Precision Engineering Research Group

Massachusetts Institute of Technology

An Instrument to Measure the Force-Displacement Characteristics of MEMS Mechanisms

Supervisors: Alexander H. Slocum, Jeffrey H. Lang

Jin Qiu, Joachim Sihler, Jian Li

In itia l shape as etchedw ith no in ternal stress.

Second stable positionafter snap through

in itia l apex height d0

Actuation forcecauses deflection

Snap through

current

Bistable Relay Principle Precision Engineering Research Group

Snap Through of Bistable Beam Precision Engineering Research Group

Front side Back side

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Fabrication Imperfectness

Unpredictable tapering of the DRIE process requires post manufacture minitoring to verify mechanical properties

Prototype (parts mostly made with the waterjet) Precision Engineering

Research Group

Prototype Close-ups Precision Engineering Research Group

Data acquisition unit with reference flexure, amplification lever, and displacement sensos

Needle used for mechanical contact

FMEMS

F()

F

Fundamental Goal:Measure the stiffness of a MEMS flexure

MEMS flexure

0 1 2 3 4 5 6 7 8 9

0 1 2 3 4 5 6 7 8 9

9 8 7 6 5 4 3 2 1 0

9 8 7 6 5 4 3 2 1 0

reference flexure

FMEMS

d d1

MEMS flexure

=d2-d1

FMEMS=kref * d2

kMEMS=FMEMS /

MEMS flexure reference flexure

Fundamental F-D curve principle Precision Engineering Research Group

Functionality of the Amplification Lever Design Precision Engineering

Research Group

d 2

a

d1

b

l

M EM S flexurereference flexure

b

t

F M dM

d2+d2 d 1+d1

d2d1

HP Barcode Readers as Displacement Sensor

10 nm resolution

bar codereader 1

bar codereader 2

d1 d2

d

m irror1

m irror2

d=d1-d2

d

i

4.5 m m3 m m 6 m m

linearrange

0.5 m m

Reference: Colin J.H. Brenan et al.: “Characterization and use of a novel optical position sensor for microposition control of a linear motor” , Rev. Sci. Instrum. 64(2), February 1993.

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Displacement Sensors 2 and 3 in differential configuration

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Displacement Sensor 1

Fundamental Principle Animation

Actual Measurement Data

Force error +/- 6.5 % (not to scale)

displacement error +/- 10 nm (not to scale)

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Pictures of Prober Tips Precision Engineering Research Group

Flextester

Market Potential Precision Engineering Research Group

Bistable microrelay used in automotive applications:

•20 milion cars/year (20*106 relays/year)•5 % of cars/year using it (1*106 relays/year)•20 relays/car/year (20*106 relays/year)•1000 relays/wafer (20*103 wafers/year)•200 days per year=========================================100 wafers/day !