MEMS force sensors fabricated using paper substrates

• US 9,682,856 B2
• Filed: 07/25/2012
• Issued: 06/20/2017
• Est. Priority Date: 08/01/2011
• Status: Expired due to Fees

• Current Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Original Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Inventors: Sun, Yu, Li, XiuJun, Liu, Xinyu, Thuo, Martin M., O'Brien, Michael, Whitesides, George
• Primary Examiner(s): West, Paul
• Assistant Examiner(s): ZHONG, XIN Y
• Application Number:
  US13/557,861
• Publication Number:
  US 20140224018A1
• Time in Patent Office: 1,791 Days
• Field of Search: 7351433
• CPC Class Codes: B81B 7/02 containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS] B81B7/04 takes precedence
• CPC Class Codes: B81C 1/0015 Cantilevers switches using MEMS H01H1/0036; electrostatic relays using micromechanics H01H59/0009; microelectro-mechanical resonators H03H9/02244
• CPC Class Codes: G01G 3/13 having piezoelectric or piezoresistive properties
• CPC Class Codes: G01L 1/18 using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/123 by piezo-resistive elements, e.g. semiconductor strain gauges
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/0862 being provided with particular means being integrated into a MEMS accelerometer structure for providing particular additional functionalities to those of a spring mass system

Abstract

MEMS devices fabricated using inexpensive substrate materials such as paper or fabric, are provided. Using paper as a substrate, low cost, simple to prepare, lightweight, disposable piezoresistive sensors, including accelerometers are prepared. Signal-processing circuitry can also be patterned on the substrate material.

The sensors can be utilized as two-dimensional sensors, or the paper substrate material can be folded to arrange the sensors in a three dimensional conformation. For example, three sensors can be patterned on a paper substrate and folded into a cube such that the three sensors are orthogonally positioned on the faces of a cube, permitting simultaneous measurement of accelerations along three orthogonal directions (x-y-z). These paper-based sensors can be mass produced by incorporating highly developed technologies for automatic paper cutting, folding, and screen-printing.

Also provided are methods of modifying paper for use as a substrate material in MEMS devices.

Claims

1. A micro-electro-mechanical systems (MEMS) device comprising:

a stationary platform;

a deflectable element integral to the stationary platform, wherein the stationary platform and deflectable element are comprised of a flexible insulating paper or fabric; and

a piezoresistive element disposed over at least a portion of the deflectable element.

2. The device of claim 1, wherein the device is a sensor.

3. The device of claim 2, further comprising a conductive inks.

4. The device of claim 3, further comprising an integrated signal processing circuit.

5. The device of claim 1 wherein the device is a three dimensional micro-electro-mechanical systems (MEMS) device comprising a flexible insulating paper or fabric substrate material.

6. The device of claim 5, wherein the device contains three sensors positioned orthogonally.

7. The device of claim 1 wherein the device is a two dimensional sensors.

8. The device of claim 7 wherein the paper or fabric is folded, creased, or pleated to increase rigidity.

9. The device of claim 1 further comprising a plastic film overlaid on the paper or fabric.

10. The device of claim 1 wherein the paper or fabric has been covalently or non-covalently modified to increase its hydrophobicity.

11. The device of claim 1 made by printing or screening of circuitry onto the paper or fabric using piezoresistive and/or conductive inks, which can then be attached to wires or other means of transmitting a signal.

12. The device of claim 1 wherein the device is a force sensor comprising an accelerometer which quantifies acceleration, wherein a proof mass is incorporated into the deflectable element, wherein a portion of the deflectable element functions as a proof mass, or wherein a proof mass is affixed to the deflectable element, wherein deformation of the proof mass, stresses the piezoresistive element, wherein the proof mass can be fabricated from the paper or fabric or another material.

13. The device of claim 10 wherein the force sensor is a force sensing cantilever beam device.

14. The device of claim 1 comprising multiple two-dimensional force-sensing devices arranged in a three-dimensional configuration.

15. The device of claim 14 comprising multiple two dimensional sensors arranged orthogonally to measure force along more than one axis simultaneously.

16. The device of claim 15 wherein a two-dimensional array of sensors is fabricated on a substrate, which is subsequently folded into a three dimensional structure to present three sensors orthogonally to simultaneously sense force along three orthogonal directions (x-y-z).

17. The device of claim 1 printed on a roll which is then applied in a manner similar to labels, with pre-applied or simultaneously applied adhesive.

18. The device of claim 1 in or on a toy.

19. The device of claim 1 applied to a shipping container.

20. A method of making the device of claim 1 comprising providing flexible insulating paper or fabric substrate material and depositing conductive material on or in a pattern thereon to create a sensor.