Haptic feedback using composite piezoelectric actuator

1. An electronic device comprising:

a touch sensitive layer configured to sense contact at a touch sensitive surface;

a display layer configured to visually display images;

a composite piezoelectric assembly that is substantially planar and has a cut-out so that the composite piezoelectric assembly forms a frame around the touch sensitive layer and forms a seal with the touch sensitive layer to protect the display layer, wherein the composite piezoelectric assembly comprises a first electrode layer, a second electrode layer, and a composite piezoelectric layer disposed between the first electrode layer and the second electrode layer, the composite piezoelectric layer having a plurality of piezoelectric rods arranged in a polymer matrix; and

a drive circuit configured to apply a voltage to the first electrode layer or the second electrode layer.

2. The electronic device according to claim 1 , wherein the piezoelectric rods span across a thickness of the composite piezoelectric layer such that each piezoelectric rod of the plurality of piezoelectric rods is in contact with the first electrode layer and the second electrode layer.

3. The electronic device according to claim 1 , wherein when the piezoelectric rods are stimulated by an alternating voltage applied to the first electrode layer and the second electrode layer, the piezoelectric rods expand and contract in a direction perpendicular to a surface of the display layer when the piezoelectric rods are stimulated by the alternating voltage.

4. The electronic device according to claim 3 , wherein the piezoelectric rods are configured to cause vibration of the polymer matrix in which the piezoelectric rods are arranged by the expansion and contraction of the piezoelectric rods.

5. The electronic device according to claim 4 , wherein the polymer matrix is adapted to isolate, from the rest of the electronic device, any vibration that is transferred to the touch sensitive layer.

6. The electronic device according to claim 1 , wherein the composite piezoelectric layer is configured to act as an adhesive tape.

7. The electronic device according to claim 6 , wherein the composite piezoelectric assembly is formed from four pieces of material arranged to form a rectangular planar portion having the cut-out in a center thereof.

8. The electronic device according to claim 1 , wherein the composite piezoelectric assembly completely surrounds the display layer.

9. The electronic device according to claim 1 , wherein the composite piezoelectric assembly only partially surrounds the display layer.

10. The electronic device according to claim 1 , wherein the composite piezoelectric layer is flexible and conforms to a shape of the display layer.

11. The electronic device of claim 1 , wherein the touch sensitive layer comprises a protective layer configured to protect other layers of the electronic device from environmental effects.

12. The electronic device of claim 1 , wherein the electronic device is a handheld computing device.

13. An electronic device comprising:

a display layer configured to visually display images;

a touch sensitive layer located on a front side of the display layer and configured to sense contact at a touch sensitive surface;

a composite piezoelectric assembly placed on the other side of the display layer away from the touch sensitive layer so that the composite piezoelectric assembly is behind the display layer, wherein the composite piezoelectric assembly comprises a first electrode layer, a second electrode layer, and a composite piezoelectric layer disposed between the first electrode layer and the second electrode layer, the composite piezoelectric layer having a plurality of piezoelectric rods arranged in a polymer matrix; and

a drive circuit configured to apply a voltage to the first electrode layer or the second electrode layer.

14. The electronic device according to claim 13 , wherein the composite piezoelectric assembly has a uniform structure that provides an equal distribution of haptic effects to all portions of the display layer.