Flexible pressure sensor

1 . A flexible pressure sensor comprising:

a lower structure; and

an upper structure on the lower structure,

wherein the lower structure comprises:

a flexible substrate; and

first electrodes on the flexible substrate and second electrodes spaced apart from the first electrodes, and

the upper structure comprises:

a support;

first protrusion structures integrally connected to the support to protrude from a bottom surface of the support; and

second protrusion structures integrally connected to the support to protrude from the bottom surface of the support, the second protrusion structures being spaced apart from the first protrusion structures,

wherein the second protrusion structures vertically overlap the first and second electrodes,

the first protrusion structures are in contact with a top surface of the flexible substrate,

the second protrusion structures are vertically spaced apart from the first and second electrodes, and

when viewed in a plan view, the first protrusion structures are configured to completely surround the second protrusion structures.

2 . The flexible pressure sensor of claim 1 , wherein each of the first protrusion structures has a first height, and

each of the second protrusion structures has a second height,

wherein the first height is greater than the second height.

3 . The flexible pressure sensor of claim 2 , wherein the first height is about 1.8 times to about 2.2 times the second height.

4 . The flexible pressure sensor of claim 1 , wherein each of the first protrusion structures and each of the second protrusion structures comprise pores, respectively.

5 . The flexible pressure sensor of claim 4 , wherein the support does not comprise the pores.

6 . The flexible pressure sensor of claim 1 , wherein a top surface of each of the first protrusion structures has a first width in a first direction, which is parallel to the top surface of the flexible substrate,

a bottom surface of each of the first protrusion structures has a second width in the first direction, and

a top surface of each of the second protrusion structures has a third width in the first direction,

wherein the first width is greater than each of the second width and the third width.

7 . The flexible pressure sensor of claim 6 , wherein a width of each of the first protrusion structures in the first direction decreases constantly from the top surface to the bottom surface of each of the first protrusion structures.

8 . The flexible pressure sensor of claim 7 , wherein a lower end of each of the second protrusion structures has a pointed shape.

9 . The flexible pressure sensor of claim 1 , further comprising first line connected to the first electrodes and second lines separately connected to each of the second electrodes,

wherein a ground voltage is applied to the first line, and

a bias voltage that is different in magnitude from the ground voltage is applied to the second lines.

10 . The flexible pressure sensor of claim 1 , wherein, when viewed in a plan view, the first electrodes and the second electrodes have a concentric circle shape.

11 . The flexible pressure sensor of claim 1 , further comprising a conductive film configured to cover the bottom surface of the support, the first protrusion structures, and the second protrusion structures,

wherein the conductive film is in contact with the flexible substrate on a region that vertically overlaps the first protrusion structures, and

the conductive film is vertically spaced apart from the first and second electrodes on a region that vertically overlaps the second protrusion structures.

12 . The flexible pressure sensor of claim 1 , wherein the first protrusion structures are configured to remain in contact with the top surface of the flexible substrate and the second protrusion structures are configured to remain vertically spaced apart from the first and second electrodes, when a bending pressure is applied to the flexible pressure sensor, and

wherein the first protrusion structures are configured to remain in contact with the top surface of the flexible substrate and the second protrusion structures are configured to selectively contact the first and second electrodes, when a vertical pressure is applied to the flexible pressure sensor.

13 . A flexible pressure sensor comprising:

a lower structure; and

an upper structure on the lower structure,

wherein the lower structure comprises:

a flexible substrate; and

first electrodes on the flexible substrate and second electrodes spaced apart from the first electrodes, and

the upper structure comprises:

a support;

first protrusion structures protruding from a bottom surface of the support; and

second protrusion structures protruding from the bottom surface of the support, the second protrusion structures being spaced apart from the first protrusion structures,

wherein each of the first protrusion structures has a first width in a first direction parallel to a top surface of the flexible substrate,

each of the second protrusion structures has a second width in the first direction,

the bottom surface of the support and a side surface of each of the first protrusion structures are angled at a first angle, and

the bottom surface of the support and a side surface of each of the second protrusion structures are angled at a second angle,

wherein the second protrusion structures vertically overlap the first and second electrodes,

the first protrusion structures are in contact with a top surface of the flexible substrate,

the second protrusion structures are vertically spaced apart from the first and second electrodes,

wherein the first width is greater than the second width, and the first angle and the second angle are the same.

14 . The flexible pressure sensor of claim 13 , wherein, when viewed in a cross-sectional view, each of the first protrusion structures has a trapezoidal shape, and

when viewed in a cross-sectional view, each of the second protrusion structures has a triangular shape.

15 . The flexible pressure sensor of claim 13 , wherein each of the first angle and the second angle ranges of about 52 degrees to about 57 degrees.

16 . The flexible pressure sensor of claim 15 , wherein each of the first protrusion structures has a first height, and

each of the second protrusion structures has a second height,

wherein the first height is 1.8 times to 2.2 times the second height.

17 . The flexible pressure sensor of claim 13 , wherein the first protrusion structures are configured to completely surround the second protrusion structures, and

the second protrusion structures are arranged in a zigzag shape in the first direction.