MEMS APPLICATIONS

OVERVIEW

MEMS Applications Overview Learning Module

Force-balance accelerometer

used for microgravity

measurements.

Macro (top) vs. MEMS (bottom)

[Courtesy of NASA]

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Microelectromechanical systems (MEMS) are very small devices or groups of devices that can integrate both mechanical and electrical components.

This unit provides a brief summary of MEMS devices already on the market. It also discusses the various fields in which MEMS are used and the possibilities for MEMS in these fields.

Unit Overview

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State three fields in which MEMS devices are

being used

State three applications of MEMS devices in

the automobile industry

State three applications for MEMS in the

medical field

Objectives

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What is a MEMS?

MEMS are constructed on one chip with

electrical circuitry for inputs and outputs

of the electromechanical components.

MEMS can consist of a combination of

components in various scales: nano,

micro, and milli.

An example is the MEMS artificial retina.

This MEMS consists of an electrode

microarray (shown in picture) that is

placed on the retina inside the eye.

This microarray interfaces with external components (a camera and

microprocessor contain in the patient’s glasses) and the brain (via the optic

nerve). The camera image is converted into a series of electrical pulses that

are sent to the brain from the microarray via the optic nerve. The brain

translates these pulses into flashes of light for a low resolution image.

This MEMS has been tested and IT WORKS! (Check out next slide)

Prototype of a MEMS Retina Implant

[Photo by Randy Montoya. Courtesy of Sandia

National Laboratories]

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Retinal Prosthesis: What the patient sees

These images show what a patient with a MEMS retinal prosthesis should see.

Increasing the number of electrodes in the retina array results in more visual

perceptions and higher resolution vision.

In 2007 six patients were successfully implanted with the first prototype Model

1 device or Argus I™ containing 16 electrodes (16 pixels - left picture).

The Argus II™ (almost 200 pixels) proved successful in phase two of clinical

trials. Patients could find doorways, distinguish colors and even read!

The third model (256 pixels – middle picture) is under development and trials

are projected for 2011.

Images generated by the DOE-funded

Artificial Retinal Implant Vision

Simulator devised and developed by Dr.

Wolfgang Fink and Mark Tarbell at the

Visual and Autonomous Exploration

Systems Research Laboratory, California

Institute of Technology.

[Printed with permission.]

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MEMS Scale – Pressure Sensors (PS)

These pictures compare a macro-

size pressure sensor (70mm in

diameter) to a MEMS pressure

sensor.

The left picture compares both

systems. The right hand pictures

compare the diaphragms. The

MEMS diaphragm is being seen

through a microscope.

To create a MEMS PS the

diaphragm and related electrical

components are reduced in size

and placed on a microchip as

illustrated in the insert on the left

picture. [Macro PS photos courtesy of Bob Willis

MEMS diaphragm courtesy of UNM/MTTC]

A pressure sensor is a device consisting of a mechanical component

(diaphragm) and electronic components.

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What are MEMS?

MEMS devices sense, think, act and communicate.

They redirect light, pump and mix fluids, and detect molecules, heat,

pressure, or motion.

The interaction of electronics, mechanics, light or fluids working

together makes up a microelectromechanical system or MEMS.

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Applications of MEMS

Applications are developed where miniaturization is beneficial:

Consumer products

Aerospace

Automotive

Biomedical

Chemical

Optical displays

Wireless and optical communications

Fluidics

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Types of MEMS Devices

Pressure sensors

Accelerometers (inertial sensors)

Micromirrors

Gear Trains

Miniature robots

Fluid pumps

Microdroplet generators

Optical scanners

Probes (neural, surface)

Analyzers

Imagers

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MEMS Sensors

Sensors are a major application for MEMS devices.

Three primary MEMS sensors

pressure sensors

chemical sensors

inertial sensors (accelerometers, gyroscopes)

MEMS sensors can be used in combinations with other sensors

for multisensing applications. For example, a MEMS can be

designed with sensors to measure the flow rate of a liquid

sample and at the same time identify any contaminates within

the sample.

