Flexural deformation sensing device and a user interface using the same

• US 8,132,468 B2
• Filed: 05/29/2008
• Issued: 03/13/2012
• Est. Priority Date: 05/29/2008
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: Nokia Corporation
• Inventors: Radivojevic, Zoran
• Primary Examiner(s): Caputo, Lisa
• Assistant Examiner(s): DAVIS, OCTAVIA L
• Application Number:
  US12/156,468
• Publication Number:
  US 20090293631A1
• Time in Patent Office: 1,384 Days
• Field of Search: 737/77
• US Class Current: 73/777
• CPC Class Codes: G01L 1/16 using properties of piezoelectric devices
• CPC Class Codes: G01L 5/167 using piezoelectric means
• CPC Class Codes: G01L 5/22 for measuring the force applied to control members, e.g. control members of vehicles, triggers
• CPC Class Codes: G06F 3/014 Hand-worn input/output arrangements, e.g. data gloves
• CPC Class Codes: H10N 30/1061 based on piezoelectric or electrostrictive fibres
• CPC Class Codes: H10N 30/302 Sensors

Abstract

A sensing device is provided for measuring flexural deformations of a surface. Such a sensing device may be used as a user interface in portable electronic devices. The sensing device comprises at least one cell. The cell comprises a first electrode, a central electrode, a second electrode, a first piezoelectric sensing layer placed between the first electrode and the central electrode, a second piezoelectric sensing layer placed between the central electrode and the second electrode, and a circuit connected to the first, second and the central electrodes. The circuit is configured to measure a first electrical signal between the first electrode and the central electrode, and a second electrical signal between the second electrode and the central electrode. At least one of the first electrical signal and the second electrical signal is responsive to an external stress applied on the sensing device.

Claims

1. An apparatus, comprising at least one cell, said cell comprising:

a first electrode,

a central electrode, a second electrode,

a first sensing layer placed between the first electrode and the central electrode,

a second sensing layer placed between the central electrode and the second electrode,

a circuit connected to the first, second and the central electrodes, said circuit being configured to measure a first electrical signal between the first electrode and the central electrode, and a second electrical signal between the second electrode and the central electrode, and

wherein at least one of the first electrical signal and the second electrical signal is responsive to an external stress applied on the cell, wherein the first sensing layer comprises piezoelectric crystallites aligned substantially in a first direction parallel to the first sensing layer, the second sensing layer comprises piezoelectric crystallites aligned substantially in a second direction parallel to the second sensing layer, and wherein the first direction and the second direction are not parallel to each other, wherein said apparatus is part of a user interface configured to accept a user input and to convert said user input into at least one of the first electrical signal and the second electrical signal, and wherein said apparatus is a flexible sensor module fitted to a part of a human body, and wherein a movement of the part of the human body produces the external stress for controlling an electronic device.

2. The apparatus of claim 1, wherein the first sensing layer and the second sensing layer each comprises a piezoelectric material.

3. The apparatus of claim 2, wherein the first sensing layer and the second sensing layer each comprises high aspect ratio crystallites of the piezoelectric material.

4. The apparatus of claim 3, wherein the high aspect ratio crystallites have a diameter of 1-100 nm and a length of 1-1000 μ

m.

5. The apparatus of claim 3, wherein the high aspect ratio crystallites are zinc oxide (ZnO) nanowires, barium titanate (BaTiO₃) nanowires, or carbon nanotubes.

6. The apparatus of claim 1, wherein the first electrical signal is a voltage difference between the first electrode and the central electrode and the second electrical signal is a voltage difference between the second electrode and the central electrode.

7. The apparatus of claim 1, wherein the first electrical signal is a change of resistance between the first electrode and the central electrode and the second electrical signal is a change of resistance between the second electrode and the central electrode.

8. The apparatus of claim 1, wherein at least one of the first electrical signal and the second electrical signal is proportional to the external stress applied on the cell.

9. The apparatus of claim 1, wherein

the apparatus comprises a plurality of cells, said plurality of cells are arranged in a two dimensional array with a plurality of rows and a plurality of columns,

the first and the second electrodes each comprises a plurality of strip electrodes and each strip electrode extends across a column of the cells,

the central electrode comprises a plurality of strip electrodes and each strip electrode extends across a row of the cells,

each of the plurality of strip electrodes of the first electrode is connected to a first bus,

each of the plurality of strip electrodes of the second electrode is connected to a second bus,

each of the plurality of strip electrodes of the central electrode are connected to a third bus,

wherein the circuit is connected to each of the strip electrodes via the first, second or the third bus, and

wherein the circuit is configured to measure the first electrical signal of each cell between the first electrode and the central electrode, and the second electrical signal of each cell between the second electrode and the central electrode.

10. The apparatus of claim 9, wherein the first sensing layer and the second sensing layer each extends across the plurality of columns and the plurality of rows, and wherein the first sensing layer comprises piezoelectric crystallites aligned substantially in a first direction parallel to the first sensing layer, the second sensing layer comprises piezoelectric crystallites aligned substantially in a second direction parallel to the second sensing layer, and wherein the first direction and the second direction are not parallel to each other.

11. The apparatus of claim 10, wherein the first direction is a direction parallel to the rows and the second direction is a direction parallel to the columns.

12. The apparatus of claim 9, wherein at least one of the first electrical signal of each cell and the second electrical signal of each cell is proportional to the external stress and said signals are used for calculating a flexural deformation of the apparatus in response to an external stress.

13. An electronic device, comprising a user interface configured to accept a user input, wherein said user interface comprises an apparatus according to claim 1, and wherein said user input is converted into at least one of the first electrical signal and the second electrical signal for communicating to the device.

14. A computer program product, comprising a computer readable storage medium storing program codes thereon for use by an electronic device, said program codes comprise:

instructions for measuring a first electrical signal and a second electrical signal, and

instructions for calculating a flexural deformation as a result of an external stress,

wherein said stress is applied on a apparatus to cause said flexural deformation of said apparatus, said apparatus comprises at least one cell, said cell comprises;

a first electrode,

a central electrode,

a second electrode,

a first sensing layer placed between the first electrode and the central electrode,

a second sensing layer placed between the central electrode and the second electrode,

a circuit connected to the first, second and the central electrodes, said circuit being configured to measure the first electrical signal between the first electrode and the central electrode, and the second electrical signal between the second electrode and the central electrode,

and wherein at least one of the first electrical signal and the second electrical signal is generated in response to the external stress, wherein the first sensing layer comprises piezoelectric crystallites aligned substantially in a first direction parallel to the first sensing layer, the second sensing layer comprises piezoelectric crystallites aligned substantially in a second direction parallel to the second sensing layer, wherein the first direction and the second direction are not parallel to each other, wherein said apparatus is part of a user interface configured to accept a user input and to convert said user input into at least one of the first electrical signal and the second electrical signal, wherein said apparatus is a flexible sensor module fitted to a part of a human body, and wherein a movement of the part of the human body produces the external stress for controlling the electronic device.

15. The computer program product of claim 14, wherein the program codes further comprise:

instructions for using the first electrical signal and/or the second electrical signal for said controlling the electronic device.