Optical transformer

An optical transformer includes a light source and an array of photovoltaic cells optically coupled to the light source, where at least a portion of the photovoltaic cells are connected in series. An optical connector such as a waveguide or an optical fiber may be disposed between an output of the light source and an input of the array of photovoltaic cells. Configured to generate a high voltage output, the optical transformer may be configured to power a device such as an actuator that provides a tunable displacement as a function of voltage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG.1is a schematic illustration of an example optical transformer according to various embodiments.

FIG.2shows a vertical cavity surface emitting laser array operable as a light source for an optical transformer in accordance with some embodiments.

FIG.3shows a vertical cavity surface emitting laser array having individual emitters in direct contact with a bottom absorbing photovoltaic cell array according to some embodiments.

FIG.4shows a bottom emitting light source having a single emitter in contact with a bottom absorbing photovoltaic cell array according to certain embodiments.

FIG.5is a perspective illustration of an example two-dimensional optical connector according to some embodiments.

FIG.6is a diagram showing an array of photovoltaic cells arranged in series according to some embodiments.

FIG.7is a diagram showing an array of photovoltaic cells arranged in series and having a tapered profile according to some embodiments.

FIG.8is a cross-sectional schematic view of a photovoltaic cell architecture showing the connection between neighboring cells according to some embodiments.

FIG.9illustrates an addressable emitter array and the selective illumination of a photovoltaic cell array according to various embodiments.

FIG.10shows an example actuator integrated with an optical transformer in accordance with certain embodiments.

FIG.11depicts an actuator system coupled with a source of electromagnetic radiation according to some embodiments.

FIG.12is an illustration of an exemplary artificial-reality headband that may be used in connection with embodiments of this disclosure.

FIG.13is an illustration of exemplary augmented-reality glasses that may be used in connection with embodiments of this disclosure.

FIG.15is an illustration of exemplary haptic devices that may be used in connection with embodiments of this disclosure.

FIG.16is an illustration of an exemplary virtual-reality environment according to embodiments of this disclosure.

FIG.17is an illustration of an exemplary augmented-reality environment according to embodiments of this disclosure.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

High voltages may be used to power a variety of different devices and systems, including high voltage relays, cathode ray tubes, e.g., to generate x-rays and particle beams, and piezoelectric actuators, e.g., to manipulate the focal length of variable focal length lenses. In this regard, a voltage transformer may be employed to increase voltage output where the generated voltage of a device or system is otherwise insufficient. Many voltage transformers, including step-up converters (booster converters) and piezo-transformers, for example, may be configured to convert relatively low DC input voltages (˜1V-2V) to output voltages greater than 1 kV. However, the design of many such voltage transformers, including the requisite inductors and capacitors, may unduly increase the size of the device (e.g., to 1 cm3and greater), which may be excessive for many applications, including wearable devices. Thus, notwithstanding recent developments, it would be advantageous to provide an economical high voltage source having a compact footprint.

The present disclosure is generally directed to voltage transformers, and more specifically to optical transformers that include an integrated array of monolithic photovoltaic cells connected in series. In certain embodiments, micrometer-scale photovoltaic cells may be arrayed to form an optical transformer having commercially-relevant dimensions. For example, in combination with a light source powered by a DC voltage source, an optical transformer (DC to DC converter) may exhibit a footprint of less than approximately 5 mm3. Example optical transformers may be configured to provide scalable output, i.e., open-circuit voltages from approximately 1V to greater than approximately 1 kV, e.g., 1, 2, 5, 10, 20, 50, 100, 200, 500, or 1000 V or more, including ranges between any of the foregoing values.

In certain embodiments, an optical transformer may include a light source and an array of photovoltaic cells optically coupled to the light source, where at least a portion of the photovoltaic cells are connected in series.

By way of example, the light source may include a surface-emitting device, e.g., a top- or bottom-emitting device such as a vertical cavity surface emitting laser (VCSEL), a vertical external cavity surface emitting laser (VECSEL), or a light-emitting diode (LED) such as an organic light emitting diode (OLED) or a resonant cavity light emitting diode (RCLED). In some embodiments, the light source may include an edge-emitting device, e.g., a laser diode or a superluminescent diode (SLED). In certain embodiments, the light source may include a single emitter or a plurality of emitters in an addressable array.

By way of example, a light source including a laser diode or a light emitting diode may include an indirect bandgap semiconductor or a direct bandgap semiconductor, such as Si, GaAs, InGaAs, AlGaAs, GaN, InGaN, AlGaN, GaP, GaAsP, AlGaInP, and the like. In some embodiments, the light source may include one or more optical elements configured to enhance light extraction and focusing efficiency, such as one or more micro lenses, total internal reflection (TIR) concentrators and/or total internal reflection-refraction (TIR-R) concentrators.

According to certain embodiments, the optical power generation of the light source and hence the output voltage of the optical transformer may be controlled by voltage or current modulation. Such modulation may be analog (e.g., current amplitude modulation) or digital (e.g., pulse width modulation). A PID control circuit may be used to control the modulation and stabilize the output voltage.

The light source may be configured to illuminate one or more photovoltaic cells within a photovoltaic cell array. Example photovoltaic cells may use a p-n junction (or p-i-n-junction) within a semiconductor to obtain a current from photons absorbed near the junction. As a direct bandgap material, gallium arsenide (GaAs) is highly absorbing to photons having an energy greater than its bandgap (Eg). Further example direct bandgap semiconductors include InGaAs, AlGaAs, GaN, InGaN, AlGaN, GaP, GaAsP, AlGaInP, and the like. In alternate embodiments, the photovoltaic cells may be manufactured from an indirect bandgap semiconductor such as silicon (Si). For instance, an example monolithic integrated micro photovoltaic cell array may include silicon, where the p-n junctions (or p-i-n junctions) may be formed by lateral doping profiles.

An alternate approach to the development of a photovoltaic cell array is through the use of metal-semiconductor Schottky barriers to replace the semiconductor-semiconductor p-n junctions. Schottky barriers may be adaptable to economical, versatile manufacturing techniques and are suitable for polycrystalline-based devices. Additionally, since the collecting junction is located at the surface of the device, the collection efficiency through decreased surface recombination may be improved relative to a p-n junction. According to still further embodiments, the photovoltaic cells may include quantum dots or a quantum well. As will be appreciated, the bandgap of a quantum dot may be adjusted through a wide range of energy levels by changing the size of the dot.

