Haptic device for use with ar / VR systems

Abstract

A haptic device uses a group of electroosmotic pumps arranged in an array to provide tactile feedback to a user of a virtual / augmented reality system. The electroosmotic pumps are arranged in defined patterns, forming an array of haptic pixels. The pumps pressurize a working fluid to cause a displacement of a flexible membrane in contact with the working fluid. A controller can be used to address individual pumps of the array and to provide simulate effects such as texture, object compliance, detents and buttons, and to provide haptic animations.

Description

CMU 2023-229TITLE HAPTIC DEVICE FOR USE WITH AR / VR SYSTEMSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit under 35 U.S.C. § 119 of U.S. ProvisionalApplication Serial No. 63 / 469,148, filed on May 26, 2023, which is incorporated herein byreference. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0002] Not applicable.BACKGROUND OF THE INVENTION

[0003] The present disclosure generally relates to haptic devices. More specifically, thedisclosure relates to a haptic device that can be used with virtual reality and augmented realitysystems.

[0004] Virtual and augmented reality (VR / AR) headsets are entering the consumermainstream, with tens of millions of headsets already sold. These devices continue to makeimpressive strides in audio-visual immersion, bringing compelling virtual experiences to life.However, when users reach out to physically interact with these virtual worlds, the sense oftouch falls flat. The most advanced consumer-grade controllers are inherently limited by theiruse of vibrotactile haptic actuators, which can only produce clicks and buzzes--an exceedinglysmall pallet of expressivity with which to represent the rich tactile world.

[0005] Many approaches to overcoming the limitations of vibrotactile actuators have beenproposed and implemented, including kinesthetic, thermal, electrotactile, and skin stretchactuation. More recently, however, considerable attention has focused on shape-changing pinand soft actuator arrays. When instrumented on the hands, these types of arrays hold thepromise of enabling fine-grained tactile feedback via high density cutaneous haptic stimulation.This is because fingertips are highly innervated, with around 500 mechanoreceptors perfingertip, and the "neural coding" of these receptors is known to preserve incredible spatial andtemporal detail, such as millimeter scale shape information and temporal "animation"information as high as 20Hz.

[0006] While prior systems offer impressive tactile capability, there are serious limitations totheir commercial impact and scale. Therefore, it would be advantageous to develop a hapticCMU 2023-229device that provides fine-grained haptic feedback while demonstrating a lower cost andreduced weight compared to existing systems.BRIEF SUMMARY

[0007] According to embodiments of the present disclosure is a haptic device comprising anarray of ‘haptic pixels’ created from electroosmotic pumps that are capable of providingsensory signals to a user’s fingertips. The array of electroosmotic pumps can be embedded ina glove, with each finger of the glove having a separate array comprised of many haptic pixels.These small embedded electroosmotic pumps generate high pressures and fast dynamic flows.The use of electroosmotic pumps enables several orders of magnitude reduction in sizecompared to existing solutions, in addition to providing reduced power consumption, weight,and cost.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0008] Figs. 1A-1C show the haptic device, according to one embodiment.

[0009] Fig. 2A shows components of an array of electroosmotic pumps.

[0010] Fig. 2B is a detailed view of a component of the array, with separate electrodes forindividual pumps visible.

[0011] Fig. 3 shows a controller and electrical components of the device.

[0012] Fig. 4 is a graph showing performance characteristics, with voltage, current andpressure shown.

[0013] Fig. 5 is another graph showing performance characteristics.

[0014] Fig. 6 is yet another graph showing performance characteristics.

[0015] Fig. 7 shows the configuration of haptic pixels of an array correlated to a virtual object.

[0016] Fig. 8 shows the activation of haptic pixels to depict compliance of a virtual object.

[0017] Fig. 9 depicts impulses of the haptic array, used to simulate slider detents.DETAILED DESCRIPTION

[0018] According to embodiments of the disclosure is a haptic device 100 comprising an array101 of electroosmotic pumps 102. Fig. 1A shows the device 100 implemented as a glovewearable by a user, with a total of five arrays 101 on the device 100. Each array 101 containsa plurality of electroosmotic pumps 102, which are referred to as ‘haptic pixels’ whenimplemented as a group in an array 101. In the example embodiment shown in Fig. 1A, thedevice 100 includes an array 101 disposed on the distal end of each fingertip of the glove. ACMU 2023-229controller 140 is located near the wrist of the glove and is capable of controlling each individualelectroosmotic pump 102 of the arrays 101. Fig. 1B shows a close-up view of the arrays 101disposed on each fingertip. Fig. 1C shows a view of a single array 101 with a bi-stable clip130 in an open position, where individual haptic pixels 102 are visible on the surface of thearray 101. In Fig.1C, several pumps 102 are activated to cause a displacement from the surfaceof the array 101, forming a ring shape.

