Mechanical meta-materials

• US 20060192465A1
• Filed: 03/11/2005
• Published: 08/31/2006
• Est. Priority Date: 03/12/2004
• Status: Active Grant

• Current Assignee: SRI International, Inc.
• Original Assignee: SRI International, Inc.
• Inventors: Kornbluh, Roy D., Prahlad, Harsha, Pelrine, Ronald E., Stanford, Scott E.
• Granted Patent: US 7,598,651 B2
• Time in Patent Office: Days
• US Class Current: 310/309
• CPC Class Codes: A61F 2002/5003 having damping means, e.g. shock absorbers
• CPC Class Codes: A61M 2025/0058 having an electroactive polymer material, e.g. for steering purposes, for control of flexibility, for locking, for opening or closing
• CPC Class Codes: A61M 2025/0063 having means, e.g. stylets, mandrils, rods or wires to reinforce or adjust temporarily the stiffness, column strength or pushability of catheters which are already inserted into the human body
• CPC Class Codes: B64C 3/48 by relatively-movable parts of wing structures
• CPC Class Codes: H02N 1/00 Electrostatic generators or motors using a solid moving electrostatic charge carrier
• CPC Class Codes: H02N 1/006 of the gap-closing type H02N1/004 takes precedence
• CPC Class Codes: Y02T 50/10 Drag reduction
• CPC Class Codes: Y10T 428/24752 Laterally noncoextensive components

Abstract

The present invention provides meta-materials with an actively controllable mechanical property. The meta-material includes a deformable structure and a set of activation elements. The activation elements are controllable between multiple states. The meta-material includes a first value for a mechanical property when one or more of the activation elements is in the first activation state and includes a second value for the mechanical property when the activation elements have been activated to the second activation state. In one aspect, the meta-material resembles a composite material where the connectivity between the component materials or shape and arrangement of the component materials is dynamically controllable so as to affect a mechanical property of the meta-material.

Claims

1. A meta-material comprising:

a deformable or reconfigurable structure; and

a set of activation elements, where each activation element a) couples to the deformable structure, b) includes a component that participates in an activation mechanism, and c) is configured to change between a first activation state and a second activation state,

wherein the meta-material includes a first value for a mechanical property when at least one of the activation elements is in the first activation state and the meta-material includes a second value for the mechanical property when the at least one activation element has been activated to the second activation state.

2. The meta-material of claim 1 wherein the deformable structure comprises a compliant layer.

3. The meta-material of claim 1 wherein each activation element includes a stiff component having a stiffness greater than a stiffness for the deformable structure.

4. The meta-material of claim 3 wherein each activation element is bendable but not extendable.

5. The meta-material of claim 3 wherein each activation element at least partially laterally overlaps an adjacent activation element.

6. The meta-material of claim 3 wherein each activation element includes an electrode disposed on one surface of the stiff component.

7. The meta-material of claim 6 wherein each activation element further includes an insulating layer disposed between the electrode and either a) an adjacent activation element or b) the deformable structure.

8. The meta-material of claim 3 wherein a first subset of activation elements attach to a first surface of the compliant layer and a second subset of activation elements attach to a second surface of the compliant layer that is opposite to the first surface.

9. The meta-material of claim 8 wherein an activation element in the first subset laterally overlaps in an activation element in the second subset when the at least one activation element has been activated to the second activation state.

10. The meta-material of claim 1 wherein each activation element in the set of activation elements includes an electrostatic clamp in the second activation state.

11. The meta-material of claim 1 wherein the meta-material is configured such that activation of one or more of the activation elements in the set of activation elements permits a third value for the mechanical property that is between the first value and the second value.

12. The meta-material of claim 1 wherein the meta-material includes a first shape when the at least one of the activation elements is in the first activation state and includes a second shape when the at least one of the activation elements has been activated to the second activation state.

