forming individual actuator outputs in the top surface.

[0100] Example 4. The device of any one of Examples 1-3, wherein each of the first group of multiple electrodes have a corresponding electrode from the second group of multiple electrodes, thereby forming an electrode pair, wherein each electrode pair is individually controllable via application of an electrical voltage to a respective electrode pair.

[0101] Example 5. The device of any one of Examples 1-4, wherein the first layer of adhesive comprises a thermoplastic adhesive, and wherein a melting point of the thermoplastic adhesive is lower than a melting point of the first electrode layer.

[0102] Example 6. The device of any one of Examples 1-5, wherein the first layer of adhesive is thermoplastic or liquid polyimide and the first layer of adhesive surrounds each electrode of the first group of multiple electrodes.

[0103] Example 7. The device of any one of Examples 1-6, wherein the first electrode layer and the second electrode layer comprise a polyimide and copper.

[0104] Example 8. The device of any one of Examples 1-7, wherein the copper is coated in nickel and gold.

[0105] Example 9. The device of any one of Examples 1-8, wherein the pumping membrane is comprised of glass fibers and a polytetrafluoroethylene (PFTE) composite.

[0106] Example 10. The device of any one of Examples 1-9, wherein the pumping membrane is a composite material including a particulate material and a binder material.

[0107] Example 11. A method of a manufacturing a fluidic pumping device, the method comprising: forming a pumping layer comprising: a pumping layer comprising: a first electrode layer, comprising a first group of multiple electrodes; a pumping membrane, wherein the pumping membrane is porous, and wherein the pumping membrane creates an interface along a flow path across which an electric field may be applied to induce electroosmotic flow of a fluid; and a second electrode layer, comprising a second group of multiple electrodes; applying a first layer of adhesive that penetrates into the pumping membrane and forms a non- porous structure that surrounds porous areas about the one or more electrodes of the first group of multiple electrodes; and applying an amount of heat to melt the first layer of adhesive, wherein the amount of heat applied does not cause the first electrode layer to melt.

[0108] Example 12. The method of manufacture of Example 11, wherein the pumping membrane is an electroosmotic pump that creates a liquid / solid interface and a flow path across which an electric field may be applied to induce electroosmotic flow of the fluid.

[0109] Example 13. The method of manufacture of any one of Examples 11-12, further comprising the operations of: adding a top layer comprising a flexible material positioned as external top layer of the device; and adding a bottom layer comprising a flexible material positioned as an external bottom layer of the device.

[0110] Example 14. The method of manufacture of any one of Examples 11-13, wherein a top surface of the top layer is deformable at multiple areas by movement of the fluid from thepumping membrane through the first group of multiple electrodes, the deformable multiple areas forming individual actuator outputs in the top surface.

[0111] Example 15. The method of manufacture of any one of Examples 11-14, wherein each of the first group of multiple electrodes have a corresponding electrode from the second group of multiple electrodes, thereby forming an electrode pair, wherein each electrode pair is individually controllable via application of an electrical voltage to a respective electrode pair.

[0112] Example 16. The method of manufacture of any one of Examples 11-15, wherein the first layer of adhesive comprises a thermoplastic adhesive, and wherein a melting point of the thermoplastic adhesive is lower than a melting point of the first electrode layer.

[0113] Example 17. The method of manufacture of any one of Examples 11-16, wherein the first layer of adhesive is thermoplastic or liquid polyimide and the first layer of adhesive surrounds each electrode of the first group of multiple electrodes.

[0114] Example 18. The method of manufacture of any one of Examples 11-17, wherein the first electrode layer and the second electrode layer comprise a polyimide and copper.

[0115] Example 19. The method of manufacture of any one of Examples 11-18, wherein the copper is coated in nickel and gold.

[0116] Example 20. The method of manufacture of any one of Examples 11-19, wherein the pumping membrane is comprised of glass fibers and a polytetrafluoroethylene (PFTE) composite.

[0117] In the foregoing disclosure, implementations of the disclosure have been described with reference to specific example implementations thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope ofimplementations of the disclosure as set forth in the following claims. The disclosure and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.