[0019] Electroosmotic pumps 102 are a type of electrokinetic pump, meaning they directlygenerate fluid pressure and flow from an applied electric field. The pumps 102 achieve this byacting on charge densities in a fluid contained within the pump 102, which are a result of thespontaneous surface chemistry interactions between the pumping membrane 111 and theworking fluid 112. This charge is pulled through the pumping membrane 111 by an appliedelectric field coming from a voltage on an external set of electrodes 113. The charge viscouslycouples to the rest of the fluid 112, causing bulk flow to occur. One advantage of anelectroosmotic pump 102 is its ability to produce fast, reversible, and pulse-free flows in anexceedingly compact and lightweight form factor, and with applied voltages 20x less than othertypes of electrokinetic pumps.

[0020] Fig. 2A is a diagram showing a plurality of electroosmotic pumps 102 arranged in afingertip array 101. When in use, this array 101 sits beneath the user’s highly sensitivefingertip. These fingerpad arrays 101 can be duplicated (one per finger) into a glove device100. As shown in Fig.2A, the array 101 comprises a silicone membrane 115 forming a contactsurface for the user’s finger, a pump membrane 111, and top and bottom printed circuit boardscontaining a plurality of electrodes 113. Further shown are other components such as spacers116, pressure sensitive adhesives 117, a fluid reservoir 118, and a reservoir cover 119.Optionally, spacers 116 can be a separate material, or it can be integrated into the part of thepumping membrane 111 by filling in the porosity of holes of the membrane 111, effectivelyblocking flow between pixels 102 and providing a solid sealing surface for the adhesives 117and remaining housing. In an integrated configuration, the pumping membrane 111 can befilled by methods such as heat sealing, liquid adhesive filling and curing, high pressurecrushing, or other methods. The pressure sensitive adhesives 117 may also be replaced by otheradhesive systems and methods, such as heat bonding, thermoplastic adhesives, heat staking,fusion bonding, ultrasonic welding, epoxy bonding, or other methods. Fig. 2B is a close-upview of the printed circuit board, with electrodes 113 for each individual electroosmotic pump102 visible. As shown in Fig. 2B, 32 individual pumps 102 are disposed on a single fingertiparray 101, with each pump 102 having a circular shape, in this example embodiment.CMU 2023-229Depending on the expected application, however, a different number of haptic pixels 102 canbe provided on each array 101 and the shape can be a shape other than a circle, that is, thepixels 102 can be an arbitrary shape, only defined by a 2D, flat geometry. Certain shapes andpacking arrangements, such as squares or hexagons, and hex packing arrangements, beingparticularly useful for high packing densities of pixels 102.

[0021] In the example embodiment shown in Fig. 1A, each pad array 101 is 5mm thickcomprising the compliant display output surface (or surface membrane) 115, a laminated pumpmembrane 111, and a fluid reservoir 118. Both the display surface 115 and the fluid reservoir118 can be cast from elastomers, such as skin-safe silicone (Smooth-On Ecoflex 00-30). In oneembodiment, these components 115 / 118 are cast using laser-etched Delrin molds and adheredto the other components of the array 101 using silicone adhesive (Smooth-On Sil-Poxy). Thepump array 101 comprises 32 laser-cut glass fiber filter (GFF) pump membranes 111 set intoholes in a laser-cut polyethylene terephthalate (PET) spacer 116 and sandwiched on both sidesby multilayer printed circuit boards with their electrodes 113 facing the interior of theassembly. Fluid 112 displaced by the pump 102 will displace the contact surface 115 directlyabove the pumping membrane 111, forming a physical deviation in the contact surface 115perceptible by the user.

[0022] Each electrode 113, which matches the size and spacing of each pump 102, or hapticpixel, is 1.6mm in diameter and is spaced with a 2.5mm horizontal pitch and a 2.36mm pitchalong rows at 58° to the horizontal. This configuration yields a haptic pixel density ofapproximately 20 pumps / cm2. Generally, a horizontal distance of less than 3mm, but morethan 0.5mm between the centers of adjacent holes would provide an acceptable pixel densityfor the fingertip, though other densities are more acceptable for other parts of the body, such at1cm to 2cm in the hand and fingers. In general, a variable pixel density can be used whichcoarsely follows the innervation density of mechanoreceptors in the skin.