13. The meta-material of claim 1 wherein the mechanical property is one of:

toughness, elastic modulus, stiffness, damping, shape, and resilience.

14. The meta-material of claim 1 further comprising a locking mechanism that reduces the energy required to maintain a position of the meta-material when the at least one of the activation element has been activated to the second activation state.

15. The meta-material of claim 1 wherein the activation element partially couples to the deformable structure.

16. The meta-material of claim 1 wherein the meta-material comprises a composite of two materials, one of the two materials includes an active or intrinsically variable material and the one or more activation elements are included in the active or intrinsically variable material.

17. The meta-material of claim 1 further comprising independent electrical communication with each activation element in the set of activation elements.

18. The meta-material of claim 1 wherein each activation element attaches to the deformable structure.

19. The meta-material of claim 1 wherein a surface of the deformable structure is not flat.

20. The meta-material of claim 1 wherein the second state includes a different connectivity between the activation elements than a connectivity between the activation elements in the first state.

21. The meta-material of claim 1 wherein the meta-material includes a different shape when the at least one activation element has been activated to the second activation state than a shape for the meta-material when the at least one activation element is in the first state.

22. A meta-material comprising:

a deformable structure; and

a set of activation elements, where each activation element a) couples to the deformable structure, b) includes a stiff component, and c) is configured to change between a first activation state and a second activation state,

wherein the meta-material includes a first stiffness when at least one of the activation elements is in the first activation state and the meta-material includes a second stiffness when the at least one activation element has been activated to the second activation state.

23. The meta-material of claim 22 wherein the deformable structure comprises a compliant layer.

24. The meta-material of claim 22 wherein the stiff component has a stiffness greater than a stiffness for the deformable structure.

25. The meta-material of claim 24 wherein each activation element is bendable but not extendable.

26. The meta-material of claim 24 wherein each activation element at least partially laterally overlaps an adjacent activation element.

27. The meta-material of claim 24 wherein each activation element includes an electrode disposed on one surface of the stiff component.

28. The meta-material of claim 27 wherein each activation element further includes an insulating layer disposed between the electrode and either a) an adjacent activation element or b) the deformable structure.

29. The meta-material of claim 24 wherein a first subset of activation elements attach to a first surface of the compliant layer and a second subset of activation elements attach to a second surface of the compliant layer that is opposite to the first surface.

30. The meta-material of claim 29 wherein an activation element in the first subset laterally overlaps in an activation element in the second subset.

31. The meta-material of claim 22 further comprising independent electrical communication with each activation element in the set of activation elements.

32. The meta-material of claim 22 wherein each activation element in the set of activation elements includes an electrostatic clamp in the second activation state.

33. The meta-material of claim 32 wherein a strength for the electrostatic clamp limits the second stiffness.

34. The meta-material of claim 32 wherein the set of activation elements is mechanically redundant.

35. The meta-material of claim 22 wherein the meta-material is configured such that activation of one or more of the activation elements in the set of activation elements permits a third stiffness that is between the first stiffness and the second stiffness.

36. The meta-material of claim 22 wherein the meta-material includes a first shape when the at least one of the activation elements is in the first activation state and includes a second shape when the at least one of the activation elements has been activated to the second activation state.

37. The meta-material of claim 22 wherein the second stiffness is tunable according to the number and location of activation elements that have been activated.

38. The meta-material of claim 37 wherein each stiff component has an elastic modulus greater than about 100 MPa.

39. The meta-material of claim 37 wherein the first stiffness is less than about 10 MPa and the second stiffness is greater than about 100 MPa.

40. A meta-material comprising:

a deformable structure; and

a set of activation elements, where each activation element a) includes a stiff component, b) couples to the deformable structure, and c) is configured to change between a first activation state and a second activation state in response to external input,

wherein the meta-material includes a first damping coefficient when at least one of the activation elements is in the first activation state and the meta-material includes a second damping coefficient when the at least one activation element has been activated to the second activation state.

