Radio-Frequency MEMS (RF-MEMS) pbandaru/mae268-sp09/Class...¢  Si cantilever MEMS (100 X 3...

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Transcript of Radio-Frequency MEMS (RF-MEMS) pbandaru/mae268-sp09/Class...¢  Si cantilever MEMS (100 X 3...

  • Radio-Frequency MEMS

    (RF-MEMS)

  • Technology Trends: One example

    Picture courtesy: M.C. Wu

  • Potential Applications of RF MEMS

  • MEMS enabled wireless transceiver

    http://www.eecs.umich.edu/~ctnguyen/mtt99.pdf

    -MEMS for on-chip capacitors (C) and inductors (L)

    - Need high Q-(quality) factors

  • Q-factors for a R-L-C circuit

    LC2π

    1 f

    Δf

    f

    R

    f 2πQ

    o

    oo Bandwidth

    Modeling a micro-

    electro-mechanical resonator

    http://www.eecs.umich.edu/~ctnguyen/mtt99.pdf

  • Voltage tunable high-Q capacitor &

    inductor

  • Traditional SAW devices vs. MEMS SAW: Surface Acoustic Wave

    Picture Courtesy: C. Nguyen

    > SAW devices, for generating frequencies are off-chip

    > MEMS offers the same high-frequency selectivity at a much

    smaller size

  • Wrist Communicator

    Slide courtesy: Al Pisano, DARPA

  • Case study

    MEMS in Biochemistry & Medicine

  • Electro-kinetic effects

    Electrophoresis: Migration of ions in a separation medium

    under the influence of an electric field

    (e.g. for DNA sequencing)

    - Electrophoresis and electroosmosis

    - Used in bio-separation technologies

    EfuqE

    Accelerating force = Frictional force

    q: electric charge

    E: electric field

    f: friction co-efficient

    uE: electrophoretic speed of ion =

    viscosity of medium

    r: radius of particle r

    qE

    6

    - +-- - -

    -

  • Electro-Osmotic Flow

    Electroosmosis: Motion of electrolytic solutions

    under the influence of an

    electric field

    -Used in micro-pumping

    (EOF: Electro-Osmotic Flow)

    Flow profiles

    - Better for analysis, as there is less band-broadening

    Anode: +

    Cathode: - ww w

    .cap italan

    aly tical.co

    .u k

    /

    EuEOF 4

    dielectric constant zeta potential

    viscosity

    Flow velocity

    E L

    V Dw

    V

    Charge density Debye length

    3

    12

    wh

    LQ P

    4

    128

    d

    LQ P

    Rectangular

    Circular

  • Dielectrophoresis

    Source: M. Madou, Principles of Microfabrication

    AC electro-kinetic effects Particles having dielectric properties experience different forces

    232 ErF rmDEP

    )2(

    )(

    mp

    mp r is proportional to

    Dielectric constant of

    particle medium

  • Dielectrophoretic separation

    - Separation of bio-molecules, cells by the application of electric fields

    E = 0 E > 0

    M. Madou and M. Heller

  • DNA (De-oxy Ribonucleic Acid) - The “molecule of life”

    DNA  RNA  Proteins

    Each cell contains 1.5 GB of information, through DNA

    Source: M. Madou, Principles of Microfabrication

  • PCR is used in molecular biology, genome sequencing, evolutionary studies …

    DNA Amplification by PCR

    Exponential increase in DNA, 1 million after 20 cycles, 1 billion after 30 cycles

  • S ch

    ab m

    u el

    le r,

    J . M

    ic ro

    m ec

    h . &

    M ic

    ro en

    g ., 1

    1 , 3

    2 9

    ( 2

    0 0

    1 )

    Applied Biosystems

    Gene-Amp PCR system 9700

    Microsystems based PCR

    - Faster heating (~ 35 oC/sec) and heat removal more rapid assays (Time reduced from 6 hours to a few minutes)

    - Smaller samples needed

    Advantages

    Issues - The Si surface is incompatible with Taq enzyme - Mixing is an issue, (low dimensions  laminar flow)

  • DNA Analysis

    D. Devoe, Univ. of Maryland

  • The NanoChip® from Nanogen Inc.

