Post on 24-Dec-2015
Outline
• Historical Perspective and Introduction
• Why make things very small
• Sensors and Actuators
• Micro/nano-scale manufacturing processes
MEMS & Nanotechnology: A Glimpse
1822: Nicéphore Niépce invents lithography to pattern a portrait. Five years later, Lemaître etched out the engraving with a strong acid
1939: First p-n junction on a semiconductor (W. Schottky)
1958: First integrated circuit developed at Texas Instruments. Jack Kilby wins the Nobel at 2000
1959: Richard Feynman dreams big (Oops, small!)
Cardinal d’Amboise
First IC
1948: First transistor (J. Bardeen, W.H. Brattain, W. Shockley) http://www.pbs.org/transistor/science/events/pointctrans.html
Why can’t we write the entire 24 volumes of Encyclopedia Brittanica on the head of a pin?
MEMS & Nanotechnology: A Glimpse
1965: Gordon Moore foretells the future of silicon industry
1965: First MEMS device? Resonant gate transistor built by Nathanson, Newell and Wickstrom
Every 2 years: # transistors double; cost remains same or decreases. On the same scale in the auto industry, cars would cost 5 cents and average 300000 mpg today
•Human hair: 50,000 nm across
•Viruses range in size from 20 to 300 nanometers (nm)
•10 hydrogen atoms in a line, 10 Angstroms (or 1 nm)
A View from Macro to Micro to Nano
Nanoparticles exist all around us – in sea, air, cigarette smoke, and diesel exhaust.
So, what is different today?
Why is the issue of nanotechnology generating so much discussion?
MEMS & Nanotechnology: A Glimpse
1989: Breakthrough in MEMS. Polysilicon micromotors built by Tai and Muller. Lateral comb drive actuator built by Tang, Nguyen and Howe
hair
RotorStator
combs
1994: Digital micro-mirror device (DMD) from Texas Instruments
1995: Commercial accelerometer from Analogue Devices
MEMS & Nanotechnology: A Glimpse
IC vs MEMS Technology
AMD K6 Microprocessor(top 6 layers only)
0.75
TI - DMD
MEMS & Nanotechnology: A Glimpse
Is there a limit?
What are the issues?Fabrication (180 nm)MaterialsPhysical mechanisms
MEMS & Nanotechnology: A Glimpse
1985: R. Smalley, R. Curl and H. Kroto discovers Buckminsterfullerene or Bucky ball. Nobel in 1996.
Nano-abacus of C60 molecules
http://jcrystal.com/steffenweber/POLYHEDRA/p_00.html
A C60 molecule
Nano materials
• Carbon nanotubes (CNTs; also known as buckytubes) are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1,[1] significantly larger than any other material. These cylindrical carbon molecules have novel properties, making them potentially useful in many applications in nanotechnology, electronics, optics, and other fields of materials science, as well as potential uses in architectural fields.
MEMS & Nanotechnology: A Glimpse
1986: (1) Atomic Force Microscope is invented.
(2) Eric Drexler publishes “Engines of Creation” www.foresight.org/EOC/Engines.pdf
NaCl on Mica
During the early decades of the 21st century, the advent of practical molecularmanufacturing technology will make it possible to fabricate inexpensively almost any conceivable structure allowed by the laws of physics.
Consequences will include immensely powerful computers, abundant and very high quality consumer goods, and microscopic devices able to cure most diseases by repairing the body from the molecular level up.
MEMS & Nanotechnology: A Glimpse
1991: Sumio Ijima discovers carbon nanotubes
http://www.photon.t.u-tokyo.ac.jp/~maruyama/wrapping.files/frame.html
1997: DNA based micromechanical device built
MEMS & Nanotechnology: A Glimpse
Nano gears
2001: Carbon nanotube based logic demonstrated
Nano bearings
Should we borrow from Nature?
NATURE vs. ENGINEERINGNATURE vs. ENGINEERING
Billions of years to evolveBillions of years to evolve Revolutionary, Ingenuity drivenRevolutionary, Ingenuity driven
Does not use metalsDoes not use metals Metals and Artificial materials Metals and Artificial materials drivendriven (e.g. Stone Age (e.g. Stone Age Iron Age) Iron Age)
Movement by sliding/contractionMovement by sliding/contraction The Wheel The Wheel
Energy storageEnergy storageGravitational/ ElasticGravitational/ Elastic Electrical and KineticElectrical and Kinetic
A wet technologyA wet technology Mostly dryMostly dry
Smooth shapesSmooth shapes Sharp corners, rectangularSharp corners, rectangular
Nanometer: A Different Perspective
• Human hair: 50,000 nm across
• Bacterial cell: a few hundred nanometers
• Seeable with unaided human eye: 10,000 nanometers
• 10 hydrogen atoms in a line
Reasons to Miniaturize
Miniaturization Attributes
Reasons
Low energy and little material consumed
Limited resources
Arrays of sensors Redundancy, wider dynamic range, increased selectivity through pattern recognition
Small Small is lower in cost, minimally invasive
Favorable scaling laws
Forces that scale with a low power become more prominent in the micro domain; if these are positive attributes then miniaturization favorable (e.g. surface tension becomes more important than gravity in a narrower capillary)
Reasons to Miniaturize
Miniaturization Attributes
Reasons
Batch and beyond batch techniques
Lowers cost
Disposable Helps to avoid contamination
Breakdown of macro laws in physics and chemistry
New physics and chemistry might be developed
Smaller building blocks
The smaller the building blocks, the more sophisticated the system that can be built
Need for Scaling
• As linear size decreases behavior changes.– Not well understood on
the nano-scale.– Scaling represents an
approximation to assist in understanding.
