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US-12619314-B2 - Ultrasonic array for haptic rendering

US12619314B2US 12619314 B2US12619314 B2US 12619314B2US-12619314-B2

Abstract

A wearable, low power, compact ultrasonic haptic device that focuses ultrasound at or below the skin's surface using a piezocomposite transducer consisting multiple arrayed acoustic pixels, each acoustic pixel comprising an array of piezocomposite pillars separated by an epoxy and topped by a metal electrode. The high efficiency of the piezocomposite transducer facilitates sufficient production of ultrasonic energy directed at a focal point at or below the surface the skin to stimulate a tactile sensation.

Inventors

  • Gary K. Fedder
  • Jace Rozsa

Assignees

  • CARNEGIE MELLON UNIVERSITY

Dates

Publication Date
20260505
Application Date
20241218

Claims (20)

  1. 1 . A device comprising: an array of pillars composed of a piezocomposite material; a plurality of electrodes, each electrode covering a subset of the array of pillars to form an acoustic pixel; and a matching layer covering the acoustic pixels, the matching layer being a having an acoustic impedance between the acoustic impedance of the piezocomposite material and the acoustic impedance of a target material; wherein the matching layer is segmented into a plurality of segments corresponding to each acoustic pixel; and wherein ultrasonic energy generated by the device is directed at a focal point at or below the surface of a user's skin to stimulate a tactile sensation.
  2. 2 . The device of claim 1 wherein the matching layer is composed of a polymer.
  3. 3 . The device of claim 2 wherein the polymer is an epoxy-based photoresist.
  4. 4 . The device of claim 3 wherein the epoxy-based photoresist is SU-8.
  5. 5 . The device of claim 1 wherein the matching layer is loaded with nanoparticles.
  6. 6 . The device of claim 2 wherein the polymer has a quantity of nanoparticles mixed therewith.
  7. 7 . The device of claim 6 wherein the nanoparticles are composed of titanium oxide.
  8. 8 . The device of claim 7 wherein the nanoparticles are mixed with the polymer in a weight ratio of approximately 30%.
  9. 9 . The device of claim 1 further comprising: an epoxy material disposed between the pillars.
  10. 10 . The device of claim 1 wherein the pillars have a height to width aspect ratio greater than or equal to 10.
  11. 11 . The device of claim 1 wherein the pillars have a square cross sectional shape and are approximately 125 μm square×1.5 mm in height.
  12. 12 . The device of claim 1 wherein the pillars are spaced 50 μm apart from each other.
  13. 13 . The device of claim 9 wherein a volume ratio of epoxy to the piezocomposite material in the device is 1:1.
  14. 14 . The device of claim 1 wherein the electrodes are composed of a layer of copper 2-3 μm in thickness.
  15. 15 . The device of claim 14 wherein the copper layer has a coating of tin layered thereon.
  16. 16 . The device of claim 1 wherein each acoustic pixel comprises a 4×4 array of pillars.
  17. 17 . The device of claim 16 wherein the device comprises a 4×8 array of acoustic pixels.
  18. 18 . The device of claim 1 wherein each acoustic pixel is driven in a longitudinal mode at a resonance frequency.
  19. 19 . The device of claim 18 wherein the ultrasonic energy is focused on mechanoreceptors under the surface of the skin.
  20. 20 . The device of claim 18 wherein the resonance frequency is approximately 1 MHz.

Description

RELATED APPLICATIONS This application is a continuation-in-part of PCT Application No. PCT/US2024/057429, filed Nov. 26, 2024, which claims the benefit of U.S. Provisional Patent Application No. 63/604,625, field Nov. 30, 2023. The contents of these applications are incorporated herein their entireties. FIELD OF THE INVENTION This invention is related to the haptic feedback and, in particular, is directed to devices for providing tactile rendering to a portion of a human body, for example, the fingertip of an individual. BACKGROUND Haptic technologies play a crucial role in many modern systems, from user electronics to virtual reality. In cooperative robotic applications, haptics is used to communicate important information to the user about the environment in which the robot is operating and is particularly useful when the robots are being operated remotely (i.e., teleoperation). This information is typically transmitted in two modes: kinesthetic (larger forces applied to the user which are felt in joints) and tactile (forces imparted to the skin). Haptics are also an important information modality for robot action to be learned through demonstration by humans. Haptic displays can provide rich tactile information through the natural means of human mechanoreceptors, thereby not overloading cognitive ability. In contrast, other possible modalities, such as conveying tactile information through a visual display, could be much more difficult and time-consuming for a human to interpret. For tactile haptics, the device ideally provides a stimulus without inhibiting the user's range of motion. In other words, tactile devices must be wearable. Therefore, technologies that are lightweight, low-power, and small are desirable. Additionally, the stimulus must be able to convincingly mimic real world surfaces and textures. These two requirements have proven challenging for current technologies. Contemporary tactile devices are still far from recreating reality in a satisfactory manner. The majority of tactile stimulation technologies rely on actuators which impart a force to the skin through direct physical contact. These actuators are typically worn on the finger along with the electrical components which drive the motors. Hydraulic, shape memory and vibrating motor actuators have been incorporated into large-scale arrays and are used to simulate movement across the skin, such as a caress. These devices typically incorporate individual actuators on the scale of millimeters to centimeters in size. Such large individual actuators are bulky and awkward to wear. Miniaturization challenges exist in scaling mechanical actuators into arrays for small areas like fingertips. Many actuators must be physically anchored to produce forces large enough to be sensed. For wearable applications, this often places a limit on how small individual stimulators can be, as extra hardware for physical anchoring takes space. Actuation for haptics also suffers from problems of localizing the stimulus. If one actuator is triggered it can often be felt in a larger area beyond the point of actuation. A spatially imprecise stimulation can reduce the effectiveness of haptic rendering. As an alternative to mechanical actuators, ultrasonic waves can be used to stimulate tactile sensations. In such applications, energy is transferred from the impinging wave to the surface of the skin through acoustic radiation force, delivering a tactile sensation to the user. Mid-air ultrasonic haptic devices are a common application which exploits this mechanism. In such applications, a large array of ultrasonic transducers focuses ultrasonic power at a given point in space. A tactile sensation is felt when the focused ultrasonic waves impinge on the skin of the user. Because the frequency range of ultrasound is outside the sensitive range for human mechanoreceptors, the carrier signal must be modulated, either spatially or temporally, at frequencies under 1 kHz. To overcome the high attenuation of ultrasound in air, these devices must be relatively large (typically over 100 transducers are used, with each transducer having a footprint on the order of a square centimeter) and have high power requirements, with peak power consumption reaching 80 W for some systems. One example of an attempt to remedy the limitations of operating in air involves placing ultrasonic transducers directly on the back of the hand, driving ultrasonic energy through the tissue and bone, and focusing to a point on the palm. While this technique reduces power consumption, the devices are still quite large and only capable of producing a single focal point on the hand at a time. Therefore, there is a need for a device which is scalable for small applications, lightweight, does not require physical anchoring and which can deliver a spatially precise stimulus. SUMMARY OF THE INVENTION The device disclosed herein addresses the deficiencies noted above and provides multiple advantages over prior ar