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MEMS Pressure Sensor

MEMS pressure sensors use a

flexible diaphragm as the

sensing device.

One side of the diaphragm is

exposed to a sealed, reference

pressure and the other side is

open to external pressure.

The diaphragm moves with a

change in the external pressure.

MEMS Pressure Sensor

[Courtesy of the MTTC, University of New

Mexico]

What are some possible applications for this type of sensor?

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MEMS in the Automotive Industry

MEMS pressure sensors sense, monitor and transmit

Tire pressure

Fuel pressure

Oil pressure

Air flow

Absolute air pressure within the intake manifold of the engine

What other applications are possible within the automotive industry?

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MEMS in the Automotive Industry

MEMS pressure sensors sense, monitor and transmit

Tire pressure

Fuel pressure

Oil pressure

Air flow

Absolute air pressure within the intake manifold of the engine

What other applications are possible within the automotive industry?

Air-bag deployment, throttle position, weight and sensing of passengers

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Pressure Sensors in BioMedical Applications

Blood PS

Intracranial PS

PS in endoscopes

Sensors for infusion pumps

RF (radio frequency) elements

incorporated into the MEMS device

allow the sensor to transmit its

measurements to an external receiver.

What are some other possibilities for

MEMS PS in the medical field?

MEMS Blood Pressure Sensors on the

head of a pin. [Photo courtesy of

Lucas NovaSensor, Fremont, CA]

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Other Pressure Sensor Applications

Barometric PS - used in wind tunnels

and for weather monitoring applications. (see picture)

"Smart Roads" - millions of MEMS

sensors are incorporated into roads to

gather and transmit information about

road conditions. (“MEMS Applications:. All About MEMS. 2002.

http://www.allaboutmems.com/memsapplications.html)

Smart Dust is a network of micro-sized

wireless MEMS sensors that

communicate with each other through

tiny transmitters. Smart dust sensors

(such as MEMS pressure sensors) could

be scattered around a building, a piece

of property, embedded in clothing, or in

road beds. (“SMART DUST - Autonomous sensing and

communication in a cubic millimeter". Dr. Kris Piser, PI. DARPA/MTO MEMS

Program, Berkley.)

Barometric Pressure Sensors

(Photo courtesy of Khalil Najafi,

University of Michigan)

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Brainstorming

Let’s do a little brainstorming for other applications of

MEMS pressure sensors.

There are other fields we didn’t discuss, so think

beyond automotive and medical. What about

aerospace, environmental, military, sports, or

consumer gaming?

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MEMS Inertial Sensors

Newton's First Law of Motion (also referred to as the law

of inertia) states, "An object at rest tends to stay at rest

and an object in motion tends to stay in motion with the

same speed and in the same direction unless acted

upon by an unbalanced force.”

MEMS inertial sensors are designed to sense a change

in an object's inertia, and then convert, or transduce

inertial force into a measurable signal. They measure

changes in acceleration, vibration, orientation and

inclination. This is done through the use of micro-sized

devices called accelerometers and gyroscopes.

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MEMS Accelerometers

The simplest MEMS accelerometer sensor is an inertial mass

suspended by springs.

The mass is deflected from its nominal position as a result of

acceleration. This deflection of the mass is converted to an

electrical signal as the sensor's output.

MEMS Accelerometer [Photo courtesy of Khalil Najafi, University of

Michigan]

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MEMS Gyroscopes

A gyroscope is generally a spinning wheel or disk with a free

axis allowing it to take any orientation (below left). Some MEMS

gyroscopes use a vibrating structure rather than the traditional

rotating disk to determine orientation (see bottom right).

MEMS Vibrating Ring Gyroscope[(Photo courtesy of Sandia National Laboratories]

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MEMS Inertial Sensors in Automobiles

Airbag deployment

"Smart" sensors for collision

avoidance and skid detection

Active suspension

Automobile navigation

Antitheft system

Headlight leveling and

positioning

Rollover detectors

3-axis High-Performance Micromachined

Accelerometer

(Each accelerometer senses movement in one

direction. Notice the markings: x-y-z. The

accelerometers are connected using polysilicon

connectors.)

