Capacitive bending sensors

• US 10,670,429 B2
• Filed: 02/09/2018
• Issued: 06/02/2020
• Est. Priority Date: 02/09/2017
• Status: Active Grant

• Current Assignee: University of British Columbia
• Original Assignee: University of British Columbia
• Inventors: Madden, John D. W., Sarwar, Mirza S.
• Primary Examiner(s): Astacio-Oquendo, Giovanni
• Application Number:
  US15/893,508
• Publication Number:
  US 20180238716A1
• Time in Patent Office: 844 Days
• Field of Search: 324500, 324537, 32475016, 32475025
• CPC Class Codes: G01B 7/22 using change in capacitance
• CPC Class Codes: G01D 5/2412 by varying overlap
• CPC Class Codes: G01L 1/144 with associated circuitry G01L1/146 and G01L1/148 take precedence
• CPC Class Codes: G01L 1/146 for measuring force distributions, e.g. using force arrays G01L1/148 takes precedence
• CPC Class Codes: G01L 5/228 using tactile array force sensors
• CPC Class Codes: G06F 2203/04103 Manufacturing, i.e. details related to manufacturing processes specially suited for touch sensitive devices
• CPC Class Codes: G06F 2203/04105 Pressure sensors for measuring the pressure or force exerted on the touch surface without providing the touch position
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06F 3/0447 Position sensing using the local deformation of sensor cells
• CPC Class Codes: G06F 3/0448 Details of the electrode shape, e.g. for enhancing the detection of touches, for generating specific electric field shapes, for enhancing display quality

Abstract

A sensor unit for detecting bending of the sensor unit comprises: a capacitive upper sensor having an upper capacitance and comprising first and second deformable upper electrodes spaced apart from one another in a Z direction, the first and second upper electrodes respectively having first and second upper shapes; and a capacitive lower sensor having a lower capacitance, spaced apart from the upper sensor in a Z direction and comprising first and second deformable lower electrodes spaced apart from one another in the Z direction, the first and second lower electrodes respectively having first and second lower shapes. For a bend of the sensor unit in a first direction, the first and second upper shapes change such that the upper capacitance decreases and the lower shapes change such that the lower capacitance increases. For a bend of the sensor unit in a second direction opposed to the first direction, the first and second upper shapes change such that the upper capacitance increases and the lower shapes change such that the lower capacitance decreases.

Claims

1. A sensor unit for detecting bending of the sensor unit, the sensor unit comprising:

a capacitive upper sensor having an upper capacitance (C_upper) and comprising first and second deformable upper electrodes spaced apart from one another in a Z direction, the first and second upper electrodes respectively having first and second upper shapes;

a capacitive lower sensor having a lower capacitance (C_lower), spaced apart from the upper sensor in a Z direction and comprising first and second deformable lower electrodes spaced apart from one another in the Z direction, the first and second lower electrodes respectively having first and second lower shapes; and

wherein, for a bend of the sensor unit in a first direction about a Y-axis orthogonal to the Z direction, the first and second upper shapes change such that the upper capacitance (C_upper) decreases and the lower shapes change such that the lower capacitance (C_lower) increases, and, for a bend of the sensor unit in a second direction about the Y-axis and opposed to the first direction, the first and second upper shapes change such that the upper capacitance (C_upper) increases and the lower shapes change such that the lower capacitance (C_lower) decreases.

2. The sensor unit according to claim 1 comprising a circuit connected to apply an upper voltage between the first and second upper electrodes to thereby cause an upper electric field (E_upper) in a vicinity of the upper sensor and connected to apply a lower voltage between the first and second lower electrodes to thereby cause a lower electric field (E_lower) in a vicinity of the lower sensor.

3. The sensor unit according to claim 2 comprising a capacitance-measurement circuit connected to generate an upper sensor signal representative of the upper sensor capacitance (C_upper) and a lower sensor signal representative of the lower sensor capacitance (C_lower).

4. The sensor unit according to claim 3 comprising a processor connected to receive the upper sensor signal and the lower sensor signal and configured to determine estimated values for the upper sensor capacitance (C_upper) and the lower sensor capacitance (C_lower) therefrom.

5. The sensor unit according to claim 4 wherein the circuit is connected to apply the upper voltage and the lower voltage at nominal voltage levels and wherein the processor is configured to determine the estimated values for the upper sensor capacitance (C_upper) and the lower capacitance (C_lower) to be a nominal upper sensor capacitance level (C_u,nom) and a nominal lower sensor capacitance level (C_l,nom) respectively when the sensor unit is not bent.

6. The sensor unit according to claim 5 wherein the processor is configured to at least one of generate and output one or more signals indicating a bend of the sensor unit in the first direction about the Y-axis when the estimated value of the upper sensor capacitance (C_upper) decreases below a threshold range around the nominal upper sensor capacitance level (C_u,nom) and the estimated value of the lower sensor capacitance (C_lower) increases above a threshold range around the nominal lower sensor capacitance level (C_l,nom).

