Engineered loading response in electroactive polymer devices having structured nanovoids

{
  "publication_number": "US10749448B2",
  "country": "US",
  "kind": "B2",
  "title": "Engineered loading response in electroactive polymer devices having structured nanovoids",
  "abstract": "A device may include a primary electrode, a secondary electrode overlapping at least a portion of the primary electrode, and an electroactive polymer element disposed between and abutting the primary electrode and the secondary electrode. The electroactive polymer element may include a nanovoided polymer material whereby resistance to deformation of the electroactive polymer element is non-linear with respect to an amount of deformation of the electroactive polymer element. Various other devices, method, and systems are also disclosed.",
  "claims": [
    "1. A device comprising: a primary electrode; a secondary electrode overlapping at least a portion of the primary electrode; and an electroactive polymer element comprising a nanovoided polymer material disposed between and abutting the primary electrode and the secondary electrode, wherein resistance to deformation of the electroactive polymer element is non-linear with respect to an amount of deformation of the electroactive polymer element.",
    "2. The device of claim 1, wherein nanovoids occupy at least approximately 10% by volume of the nanovoided polymer material.",
    "3. The device of claim 1, wherein a distribution of nanovoids within the electroactive polymer element is substantially homogenous.",
    "4. The device of claim 1, wherein the electroactive polymer element has a thickness of 100 nanometers to 10 micrometers.",
    "5. The device of claim 1, wherein a distribution of nanovoids within the electroactive polymer element varies with thickness of the electroactive polymer element.",
    "6. The device of claim 1, wherein a distribution of nanovoids within the electroactive polymer element varies laterally between the primary electrode and the secondary electrode.",
    "7. The device of claim 1, wherein the electroactive polymer element has a strain energy greater than an electrostatic energy when an electric field of approximately 10% to approximately 90% of a dielectric strength of the electroactive polymer element is applied between the primary electrode and the secondary electrode.",
    "8. The device of claim 1, wherein a stress-strain curve of the electroactive polymer element has a slope that increases with increasing strain.",
    "9. The device of claim 1, wherein a stress-strain curve of the electroactive polymer element includes a negative slope.",
    "10. The device of claim 1, wherein the electroactive polymer element comprises particles of a material having a high dielectric constant, the particles having an average diameter between approximately 10 nm and approximately 1000 nm.",
    "11. The device of claim 10, wherein the material having the high dielectric constant comprises barium titanate.",
    "12. An electroactive device comprising: a primary electrode; a secondary electrode overlapping at least a portion of the primary electrode; and an electroactive polymer element comprising a nanovoided polymer material disposed between and abutting the primary electrode and the secondary electrode, wherein the electroactive polymer element exhibits a negative effective Poisson's ratio along at least one dimension.",
    "13. The electroactive device of claim 12, wherein nanovoids occupy at least approximately 10% by volume of the nanovoided polymer material.",
    "14. The electroactive device of claim 12, wherein a distribution of nanovoids within the electroactive polymer element is substantially homogenous.",
    "15. The electroactive device of claim 12, wherein the electroactive polymer element has a thickness of 100 nanometers to 10 micrometers.",
    "16. The electroactive device of claim 12, wherein: the electroactive polymer element is configured to contract in a direction parallel to an electric field generated between the primary electrode and the secondary electrode, and the electroactive polymer element is configured to contract in at least one direction orthogonal to the electric field.",
    "17. A method comprising: forming a primary electrode; forming an electroactive polymer element comprising a nanovoided polymer material directly over the primary electrode; and forming a secondary electrode opposite the primary electrode and directly over the electroactive polymer element, wherein the electroactive polymer element exhibits at least one of: a negative effective Poisson's ratio along at least one dimension, or non-linear resistance to deformation with respect to an amount of deformation of the electroactive polymer element.",
    "18. The method of claim 17, wherein the electroactive polymer element exhibits a negative effective Poisson's ratio along each of a pair of mutually orthogonal dimensions.",
    "19. The method of claim 17, wherein the electroactive polymer element has a strain energy greater than an electrostatic energy when an electric field of approximately 10% to approximately 90% of a dielectric strength of the electroactive polymer element is applied between the primary electrode and the secondary electrode.",
    "20. The method of claim 17, wherein a stress-strain curve of the electroactive polymer element includes a negative slope."
  ],
  "description_excerpt": "Electroactive polymer (EAP) materials may change their shape under the influence of an electric field. EAP materials have been investigated for use in various technologies, including actuation, sensing and/or energy harvesting. Lightweight and conformable, electroactive polymers may be incorporated into wearable devices such as haptic devices and are attractive candidates for emerging technologies including virtual reality/augmented reality devices where a comfortable, adjustable form factor is desired.\n\nVirtual reality (VR) and augmented reality (AR) eyewear devices or headsets, for instance, may enable users to experience events, such as interactions with people in a computer-generated simulation of a three-dimensional world or viewing data superimposed on a real-world view. VR/AR eyewear devices and headsets may also be used for purposes other than recreation. For example, governments may use such devices for military training, doctors may use such devices to simulate surgery, and engineers may use such devices as design visualization aids.\n\nTraditionally, these and other applications that use electroactive polymers leverage the Poisson's ratio of the polymer material to generate a lateral expansion as a response to compression between conductive electrodes. Notwithstanding recent developments, it would be advantageous to provide electroactive polymer materials having improved deformational control, including materials exhibiting variable or even negative stiffness.\n\nAs will be described in greater detail below, the instant disclosure relates to electroactive devices including a nanovoided polymer material.",
  "cpc": [
    "H02N 1/006",
    "G02B 2027/0178",
    "G02B 27/017",
    "G02B 27/0172",
    "G02B 27/0176",
    "G02B 3/14",
    "H10N 30/01",
    "H10N 30/50",
    "H10N 30/852",
    "H10N 30/857",
    "H10N 30/877",
    "H10N 30/878"
  ],
  "ipc": [
    "G02B 3/14",
    "H02N 1/00",
    "H10N 30/098",
    "H10N 30/857"
  ],
  "assignees": [
    "Facebook Technologies LLC"
  ],
  "inventors": [
    "Jack Lindsay",
    "Katherine Marie Smyth",
    "Thomas John Farrell Wallin",
    "Andrew John Ouderkirk",
    "Tanya Malhotra",
    "Austin Lane",
    "Christopher Yuan Ting Liao",
    "Yigit Menguc"
  ],
  "filing_date": "2018-11-30",
  "publication_date": "2020-08-18",
  "grant_date": "2020-08-18",
  "priority_date": "2018-11-30",
  "application_number": "US-201816205257-A",
  "family_id": "66821331",
  "cited_by_count": 25,
  "citations": [
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    "US7956520B2",
    "US8222799B2",
    "US20180093456A1"
  ]
}