Claims

CLAIMSWhat is claimed is:

1. A device comprising: a pumping layer comprising: a first electrode layer, comprising a first group of multiple electrodes; a pumping membrane, wherein the pumping membrane is porous, and wherein the pumping membrane creates an interface along a flow path across which an electric field may be applied to induce electroosmotic flow of a fluid; a first layer of adhesive that penetrates into the pumping membrane and forms a non-porous structure that surrounds porous areas about the one or more electrodes of the first group of multiple electrodes; and a second electrode layer, comprising a second group of multiple electrodes.

2. The device of claim 1, further comprising: a top layer comprising a flexible material positioned as external top layer of the device; and a bottom layer comprising a flexible material positioned as an external bottom layer of the device.

3. The device of claim 2, wherein a top surface of the top layer is deformable at multiple areas by movement of the fluid from the pumping membrane through the first group of multiple electrodes, the deformable multiple areas forming individual actuator outputs in the top surface.

4. The device of claim 1, wherein each of the first group of multiple electrodes have a corresponding electrode from the second group of multiple electrodes, thereby forming an electrode pair, wherein each electrode pair is individually controllable via application of an electrical voltage to a respective electrode pair.

5. The device of claim 1, wherein the first layer of adhesive comprises a thermoplastic adhesive, and wherein a melting point of the thermoplastic adhesive is lower than a melting point of the first electrode layer.

6. The device of claim 5, wherein the first layer of adhesive is thermoplastic or liquid polyimide and the first layer of adhesive surrounds each electrode of the first group of multiple electrodes.

7. The device of claim 1, wherein the first electrode layer and the second electrode layer comprise a polyimide and copper.

8. The device of claim 1, wherein the copper is coated in nickel and gold.

9. The device of claim 1, wherein the pumping membrane is comprised of glass fibers and a polytetrafluoroethylene (PFTE) composite.

10. The device of claim 1, wherein the pumping membrane is a composite material including a particulate material and a binder material.

11. A method of a manufacturing a fluidic pumping device, the method comprising: forming a pumping layer comprising:a first electrode layer, comprising a first group of multiple electrodes; a pumping membrane, wherein the pumping membrane is porous, and wherein the pumping membrane creates an interface along a flow path across which an electric field may be applied to induce electroosmotic flow of a fluid; and a second electrode layer, comprising a second group of multiple electrodes; and applying a first layer of adhesive that penetrates into the pumping membrane and forms a non-porous structure that surrounds porous areas about the one or more electrodes of the first group of multiple electrodes.

12. The method of manufacture of claim 11, wherein the pumping membrane is an electroosmotic pump that creates a liquid / solid interface and a flow path across which an electric field may be applied to induce electroosmotic flow of the fluid.

13. The method of manufacture of claim 11, further comprising the operations of: adding a top layer comprising a flexible material positioned as external top layer of the device; and adding a bottom layer comprising a flexible material positioned as an external bottom layer of the device.

14. The method of manufacture of claim 13, wherein a top surface of the top layer is deformable at multiple areas by movement of the fluid from the pumping membrane through the first group of multiple electrodes, the deformable multiple areas forming individual actuator outputs in the top surface.

15. The method of manufacture of claim 11, wherein each of the first group of multiple electrodes have a corresponding electrode from the second group of multipleelectrodes, thereby forming an electrode pair, wherein each electrode pair is individually controllable via application of an electrical voltage to a respective electrode pair.

16. The method of manufacture of claim 11, wherein the first layer of adhesive comprises a thermoplastic adhesive, and wherein a melting point of the thermoplastic adhesive is lower than a melting point of the first electrode layer.

17. The method of manufacture of claim 16, wherein the first layer of adhesive is thermoplastic or liquid polyimide and the first layer of adhesive surrounds each electrode of the first group of multiple electrodes.

18. The method of manufacture of claim 11, wherein the first electrode layer and the second electrode layer comprise a polyimide and copper.

19. The method of manufacture of claim 11, wherein the copper is coated in nickel and gold.

20. The method of manufacture of claim 11, wherein the pumping membrane is comprised of glass fibers and a polytetrafluoroethylene (PFTE) composite.

21. The method of manufacture of claim 11, further comprising: applying an amount of heat to melt the first layer of adhesive, wherein the amount of heat applied does not cause the first electrode layer to melt.

Images