[0023] The printed circuit boards containing the electrodes 113 can be adhered to the spacerlayer 116 using laser-cut pressure-sensitive adhesive sheets 117 (3M 467MP), and the completepump assembly (i.e. membrane 111, spacer 116, and electrodes 113) is 0.88mm thick. Anultraviolet laser (LPKF U4) can be used to process the spacers 116 and a CO2 laser (ULS VLS4.60) can be used to process the pressure sensitive adhesive 117 and Delrin mold. Each printedcircuit board has a 32-position surface-mount fat flex cable connector 120 (Molex 530480-3200) soldered to its non-electrode side. Polyimide tape (3M 1205) applied across theconnector vias on the electrode-sides of the board provides insulation between the connectors.Before use, propylene carbonate as the working fluid 112 can be injected into the reservoir 118CMU 2023-229using a hypodermic needle and the remaining air is evacuated using the same method. Inaddition to propylene carbonate, other fluids such as ethylene carbonate, isopropyl alcohol,acetone, deionized water, additional cyclic carbonates, acetonitrile, other high purity organicsolvents, formahide, glycerol, any high dielectric strength, low ionic conductivity liquid orcombinations of these liquids can be used as the working fluid 112.

[0024] The pad array 101 can be mounted to the finger using a custom hinged finger clip 130,as shown in Figs. 1B-1C. The clip 130 is used to keep the pad array 101 in reliable contactpressure and position on the finger pad of the user, as this can increase performance. In theembodiment shown in Figs. 1B-1C, the clip 130 comprises a pair of low spring constant rubberbands, or springs 131, (ex. 3 / 16" orthodonic bands) holding the array 101 and an adjacentcontact pad 132 in compression. The pivoting design of the clip 130 also accommodatesfingers of varying thicknesses. Above the fingernail, a small piece of soft silicone is used toimprove comfort and to help maintain position. As shown in Fig. 1C, the clip 130 is designedto be bi-stable, such that it flips and stays open. This allows a user to remove a fingerpad array101 when not in use without removing the glove, which allows them to, for example, type ona keyboard or use a touchscreen. In one embodiment, two sizes of finger clips can be used--one for the four fingers and one for the thumb. In the example embodiment shown in Figs. 1B-1C, a complete clip 130 with pad array 101 weighs 6.2g.

[0025] The drive electronics, or controller 140, is designed to be modular and can expand froma single finger (32 haptic pixels) to a whole hand (160 haptic pixels). The controller 140, inone example embodiment, can be built around a Teensy 4.0 microcontroller and high voltage(300V) 64-channel shift register (Microchip HV507) module boards. Fig. 3 depicts a generallayout of the controller 140 and associated electronics. As shown in Fig. 3, the controller 140may comprise a microcontroller board 141, a high voltage DC / DC converter 142, and a singlehigh voltage serial-to-parallel drive module 143. The drive module 143 may contain the shiftregister. The bottom portion of Fig. 3 shows the controller 140 and associated electronicsassembled with two fingerpad arrays 101 powered by one high voltage drive module 143. Theassociated electronics may also include a wireless communication module and a power source,such as a battery.

[0026] The microcontroller 140 communicates with the high voltage shift registers of the drivemodule 143 via a logic level converter using a low voltage digital serial peripheral interface(SPI) protocol. A total of six HV507 shift registers can be daisy-chained at once (two driversper module board), corresponding to six possible pad arrays 101 being driven by a singlemicrocontroller 140 (1 shift register per pad array). Each haptic pixel requires two output lines,CMU 2023-229one connected to each pump electrode 113. Pumps 102 are off with a configuration of 0V / 0Vor 300V / 300V, and they are driven in opposite directions (inflating or deflating) withconfigurations of 0V / 300V and 300V / 0V.

