NATO Advanced Study Institute RESPONSIVE SYSTEMS … / MEMS Course Brussels, September 10-19, 2001
Laboratoire de Mécanique Appliquée – UMR CNRS 6604 – Université de Franche Comté Institut des Microtechniques de Franche Comté
5.2 High-Driving Force
Electrostatic Actuators using Contact Interactions
A/ Elementary Actuation Cells B/ Annular Microactuators
NATO Advanced Study Institute RESPONSIVE SYSTEMS … / MEMS Course Brussels, September 10-19, 2001
Laboratoire de Mécanique Appliquée – UMR CNRS 6604 – Université de Franche Comté Institut des Microtechniques de Franche Comté
How shall we design
high-driving force electrostatic actuators involving electrostatic field interactions ?…
- Shaping limitations (small structural heights…) - Micrometer gap requirements
- Material limitations…
Stator/rotor frictional contact interactions overcomes most of current SM- related design constraints, while keeping the
same actuator’s overall size.
NATO Advanced Study Institute RESPONSIVE SYSTEMS … / MEMS CourseBrussels, September 10-19, 2001
Laboratoire de Mécanique Appliquée – UMR CNRS 6604 – Université de Franche Comté Institut des Microtechniques de Franche Comté
Pull-in Effect Analysis using “Linear” Suspension
0 d
0/2 d
min= 2d
0/3 d
0k. d
0D istanc e inte r-a rm atu re s : d ()
0d d k F
mécz− ⋅ − =
2 20
2 1
d V S F
ir élzε ε =
V
1= V
pull-in/2
V
2= V
pull-inV
3= 2.V
pull-inFo rc e : F
d F d F P
élz méczinpull∂ ∂ = ∂ ∂
−/ d
0d (S) k = ct e
0min 0 32
3 2 d d d avec S kd V
inpull r inpull
= = =
− −
ε ε Ar m atu re m obile
E lect ro de fi xe
NATO Advanced Study Institute RESPONSIVE SYSTEMS … / MEMS CourseBrussels, September 10-19, 2001Laboratoire de Mécanique Appliquée – UMR CNRS 6604 – Université de Franche Comté Institut des Microtechniques de Franche Comté
Electrostatic Driving Forces Available on the Silicon Wafer Level
d ai r ( a)
h F
x (a)x y z
l
F
x (b)L
ai r ( a)
l F
z (c)d L
ai r ( a)
l F
z (d)e is ola nt ( i) L
F
z (e)e p L
is ola nt F
x (e)l
(a)(b)(c)(d)(e)(f) 20 )(
2 1
hdEFar axεε=()
dVE/
= *2)(10 7
µNFax −⋅=20 )(
2 1
ldEFar bxεε=()
dVE/
= *)( )(50
≈=h lF Fax bx
20 )(
2 1
lLEFar czεε=()
dVE/
= *3)( )(10 25, 1
⋅≈=hd lLF Fax cz 20 )(2 1
lLEFir dzεε=()
eVE/
= *52)( )(10 4, 1
⋅≈=he lLdF Far irax dzε ε
()
)()(dz ezFVKF⋅≈**)(
1500
µNFex≈()
**4)( )( 2)( )(
10 2
⋅≈⇒ ⋅⋅≈ax ex ar irax ex
F F he lLdVKF Fε εµ
L l m L
n l
)()(ex fxFnmF××=* h =1µm ; d =2µm ; l =50µm ; L =50µm ; e =0,5µm ; p=0,75µm ; ε
ir=7 ;
ε
ar=1 et V =180 Volt s Π 2 !
See Bottom-up Design Methodology
NATO Advanced Study Institute RESPONSIVE SYSTEMS … / MEMS Course Brussels, September 10-19, 2001
Laboratoire de Mécanique Appliquée – UMR CNRS 6604 – Université de Franche Comté Institut des Microtechniques de Franche Comté
Actuation Cell using Contact Interactions
Plaque
+/- V
Plot de Contact
Substrat
∆x
Doc. LMARC
Polysilicon Plate
Contact Plot
NATO Advanced Study Institute RESPONSIVE SYSTEMS … / MEMS CourseBrussels, September 10-19, 2001
Laboratoire de Mécanique Appliquée – UMR CNRS 6604 – Université de Franche Comté Institut des Microtechniques de Franche Comté
Avoiding Pull-in Effect using “Non-Linear” Mechanical Response of Actuation Cells
0 10 20 30 40 50 60 70 80050100150200250300350Tension d’alimentation (V)
Taux de contact (%)
L = 53µml = 60µmT = 1,6µmh = 0,75µm
LcL t h
Taux de contact K = Lc / L
0 5 10 15 20 25 30 35 40 45 50
0102030405060Abscisse longitudinale (µm)
Distriubtion de pression (MPa)
250V
170V130V
90V
70V
p
(a)
(b )
NATO Advanced Study Institute RESPONSIVE SYSTEMS … / MEMS Course Brussels, September 10-19, 2001
Laboratoire de Mécanique Appliquée – UMR CNRS 6604 – Université de Franche Comté Institut des Microtechniques de Franche Comté
On-Chip Mechanical Power Measurement on Electrostatic Actuation Cells using Contact Interactions
Video Photographs Showing Elastic Deflections of Polysilicon Beams Connected to Elementary Actuation Cells. Deflection Analysis Allows Driving Characteritics of Cells to be
Measured. Tests Pointed out Mechanical Power as High as 1000 Watts /gr ! Doc. LMARC / web site: www.micromachines.univ-fcomte.fr
NATO Advanced Study Institute RESPONSIVE SYSTEMS … / MEMS CourseBrussels, September 10-19, 2001
Laboratoire de Mécanique Appliquée – UMR CNRS 6604 – Université de Franche Comté Institut des Microtechniques de Franche Comté
Electrostatic Actuation Cell Using Frictional Contact Interactions
- Lateral Size - Overall thickness - Nominal Driving V o lt age
- Cut-off Actuation Frequency - T ime Const ant - S tepping M o tion (open l o op frequenc y control) - Lifetim e - S p eed - Element ary Driving Force - Actuation Cell Density per Unit Area - Driving Force per Unit Ar ea 50 × 50 microns 2 microns 100 V o lt s
> 500 kH z < 2µs down to 10nm
... up to 10
8cy cles ... up to 10 cm/s ... up to 1500 µN 250 / mm
2up to 0.4N / mm
2Doc. LMARC / web site: www.micromachines.univ-fcomte.fr
NATO Advanced Study Institute RESPONSIVE SYSTEMS … / MEMS Course Brussels, September 10-19, 2001
Laboratoire de Mécanique Appliquée – UMR CNRS 6604 – Université de Franche Comté Institut des Microtechniques de Franche Comté
High Torque Electrostatic Micromotors using Stator/Rotor Contact Interactions
φ 500 microns annular motors, (a)Video sequence showing motors actuated through
electrostatic probing, (b) SEM micrograph showing distributed elementary actuation cells.