    DNA Analysis, Point of Care (POC)

    Analyte Specific Reagents

    Cardiovascular Disease

    Hypertension

    Drug Metabolism/Cancer

    Cancer

    Deafness

    w w

    w .n

    a n

    o g en

    .c o m

  • Electro-wetting for liquid transport

    - Instead of pumping, electric fields may be used to move fluids

    - Tailoring hydro-phobicity/-philicity of a surface

    - Surface tension scales as “l”, while mass scales as “l3”

  • Principles of Electro-wetting

    2 )0()(

    2CV VV slsl

    Young equation:

    lv

    svsl

    Lippmann equation

    The solid-liquid interfacial tension sl can be controlled by electric

    potential across the interface

    lv

    slsv

    γ

    γγ cos

    cosθγγγ lvslsv

    Applying V  Reducing slreducing  more wetting and vice versa

  • A digital micro-fluidic circuit

    S .K

    .C h

    o e

    t a l,

    J o u

    rn a l

    o f

    M E

    M S

    , v o l.

    1 2 , n

    o . 1 , p

    a g e

    7 2 , 2 0 0 3

  • LabCD: A Bio-analytic -TAS

    r dt

    dPc 2

    r dt

    dPc 2

    Pumping force Density of liquid

    Angular velocity of CD platform

    Radial distance from center

  • BIOSENSORS

    Cantilever based sensing

  • Detection of biomolecules by simple mechanical transduction:

    - cantilever surface is covered by receptor layer (functionalization)

    - biomolecular interaction between receptor and target molecules (molecular recognition)

    - interaction between adsorbed molecules induces surface stress change

    bending of cantilever

    target molecule

    receptor molecule

    gold

    SiNx cantilever

    deflection d

    target binding

    Bio-molecule sensing

    B. Kim et al, Institut für Angewandte Physik - Universität Tübingen

  • f

    A

    A

    f

    eff

    1 m

    k

    2

    1 f

    mm

    k

    2

    1 f

    eff

    2

    m

    f2

    A mass sensitive resonator transforms an additional mass loading into a resonance frequency shift mass sensor

    f1

    f1

    f2

    B. Kim et al, Institut für Angewandte Physik - Universität Tübingen

    A cantilever as a mass-sensitive detector

  • surface layer substrate

    Stoney formula = surface stress change

    t = thickness of the beam

    L = length of the beam

    E = Young’s modulus of the material

    = Poisson ratio of the material

    d = deflection of the end of the beam

    d L

    tE 2

    2

    )1(3

    Surface Stress induced bending

    Cantilever bending can potentially detect single molecules, however they are

    noise limited

  • B. Kim et al, Institut für Angewandte Physik - Universität Tübingen

    Detection scheme

    Optical detection of analyte binding

  • NANO-ELECTRO MECHANICAL SYSTEMS

  • Everything is going to get smaller

    AVIONICS ROADMAP

    (Toomarian, NASA Jet Propulsion Laboratory, 2000)

    “Thinking spacecraft”

    “Smart dust”

  • What does the future hold in micro-systems?

    1. Nano-Electro-Mechanical Systems

    - Carbon Nanotubes as Mechanical elements

    2. Electro-mechanical cantilevers

    3, Is there a molecular future?

    Are NEMS the next wave of technology?

  • Nano-Electro-Mechanical Systems

    N E

    M S

    , S

    . E

    . L y s h

    e v s k i, 2

    0 0

    1

    • Differs from “classical” mechanical systems

    • A new mode of thinking and operation

  • N. Taniguchi, "On the Basic Concept of 'Nano-Technology',"

    Proc. Intl. Conf. Prod. Eng. Tokyo, Part II, Japan Society of Precision Engineering, 1974

    Nano-technology

    “Nano-technology' mainly consists of the processing of

    separation, consolidation, and deformation of materials by

    one atom or one molecule.” - N. Taniguchi, 1974.

  • NEMS

    (Nano-Electro-Mechanical Systems)

    Vibrational frequency of system

    keff: effective force constant l

    meff: effective mass l 3

     increases as l (linear dimension) decreases

     Faster device operation

    Si cantilever MEMS (100 X 3 X 0.1 m): 19 KHz

    NEMS (0.1 X 0.01 X 0.01 m): 1.9 GHz

    Promise true Nano-technology !

    better force sensitivities (10-18 N)

    larger mechanical factors (10-15 g)

    higher mass sensitivity (molecular level)

    heat capacities, below a yoctocalorie

    than MEMS

    (Roukes, NEMS, Hilton Head 2000)

    eff

    eff

    o m

    k

  • MEMS vs. NEMS

    Fabrication

    Essentially micro-electronics (CMOS) Involves molecular scale

    Based, photo-lithography manipulation, electron-lithography

    Materials

    Silicon based SiC, GaAs (III-V semiconductors)

    Transduction mechanisms

    Electrostatic, mainly Indirect means, e.g. piezo-electric, thermal

    Mechanics of Materials

    Continuum mechanics sufficient Atomistic