[0027] Fully loaded, the microcontroller 140 can adjust 384 high voltage output lines, or 192haptic pixels. For use in a glove embodiment of the device 100, however, the controller 140typically drives a single pad array 101 (64 outputs lines / 32 haptic pixels), or five pad arrays101 (320 output lines / 160 haptic pixels). The high voltage shift registers can be supplied powerthrough an off-the-shelf adjustable high voltage capacitor charging DC / DC converter 142 anda 5V-to-300V flyback boost converter for a wireless implementation. As a safety measure, ahigh-side switch, controlled via firmware in the controller 140, can be used to disconnect powerto the device 100 when not in use. The use of high channel count, high voltage shift registers,the development of a modular platform, and the custom 5V-to-300V DC / DC converter 142(with latching and safety monitoring circuitry) permit low-weight, low-cost implementation ofa haptic device 100 compared to prior attempts.

[0028] The firmware translates the bits coming from the application software into an outputstate for the pad arrays 101. Application software may include, but is not limited to, a virtualenvironment running in Unity on a host PC, or a custom Java application running ademonstration and debugging platform. The firmware also initializes and controls variousaspects of the high-voltage system. Updates to the pad arrays 101 are sent from the applicationlayer to the microcontroller 140 using USB serial connection, running at a baud rate of 250,000bits / second. A single command is structured with a pad array address (which finger to update)and a payload of 64 bytes (the data to update). Upon receipt, the firmware immediately updatesthe new pad array status.

[0029] Pad arrays 101 are daisy-chained on a single SPI port, which runs at a clock of 8MHz.Fully loaded, this means an entire hand, 320 outputs, can be updated in 40µs. This firmwarestructure means pad array 101 behavior can be controlled directly at the application level. Acommand structure can be added to send additional device 100 commands (such asenable / disable the PSU), and data addressing can be implemented to route the data bytes to thecorrect pad array 101.

[0030] In the glove embodiment of the device 100 depicted in Fig. 1A, the haptic fingerpadarrays 101 are duplicated to instrument every finger of the user. Comfort and the ease ofdonning and doffing are maximized to minimize any unwanted tactile stimuli. As theassociated electronics are potentially the main source of interference with the naturalCMU 2023-229movement of the hands, their bulk and resistance to motion is reduced. Further, the controller140 and drive electronics are mounted to the wrist of the glove 100, keeping finger mass low.

[0031] In total, the glove device 100, including base glove, drive electronics / controller 140,haptic arrays 140, cables, and an overglove, weighs 147g. Including an off-the-shelf RaspberryPi Zero 2 W for wireless operation and a 4.44Wh battery raises the mass to 207g. Assumingcontinuous presentation of haptic animations (186mW per array) to all fingers, and a measuredsystem overhead power consumption from the Raspberry Pi and Teensy of 1.3W, it is estimatedthat total system battery life is roughly 2 hours for the five-finger wireless glove device 100seen in Fig. 1A.

[0032] The performance characteristics of the device 100 compares favorably to other hapticdevices. For reference, the ‘gold standard’ currently for these types of haptic displays calls for400 pixels at 1mm pitch, which are capable of 1µm to 2mm displacements from 0Hz to 300Hz.One performance characteristic often analyzed is the pressure exerted against the skin of theuser. In order to displace the skin, the array 101 should be able to apply enough hydraulicpressure to overcome the distributed pressing force coming from the finger. This pressure canoften range from 10-30kPa for a light touch needed for contact patch spreading of the fingertip(<1N total applied force). This characteristic can be measured by hydraulically coupling aMEMS absolute pressure sensor to the top of individual pixels (i.e. pumps 102) and recordingthe response due to an applied voltage.

[0033] Results of the pressure evaluation are shown in Fig. 4, which depicts system responseto a triangle wave. Frequency was fixed at 1Hz, and data was collected in 10s increments. Fig.4 shows the current and pressure responses. Currents are generally in the 0.1mA peak range,while peak pressure is nearly 50kPa, above the maximum specified in the above-referencedstandard. The response of the device 100 is overall relatively linear, with both current andpressure retaining the triangle wave shape. Further, the pressure transitions are especially fast.

[0034] Surface deformation is another performance characteristic that has an impact on overallperformance, as skin displacement directly impacts haptic performance. No-load displacementcan be measured to evaluate best case deformation response. Actual displacement in use canbe lower due to loading from the user’s skin. Acceptable displacement for haptic perceptionvaries depending on mechanoreceptor type, frequency, and contact location, but generallydisplacements between 0.1-1.0mm are acceptable for low frequency (<1Hz) perception, whiledeformation in the 1µm range can be felt at high frequency (>100Hz).