Doc. LMARC / web site: www.micromachines.univ-fcomte.fr
30
TorsioActuatioCell
Contact
30µm
Elementary Actuation Cells
Contact Plots
NATO Advanced Study Institute RESPONSIVE SYSTEMS … / MEMS Course Brussels, September 10-19, 2001
Laboratoire de Mécanique Appliquée – UMR CNRS 6604 – Université de Franche Comté Institut des Microtechniques de Franche Comté
Incompatibility in Size with Macroscopic Testing Equipment
0 100 200 300 400 500 600 700 800
125 135 145 155 165 175 185 195 205 215 Buckling Beam Free Length (µm)
Buckling Torque (nN.m)
Polysilicon Young Modulus Buckling Beam Thickness Buckling Beam Width Buckling Beam Inner Radii Buckling Beam Outer Radii
: 170GPa : 1.7µm : 12µm : 113µm : 125µm Buckling Beam 100 µm
Doc. LMARC / web site: www.micromachines.univ-fcomte.fr
NATO Advanced Study Institute RESPONSIVE SYSTEMS … / MEMS Course Brussels, September 10-19, 2001
Laboratoire de Mécanique Appliquée – UMR CNRS 6604 – Université de Franche Comté Institut des Microtechniques de Franche Comté
On-Chip Measurement of Torque/speed Characteristics on the Micrometer Scale
Parallel test units allowing on-chip measurement of continuous torque/speed characteristics through electrostatic probing.
Doc. LMARC / web site: www.micromachines.univ-fcomte.fr
NATO Advanced Study Institute RESPONSIVE SYSTEMS … / MEMS Course Brussels, September 10-19, 2001
Laboratoire de Mécanique Appliquée – UMR CNRS 6604 – Université de Franche Comté Institut des Microtechniques de Franche Comté
Torque/Speed Acquisition on Micrometer Size Electrostatic Micromotors
100 µm
Graduation Needle
Torque Sensor
Doc. LMARC / web site: www.micromachines.univ-fcomte.fr
NATO Advanced Study Institute RESPONSIVE SYSTEMS … / MEMS CourseBrussels, September 10-19, 2001
Laboratoire de Mécanique Appliquée – UMR CNRS 6604 – Université de Franche Comté Institut des Microtechniques de Franche Comté
On-chip Acquisition of Loading Characteristics using Automatic Motion Analysis
250 µm
b)
Doc. LMARC / web site: www.micromachines.univ-fcomte.fr
- Automatic Motion Analysis Software - High Resolution CCD Camera (up to 4096 x 4096 pixels)
NATO Advanced Study Institute RESPONSIVE SYSTEMS … / MEMS Course Brussels, September 10-19, 2001
Laboratoire de Mécanique Appliquée – UMR CNRS 6604 – Université de Franche Comté Institut des Microtechniques de Franche Comté
On-chip Loading Characteristic Acquisition Φ 500 microns Electrostatic Micromotor
50 µm 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
0 1 2 3 4 5 6 7
Mechanical Sensor Angular Position (deg)
Angular Elastic Stiffness ( µN.m/deg )
a)
Rotation Speed (rpm)
0 0.5 1 1.5 2 2.5 3 3.5 4
200Hz 1kHz 5kHz Driving frequencies
Driving voltage : 100V
0 20 40 60 80 100 120 140 160
0 0.2 0.4 0.6 0.8 1 1.2
Mechanical Power (nW)
Driving Torque (µN.m)
-
Low Driving Voltage (100 Volts)
Low Driving Frequency (Max. 5 kHz) Driving Characteristics
Angular Characteristic of the Torque Sensor
Doc. LMARC / web site: www.micromachines.univ-fcomte.fr
NATO Advanced Study Institute RESPONSIVE SYSTEMS … / MEMS Course Brussels, September 10-19, 2001
Laboratoire de Mécanique Appliquée – UMR CNRS 6604 – Université de Franche Comté Institut des Microtechniques de Franche Comté
High-Torque Micrometer-Size Annular Micromotors: Driving Characteristics
- External diameter
- Overall thickness 500 microns
2 microns
NATO Advanced Study Institute RESPONSIVE SYSTEMS … / MEMS Course Brussels, September 10-19, 2001
Laboratoire de Mécanique Appliquée – UMR CNRS 6604 – Université de Franche Comté Institut des Microtechniques de Franche Comté