As disclosed herein, plural photovoltaic cells within an array may be at least partially connected in series. In some embodiments, groups of cells may be connected in parallel to control (e.g., increase) the output current. That is, a photovoltaic cell array may include sub-arrays respectively configured in series and in parallel. Moreover, according to some embodiments, individual photovoltaic cells may be illuminated selectively to control the output voltage of the optical transformer. In certain embodiments, to improve the light absorption efficiency, the light source may have an emission spectrum selected to overlap the absorption profile of the photovoltaic cells.

The photovoltaic cell array may further include one or more bypass diodes, which may be connected in parallel to an individual cell or groups of cells to enable current flow through (around) unilluminated or damaged cells. Such bypass diodes may be integrated during wafer-level processing of the photodiodes or connected to the array as discrete elements.

In some embodiments, individual photovoltaic cells may include a compound semiconductor and may be formed en masse during wafer-level processing. Alternatively, individual photovoltaic cells may be formed separately and then transferred (e.g., by pick-and-place or wafer bonding) to a carrier substrate.

In some embodiments, the light source and the photovoltaic cell array may be in direct contact. In some embodiments, an optical connector may be disposed between the light source and the photovoltaic cell array to guide emitted light from the light source to the photovoltaic cells within the array. An optical connector may include any material suitable for guiding light, including glass, polymer, and/or semiconductor compositions. The optical connector may include crystalline or amorphous materials, for example. In some embodiments, the optical connector may include a gas or a liquid. The optical connector may be electrically insulating. To inhibit reflective losses, in certain embodiments, the optical connector may be characterized by a refractive index of at least 1.5.

In some embodiments, the light source may include N emitters and the photovoltaic cell array may include N corresponding photovoltaic cells. In further embodiments, the number of emitters may exceed the number of photovoltaic cells. In still further embodiments, the number of photovoltaic cells may exceed the number of emitters. The optical connector may further include a micro lens array or other elements configured to focus emitted light onto individual photovoltaic cells, e.g., onto a center of respective photovoltaic cells.

The following will provide, with reference toFIGS.1-17, detailed descriptions of optical transformers, i.e., optically-driven voltage converters, as well as devices and systems using such optical transformers. The discussion associated withFIG.1includes a description of an example optical transformer. The discussion associated withFIGS.2-5includes a description of various components of an optical transformer. The discussion associated withFIGS.6and7includes a description of example configurations of a photovoltaic cell array. The discussion associated withFIG.8includes a description of an example photovoltaic cell architecture. The discussion associated withFIG.9includes a description of an addressable light source and a corresponding photovoltaic cell array. The discussion associated withFIGS.10and11includes a description of example high voltage devices. The discussion associated withFIGS.12-17relates to exemplary virtual reality and augmented reality device architectures that may include an optical transformer as disclosed herein.

Referring toFIG.1, shown is a perspective view of an example optical transformer. Optical transformer100may include a light emitter110, a photovoltaic cell array120facing the light emitter110, and an optical connector130disposed between the light emitter110and the photovoltaic cell array120. In certain embodiments, the optical transformer100may further include a cooling element (not shown), such as an active cooling element or a passive cooling element adapted to control the temperature during use of one or more of the light emitter110and the photovoltaic cell array120.

Light emitter110may include an array of individual emitters114and may be powered with a voltage source140. In certain embodiments, light emitter110may include a laser or a light-emitting diode. Example lasers may include a vertical cavity surface emitting laser (VCSEL) or a vertical external cavity surface emitting laser (VECSEL). A light-emitting diode (LED) may include an organic light emitting diode (OLED) or a resonant cavity light emitting diode (RCLED).

An OLED device, for instance, may include, from bottom to top, a glass substrate, a conducting anode such as indium tin oxide (ITO), a stack of organic layers, and a cathode layer. In certain examples, the device may include a transparent anode and a reflective cathode layer such that light generated by the device may be emitted through the substrate, i.e., a bottom-emitting device. In further examples, the OLED device may include a reflective anode and a transparent cathode such that light generated by the device may be emitted through the top transparent electrode, i.e., a top-emitting device.

Light emitter110may be configured to emit photons that may be guided through the optical connector130to the photovoltaic cell array120. The optical connector130may include a waveguide, for example, such as a planar waveguide. In certain embodiments, the optical connector130may include a dimmer unit, which may be adapted to tune the output voltage of the optical transformer, e.g., to finer increments.

Photovoltaic cell array120may include a plurality of individual photovoltaic elements124, at least a portion of which may be interconnected in series. Example photovoltaic cell arrays may include at least approximately 25 photovoltaic cells, e.g., 25, 50, 75, 100, or 200 or more photovoltaic cells, including ranges between any of the foregoing values. As will be appreciated, by arranging at least a portion of the photovoltaic cells124in series, the output voltage150of the array120may be greater than the open circuit voltage of an individual element124. For instance, the open circuit voltage of an array of N photovoltaic elements may be approximately N times the open circuit voltage of an individual photovoltaic element within the array. As used herein, the term “open circuit voltage” may, in some examples, refer to the electrical potential difference between two terminals of a device when disconnected from any circuit, i.e., the voltage in the absence of an external load.

In the illustrated embodiment, the light emitter110and the photovoltaic cell array120each present a planar geometry. According to further embodiments, either or both of the light emitter110and the photovoltaic cell array120may include a non-planar surface, such as a convex surface or a concave surface.

According to some embodiments, as disclosed herein, the light emitter110may include a laser. Referring toFIG.2, an example light emitter may include a vertical-cavity surface-emitting laser (VCSEL) array210. The VCSEL array210may include a square array of individual emitters214that may be connected in parallel or, according to some embodiments, addressed individually. In embodiments where the light emitter110includes a laser, the optical transformer may further include an optical insulator unit (not shown) to suppress instabilities associated with the laser.

According to further embodiments, an example bottom-emitting light source is shown inFIG.3. Light source (e.g., VCSEL array)310, which includes a plurality of individual emitters314, may be in direct contact with a bottom-absorbing photovoltaic cell array320. In certain embodiments, as illustrated, a transparent adhesive layer335may be disposed between the light source310and the photovoltaic cell array320. Transparent adhesive layer335may be configured to mitigate reflective losses between the light source310and the photovoltaic cell array320.

A further example light source is shown inFIG.4. In the example embodiment ofFIG.4, bottom-emitting light source (e.g., LED)410may include a single emitter414and may be bonded to a bottom-absorbing photovoltaic cell array420via a transparent adhesive layer435. In alternate embodiments, the transparent adhesive layer435may be omitted such that the light source410may be in direct contact with the photovoltaic cell array420.