[0035] Fig. 5 shows the results of displacement evaluation, where a 0.1Hz square wave of + / -250V was applied to single pixels and corresponding current and pixel displacement (peakCMU 2023-229height) was recorded. As shown in Fig. 5, most pixels underwent rapid inflation, achieving0.3-0.5mm displacement within the first 0.5s. For reference, this is approximately the heightof a standard Braille dot (0.48mm). This initial rapid filling phase corresponds to the pixelapproaching a half-sphere shape, as the radius of the pixels is roughly 0.8mm. After this,deformation rate slows as the stiffness of the pump 102 greatly increases. On average, pixelsreached max displacement of just over 1mm after 3 seconds. This level of deformation issufficient for static indentation tasks, as well as for short-time (<1s) tactile animations.

[0036] While the transient response from square wave inflations can be seen in Fig. 5,evaluation of high-frequency performance can be useful for stimuli such as buzzes and textures,where a human response is most sensitive to 10-300Hz frequencies. Fig. shows displacementrecordings for seven different four-second long sine waveforms: 5, 10, 20, 40, 80, 160, and320Hz. Applied voltage was fixed at + / -250V. As can be seen, displacement decreasessystematically with increasing frequency. Notably, although the range of displacements at highfrequency is small, approaching <10µm peak-to-peak, they are still easily within the range ofhuman tactile perception, as humans are capable of sensing displacements under 2µm peak-to-peak at frequencies over 100 Hz.

[0037] Finally, power consumption can be an important factor when the devices are poweredby batteries or other wireless technologies. Power consumption of one actuator array 101 wasrecorded at 100Hz with the onboard voltage and current monitors under various conditions.The baseline power draw is 61mW at all times. These power characteristics compare favorablyto other haptic technologies and permit wireless operation.

[0038] The haptic device 100 is capable of a wide pallet of effects. Feedback can vary in bothtime and space, as well as interesting combinations of the two. In the following paragraphs, thecapabilities of the device 100 are described through a VR design lens, focusing on the tactileproperties of virtual objects one might want in VR / AR scenes.

[0039] Object Contact and Impression Geometry

[0040] The most basic, yet fundamental haptic effect conveyed to users in VR / AR systems isa sense that they have come into physical contact with a virtual surface or object. The highresolution of the arrays 101 permits the device 100 to convey partial and complex contact. Toimplement this technique, a series of small sphere colliders are arranged in virtual 3D space,being locked to the tracked position of the hand. These positions are automatically updated byhand tracking functionality of the system, and the locations of these colliders can be configured,in Unity or another virtual spatial environment software, to match the real-world geometry ofthe fingerpad haptic array 101. Hand tracking, which may be provided in the virtualCMU 2023-229environment, can be accomplished using optical or electromagnetic sensors. For example, anelectromagnetic sensor could include . Colliders are software objects that emulate physicalcontact. This is instantiated in Unity by a custom Unity prefab which is attached to any fingeraugmented with haptics (i.e., all five fingers in the glove implementation of the device 100).However this contact collider can be computed by the virtual environment by looking at theouter bounds of a virtual sphere and checking all other nearby virtual objects (via Euclideandistance) to see if the boundaries geometrically overlap. When users reach out to interact witha virtual object, the colliders are triggered based on the VR contact geometry.

[0041] In the main loop of the Unity-based software, the device 100 checks the collision statusof all haptic pixels or pumps 102. On geometry such as the edge or corner of a box, only asubset of sphere colliders are in contact and therefore triggered, creating the haptic impressionof an edge or point, as shown in Fig.7. The objects (top row) and the corresponding array 101configuration (bottom row) depicted in Fig. 7 include, from left to right, smooth marble, arough and irregular rock, a rigid bottle, and a bumpy basketball. The state of all haptic pixels102 is streamed over USB (60 FPS) or wirelessly to the device hardware, ensuring that userscan translate their fingers over virtual geometry to explore features in real time.

[0042] This contact-based cutaneous feedback can also create the sensation of grip of a virtualobject. Here, the device 100 can use the Oculus hand tracking SDK to trigger a grasp of theobject paired with the same collision logic as before, checking each haptic pixel 102 for contactwith the virtual object, and conveying overlaps to the fingertip haptic arrays 101.