41. The meta-material of claim 40 wherein each activation element includes a stiff component having a stiffness greater than a stiffness for the deformable structure.

42. The meta-material of claim 41 wherein each activation element includes an electrode disposed on one surface of the stiff component.

43. The meta-material of claim 40 wherein each activation element in the set of activation elements includes an electrostatic clamp in the second activation state that is not strong enough to withstand an external force being damped.

44. A meta-material comprising:

a deformable structure; and

a set of activation elements, where each activation element includes a stiff component that couples to the deformable structure,

wherein the meta-material includes a first value for a mechanical property when at least one of the activation elements is not electrostatically clamped to another activation element and the meta-material includes a second value for the mechanical property when the at least one activation element has been electrostatically clamped to another activation element.

45. The meta-material of claim 44 wherein the stiff component comprises a conductive material.

46. The meta-material of claim 44 wherein the stiff component comprises a coupling portion that couples to the deformable structure and an electrostatic clamping portion.

47. The meta-material of claim 44 further comprising an electrode attached to the stiff component.

48. The meta-material of claim 44 wherein each activation element at least partially laterally overlaps an adjacent activation element.

49. The meta-material of claim 48 wherein each activation element further includes an insulating layer disposed between the electrode and either a) an adjacent activation element or b) the deformable structure.

50. The meta-material of claim 44 wherein the deformable structure comprises a compliant layer.

51. The meta-material of claim 50 wherein a first subset of activation elements attach to a first surface of the compliant layer and a second subset of activation elements attach to a second surface of the compliant layer that is opposite to the first surface.

52. The meta-material of claim 51 wherein an activation element in the first subset laterally overlaps in an activation element in the second subset.

53. The meta-material of claim 44 further comprising independent electrical communication with each activation element in the set of activation elements.

54. The meta-material of claim 44 wherein each activation element attaches to the deformable structure.

55. The meta-material of claim 44 wherein a surface of the deformable structure is not flat.

56. A method of controlling a mechanical property for a meta-material, the meta-material comprising a deformable structure and a set of activation elements coupled to the deformable structure, the method comprising:

activating at least one activation element from a first activation state to a second activation state,

wherein the meta-material includes a first value for the mechanical property when the at least one activation element is in the first activation state and the meta-material includes a second value for the mechanical property when the at least one activation element has been activated to the second activation state.

57. The method of claim 56 wherein activating the at least one activation element comprises applying an electrostatic clamping voltage to the least one activation element.

58. The method of claim 57 wherein the set of activation elements is mechanically redundant.

59. The method of claim 58 wherein the electrostatic clamping voltage includes an AC signal.

60. The method of claim 56 wherein the mechanical property is one of:

toughness, elastic modulus, stiffness, damping, shape, and resilience.

61. The method of claim 56 further comprising activating the at least one activation element to a third activation state and the meta-material includes a third value for the mechanical property when the at least one activation element is in the third activation state.

62. The method of claim 56 wherein each activation element at least partially laterally overlaps an adjacent activation element.

63. The method of claim 56 wherein a surface of the deformable structure is not flat.

64. The method of claim 56 wherein the second state includes a different connectivity between the activation elements than a connectivity between the activation elements in the first state.

65. The method of claim 56 wherein the meta-material includes a different shape when the at least one activation element has been activated to the second activation state than a shape for the meta-material when the at least one activation element is in the first state.

66. A method of varying stiffness using a meta-material that comprises a deformable structure and a set of activation elements coupled to the deformable structure, the method comprising:

activating at least one activation element from a first activation state to a second activation state,

wherein the at least one activation element includes a modulus of elasticity greater than that of the deformable structure, and

wherein the meta-material includes a first stiffness when the at least one activation element is in the first activation state and the meta-material includes a second stiffness when the at least one activation element has been activated to the second activation state.

67. The method of claim 66 further comprising de-activating the at least one activation element from the second activation state to the first activation state.