• Scaling helps to explain nature and can also be used to design devices.
Scaling
• If a system is reduced isomorphically in size (i.e. scaled down with all dimensions of the system decreased uniformly), the changes in length, area and volume ratios alter the relative influence of various physical effects.
• Sometimes these effect the operation in unexpected ways.
Scaling of Length, Surface Area and Volume
• What happens as an object shrinks?– Area L2
– Volume L3
L
LL
Why Whales Swim Faster
L3
L2
22
2
1LAuCF DD
where CD: drag coefficient ρ: density of fluid A: largest projected area of the body u: velocity
Scaling of Mechanical Systems
13
2 L
L
L
mass
forceonaccelerati
In nano-mechanical systems accelerations are large.
01 ))(())(( LLLtimeonacceleratispeed
Lfrequencyscaletimesticcharacteri 1__
Speed is length scale invariant.
Electrostatic Motors
+-
+-
-
Polysilicon micromotor:
• Rotor sits atop a 0.5mm layer of polysilicon that acts as an electrostatic shield.
• Rotor, hub, stators formed from 1.5mm polysilicon.
• A 2.0mm polysilicon disk is attached to rotor.
Thermal Actuation
The current flow produces Joule heating that in turn imparts a large thermal stress on the device, concentrated in the long thin beam. The thermal expansion of the thin beam causes the device to bend at the short thin beam. The blade rotates in the plane of the substrate.
Ideal Sensor
• Zero Mass: no additional mass, no thermal compensation (no latent heat energy stored), thermally equilibrate infinitely rapid, infinitely wide dynamic response.
• Zero physical size: Could be installed virtually anywhere, extreme spatial resolution by arrays.
• Zero energy.
Historically, most successful applications of MEMS techniques fall in the “Sensors” category.
MEMS Sensors are close. They offer high sensitivity, can be batch fabricated (low cost, high volume), some times wireless and are robust
Mechanical Sensing
• Micro-mechanical structures at heart of design process• Beams that act as springs• Experience force and/or displacement• Deform under force, pressure, flow, etc.• Measure deflection
• Deflection equations developed for macro-scale and assume:• Material properties do not change• No residual stresses
Silicon is generally used for micro-mechanical structures.
Sensor and Transducer
• Sensor: Converts force to displacement
• Sensitivity: 1/k• Transducer : Apply force to get displacement• k can be constant or varying with force
kFx /
Cantilever Beam
3/3 LEIk The left cantilever bends as the protein PSA binds to the antibody. The other cantilevers are exposed to different
proteins found in human blood serum.
Mechanical Sensing
• Micro-mechanical structures at heart of design process• Beams that act as springs• Experience force and/or displacement• Deform under force, pressure, flow, etc.• Measure deflection
• Deflection equations developed for macro-scale and assume:• Material properties do not change• No residual stresses
Silicon is generally used for micro-mechanical structures.
Sensor and Transducer
• Sensor: Converts force to displacement
• Sensitivity: 1/k• Transducer : Apply force to get displacement• k can be constant or varying with force
kFx /
Cantilever Beam
3/3 LEIk The left cantilever bends as the protein PSA binds to the antibody. The other cantilevers are exposed to different
proteins found in human blood serum.
Accelerometers
Applications: Inertial guidance system, airbags, vibration measurement
When the reference frame is accelerated, the acceleration is transferred to the proof mass through the spring. The stretching of the spring, which is measured by a position sensor (represented as a length scale in the figure), gives the acceleration when the proof mass is known.
Natural frequency
Damping coefficient
Biological Sensing
Diagram of interactions between target and probe molecules on cantilever beam. Specific biomolecular interactions between target and probe molecules alter the intermolecular nanomechanical interactionswithin a self-assembled monolayer on one side of a cantilever beam. This can produce a sufficiently large force to bend the cantilever beam and generate motion.