Lecture 1a
Role of Structures and Mechanisms
in MEMS
A general overview of structural aspects of MEMS .
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.1
Contents
• Structures, Mechanisms, and MEMS
• Early MEMS devices
• Kinematic pairs and mechanisms in MEMS:
excitement vs. practicality
• Deformable structures in MEMS
• Example 1: tilting micro-mirrors
• Example 2: micromanipulation
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.2
Structures and Mechanisms
• Structures support and transmit loads.
• Mechanisms transfer/transform motion AND
support and transmit loads.
• Another view: both transfer and transform energy
(load*motion)
• There is no need to limit this energy to mechanical
energy.
Microelectromechanical Systems (MEMS)
• Most MEMS are sensors and actuators, i.e., they
are transducers.
• Transducers are energy transformers and
transmitters.
If we limit MEMS to mechanical energy domain or if we expand the
Willis to other domains, the role
scope of energy in structures/mechanisms
of structures and mechanisms in MEMS is easily apparent.
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.3
Accepted size range for MEMS
Nanotechnology
10 nm
Microsystems
Meso
Macrosystems
1 um
100 um
10 mm
1m
Plain old machines
Humans
Animals
Plamts
Planes, trains, and automobiles
10 m
100 mm
Packaged ICs
Packaged MEMS
Lab-on-a-chip
Optical fibers
1 mm
MEMS
10 um
Bacteria
Biological cells
Dust particles
Dia. of human hair
Molecules
DNA
0.1 um
Smallest microelectronic features
1 nm
Nanostructures
Virus
A
Atoms
0
Micro-machining
Nano-machining
Precision machining
Macro-machining
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.4
MEMS devices in 1970’s and early 80’s
Ink-jet printer head
Bassous E., Taub H.H., Kuhn L. “Ink jet printing nozzle arrays etched in silicon” Appl. Phys. Lett. 31, 135
(1977)
Micro mirrors for steering light
Petersen K.E. "Micromechanical light modulator array fabricated on silicon" Appl. Phys. Lett. 31, 521-523
(1977)
Petersen K.E. “Silicon torsional scanning mirror” IBM J. Res. Dev. 24, 631-637 (1980)
Accelerometer
Roylance L.M., Angell J.B. “A batch fabricated silicon accelerometer” IEEE Trans. on Electron Devices 26,
1911-1917 (1979)
Optical fiber connector
Schroeder C.M. "Accurate silicon spacer chips for an optical fiber cable connector" Bell. Syst. Tech. J. 57,
91-97 (1977)
Microfluidic device
Terry S.C., Jerman J.H., Angell J.B. “A gas chromatograph air analyzer fabricated on a silicon wafer” IEEE
Trans on Electron Devices 26, 1880-1886 (1979)
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.5
MEMS devices in 1970’s and early 80’s
Pressure sensors
Clark S.K., Wise K.D. “Pressure sensitivity in anisotropically etched thin diaphragm pressure sensors” IEEE
Trans. on Electron Devices TED-26, 1887-1896 (1979)
Ko W.-H., Hynecek J., Boettcher S.F. “Development of a miniature pressure transducer for biomedical
applications” IEEE Trans. on Electron Devices T-ED26, 896-1905 (1979)
Other types of sensors
Kimura K. “Microheater and microbolometer using microbridge of SiO2 film on silicon” Elect. Lett. 17,
80-82 (1981)
Najafi K., Wise K.D., Mochizuki T. “A high-yield IC-compatible multichannel recording array” IEEE
Trans on Electron Devices 32, 1206-1211 (1985)
Stemme G. “A monolithic gas flow sensor with polyimide as thermal insulator” IEEE Trans. on Electron
Devices TED-33, 1470-1464 (1986)
Optical switching and multiplexing
Gustafsson K., Hök B. “Fiberoptic switching and multiplexing with a micromechanical scanning mirror” Proc. 4th Int.
Conf. on Solid-State Sensors and Actuators, Tokyo, June 3-5, P 212 (1987)
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.6
What is common to all those early
MEMS devices?
• A beam or a diaphragm
• A bulk-micromachined silicon, glass, etc.
• Electrical and electronic components for
sensing a signal
Micro-electro-mechanical systems (MEMS)
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.7
A MEMS accelerometer made in
1979
Bulk micro
machining
Piezoresistor
-based
sensing
Roylance L.M., Angell J.B. “A batch fabricated silicon accelerometer” IEEE Trans. on Electron Devices 26, 1911-1917
(1979)
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.8
Bulk micromachining
Isotropic etching
With agitation
Without agitation
Anisotropic etching
(111) plane
(100) silicon
Slanted
surfaces
(111)
(110) silicon
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.9
Kinematic joint-based motion in
MEMS
• The excitement began only after a rotary
motor, revolute (pin) joints, and prismatic
(sliding) joints were demonstrated.
