Micromechanical contact load force sensor for sensing magnitude and distribution of loads and tool employing micromechanical contact load force sensor

• US 5,656,785 A
• Filed: 08/07/1995
• Issued: 08/12/1997
• Est. Priority Date: 08/07/1995
• Status: Expired due to Fees

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Cho, Steve T., Trainor, Christopher V., Hopkins, Ralph E. III
• Primary Examiner(s): Chilcot, Richard
• Assistant Examiner(s): Noori, Max H.
• Application Number:
  US08/511,658
• Time in Patent Office: 736 Days
• Field of Search: 73/760, 73/780, 73/862, 73/862.046, 73/862.473, 73/862.052
• US Class Current: 73/862.46
• CPC Class Codes: A61B 2090/064 for measuring force, pressure or mechanical tension
• CPC Class Codes: A61F 2/3859 Femoral components
• CPC Class Codes: A61F 2/389 Tibial components A61F2/3868 takes precedence
• CPC Class Codes: A61F 2/4603 for insertion or extraction of endoprosthetic joints or of accessories thereof
• CPC Class Codes: A61F 2/461 of knees
• CPC Class Codes: A61F 2/4657 Measuring instruments used for implanting artificial joints for surgical instruments A61B90/06
• CPC Class Codes: A61F 2/583 Hands; Wrist joints
• CPC Class Codes: A61F 2/586 Fingers
• CPC Class Codes: A61F 2002/4666 for measuring force, pressure or mechanical tension
• CPC Class Codes: A61F 2002/5061 the sense of touch
• CPC Class Codes: A61F 2002/704 computer-controlled, e.g. robotic control
• CPC Class Codes: A61F 2002/7635 for measuring force, pressure or mechanical tension
• CPC Class Codes: B25J 13/084 Tactile sensors in general G01L5/16, G01L5/22
• CPC Class Codes: G01L 1/146 for measuring force distributions, e.g. using force arrays G01L1/148 takes precedence
• CPC Class Codes: G01L 1/148 using semiconductive material, e.g. silicon
• CPC Class Codes: G01L 5/228 using tactile array force sensors

Abstract

A micromechanical contact load force sensor is disclosed. The force sensor comprises an array of capacitive load cells on a substrate. The force sensor is able to sense high loads, on the order on 10⁹ N/m², and distribute the load over a suitable number of the cells of the array while minimizing crosstalk between adjacent cells. The force sensor is useful in biological and robotic applications.

Claims

1. A micromechanical contact load force sensor comprising:

an array of deformable capacitive elements connected in electrical communication in columns along an insulating substrate and in electrical communication in rows through a semiconductor material bonded to said substrate,

said semiconductor material provided as an array of unitary bodies each extending continuously from said insulating substrate adjacent capacitive gaps to an array of isolated bearing surfaces above said capacitive gaps, each bearing surface positioned above an associated capacitive element of said array of capacitive elements to define an array of load cells, wherein a change in capacitance is effected by deformation of one of said unitary bodies above said capacitive gaps.

2. The micromechanical contact load force sensor of claim 1, wherein said bearing surfaces are isolated by valleys formed in said semiconductor material.

3. The micromechanical contact load force sensor of claim 2, wherein said bearing surfaces are spaced a predetermined distance and said valleys have a predetermined depth to minimize crosstalk between adjacent load cells.

4. The micromechanical contact load force sensor of claim 1, wherein said unitary bodies of semiconductor material have a thickness extending above said array of capacitive elements sufficient to support a load of approximately 10⁹ N/m².

5. The micromechanical contact load force sensor of claim 1, wherein said unitary bodies of semiconductor material have a thickness of at least 100 μ

m.

6. The micromechanical contact load force sensor of claim 1, wherein said insulating substrate is glass.

7. The micromechanical contact load force sensor of claim 1, wherein said semiconductor material is silicon.

8. The micromechanical contact load force sensor of claim 1, wherein each capacitive element of said array of capacitive elements comprises a first capacitive plate affixed to said substrate and a second capacitive plate spaced by a capacitive gap from said first capacitive plate and formed of an element diffused into said semiconductor material.

9. The micromechanical contact load force sensor of claim 8, wherein said element diffused into said semiconductor material comprises boron, phosphorous, antimony, arsenic, gallium, indium, or aluminum.

10. The micromechanical contact load force sensor of claim 8, wherein said first capacitive plate comprises a metal bonded to said substrate.