[0043] Static Contact Texture

[0044] A slight variant of object contact can be implemented to enable a new expressivedimension of contact texture. Instead of activating all pixels 102 that have collided with avirtual object, the device 100 applies additional logic to activate only a subset of haptic pixels102 according to a predefined pattern that is stored as metadata for virtual objects. Fig.7 offersan example of a user gripping four objects with different contact textures, ranging from smooth,to rough, to ridged, to bumpy.

[0045] Spatial Textures

[0046] Imbuing virtual objects with spatially-varying textures adds a high degree ofexpressivity, which can be used to unlock truly immersive tactile AR / VR experiences. Twomethods can be run on the device 100 for implementing textures. The first method usespredefined mathematical functions to generate haptic patterns correlated to functionparameters. For instance, to create a ridged texture like corrugated metal, the device 100 canuse a sine function with the appropriate coefficient that varies in response to a user’s lateralCMU 2023-229motions. Other arbitrary mathematical functions can also be used. The device 100 can similarlycreate irregular, high-frequency textures like sandpaper using random or Perlin noise functions.

[0047] The second method uses absolute spatial mapping, which can be more versatile andeasier to design. In this second method, the device 100 attaches not only visual textures toobjects in the virtual environment, but also invisible haptic texture layers based on the visuals.The transformation function is straightforward--when in collision with the textured surface,every contacting haptic pixel 102 uses the object’s haptic texture like a lookup table. Somehaptic texture pixels correlate to the contacting haptic pixel being on, while other haptic pixelsare off. This happens at 60 FPS, meaning that as a user’s hand translates across an object’ssurface, the textural haptic effect properly translates and scales with velocity. Note, this limitstemporal texture information to 30Hz due to Nyquist, however this more than enoughbandwidth for the textures.

[0048] Haptic Animations

[0049] The arrays 101 of the device 100 not only have high spatial resolution, but also offerhigh frequency response. The high frequency response can be utilized to play haptic"animations" on the finger arrays 101, which is particularly useful in creating object-bound andenvironmental effects. For example, haptic animations can include fan wind (directionalswiping animations), water drops (haptically actuating a quickly expanding sphere), andelectrical sparks (using random high-frequency pixel actuation). There are also certain classesof objects that generate haptic effects on a statically held finger, such as touching a finger to arunning motor (synchronized 10Hz oscillation rendered on all contacting haptic pixels.

[0050] Object Compliance

[0051] The device 100 can imbue virtual objects with varying levels of compliance, adding tothe canvas of effects that can be applied to create rich virtual worlds. For this, the device 100varies contact area in response to compression. Put simply, the more a user compresses a virtualobject, the more haptic pixels 102 that are activated, radiating outward from the point ofcontact, increasing pressure integrated on the fingertips. The actuation is spatially mapped tohow far the user’s finger is pressed into the virtual object, so compliance properly scales withvelocity, like in spatial textures. Fig. 8 provides an illustrative example of this progression.For softer compliance, such as the virtual spring in Fig. 8, more haptic pixels 102 are graduallyactuated as the user’s fingers descend into the material. The rate of change affects theperception of compliance.

[0052] UI Widget HapticsCMU 2023-229

[0053] Finally, a specialized but high-value haptic effect is that of "clicks"--transient impulsesand other event-driven effects that add realism and useful confirmatory feedback to userinterface widgets. Two "click" examples include a brief full-array 200ms impulse when abutton passes a depression threshold (e.g. 5mm) and a scroll / slide bar can offer "detents" whenpassing specific values or elements. The “detents” effect is shown in Fig. 9, where brief (e.g.200ms) impulses are activated for each detent. Thus, when a user slides their finger a distancefrom the slider origin, the impulse will activate to simulate each detent. As another example,the device 100 can provide buttons with a buckling-spring effect. More specifically thesebuttons exhibit some compliance (see previous section), allowing the finger to depress thebutton approximately 1cm before the spring buckles and the button surface snaps down, turningoff the haptic array and removing any finger pressure.

[0054] When used in this specification and claims, the terms "comprises" and "comprising"and variations thereof mean that the specified features, steps, or integers are included. Theterms are not to be interpreted to exclude the presence of other features, steps or components.

[0055] The invention may also broadly consist in the parts, elements, steps, examples and / orfeatures referred to or indicated in the specification individually or collectively in any and allcombinations of two or more said parts, elements, steps, examples and / or features. Inparticular, one or more features in any of the embodiments described herein may be combinedwith one or more features from any other embodiment(s) described herein.