[Image courtesy of Khalil Najafi, University of Michigan]

Polysilicon Connectors

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Airbag Deployment Sensor

The type of inertial sensor used in

air-bags is called a shock sensor

using 3 accelerometers.

The sensor has an accelerometer

for each orthogonal direction (x, y,

and z) and corresponding

circuitry.

Compared to the macro device, a

MEMS provides a quicker

response to rapid deceleration

and more reliable functionality. It

is cheaper and smaller in size.3-axis Accelerometer for airbag deployment

[Courtesy of Sandia National Laboratories]

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Other Applications of MEMS Inertial Sensors

Motion and shock detection

Vibration detection and

measurement

Measurement of tilt and inclination

Anti-theft devices

Home security devices

Computer screen scrolling and

zooming devices

Gaming devices for portables and

PC's (e.g. Wii and Playstation)

Image stabilizer cameras and

phones

MEMS Vibrating Gyroscope

[(Photo courtesy of Sandia National

Laboratories]

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Other Types of MEMS

In addition to sensors, MEMS consist of pumping devices, gear

trains, moveable mirrors, miniature robots, tweezers, tools and

lasers.

These devices have found numerous applications with various fields

such as biomedical, optical, wireless networks, aerospace, and

consumer products.

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MEMS in the Medical Field

Precise dispensers for small

amounts of liquids found in

needleless injectors and drug

delivery systems.

Sub-dermal glucose for monitoring

monitor glucose levels and deliver of

the insulin. (See figure)

Medical diagnostics for blood

analysis, cells counts and urinalysis.

Polymerase chain reaction (PCR) for

DNA replication.

DNA microarrays for testing of

genetic diseases and other

biological markers.

MiniMed Paradigm[R] 522 insulin pump, with

MiniLinkTM] transmitter and infusion set.

A chemical sensor (C) measures the blood glucose

and a transmitter (D) that sends the measurement to

the a computer in (A). (A) also contains a

micropump that delivers a precise amount of insulin

through the cannula (B) to the patient. This is a

continuous bioMEMS monitoring and drug delivery

system.(Printed with permission from Medtronic Diabetes)

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Clinical Laboratory Testing

The picture to the right shows a lab-on-a-

chip (LOC). This device literally takes the

laboratory testing of biomolecular samples

(e.g. blood, urine, sweat, sputum) out of the

typical medical lab and places it in the field

and even at home.

Using microfluidics and chemical sensors,

this MEMS or bioMEMS can

simultaneously identify multiples analytes

(substances being analyzed).

An example of a home LOC is the home

pregnancy test. This bioMEMS uses a

reactive coating that identifies a specific

protein found in the urine of pregnant

women.

Lab-on-a-chip (LOC)

Printed with permission. From Blazej,R.G.,Kumaresan,P. and Mathies, R.A.

PNAS 103,7240-7245 (2006).

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Other Biomedical Applications

What are some other current and potential

applications of MEMS in the medical field?

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Optical Applications of MEMS

The objective for optical MEMS is to integrate optical, mechanical

and electronic functions into one device. Optical MEMS have

already been quite successful in display technologies.

Two commercial devices – Digital Mirror Devices and Grating Light

Valve - redirect light to create high definition imaging from digital

signals. Both of these devices are used in video projection

systems such as rear and front projection televisions.

Texas Instrument's Digital Mirror Devices (DMD) have been

used for several years in a variety of projection systems

including video projection and digital cinema. The

technology is called digital light processing or DLPTM, a

trademark owned by Texas Instruments, Inc.

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TI’s DLP (digital light processing) System

A DMD is an array of micromirrors (left figure). Each micromirror (between 5um

and 20um square) is designed to tilt into (ON) or away from (OFF) the light source.

The mirror tilts when a digital signal energizes an electrode beneath the mirror.

One mirror can be turned OFF and ON as many as 30,000 times per second.