11. A micromechanical contact load force sensor comprising:

an insulating substrate;

an array of capacitive load cells formed on said insulating substrate, comprising;

a plurality of first capacitive plates formed on said insulating substrate in a spaced array, said first capacitive plates further being in electrical communication in columns,

a semiconductor material bonded to said insulating substrate, a plurality of second capacitive plates supported by said semiconductor material to overlie associated ones of said first capacitive plates with a capacitive gap therebetween, said semiconductor material extending as a deformable continuous mass from said insulating substrate on opposed sides immediately adjacent said capacitive gaps to a bearing surface above each of said first and second capacitive plates, said semiconductor material electrically isolated in columns, said semiconductor material having a plurality of valleys provided therein between adjacent bearing surfaces to separate said adjacent bearing surfaces while allowing electrical communication in rows through said semiconductor material, said semiconductor material extending as a continuous mass from a low point of each of said plurality of valleys to said insulating substrate.

12. The micromechanical load force sensor of claim 11, wherein said valleys are defined by angled side walls.

13. The micromechanical load force sensor of claim 11, wherein said continuous mass of semiconductor material extending above said first and second capacitive plates has a thickness sufficient to support a load of approximately 10⁹ N/m².

14. The micromechanical load force sensor of claim 11, wherein said continuous mass of semiconductor material extending above said first and second capacitive plates has a thickness of at least 100 μ

m.

15. The micromechanical load force sensor of claim 11, wherein said bearing surfaces are spaced a predetermined distance and said valleys have a predetermined depth to minimize crosstalk between adjacent load cells.

16. The micromechanical load force sensor of claim 11, wherein said insulating substrate is glass.

17. The micromechanical load force sensor of claim 11, wherein said semiconductor material is silicon.

18. The micromechanical load force sensor of claim 11, wherein said first capacitive plates are formed by a metal.

19. The micromechanical load force sensor of claim 11, wherein said second capacitive plates are formed by a boron-diffused layer in said semiconductor material.

20. A tool for sensing magnitude and distribution of loads comprising:

a support surface;

a tactile array of capacitive load cells comprising;

an insulating substrate supported by said support surface;

a plurality of first capacitive plates formed on said insulating substrate in a spaced array, said first capacitive plates further being in electrical communication in columns,

a semiconductor material bonded to said insulating substrate, a plurality of second capacitive plates supported by said semiconductor material to overlie associated ones of said first capacitive plates with a capacitive gap therebetween, said semiconductor material extending as a deformable continuous mass from said insulating substrate on opposed sides immediately adjacent said capacitive gaps to a bearing surface above each of said first and second capacitive plates, said semiconductor material electrically isolated in columns, said semiconductor material having a plurality of valleys provided therein between adjacent bearing surfaces to separate said adjacent bearing surfaces while allowing electrical communication in rows through said semiconductor material, said semiconductor material extending as a continuous mass from a low point of each of said plurality of valleys to said insulating substrate.

21. The tool of claim 20, wherein said support surface comprises two arms, said tactile array being disposed on one of said arms, a further tactile array being disposed on another of said arms.

22. The tool of claim 21, wherein said arms are curved.

23. The tool of claim 20, further including a handle.

24. The tool of claim 23, wherein said handle is detachable.

25. The tool of claim 20, further comprising an electrical connection connectable to a readout device.

26. The tool of claim 20, wherein said tool is configured to comprise a total knee arthroplasty force balance sensing device.

27. The tool of claim 20, wherein said tool is configured to comprise a robotic hand.

28. The tool of claim 20, wherein said tool is configured to comprise a robotic glove.

29. The tool of claim 20, wherein said valleys are defined by angled side walls.

30. The tool of claim 20, wherein said continuous mass of semiconductor material extending above said first and second capacitive plates has a thickness sufficient to support a load of approximately 10⁹ N/m².

31. The tool of claim 20, wherein said continuous mass of semiconductor material extending above said first and second capacitive plates has a thickness of at least 100 microns.

32. The tool of claim 20, wherein said bearing surfaces are spaced a predetermined distance and said valleys have a predetermined depth to minimize crosstalk between adjacent load cells.

33. The tool of claim 20, wherein said insulating substrate is glass.

34. The tool of claim 20, wherein said semiconductor material is silicon.

35. The tool of claim 20, wherein said first capacitive plates are formed by a metal.

36. The tool of claim 20, wherein said second capacitive plates are formed by a boron-diffused layer in said semiconductor material.