[0056] Protection may be sought for any features disclosed in any one or more publisheddocuments referenced herein in combination with the present disclosure. Although certainexample embodiments of the invention have been described, the scope of the appended claimsis not intended to be limited solely to these embodiments. The claims are to be construedliterally, purposively, and / or to encompass equivalents.

Claims

CMU 2023-229CLAIMSWhat is claimed is:

1. A haptic device comprising:a array comprising:a plurality of electroosmotic pumps,a working fluid contained within the plurality of electroosmotic pumps, anda flexible membrane capping the plurality of electroosmotic pumps andcontacting a portion of the working fluid, wherein the flexiblemembrane has an outer surface adapted to abut skin of a user; anda controller electrically connected to the plurality of electroosmotic pumps, whereinactivation generates an increase in a pressure of the working fluid to causedistention of the flexible membrane associated with an activated electroosmoticpump of the plurality of electroosmotic pumps.

2. The device of claim 1, wherein the working fluid is contained only within the array.

3. The device of claim 1, wherein the controller is electrically connected to the plurality ofelectroosmotic pumps through a flexible wiring network.

4. The device of claim 1, wherein the array further comprises a reservoir in fluidcommunication with each electroosmotic pump of the plurality of electroosmotic pumps.

5. The device of claim 1, wherein the plurality of electroosmotic pumps comprises:a pumping membrane defining a grouping of holes arranged in a pattern;an individual electrode associated with each hole in the grouping of holes, wherein eachindividual electrode is in electrical communication with the controller.

6. The device of claim 5, wherein the grouping of electrodes are disposed on a printed circuitboard.

7. The device of claim 5, wherein the grouping of holes has a distance between a center ofadjacent holes of less than 3mm.CMU 2023-2298. The device of claim 1, wherein a density of the grouping of holes is varied for use on differentbody parts of the user.

9. The device of claim 1, further comprising:a clip holding the array and a contact pad adapted to press against a user’s fingernail,wherein the array and the contact pad are held in compression against a user’sfinger via a spring.

10. The device of claim 9, wherein the spring comprises a low spring constant rubber bandconnected at a first end to the array and a second end to the contact pad, wherein the clip furthercomprises a pivotable hinge adapted to stably occupy an open or a closed position.

11. The device of claim 1, wherein the controller comprises:a controller board,a high voltage DC / DC converter, anda high voltage drive module.

12. The device of claim 11, wherein the controller comprises:a communication link to a virtual environment, wherein the virtual environmentincludes object tracking and hand tracking.

13. The device of claim 12, wherein the hand tracking is provided by optical or electromechanicsensing.

14. The device of claim 12, wherein the communication link is wireless.

15. The device of claim 11, wherein the high voltage DC / DC converter includes a latchingswitch is adapted to disconnect power to the array upon command from the controller.

16. The device of claim 1, wherein each electroosmotic pump is capable of displacing theflexible membrane in a range of 1µm to 2mm17. The device of claim 1, wherein each electroosmotic pump is capable of activating anddeactivating in response to a signal from the controller at a frequency of 0Hz to 300Hz.CMU 2023-22918. The device of claim 1, wherein each electroosmotic pump is capable of pressuring theworking fluid to at least 10 kPa.

19. A method of controlling a haptic device having a plurality of haptic pixels arranged in anarray, the method comprising:activating one or more of the plurality of haptic pixels in the array, wherein eachactivated haptic pixel corresponds to a contact point with a virtual object.

20. The method of claim 19, wherein the one or more activated haptic pixels corresponds to apre-defined pattern associated with a static contact texture.

21. The method of claim 19, wherein the one or more activated haptic pixels is changed over aperiod of time to form a haptic pattern.

22. The method of claim 21, wherein the haptic pattern comprises a mathematical function thatvaries in response to a user’s lateral motion.

23. The method of claim 21, wherein the haptic pattern comprises a series of textures correlatedto a lookup table associated with a texture.

24. The method of claim 19, wherein the one or more activated haptic pixels is changed at afrequency.

25. The method of claim 19, wherein the one or more activated haptic pixels increases ordecreases over a time period to simulate a changing contact area with a virtual object.

26. The method of claim 19, wherein the one or more activated haptic pixels increases ordecreases over a time period to simulate a changing level of grip on a virtual object.

22. The method of claim 19, wherein the one or more activated haptic pixels is cycled to aninactivated state in pulses ranging up to 200 ms.

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