Referring toFIG.5, shown is an optical connector according to some embodiments. As in the illustrated embodiment, optical connector530may include a substantially planar structure. Optical connector530, e.g., planar waveguide, may include an optically-transparent material such as silicon dioxide, silicon nitride, silicon oxynitride, or titanium dioxide, for example. Sidewalls535of the optical connector530may be polished and/or coated, e.g., with a metallization layer (not shown), to increase the refractive index contrast between the optical connector and the surrounding environment. Optical connector530(such as optical connector130) may be located between the output of a light source (e.g., light emitter110) and the input of a photovoltaic cell array (e.g., photovoltaic cell array120) and may be configured to efficiently transmit light from the light source to the photovoltaic cell array.

As noted above with reference toFIG.1, a photovoltaic cell array may include multiple photovoltaic elements that are electrically connected in series. Referring toFIG.6, illustrated schematically is an example photovoltaic cell array620having plural such photovoltaic elements624. In the illustrated embodiment, photovoltaic cell array620may include plural rows of interconnected photovoltaic elements624.

Referring toFIG.7, illustrated is a further example photovoltaic cell array720. Photovoltaic cell array720may include plural photovoltaic elements724arranged in non-parallel rows, i.e., rows having a tapered configuration, where a distance (d) between corresponding elements in adjacent rows may be variable. For instance, the intercell distance (d) may increase (or decrease) monotonically along or across a row. According to some embodiments, such a tapered configuration may be used to inhibit leakage or electric breakdown by defining the intercell distance (d) as a function of the intercell voltage. That is, the distance between cells having a greater intercell potential may be increased relative to the distance between cells having a lesser intercell potential, which may improve device lifetime and/or performance.

Referring toFIG.8, shown is a cross-sectional schematic diagram of a photovoltaic cell array highlighting the region between neighboring cells. The illustrated photovoltaic cell array820includes a first photovoltaic cell824aand an adjacent second photovoltaic cell824b. The structure includes, from bottom to top, a semiconductor substrate862, an n-type semiconductor layer864, a p-type semiconductor layer866, and a highly-doped p-type semiconductor contact layer868. A p-n junction870may be formed at the interface between the n-type semiconductor layer864and the p-type semiconductor layer866.

The semiconductor substrate862may include GaAs, for example, and the overlying semiconductor layers864,866, and868may include suitably doped homoepitaxial layers, i.e., doped GaAs. In accordance with some embodiments, Applicants have shown that GaAs-based photovoltaic cells may have an open circuit voltage of approximately 1V, whereas larger open circuit voltages may be achieved by using wider bandgap material systems, such as AlGaAs or GaN. According to further embodiments, the photovoltaic cells may include an indirect bandgap semiconductor such as silicon.

Each individual photovoltaic cell824a,824bmay be formed using conventional photolithography techniques by etching a via870through the contact layer868and the p-type semiconductor layer866to expose a top surface of the n-type semiconductor layer864within one region of the via870and a top surface of the substrate862within a second region of the via870. A passivation layer880may be formed within the first and second regions of the via870, i.e., directly overlying the n-type semiconductor layer864and the substrate862, respectively. As will be appreciated, the passivation layer880may enable an intercell connection in series without undo parallel leakage current.

A metallization (conductive) layer890may be deposited over substrate862, including within via870. In particular embodiments, metallization layer890may be formed directly over the n-type semiconductor layer864of first photovoltaic cell824aand extend over a portion of the passivation layer880to contact an upper surface of the contact layer868of second photovoltaic cell824b. Metallization layer890may form an ohmic contact with an upper surface of the highly-doped p-type contact layer868.

Photovoltaic cells824a,824b, etc. may have an individual cell size (e.g., length and/or width) (w) and may be arrayed at a constant or variable pitch (I). The cell size (w) and the pitch (I) may independently range from approximately 10 micrometers to approximately 250 micrometers, e.g., 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, 150, 200, or 250 micrometers, including ranges between any of the foregoing values.

According to some embodiments, individual emitters within an emitter array may be independently addressable and configured to illuminate a subset of the photovoltaic elements within a photovoltaic cell array. Referring toFIG.9, for example, light emitter910may include a plurality of individual emitters that can be switched on (e.g., emitter914a) or off (e.g., emitter914b) to selectively illuminate photovoltaic cells924a,924b, respectively, within photovoltaic cell array920. Light emitter910may include an addressable array of VCSELs or LEDs, for example. The individual emitters, e.g., emitter914aand emitter914b, may be configured to emit light simultaneously, sequentially, or in combinations thereof. Moreover, one or a plurality of different voltage and/or current levels may be set to control the intensity of the high voltage output. According to some embodiments, multiple contact taps may be used to select different voltage output levels.

According to certain embodiments, photovoltaic cell array920may further include bypass diodes928, which may be connected in parallel to individual cells or groups of cells to enable current flow around damaged cells or non-illuminated cells (e.g., photovoltaic cell924b). Furthermore, a light emitter and/or photovoltaic cell array may include redundant features or elements configured to accommodate failure of one or more components. A smart drive scheme, for instance, may re-route power around damaged pixels or cells.

The optical transformers disclosed herein may be incorporated into a variety of devices and systems. An example device may include an actuator, such as a piezoelectric actuator or an electroactive actuator. Turning toFIG.10, for example, shown is an optical transformer integrated with a bender beam actuator. Optical transformer1000may include a light emitter1010, a photovoltaic cell array1020facing the light emitter1010, and an optical connector1030disposed between the light emitter1010and the photovoltaic cell array1020.

Light emitter1010may include an array of individual emitters (not shown) and may be powered with a voltage source1040. As disclosed herein, light emitter1010may include a laser or a light-emitting diode. Photovoltaic cell array1020may include a plurality of photovoltaic cells1024. At least a portion of the photovoltaic cells1024may be electrically connected in series. Optical transformer1000may further include a high voltage output1050.

Optical transformer1000may be mounted directly on actuator1090, which may include an electroactive layer1092disposed between a primary (overlying) electrode1096and a secondary (underlying) electrode (not shown). In certain embodiments, optical transformer1000may be mounted directly on the electroactive layer1092, which may advantageously obviate the need for high voltage wiring and enable the realization of a compact architecture. The electroactive layer1092may include a ceramic or other dielectric material, for example, and the electrodes may each include one or more layers of any suitable conductive material(s), such as transparent conductive oxides (e.g., TCOs such as ITO), graphene, etc. High voltage output1050may be connected to primary electrode1096, for example.