68. The method of claim 67 wherein the de-activation occurs before overcoming one of a) an activation strength for the at least one activation element, or b) the modulus of elasticity for the at least one activation element.

69. The method of claim 67 further comprising re-activating the at least one activation element from the first activation state to the second activation state.

70. The method of claim 66 further comprising activating a different number of activation elements from the first activation state to the second activation state so the meta-material includes a third stiffness when the different number of activation elements has been activated to the second activation state.

71. The method of claim 66 wherein the third stiffness is less than second stiffness and greater than the first stiffness.

72. The method of claim 66 wherein the third stiffness causes the meta-material to match a resonance frequency witnessed by an object that includes the meta-material.

73. The method of claim 66 wherein the third stiffness causes an object that includes the meta-material to avoid a resonance frequency witnessed by the object without the stiffness change.

74. The method of claim 66 wherein activating the at least one activation element comprises applying an electrostatic clamping voltage to the least one activation element.

75. The method of claim 74 wherein the set of activation elements is mechanically redundant.

76. The method of claim 75 wherein the electrostatic clamping voltage includes an AC signal.

77. The method of claim 66 wherein each activation element at least partially laterally overlaps an adjacent activation element.

78. The method of claim 66 wherein the second state includes a different connectivity between the activation elements than a connectivity between the activation elements in the first state.

79. The method of claim 66 wherein the meta-material includes a different shape when the at least one activation element has been activated to the second activation state than a shape for the meta-material when the at least one activation element is in the first state.

80. The method of claim 66 wherein the first stiffness is less than about 10 MPa and the second stiffness is greater than about 100 MPa.

81. A method of changing shape of a meta-material, the meta-material comprising a deformable structure and a set of activation elements coupled to the deformable structure, the method comprising:

at least partially de-activating one or more activation elements;

applying a force to the deformable structure such that the meta-material acquires a new shape; and

activating the one or more activation elements when the meta-material acquires the new shape.

82. The method of claim 81 wherein the activation elements are de-activated such that the meta-material is compliant to an external force that moves the deformable structure.

83. The method of claim 81 wherein the activation elements are de-activated such that the meta-material decreases in stiffness from a first stiffness to a second stiffness.

84. The method of claim 81 wherein the first stiffness is greater than about 100 MPa and the second stiffness is less than about 10 MPa.

85. The method of claim 81 wherein the meta-material is included in one of:

an airplane or other air vehicle, a car or other land vehicle or a robot, orthotic, prosthetic or unmanned system.

86. The method of claim 81 wherein activating the one or more activation elements comprises applying an electrostatic clamping voltage to one or more activation elements.

87. The method of claim 86 wherein the set of activation elements is mechanically redundant.

88. The method of claim 87 wherein the electrostatic clamping voltage includes an AC signal.

89. The method of claim 81 wherein each activation element at least partially laterally overlaps an adjacent activation element.

90. The method of claim 81 wherein the second state includes a different connectivity between the activation elements than a connectivity between the activation elements in the first state.

91. A method of absorbing energy using a meta-material, the meta-material comprising a deformable structure and a set of activation elements coupled to the deformable structure, the method comprising:

activating at least one activation element from a first activation state to a second activation state,

wherein the meta-material includes a first value for a mechanical property when the at least one activation element is in the first activation state and the meta-material includes a second value for the mechanical property when the at least one activation element has been activated to the second activation state; and

applying a force to the meta-material such that the deformable structure deforms.

92. The method of claim 91 wherein activating the at least one activation element comprises applying an electrostatic clamping voltage to the least one activation element.

93. The method of claim 91 wherein the mechanical property is one of:

toughness, elastic modulus, stiffness, damping, shape and resilience.

94. The method of claim 91 wherein each activation element at least partially laterally overlaps an adjacent activation element.

95. The method of claim 91 wherein the second state includes a different connectivity between the activation elements than a connectivity between the activation elements in the first state.