Silicon Menagerie - Biomechatronics | MIT Media Lab

Silicon Menagerie
ANTS – A Sensor Perspec/ve MAS.S63 JoeP Ants Make Sounds •  Stridula/on –  ‘Rubbing parts of their rear sec/on or gaster together’ –  hCp://home.olemiss.edu/~hickling –  hCp://blog.wildaboutants.com/2010/01/28/ant-­‐
stridula/on/ •  Nobody knows exactly how they ‘hear’ – probably with legs or hair on antennae –  Only contact or near-­‐field vibra/on R. Hickling and R. L. Brown, "Analysis of acous/c communica/on by ants" Journ. Acoust. Soc. Amer.,Vol. 108, No. 4, pp 1920-­‐1929, 2000. 2/04
JAP
Acoustic Transducers
•  Measure dynamic range
to moving diaphragm
•  Carbon mic
•  Condensor mic
•  Electret mic
–  Foil electret mic
–  FEP material polarized
with corona discharge
–  Wideband
•  10-3 Hz to hundreds of MHz
–  Usually have integrated
FET
http://www.openmusiclabs.com/learning/sensors/electret-microphones
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JAP
MEMs Microphones
•  Many Manufacturers
–  Akustica (direct digital output), Infineon, Panasonic,
etc.
•  Very small - surface-mount chip
•  Have integrated amplifier and sometimes ADC
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Ants are Endocrinal Adepts blog.wildaboutants.com Pheromone Trails… Town ant workers following an ar/ficial trail made by drawing a very dilute solu/on of the ant's trail pheromone methyl 4-­‐methylpyrrole-­‐2-­‐carboxylate. (USDA.gov) Chemical Markers…. •  Probably need to lay down a vola/le, and sniff for vapors just above… –  What type? –  Generally put an agent on a sensor and look for a reac/on, or s/mulate material and look for response –  Electrochemical, resis/ve, cataly/c, op/cal (color to spectroscopy), resonant (mass perturba/on), molecular size/weight… (see presenta/on that follows) –  E.g., hCp://www.sensorsmag.com/list/sensors/chemical-­‐
gas-­‐129 –  You can try ‘wild ideas’ here, but stay safe (e.g., no radioisotopes, carcinogens, or toxins) Ideas for other marker types… •  Drop a paint, ink, or colored dust… –  Will need to search to acquire trail; op/cal sensors might be noisy, but could employ florescence s/mulated by a UV LED, for example… •  Drop magne/c or ferrous par/cles –  Use a magne/c sensor or metal detector •  Deposit other kinds of detectable markers… 2/04
JAP
Color Sensors
Color Light Sensor - Avago ADJD-S371-Q999"
http://www.sparkfun.com/commerce/product_info.php?products_id=8618"
Features:
• 10 bit per channel resolution
• Independent gain selection for each channel
• Wide sensitivity: 0.1k - 100k lux
• Two wire serial communication
• Built in oscillator/selectable external clock
• Low power mode (sleep mode)
• Integrated solution with sensor, LED and separator in module for ease of design
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JAP
Magnetic Field Sensors
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JAP
Permalloy
Differential
strapping for
compasses
+/- 2 Gauss max range
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JAP
Integrated Magnetometers
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JAP
Beat frequency metal detector
Wireless “boot” coil and AM radio
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JAP
Flux Transmission Metal Detector
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JAP
Pulse Induction Metal Detector
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JAP
The Wiegand Effect
Weigand pulses tend to be
short (HF components!)
Shaft encoder w.
alternating poles on disk
Shaft encoder w.
distributed Weigand wires
•  Metal wire made with large Magnitization hysteresis
–  At a certain magnetic field strength, all domains reverse
together
–  Produces a voltage pulse (e.g., 2-6 V into 24K Ohms) when
domains switch.