Thus, according to some embodiments, an actuation system may include (i) an optical transformer having a light source and a serial array of photovoltaic cells optically coupled to the light source, and (ii) an actuator having a primary electrode, a secondary electrode overlapping at least a portion of the primary electrode, and an electroactive layer disposed between and abutting the primary electrode and the secondary electrode, where the primary electrode is electrically connected to an output of the optical transformer.

According to certain embodiments, actuator1090may include a unimorph or a bimorph construction. A “unimorph” construction may, in some examples, refer to a device having a single electroactive layer sandwiched between paired electrodes. A “bimorph” construction may, in some examples, refer to a device including two electroactive layers each sandwiched between opposing electrodes. According to certain embodiments, actuator1090may have a length and a width that independently vary from approximately 5 mm to approximately 50 mm, e.g., 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 mm, including ranges between any of the foregoing values.

As used herein, “electroactive layer” or “electroactive ceramic” may, in some examples, refer to materials that exhibit a change in size or shape when stimulated by an electric field. In the presence of an electrostatic field (E-field), an electroactive material may deform (e.g., compress, elongate, bend, etc.) according to the magnitude and direction of the applied field. Generation of such a field may be accomplished by placing the electroactive material between two electrodes, i.e., a primary electrode and a secondary electrode, each of which is at a different potential. As the potential difference (i.e., voltage difference) between the electrodes is increased (e.g., from zero potential) the amount of deformation may also increase, principally along electric field lines. This deformation may achieve saturation when a certain electrostatic field strength has been reached. With no electrostatic field, the electroactive material may be in its relaxed state undergoing no induced deformation, or stated equivalently, no induced strain, either internal or external.

Example electroactive ceramics may include one or more electroactive, piezoelectric, antiferroelectric, relaxor, or ferroelectric ceramics, such as perovskite ceramics, including lead titanate, lead zirconate, lead zirconate titanate (PZT), lead magnesium niobate, lead zinc niobate, lead indium niobate, lead magnesium tantalate, lead magnesium niobate-lead titanate (PMT-PT), lead zinc niobate-lead titanate (PZN-PT), lead indium tantalate, barium titanate, lithium niobate, potassium niobate, sodium potassium niobate, bismuth sodium titanate, and bismuth ferrite, as well as solid solutions or mixtures thereof. Example non-perovskite piezoelectric ceramics include quartz and gallium nitride. According to some embodiments, an electroactive ceramic may be doped with one or more dopants selected from calcium, lanthanum, europium, neodymium, scandium, and erbium. According to some embodiments, an electroactive material may include a dielectric material. Example dielectric compositions may have a composite (i.e., multi-phase) architecture that may include a liquid or gaseous material dispersed throughout a solid matrix.

In certain embodiments, the electroactive ceramics disclosed herein may be perovskite ceramics and may be substantially free of secondary phases, i.e., may contain less than approximately 2% by volume of any secondary phase, including porosity, e.g., less than 2%, less than 1%, less than 0.5%, less than 0.2%, or less than 0.1%, including ranges between any of the foregoing values. Further example secondary phases may include pyrochlores, which may adversely impact the material's piezoelectric response. In certain embodiments, the disclosed electroactive ceramics may be birefringent, which may be attributable to the material including plural distinct domains or regions of varying polarization having different refractive indices, such that the refractive index experienced by light passing through the material may be a function of the propagation direction of the light as well as its polarization.

Ceramic electroactive materials, such as single crystal piezoelectric materials, may be formed, for example, using hydrothermal processing or by a Czochralski method to produce an oriented ingot, which may be cut along a specified crystal plane to produce wafers having a desired crystalline orientation. Further methods for forming single crystals include float zone, Bridgman, Stockbarger, chemical vapor deposition, physical vapor transport, solvothermal techniques, etc. A wafer may be thinned, e.g., via lapping or grinding, and/or polished, and transparent electrodes may be formed directly on the wafer, e.g., using chemical vapor deposition or a physical vapor deposition process such as sputtering or evaporation.

In addition to the foregoing, polycrystalline piezoelectric materials may be formed, e.g., by powder processing. Densely-packed networks of high purity, ultrafine polycrystalline particles can be highly transparent and may be more mechanically robust in thin layers than their single crystal counterparts. For instance, optical grade lanthanum-doped lead zirconate titanate (PLZT) having >99.9% purity may be formed using sub-micron (e.g., <2 μm) particles. In this regard, substitution via doping of Pb2+at A and B-site vacancies with La2+and/or Ba2+may be used to increase the transparency of perovskite ceramics such as PZN-PT, PZT and PMN-PT.

According to some embodiments, ultrafine particle precursors can be fabricated via wet chemical methods, such as chemical co-precipitation, sol-gel and gel combustion. Green bodies may be formed using tape casting, slip casting, or gel casting. High pressure and high temperature sintering using techniques such as hot pressing, high pressure (HP) and hot isostatic pressure, spark plasma sintering, and microwave sintering, for example, may be used to improve the ceramic particle packing density. Thinning via lapping, grinding and/or polishing may be used to decrease surface roughness to achieve thin, highly optically transparent layers that are suitable for high displacement actuation. As measured by atomic force microscopy (AFM) or interferometry, an electroactive ceramic may have an RMS surface roughness of less than approximately 5 nm, e.g., approximately 1, 2, or 5 nm, including ranges between any of the foregoing values.

The electroactive ceramic may be poled to achieve a desired dipole alignment. As used herein, “poling” to form a “poled” material may, in some examples, refer to a process whereby an electric field is applied to an electroactive ceramic. The effect of poling may include an alignment of the various domains within the material to produce a net polarization in the direction of the applied field.

Ceramics having a preferred crystallographic orientation (i.e., texture) may be formed by various methods, including electrophoresis, slip casting, electric field alignment, magnetic field alignment, high pressure sintering, uniaxial pressing, temperature gradients, spark plasma sintering, directional solidification, templated grain growth, rolling, and shear alignment.

In some embodiments, an actuator may include paired electrodes, which allow the creation of the electrostatic field that forces constriction of the electroactive layer. In some embodiments, an “electrode,” as used herein, may refer to an electrically conductive material, which may be in the form of a thin film or a layer. Electrodes may include relatively thin, electrically conductive metals or metal alloys and may be of a non-compliant or compliant nature.