There are thousands of mirrors in an array with less than 1 μm spacing between

them. The DLP 1080p technology delivers more than 2 million pixels for true

1920x1080p resolution. The diagram on the right illustrates how the DLP system

works

Levels of a DMD Array (left) and How a DLP system works (right).[Images Courtesy of Texas Instruments]

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The Grating Light Valve (GLV)

The GLV device developed by Silicon Light

Machines, is another micro optical based system.

This microdevice consists of several silicon

nitride ribbons coated with aluminum. A set of

four ribbons (two fixed and two moveable)

produce a 20 μm square pixel.

The ribbons are held "up" by the tensile

strength of the material (silicon nitride and

aluminum).

The moveable ribbons are "moved" up and

down electrostatically. Electrodes are placed

under the moveable ribbons. Variable voltages

applied to the electrodes pull the ribbons down.

When no voltage is applied, the tensile

strength of the ribbon will allow it to snap back.

GLVs are used in high definition TVs and are

being investigated for use in maskless

photolithography.

Grating Light Valve (GLV) – top view and side view

showing actuated state and unactuated state

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Other Optical Applications of MEMS

Optical Communication Networks

Tunable lasers and filters

Display screens on cell phones and

PDAs

Variable optical attenuators

Optical Spectrometers

Bar code readersMEMS Pop-up mirror for optical applications.

Notice the hinge allowing for the different

angles needed to direct light in different

directions. Also notice the track that assists in

positioning the mirror at the correct angle.

[Image Courtesy of Sandia National

Laboratories

SUMMITTM Technologies,

www.mems.sandia.gov]

MEMS micromirror arrays are the key

components for optical communication

networks. The micromirrors act as

switches directing light from a fiber optic

to a specific output port by moving up and

down, left to right or swiveling to a desired

position.

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Other Applications of MEMS

MEMS nozzles and pumps

for inkjet printers

RF devices – Switches,

phase shifter resonators,

filters and variable antennas

Fuel delivery systems that

can control propellant

motion

Coating sensors that

compensate for coating

problems (adhesion, surface

tension)

MEMS-based InkJet Printhead

Piezoelectric or bubble jet based injection methods

meeting the demand for higher and better resolution

printing (smaller droplets). The graphic below illustrates a

piezoelectric printhead. When a voltage is applied across

the piezoelectric crystal, a minute amount of ink is

released into the nozzle.

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MEMS Microgrippers

Grippers or tweezers used in a variety of fields to clasp, pick up,

and move micron to nanosize components. The microgrippers

(50 microns thick), developed by Zyvex Corporation, pick and

place other microdevices in an automated microassembly

process. The gripper on the left opens to 100 microns. The

gripper on the right opens to 125 microns.

Zyvex Microgrippers

[Printed with permission © 2002 Zyvex]

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Review

What type of MEMS device(s) could be used for the following applications?

Wii hand controller

Detect the presence of a specific molecule (chemical or biological)

Transmit data in a digital communications network

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Review

What type of MEMS device(s) could be used for

the following applications?

Wii hand controller

Inertial sensor (accelerometer and/or gyroscope)

Detect the presence of a specific molecule

(chemical or biological)

Chemical sensor

Transmit data in a digital communications

network

MEMS mirrors that can rotate, bend, turn

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The automotive industry was one of the first

industries to embrace the use of MEMS.

Since then, MEMS have found applications

in wireless communications, biomedical,

aerospace, and consumer products (to

name a few).

The potential uses for MEMS are endless.

Summary

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Copyright 2009 – 2011 by the Southwest Center for Microsystems Education and The Regents of the University of New Mexico.

Southwest Center for Microsystems Education (SCME)

800 Bradbury Drive SE, Suite 235

Albuquerque, NM 87106-4346

Phone: 505-272-7150

Website: www.scme-nm.org email contact: mpleil@unm.edu

The work presented was funded in part by the National Science Foundation Advanced Technology Education program, Department of Undergraduate Education grants: 0830384 and 0402651.

Acknowledgements