7. The sensor unit according to claim 5 wherein the processor is configured to at least one of generate and output one or more signals indicating a bend of the sensor unit in the second direction about the Y-axis when the estimated value of the upper sensor capacitance (C_upper) increases above a threshold range around the nominal upper sensor capacitance level (C_u,nom) and the estimated value of the lower sensor capacitance (C_lower) decreases below a threshold range around the nominal lower sensor capacitance level (C_l,nom).

8. The sensor unit according to claim 1 wherein the sensor unit comprises a neutral bending plane and wherein the upper sensor and the lower sensor are on opposite sides of the neutral bending plane.

9. The sensor unit according to claim 8 wherein the upper sensor is spaced apart from the neutral bending plane in the Z direction by an upper sensor neutral spacing and the lower sensor is spaced apart from the neutral bending plane in the Z direction by a lower sensor neutral spacing and the upper sensor neutral spacing is substantially equal to the lower sensor neutral spacing.

10. The sensor unit according to claim 8 wherein the upper sensor is spaced apart from the neutral bending plane in the Z direction by an upper sensor neutral spacing and the lower sensor is spaced apart from the neutral bending plane in the Z direction by a lower sensor neutral spacing and the upper sensor neutral spacing is substantially unequal to the lower sensor neutral spacing.

11. The sensor unit according to claim 1 wherein the first and second upper electrodes and the first and lower electrodes are substantially transparent at visible light wavelengths.

12. The sensor unit according to claim 1 wherein the first and second upper electrodes and the first and lower electrodes have transmissivities of over 90% at visible light wavelengths.

13. The sensor unit according to claim 1 wherein the first and second upper electrodes and the first and second lower electrodes are fabricated from ionically conductive hydrogel.

14. The sensor unit according to claim 1 wherein the first and second upper electrodes and the first and second lower electrodes are fabricated from at least one of:

a metal mesh;

silver nanowires, carbon nanotubes and one or more conducting polymers.

15. The sensor unit according to claim 1 wherein at least one of the first and second lower electrodes is elastically deformable.

16. The sensor unit according to claim 1 wherein at least one of the first and second upper electrodes is elastically deformable.

17. The sensor unit according to claim 1 wherein the first and second upper shapes changing comprises the first and second upper electrodes changing in cross-sectional area in a plane orthogonal to the Z direction.

18. The sensor unit according to claim 1 wherein the first and second lower shapes changing comprises the first and second lower electrodes changing in size in a plane orthogonal to the Z direction.

19. A sensor unit for detecting bending of the sensor unit, the sensor unit comprising:

a capacitive sensor having a capacitance (C) and comprising first and second deformable electrodes spaced apart from one another in a Z direction, the first and second upper electrodes respectively having first and second shapes;

wherein, for a bend of the sensor unit in a first direction about a Y-axis orthogonal to the Z direction, at least one of the first and second shapes change such that the capacitance (C) increases, and, for a bend of the sensor unit in a second direction about the Y-axis and opposed to the first direction, at least one of the first and second shapes change such that the capacitance (C) decreases.

20. A sensor array comprising

a plurality of Y direction oriented sensor unit columns, each sensor unit column comprising a plurality of sensor units generally aligned with one another in the Y direction and each sensor unit column oriented such that the plurality of sensor units form a plurality of X direction oriented sensor unit rows, each sensor unit row comprising a subset of the plurality of sensor units generally aligned with one another in an X direction;

and

wherein each of the plurality of sensor units comprises a sensor unit comprising;

a capacitive upper sensor having an upper capacitance (C_upper) and comprising first and second deformable upper electrodes spaced apart from one another in a Z direction, the first and second upper electrodes respectively having first and second upper shapes;

a capacitive lower sensor having a lower capacitance (C_lower), spaced apart from the upper sensor in a Z direction and comprising first and second deformable lower electrodes spaced apart from one another in the Z direction, the first and second lower electrodes respectively having first and second lower shapes; and

wherein, for a bend of the sensor unit in a first direction about a Y-axis orthogonal to the Z direction, the first and second upper shapes change such that the upper capacitance (C_upper) decreases and the lower shapes change such that the lower capacitance (C_lower) increases, and, for a bend of the sensor unit in a second direction about the Y-axis and opposed to the first direction, the first and second upper shapes change such that the upper capacitance (C_upper) increases and the lower shapes change such that the lower capacitance (C_lower) decreases.

21. A method for fabricating a sensor unit, the method comprising:

embedding a capacitive upper sensor within a dielectric material of the sensor unit at a first location spaced apart from a neutral bending plane of the sensor unit in a positive-Z direction; and

embedding a capacitive lower sensor within the dielectric material of the sensor unit at a second location spaced apart from the neutral bending plane of the sensor unit in a negative-Z direction.

22. The method according to claim 21 wherein the capacitive upper sensor comprises first and second deformable upper electrodes spaced apart from one another in the positive-Z direction and the capacitive lower sensor comprises first and second deformable lower electrodes spaced apart from one another in the negative-Z direction.