In some embodiments, the electrode or electrode layer may be self-healing, such that damage from local shorting of a circuit can be isolated. Suitable self-healing electrodes may include thin films of materials which deform or oxidize irreversibly upon Joule heating, such as, for example, aluminum.

In some embodiments, a primary electrode may overlap (e.g., overlap in a parallel direction) at least a portion of a secondary electrode. The primary and secondary electrodes may be generally parallel and spaced apart and separated by a layer of electroactive material.

In some embodiments, the electrodes described herein (e.g., the primary electrode, the secondary electrode, or any other electrode including any common electrode) may be fabricated using any suitable process. For example, the electrodes may be fabricated using physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), evaporation, spray-coating, spin-coating, dip-coating, screen printing, Gravure printing, ink jet printing, aerosol jet printing, doctor blading, and the like. In further aspects, the electrodes may be manufactured using a thermal evaporator, a sputtering system, stamping, and the like.

In some embodiments, a layer of electroactive material may be deposited directly on to an electrode. In some embodiments, an electrode layer may be deposited directly on to the electroactive material. In some embodiments, electrodes may be prefabricated and attached to an electroactive material. In some embodiments, an electrode may be deposited on a substrate, for example a glass substrate or flexible polymer film. In some embodiments, the electroactive material layer may directly abut an electrode. In some embodiments, there may be an insulating layer, such as a dielectric layer, between a layer of electroactive material and an electrode.

The electrodes may be used to affect large scale deformation, i.e., via full-area coverage, or the electrodes may be patterned to provide spatially localized stress/strain profiles. In particular embodiments, a deformable optical element and an electroactive layer may be co-integrated whereby the deformable optic may itself be actuatable. In addition, various methods of forming optical elements are disclosed, including solution-based and solid-state deposition techniques.

A further example high voltage system is shown schematically inFIG.11, which includes an optical transformer integrated with a bimorph actuator. Optical transformer1100may include a light source1110optically coupled to a plurality of photovoltaic elements1124via optical connector1130. Optical connector1130may be an optical fiber and may include a tapered input1130a, fiberoptic main body1130b, and output guides1130c. Output guides1130cmay be configured to efficiently direct light from the fiber main body1130bto the individual photovoltaic elements1124.

Circuit1180may be configured to convey the electrical (high voltage) output from photovoltaic elements1124to actuators1190a,1190b. According to some embodiments, each actuator1190a,1190bmay include a pair of electrodes and an electroactive layer disposed between the electrodes. According to some embodiments, the bimorph actuators1190a,1190bmay include a shared electrode between the electroactive layers.

As disclosed herein, an optical transformer having a commercially-relevant form factor may be configured to convert a low (˜1-2V) DC input voltage to a high (>1 kV) DC output voltage. The optical transformer may include a light source optically coupled to an array of photovoltaic cells. The light source may be a surface-emitting device or an edge-emitting device and may include a laser or a light emitting diode, for example. The photovoltaic cells, which are at least partially connected in series, may include a direct band gap semiconductor such as GaAs or InGaAs. Photons produced by the DC-powered light source may be directed via an optical connector, e.g., waveguide or fiber optic element, to the photovoltaic cells to produce electrical carriers that generate a high electrical voltage across the array.

In certain embodiments, areal dimensions of the individual photovoltaic cells may range from approximately 1 μm×1 μm to approximately 250 μm×250 μm. In certain embodiments, the photovoltaic cells may be illuminated selectively to control the output voltage. That is, the light source may include an addressable array of emitters that can be switched on or off to illuminate a given number of photovoltaic cells.

Voltage or current modulation may be used to control the optical power generated by the light source and accordingly adjust the output voltage. According to some embodiments, the optical transformer may be integrated into a variety of high voltage systems or devices, including a piezoelectric or electrostatic actuator.

EXAMPLE EMBODIMENTS

Example 1: An optical transformer includes a light source and an array of photovoltaic cells optically coupled to the light source, where at least a portion of the photovoltaic cells are connected in series.

Example 2: The optical transformer of Example 1, where the light source includes a surface-emitting device or an edge-emitting device.

Example 3: The optical transformer of any of Examples 1 and 2, where the light source includes a laser or a light-emitting diode.

Example 4: The optical transformer of any of Examples 1-3, where the light source includes a plurality of independently-controlled emitters.

Example 5: The optical transformer of any of Examples 1-4, where the light source further includes an optical element adapted to focus light generated by the light source.

Example 6: The optical transformer of any of Examples 1-5, where an emission spectrum of the light source at least partially overlaps an absorption profile of the array of photovoltaic cells.

Example 7: The optical transformer of any of Examples 1-6, further including a cooling element configured to control a temperature of the light source.

Example 8: The optical transformer of any of Examples 1-7, where the photovoltaic cells include a direct bandgap compound semiconductor.

Example 9: The optical transformer of any of Examples 1-8, where the photovoltaic cells include at least one structure selected from a p-n junction, a Schottky diode, a quantum well, and a quantum dot.

Example 10: The optical transformer of any of Examples 1-9, where at least a portion of the photovoltaic cells are connected in parallel.

Example 11: The optical transformer of any of Examples 1-10, where the array of photovoltaic cells includes one or more bypass diodes.

Example 12: The optical transformer of any of Examples 1-11, where the photovoltaic cells are disposed within multiple sub-arrays each having a voltage output port.

Example 13: The optical transformer of any of Examples 1-12, further including an optical connector disposed between an output of the light source and an input of the array of photovoltaic cells.

Example 14: The optical transformer of any of Examples 1-13, where a volume of the optical transformer is less than approximately 5 mm3.

Example 15: An actuation system includes (i) an optical transformer having a light source and a serial array of photovoltaic cells optically coupled to the light source, and (ii) an actuator having (a) a primary electrode, (b) a secondary electrode overlapping at least a portion of the primary electrode, and (c) an electroactive layer disposed between and abutting the primary electrode and the secondary electrode, where the primary electrode is electrically connected to an output of the optical transformer.

Example 16: The actuation system of Example 15, where the optical transformer is mounted on the actuator.

Example 17: A method includes applying an input voltage to a light source to form rays of electromagnetic radiation and illuminating the electromagnetic radiation onto a serial array of photovoltaic cells.

Example 18: The method of Example 17, where the light source includes an array of emitters and the input voltage is applied to a subset of the emitters.

