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based on SmartMaterials

Bishakh Bhattacharya and Nachiketa Tiwari

Indian Institute of Technology, Kanpur

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Lecture 40: MEMSbased Actuators

"Courtesy Sandia National Laboratories,SUMMiT Technologies,mems.sandia.gov"

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ezoe ec r c nc worm ev ces

Inchworm devices for Actuation

Rainbow and Thunder Actuation

Active Elasto-dynamic Motion

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A Case history of Sensor

u v

MEMS based Accelerometers

How to develop MEMS?

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Till 1960 Radio was the only electronics system

Engine systems were controlled mechanically

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conven ona mec anca y ac ua e gn on an

fuel systems weren't precise enough to control

1960-70: Electronic ignition system was

Crankshaft position sensor

Airflow rate sensor

Throttle position sensor

Microcontroller to control i nition

http://auto.howstuffworks.com/engine3.htm

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Late 1970: ABS (Antilock Brake Device)

Sense locking of wheels and modulate hydraulicpressure to minimize sliding

Mid 1990: TCS(Traction Control System)

Sense slippage during acceleration and modulatepower to prevent slipping

More advances like VDS (Vehicle Dynamics

Control), Millimeter wave Radar Technology withGPS based traffic updating etc.

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ensors xposure to a spec c

Physical/Chemical/Biological Phenomenonwould produce a significant output signal(electrical/mechanical/optical/acoustic etc.)

Actuators Accept a Control Commandmostl in the form of an electric si nal and

produce a change in the physical system by

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Wh MEMS based S stems?

MEMS as the name suggests refers tomcro-sca e e ectro-mec anca systems.

Th v nt f MEM t m v rmacro systems are:

, high sensitivity, easy to integrate/communicate

low noise, high machine precision

decreased cost due to removal of manualassembly and substitution by batch fabrication)

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Earliest MEMS products: MEMS

Accelerometer & ..

Sensing, Piezoresistivity, Piezoelectricity,ptical Inter erometry, thermal expansion

-

developed at Stanford in 1979!

yroscopes e ner a easuremen n s

(IMUs) Digital Micro Mirrors (DMMs)

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MEMS Accelerometers: Fact

between them. When a voltage is applied to one of

,stored on the surfaces of the plates will cause an

.

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0 = absolute permittivity of free space (8.85 10-12)

r = re a ve perm v y e ec rc cons an o

medium in gap between plates =

d = plate separation (displacement)

There are three ways to change the capacitance of the-

Variation of the shared area of the plates (A)

ara on o e e ec rc cons an r

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MEMS Accelerometers: based

x Ref:

2

212

xd

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Active Control of Optical Aperture

Source:A. P.

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MEMS based Actuators

MEMS as the name suggests refers tomcro-sca e e ectro-mec anca systems.

A t m tiv t r A li ti n : Airbag System

u Active Suspension

Consumer Sector Applications:

Subwoofers

ports ra nng evces

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c now e gemen : ona a a u e n vers y

A lication of AC between the electrode and silicon

develops electrostatic force and create oscillation.

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.

times Youngs Modulus of Steel bout 700a, u as g as umnumKg/m3

It is mechanically stable and can be easilydeveloped by using micro-fabrication

.

For signal transductions, p or n type

semiconductors can be readily integrated withthe Si subsrtate.

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Melting point around 1400 degree centigrade

smaller than Aluminium

Very Flat for coating

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Sin le Cr stal Silicon

Czocharlski Method Raw Silica (Quatzite) ismolten in a chamber. The crystal formation

process is initiated with a seed crystal which isgradually pulled to get the complete biggercrystal.

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Three common techniques

used for MEMS fabrications Bulk Micromachining removal of

materials from Bulk substrates either bisotropic or anisotropic wet etching

Wafer bonding - using precisely alignedwafers

fabrication

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Micro-mechatronics by Uchino &

Giniewicz, Marcel, Dekke Microsensors MEMS and Smart Devices,

,

Donald Lab at Duke University

Fundamentals of Microfabrication, Marc

, , .

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