– At U. C. Berkeley, MIT, and Bell Labs
– The reason for the excitement was batchfabrication of “assembled” micro-mechanisms
without assembly.
– Crucial development: sacrificial layer process
using polysilicon as the structural layer.
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.10
Early MEMS with kinematic joints
Gears
M. Mehregany, K.J. Gabriel, and W.S.N. Trimmer, "Micro Gears and Turbines Etched from Silicon," Sensors and
Actuators, vol. 12, pp. 341-348, Nov./Dec. 1987
Revolute joints and linkages
L.S. Fan, Y.C. Tai, R.S. Muller, "Integrated Movable Micromechanical Structures for Sensors and Actuators," IEEE Trans. on
Electron Devices, Vol. ED-35, No. 6, pp. 724-730, June 1988.
M. Mehregany, K.J. Gabriel, and W.S.N. Trimmer, "Fabrication of Integrated Polysilicon Mechanisms,"
IEEE Trans. Electron Devices, vol. ED-35, no. 6, pp. 719-723, June 1988.
Micro rotary motors
Y.C. Tai and R.S. Muller, "IC-processed Electrostatic Synchronous Motor," Sensors and Actuators, Vol. 20, No. 1&2, pp. 4956, Nov. 15, 1989.
M. Mehregany, S.F. Bart, L.S. Tavrow, J.H. Lang, S.D. Senturia, and M.F. Schlecht, "A Study of Three Microfabricated
Variable-Capacitance Motors," Sensors and Actuators, vol. A21–A23, pp. 173-179, 1990.
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.11
Electrostatic micro rotary motor
Sacrificial layer process to make a revolute joint
MUMPs process (MCNC)
Ravi Jain, undergraduate at Penn.
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.12
Sandia’s micro mechanisms
Courtesy of Sandia laboratories,
Albuquerque, New Mexico
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.13
Sandia’s in-plane revolute joint
Pin
Rotor
Substrate
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.14
Floating in-plane revolute joints
using only two structural layers
Floating Pin Joints Fabricated From Two Layers of Polysilicon at the Micro Level
(Deanne Clements, Larry L. Howell, Nathan Masters, and Brent L. Weight) at Brigham
Young University.
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.15
Pister’s out-of-plane revolute joint
A surface micromachined hinge
(Kris Pister, Berkeley)
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
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Floating revolute joint
Mask
layout
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.17
Why aren’t kinematic joints not
well suited for MEMS?
• More difficult to fabricate
• Friction and wear
– Main cause for structural failure
• Clearance in microfabricated kinematic joints is
huge
– Less accurate than deformable structures
• Some assembly may be required
– Cannot be justified economically
• Not always amenable for different types of
actuation
• Stiction
– Surfaces in close proximity tend to stick together
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.18
Example 1: tilting micro-mirrors:
single-axis
(Source: www.howstuffworks.com)
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.19
Agere (Lucent)’s two-axis mirrors
Raised above using Pister-type revolute joints
Surpentine “torsional” springs
-- to get large angles of rotation
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.20
Steerable vertical mirrors
A surpentine torsional spring
Khiem Ng,
Central High School,
Philadelphia
2002
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.21
Example 2: Micro-manipulation of
biological cells
Laser tweezers and
scissors operating on a
cell (Berns, 1998)
Cell injection using
micro pipettes
(Nelson, 2000)
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.22
Polysilicon microgrippers
C. J. Kim, A. Pisano, and R. S. Muller, Silicon-processes overhanging microgripper, JMEMS, Vol. 1,
No. 1, 1992, pp. 31-36.
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.23
Minimally invasive capture of cells
using a micro cage
C. J. Kim, UCLA
Bi-metal cantilevers
curled due to residual
stress.
Opened with
actuating the bottom
membrane
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.24
Actuation in liquid environments is
difficult
Beam
width =
375 m
Micro
probe
(top view)
Markers
In-plane hydraulic/pneumatic
actuation using a vertical
membrane.
Sponge
CCD camera view of the micro
device with a micro object
Manipulation using
compliant mechanisms
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.25
Main points
• Kinematic joints in MEMS are cool but
have limited (or no) practical use.
• Simple deformable structures have been
used wisely by MEMS researchers.
– Two examples to illustrate this point follow…
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.26
Electrostatic comb-drive actuator–
a clever structural design
Folded-beam suspension
Moving
combs
Shuttle
mass
Misaligned
parallel-plate
capacitor
anchor
Fixed
combs
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.27
Cancer detection using a cantilever
The presence of the virus
makes the cantilevers bend.
A.
Majumdar, Berkeley
Stiff Structures, Compliant Mechanisms, and MEMS: A short course offered at IISc, Bangalore, India. Aug.-Sep., 2003. G. K. Ananthasuresh
Slide 1a.28