Example 19: The method of any of Examples 17 and 18, where illuminating the array of photovoltaic cells includes directing the electromagnetic radiation through an optical connector disposed between an output of the light source and an input of the array of photovoltaic cells.

Example 20: The method of any of Examples 17-19, where the light source is controlled by current modulation or voltage modulation.

Turning toFIG.12, augmented-reality system1200generally represents a wearable device dimensioned to fit about a body part (e.g., a head) of a user. As shown inFIG.12, system1200may include a frame1202and a camera assembly1204that is coupled to frame1202and configured to gather information about a local environment by observing the local environment. Augmented-reality system1200may also include one or more audio devices, such as output audio transducers1208(A) and1208(B) and input audio transducers1210. Output audio transducers1208(A) and1208(B) may provide audio feedback and/or content to a user, and input audio transducers1210may capture audio in a user's environment.

As shown, augmented-reality system1200may not necessarily include an NED positioned in front of a user's eyes. Augmented-reality systems without NEDs may take a variety of forms, such as head bands, hats, hair bands, belts, watches, wrist bands, ankle bands, rings, neckbands, necklaces, chest bands, eyewear frames, and/or any other suitable type or form of apparatus. While augmented-reality system1200may not include an NED, augmented-reality system1200may include other types of screens or visual feedback devices (e.g., a display screen integrated into a side of frame1202).

The embodiments discussed in this disclosure may also be implemented in augmented-reality systems that include one or more NEDs. For example, as shown inFIG.13, augmented-reality system1300may include an eyewear device1302with a frame1310configured to hold a left display device1315(A) and a right display device1315(B) in front of a user's eyes. Display devices1315(A) and1315(B) may act together or independently to present an image or series of images to a user. While augmented-reality system1300includes two displays, embodiments of this disclosure may be implemented in augmented-reality systems with a single NED or more than two NEDs.

In some embodiments, augmented-reality system1300may include one or more sensors, such as sensor1340. Sensor1340may generate measurement signals in response to motion of augmented-reality system1300and may be located on substantially any portion of frame1310. Sensor1340may represent a position sensor, an inertial measurement unit (IMU), a depth camera assembly, or any combination thereof. In some embodiments, augmented-reality system1300may or may not include sensor1340or may include more than one sensor. In embodiments in which sensor1340includes an IMU, the IMU may generate calibration data based on measurement signals from sensor1340. Examples of sensor1340may include, without limitation, accelerometers, gyroscopes, magnetometers, other suitable types of sensors that detect motion, sensors used for error correction of the IMU, or some combination thereof.

Augmented-reality system1300may also include a microphone array with a plurality of acoustic transducers1320(A)-1320(J), referred to collectively as acoustic transducers1320. Acoustic transducers1320may be transducers that detect air pressure variations induced by sound waves. Each acoustic transducer1320may be configured to detect sound and convert the detected sound into an electronic format (e.g., an analog or digital format). The microphone array inFIG.2may include, for example, ten acoustic transducers:1320(A) and1320(B), which may be designed to be placed inside a corresponding ear of the user, acoustic transducers1320(C),1320(D),1320(E),1320(F),1320(G), and1320(H), which may be positioned at various locations on frame1310, and/or acoustic transducers1320(I) and1320(J), which may be positioned on a corresponding neckband1305.

In some embodiments, one or more of acoustic transducers1320(A)-(F) may be used as output transducers (e.g., speakers). For example, acoustic transducers1320(A) and/or1320(B) may be earbuds or any other suitable type of headphone or speaker.

The configuration of acoustic transducers1320of the microphone array may vary. While augmented-reality system1300is shown inFIG.13as having ten acoustic transducers1320, the number of acoustic transducers1320may be greater or less than ten. In some embodiments, using higher numbers of acoustic transducers1320may increase the amount of audio information collected and/or the sensitivity and accuracy of the audio information. In contrast, using a lower number of acoustic transducers1320may decrease the computing power required by an associated controller1350to process the collected audio information. In addition, the position of each acoustic transducer1320of the microphone array may vary. For example, the position of an acoustic transducer1320may include a defined position on the user, a defined coordinate on frame1310, an orientation associated with each acoustic transducer1320, or some combination thereof.

Acoustic transducers1320(A) and1320(B) may be positioned on different parts of the user's ear, such as behind the pinna or within the auricle or fossa. Or, there may be additional acoustic transducers1320on or surrounding the ear in addition to acoustic transducers1320inside the ear canal. Having an acoustic transducer1320positioned next to an ear canal of a user may enable the microphone array to collect information on how sounds arrive at the ear canal. By positioning at least two of acoustic transducers1320on either side of a user's head (e.g., as binaural microphones), augmented-reality device1300may simulate binaural hearing and capture a 3D stereo sound field around about a user's head. In some embodiments, acoustic transducers1320(A) and1320(B) may be connected to augmented-reality system1300via a wired connection1330, and in other embodiments, acoustic transducers1320(A) and1320(B) may be connected to augmented-reality system1300via a wireless connection (e.g., a Bluetooth connection). In still other embodiments, acoustic transducers1320(A) and1320(B) may not be used at all in conjunction with augmented-reality system1300.

Acoustic transducers1320on frame1310may be positioned along the length of the temples, across the bridge, above or below display devices1315(A) and1315(B), or some combination thereof. Acoustic transducers1320may be oriented such that the microphone array is able to detect sounds in a wide range of directions surrounding the user wearing the augmented-reality system1300. In some embodiments, an optimization process may be performed during manufacturing of augmented-reality system1300to determine relative positioning of each acoustic transducer1320in the microphone array.

In some examples, augmented-reality system1300may include or be connected to an external device (e.g., a paired device), such as neckband1305. Neckband1305generally represents any type or form of paired device. Thus, the following discussion of neckband1305may also apply to various other paired devices, such as charging cases, smart watches, smart phones, wrist bands, other wearable devices, hand-held controllers, tablet computers, laptop computers and other external compute devices, etc.

As shown, neckband1305may be coupled to eyewear device1302via one or more connectors. The connectors may be wired or wireless and may include electrical and/or non-electrical (e.g., structural) components. In some cases, eyewear device1302and neckband1305may operate independently without any wired or wireless connection between them. WhileFIG.13illustrates the components of eyewear device1302and neckband1305in example locations on eyewear device1302and neckband1305, the components may be located elsewhere and/or distributed differently on eyewear device1302and/or neckband1305. In some embodiments, the components of eyewear device1302and neckband1305may be located on one or more additional peripheral devices paired with eyewear device1302, neckband1305, or some combination thereof.

