High-Efficiency Compact Miniaturized Energy Harvesting And Storage Device

• US 20100314968A1
• Filed: 12/04/2009
• Published: 12/16/2010
• Est. Priority Date: 06/15/2009
• Status: Active Grant

• Current Assignee: Farrokh Mohamadi
• Original Assignee: Farrokh Mohamadi
• Inventors: Mohamadi, Farrokh
• Granted Patent: US 8,283,840 B2
• Time in Patent Office: Days
• US Class Current: 310/319
• CPC Class Codes: H02N 2/186 Vibration harvesters
• CPC Class Codes: H10N 30/06 Forming electrodes or interconnections, e.g. leads or terminals
• CPC Class Codes: H10N 30/30 with mechanical input and electrical output, e.g. functioning as generators or sensors
• CPC Class Codes: H10N 30/87 Electrodes or interconnections, e.g. leads or terminals
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

An energy harvesting and storage system includes an array of piezoelectric electrodes, in which the piezoelectric electrodes generate electrical energy from mechanical displacements of the piezoelectric electrodes; and an array of capacitor electrodes disposed in proximity to the piezoelectric electrodes, in which the array of capacitor electrodes stores a portion of the energy generated by the piezoelectric electrodes. An energy system includes a substrate including an array of micro-post electrodes connected to a cathode layer of the substrate; an isolation material covering the array of micro-post electrodes; and an anode layer including electrodes filling the remaining region between the isolation material-covered micro-post electrodes, in which the anode layer, electrodes, isolation material, micro-post electrodes, and substrate are monolithically coupled.

Claims

1. An energy harvesting system comprising:

an array of piezoelectric electrodes, wherein the piezoelectric electrodes generate electrical energy from mechanical displacements of the piezoelectric electrodes; and

an array of capacitor electrodes interspersed with the piezoelectric electrodes, wherein the array of capacitor electrodes stores a portion of the energy generated by the piezoelectric electrodes.

2. The system of claim 1, wherein:

the array of capacitor electrodes is disposed interdigitally with the array of piezoelectric electrodes.

3. The system of claim 1, wherein:

the array of piezoelectric electrodes comprises high aspect ratio posts, wherein the aspect ratio of the posts is low enough to avoid collapse from lateral adhesion forces between the high aspect ratio posts.

4. The system of claim 3, wherein:

the aspect ratio L/2r is lower than a critical aspect ratio given by the formula;

(0.57E^1/3(2d)^1/2)/(γ

_s(2r)^1/6(1−

v²)^1/12)

wherein r is a radius of a post, L is a height of the post, d is half of a pitch between posts, γ

_s is a surface energy, v is a Poisson ratio of the post material, and E is an extendability factor of the post material.

5. The system of claim 1, wherein:

an area density of electrodes is at least 400 per square millimeter.

6. The system of claim 1, further comprising:

a cathode layer formed in the substrate of the array of capacitive electrodes.

7. The system of claim 1, further comprising:

an anode layer of polysilicon deposited on the array of capacitive electrodes.

8. The system of claim 1, wherein:

the piezoelectric electrodes comprise lead zirconate titanate (PZT).

9. The system of claim 1, wherein:

a pitch between electrodes is no greater than 50 microns.

10. The system of claim 1, wherein:

a diameter of the posts is no greater than 5 microns.

11. An energy system comprising:

a substrate including an array of micro-post electrodes connected to a cathode layer of the substrate;

an isolation material covering the array of micro-post electrodes; and

an anode layer including electrodes filling the remaining region between the isolation material-covered micro-post electrodes, wherein the anode layer, electrodes, isolation material, micro-post electrodes, and substrate are monolithically coupled.

12. The system of claim 11, wherein:

the isolation material is a piezoelectric material for functioning as an energy generation system.

13. The system of claim 11, wherein:

the isolation material is a dielectric material for functioning as an energy storage system.

14. The system of claim 11, wherein:

the substrate comprises an ionizable material.

15. The system of claim 11, wherein:

the substrate comprises silicon implanted with arsenic to form the cathode layer.

16. The system of claim 11, wherein:

the isolation material is a piezoelectric material; and

the anode layer is configured to transmit pressure to the piezoelectric material.

17. A method comprising:

piezoelectrically converting mechanical strain energy from an induced mechanical stress on an array of piezoelectric electrode posts into electrical energy; and

using a geometrical arrangement of an array of capacitor electrode posts and the array of piezoelectric electrode posts to capacitively store the electrical energy in the array of capacitor electrode posts.

18. The method of claim 17, further comprising:

inducing mechanical stress from vibrations of a proof mass on the array of piezoelectric electrode posts.

19. The method of claim 17, wherein:

the array of capacitor electrode posts is geometrically arranged with the array of piezoelectric electrode posts interdigitally.

20. The method of claim 17, wherein:

the array of capacitor electrode posts is geometrically arranged with the array of piezoelectric electrode posts by nesting.

21. The method of claim 17, wherein:

a voltage of the stored electrical energy is adjusted in accordance with a determination of a pitch between the electrodes.

22. The method of claim 17, wherein:

an aspect ratio of the piezoelectric electrode posts is determined in accordance with avoiding collapse of the posts due to adhesion forces between the posts.

23. The method of claim 17, wherein:

the arrays of electrode posts are formed with an area density of at least 400 per square millimeter.

24. A method of manufacturing an energy generation and storage device, the method comprising:

forming an array of silicon posts on a substrate;

making an elastomeric mold of the array of silicon posts having wells corresponding to the posts;

casting an array of piezoelectric electrode posts from the mold;

orienting the array of piezoelectric electrode posts so as to be interdigitally aligned with the array of silicon posts; and

disposing the array of piezoelectric electrode posts and the array of silicon posts so as to be interdigitally arranged with each other.

25. A method of manufacturing an energy generation and storage device, the method comprising:

etching an array of posts in a silicon substrate using reactive ion etching process;

implanting and annealing the silicon substrate to form a cathode layer;

forming one of either a piezoelectric or a dielectric layer on the array of posts; and

depositing a layer of doped polysilicon on the array of posts to form an anode layer.