Neckband1305may be communicatively coupled with eyewear device1302and/or to other devices. These other devices may provide certain functions (e.g., tracking, localizing, depth mapping, processing, storage, etc.) to augmented-reality system1300. In the embodiment ofFIG.13, neckband1305may include two acoustic transducers (e.g.,1320(I) and1320(J)) that are part of the microphone array (or potentially form their own microphone subarray). Neckband1305may also include a controller1325and a power source1335.

Acoustic transducers1320(I) and1320(J) of neckband1305may be configured to detect sound and convert the detected sound into an electronic format (analog or digital). In the embodiment ofFIG.13, acoustic transducers1320(I) and1320(J) may be positioned on neckband1305, thereby increasing the distance between the neckband acoustic transducers1320(I) and1320(J) and other acoustic transducers1320positioned on eyewear device1302. In some cases, increasing the distance between acoustic transducers1320of the microphone array may improve the accuracy of beamforming performed via the microphone array. For example, if a sound is detected by acoustic transducers1320(C) and1320(D) and the distance between acoustic transducers1320(C) and1320(D) is greater than, e.g., the distance between acoustic transducers1320(D) and1320(E), the determined source location of the detected sound may be more accurate than if the sound had been detected by acoustic transducers1320(D) and1320(E).

Controller1325of neckband1305may process information generated by the sensors on neckband1305and/or augmented-reality system1300. For example, controller1325may process information from the microphone array that describes sounds detected by the microphone array. For each detected sound, controller1325may perform a direction-of-arrival (DOA) estimation to estimate a direction from which the detected sound arrived at the microphone array. As the microphone array detects sounds, controller1325may populate an audio data set with the information. In embodiments in which augmented-reality system1300includes an inertial measurement unit, controller1325may compute all inertial and spatial calculations from the IMU located on eyewear device1302. A connector may convey information between augmented-reality system1300and neckband1305and between augmented-reality system1300and controller1325. The information may be in the form of optical data, electrical data, wireless data, or any other transmittable data form. Moving the processing of information generated by augmented-reality system1300to neckband1305may reduce weight and heat in eyewear device1302, making it more comfortable to the user.

Power source1335in neckband1305may provide power to eyewear device1302and/or to neckband1305. Power source1335may include, without limitation, lithium ion batteries, lithium-polymer batteries, primary lithium batteries, alkaline batteries, or any other form of power storage. In some cases, power source1335may be a wired power source. Including power source1335on neckband1305instead of on eyewear device1302may help better distribute the weight and heat generated by power source1335.

As noted, some artificial-reality systems may, instead of blending an artificial reality with actual reality, substantially replace one or more of a user's sensory perceptions of the real world with a virtual experience. One example of this type of system is a head-worn display system, such as virtual-reality system1400inFIG.14, that mostly or completely covers a user's field of view. Virtual-reality system1400may include a front rigid body1402and a band1404shaped to fit around a user's head. Virtual-reality system1400may also include output audio transducers1406(A) and1406(B). Furthermore, while not shown inFIG.14, front rigid body1402may include one or more electronic elements, including one or more electronic displays, one or more inertial measurement units (IMUS), one or more tracking emitters or detectors, and/or any other suitable device or system for creating an artificial reality experience.

Artificial-reality systems may include a variety of types of visual feedback mechanisms. For example, display devices in augmented-reality system1300and/or virtual-reality system1400may include one or more liquid crystal displays (LCDs), light emitting diode (LED) displays, organic LED (OLED) displays, and/or any other suitable type of display screen. Artificial-reality systems may include a single display screen for both eyes or may provide a display screen for each eye, which may allow for additional flexibility for varifocal adjustments or for correcting a user's refractive error. Some artificial-reality systems may also include optical subsystems having one or more lenses (e.g., conventional concave or convex lenses, Fresnel lenses, adjustable liquid lenses, etc.) through which a user may view a display screen.

In addition to or instead of using display screens, some artificial-reality systems may include one or more projection systems. For example, display devices in augmented-reality system1300and/or virtual-reality system1400may include micro-LED projectors that project light (using, e.g., a waveguide) into display devices, such as clear combiner lenses that allow ambient light to pass through. The display devices may refract the projected light toward a user's pupil and may enable a user to simultaneously view both artificial-reality content and the real world. Artificial-reality systems may also be configured with any other suitable type or form of image projection system.

Artificial-reality systems may also include various types of computer vision components and subsystems. For example, augmented-reality system1200, augmented-reality system1300, and/or virtual-reality system1400may include one or more optical sensors, such as two-dimensional (2D) or 3D cameras, time-of-flight depth sensors, single-beam or sweeping laser rangefinders, 3D LiDAR sensors, and/or any other suitable type or form of optical sensor.

An artificial-reality system may process data from one or more of these sensors to identify a location of a user, to map the real world, to provide a user with context about real-world surroundings, and/or to perform a variety of other functions.

Artificial-reality systems may also include one or more input and/or output audio transducers. In the examples shown inFIGS.12and14, output audio transducers1208(A),1208(B),1406(A), and1406(B) may include voice coil speakers, ribbon speakers, electrostatic speakers, piezoelectric speakers, bone conduction transducers, cartilage conduction transducers, and/or any other suitable type or form of audio transducer. Similarly, input audio transducers1210may include condenser microphones, dynamic microphones, ribbon microphones, and/or any other type or form of input transducer. In some embodiments, a single transducer may be used for both audio input and audio output.

As noted, artificial-reality systems1200,1300, and1400may be used with a variety of other types of devices to provide a more compelling artificial-reality experience. These devices may be haptic interfaces with transducers that provide haptic feedback and/or that collect haptic information about a user's interaction with an environment. The artificial-reality systems disclosed herein may include various types of haptic interfaces that detect or convey various types of haptic information, including tactile feedback (e.g., feedback that a user detects via nerves in the skin, which may also be referred to as cutaneous feedback) and/or kinesthetic feedback (e.g., feedback that a user detects via receptors located in muscles, joints, and/or tendons).

Haptic feedback may be provided by interfaces positioned within a user's environment (e.g., chairs, tables, floors, etc.) and/or interfaces on articles that may be worn or carried by a user (e.g., gloves, wristbands, etc.). As an example,FIG.15illustrates a vibrotactile system1500in the form of a wearable glove (haptic device1510) and wristband (haptic device1520). Haptic device1510and haptic device1520are shown as examples of wearable devices that include a flexible, wearable textile material1530that is shaped and configured for positioning against a user's hand and wrist, respectively. This disclosure also includes vibrotactile systems that may be shaped and configured for positioning against other human body parts, such as a finger, an arm, a head, a torso, a foot, or a leg. By way of example and not limitation, vibrotactile systems according to various embodiments of the present disclosure may also be in the form of a glove, a headband, an armband, a sleeve, a head covering, a sock, a shirt, or pants, among other possibilities. In some examples, the term “textile” may include any flexible, wearable material, including woven fabric, non-woven fabric, leather, cloth, a flexible polymer material, composite materials, etc.

One or more vibrotactile devices1540may be positioned at least partially within one or more corresponding pockets formed in textile material1530of vibrotactile system1500. Vibrotactile devices1540may be positioned in locations to provide a vibrating sensation (e.g., haptic feedback) to a user of vibrotactile system1500. For example, vibrotactile devices1540may be positioned to be against the user's finger(s), thumb, or wrist, as shown inFIG.15. Vibrotactile devices1540may, in some examples, be sufficiently flexible to conform to or bend with the user's corresponding body part(s).

A power source1550(e.g., a battery) for applying a voltage to the vibrotactile devices1540for activation thereof may be electrically coupled to vibrotactile devices1540, such as via conductive wiring1552. In some examples, each of vibrotactile devices1540may be independently electrically coupled to power source1550for individual activation. In some embodiments, a processor1560may be operatively coupled to power source1550and configured (e.g., programmed) to control activation of vibrotactile devices1540.

Vibrotactile system1500may be implemented in a variety of ways. In some examples, vibrotactile system1500may be a standalone system with integral subsystems and components for operation independent of other devices and systems. As another example, vibrotactile system1500may be configured for interaction with another device or system1570. For example, vibrotactile system1500may, in some examples, include a communications interface1580for receiving and/or sending signals to the other device or system1570. The other device or system1570may be a mobile device, a gaming console, an artificial-reality (e.g., virtual-reality, augmented-reality, mixed-reality) device, a personal computer, a tablet computer, a network device (e.g., a modem, a router, etc.), a handheld controller, etc. Communications interface1580may enable communications between vibrotactile system1500and the other device or system1570via a wireless (e.g., Wi-Fi, Bluetooth, cellular, radio, etc.) link or a wired link. If present, communications interface1580may be in communication with processor1560, such as to provide a signal to processor1560to activate or deactivate one or more of the vibrotactile devices1540.

Vibrotactile system1500may optionally include other subsystems and components, such as touch-sensitive pads1590, pressure sensors, motion sensors, position sensors, lighting elements, and/or user interface elements (e.g., an on/off button, a vibration control element, etc.). During use, vibrotactile devices1540may be configured to be activated for a variety of different reasons, such as in response to the user's interaction with user interface elements, a signal from the motion or position sensors, a signal from the touch-sensitive pads1590, a signal from the pressure sensors, a signal from the other device or system1570, etc.

Although power source1550, processor1560, and communications interface1580are illustrated inFIG.15as being positioned in haptic device1520, the present disclosure is not so limited. For example, one or more of power source1550, processor1560, or communications interface1580may be positioned within haptic device1510or within another wearable textile.

Haptic wearables, such as those shown in and described in connection withFIG.15, may be implemented in a variety of types of artificial-reality systems and environments.FIG.16shows an example artificial-reality environment1600including one head-mounted virtual-reality display and two haptic devices (i.e., gloves), and in other embodiments any number and/or combination of these components and other components may be included in an artificial-reality system. For example, in some embodiments there may be multiple head-mounted displays each having an associated haptic device, with each head-mounted display and each haptic device communicating with the same console, portable computing device, or other computing system.

Head-mounted display1602generally represents any type or form of virtual-reality system, such as virtual-reality system1400inFIG.14. Haptic device1604generally represents any type or form of wearable device, worn by a use of an artificial-reality system, that provides haptic feedback to the user to give the user the perception that he or she is physically engaging with a virtual object. In some embodiments, haptic device1604may provide haptic feedback by applying vibration, motion, and/or force to the user. For example, haptic device1604may limit or augment a user's movement. To give a specific example, haptic device1604may limit a user's hand from moving forward so that the user has the perception that his or her hand has come in physical contact with a virtual wall. In this specific example, one or more actuators within the haptic advice may achieve the physical-movement restriction by pumping fluid into an inflatable bladder of the haptic device. In some examples, a user may also use haptic device1604to send action requests to a console. Examples of action requests include, without limitation, requests to start an application and/or end the application and/or requests to perform a particular action within the application.

While haptic interfaces may be used with virtual-reality systems, as shown inFIG.16, haptic interfaces may also be used with augmented-reality systems, as shown inFIG.17.FIG.17is a perspective view a user1710interacting with an augmented-reality system1700. In this example, user1710may wear a pair of augmented-reality glasses1720that have one or more displays1722and that are paired with a haptic device1730. Haptic device1730may be a wristband that includes a plurality of band elements1732and a tensioning mechanism1734that connects band elements1732to one another.

One or more of band elements1732may include any type or form of actuator suitable for providing haptic feedback. For example, one or more of band elements1732may be configured to provide one or more of various types of cutaneous feedback, including vibration, force, traction, texture, and/or temperature. To provide such feedback, band elements1732may include one or more of various types of actuators. In some embodiments, an actuator may include a layer of nanovoided polymer sandwiched between conductive electrodes. In one example, each of band elements1732may include a vibrotactor (e.g., a vibrotactile actuator) configured to vibrate in unison or independently to provide one or more of various types of haptic sensations to a user. Alternatively, only a single band element or a subset of band elements may include vibrotactors.

Haptic devices1510,1520,1604, and1730may include any suitable number and/or type of haptic transducer, sensor, and/or feedback mechanism. For example, haptic devices1510,1520,1604, and1730may include one or more mechanical transducers, piezoelectric transducers, and/or fluidic transducers. Haptic devices1510,1520,1604, and1730may also include various combinations of different types and forms of transducers that work together or independently to enhance a user's artificial-reality experience. In one example, each of band elements1732of haptic device1730may include a vibrotactor (e.g., a vibrotactile actuator) configured to vibrate in unison or independently to provide one or more of various types of haptic sensations to a user.