•  Also produces a magnetic field pulse (J-Wires for library-book
antitheft systems)
–  Pulse can be readout for magnetic field switch
–  Products exist…
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Ringdown Tag Readers
•  Very simple, inexpensive prototype tag reader detects Magnetostrictor
(Sensormatic) shoplifting tags
–  In-store sysems can reach circa 12 feet in range
–  High-Q mechanical structures (not so good with LC)
–  By cutting tag to different lengths, we get several (4-6) bits of very cheap ID
•  Slow
–  Must sit at frequencies of interest and interrogate
Media Lab Ringdown Prototypes
Paradiso & Hsiao
1997 Prototype, running 30-150 kHz
Potentially good range, but slow
Response (e.g., 10 ms/tag)
Triac-switched capacitor ladder for tuning
search coil on transmit, Comp. MOSFET drivers
Special Nodes – “Breadcrumb” Relay Geqng RF penetra/on down tunnels or into spaces where no link exists •  Nodes carried by worker in “bag” •  System prompts worker to drop a new relay node when at range limit of RF link •  Worker is also prompted to collect nodes when returning •  System can alert if link spontaneously breaks 2/04
JAP
Synchronous Detection
- Also called a “Lock-in” Amplifier
- Also a “Matched Filter” of sorts
- Can regenerate carrier with PLL if no
connection
f
Quadrature
demodulation
eliminates need to
chase phase
4-Quadrant
multiplication
suppresses the carrier
Tight low-pass filter gives
extremely high noise rejection!
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JAP
Synchronous Detection
Note: synchronous
detection works
only if signal stays
linear (and doesn’t
saturate).
A bandpass filter
can be inserted
here to limit noise
sensitivity
Phase Shifter
Mixer
Mixer can be
switched system as
at left, or 4-quadrant
multiplier like an
AD633
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2/04
JAP
Ant Antennae
Chemical, Tactile, vibratory, airflow, inertial, thermal(?) sensors…
Plus they are actuated!
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The “Tribble”
Electronic “skin” as a dense sensor network
Over 500 sensing channels
Whisker, pressure, light,
sound
Each of 32 tiles actuates
RGB LED, speaker, vibrator
All tiles talk only to neighbors
Inhibition/excitation,
compression algorithms
Josh Lifton, Mike Broxton - Demo at 1CC
Sensor Net Array, Kapton Embedded (SNAKE) Skin
•  All on flex
•  Embedded strain gauges
•  Covered by a layer of QTC
pressure-measuring material
•  Piezo whiskers
•  Optical sensors, microphones,
temperature
•  Peer-Peer network
•  High-Speed I2C backbone
•  Scalable!
Jerry Barroeta-Perez
4/08
ChainMail - Scalable Sensate Surface
JAP
•  Rigid nodes,
flex connects
•  Multimodal:
–  Light
–  Sound
–  Whiskers
–  Pressure
–  Temperature
–  Bend
•  Videos on
YouTube
BehramShort.mov
Behram Mistree
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4/08
Other Whiskers in Research
JAP
Also MEMs whisker arrays
(see IEEE Sensors)
MIT Seal Whisker (note the taper)
Heather Beem, Matthew Hildner and Michael Triantafyllou
UC Berkeley carbon nanotube & silver nanoparticles on polymer fiber whisker
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4/08
Capacitive Whisker?
JAP
•  Use loading mode – can sense proximity and
contact of conducting objects (or wet dielectric
ones)
•  Not in terrestrial animals so far as I know…
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2/04
JAP
Loading Mode Sensing
Most common “capacitive” sensing
(e.g., “elevator buttons”)
1- Set pin to output, and pull down
2- After brief wait, declare as logic input
3- Measure T until input goes to “1”
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2/04
JAP
Minimal Capacitive loading circuit
1
Pin 1 Output
>1 Meg Ohm
R
PIC or
other uP
δt
δt
2
Sense
Plate
User
C
Pin 2 Input
•  Pin 1 is digital output, pin 2 is digital input
•  Toggle state of pin 1 and measure time needed for state
of pin 2 to flip
–  Time difference increases with R and C
•  Fix R, hence C is measured
•  Loading mode measurement – range typically few cm
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JAP
Conductive Polymers and FSR’s
•  Microphotograph, showing conductive ink and
metalization from Interlink FSR
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JAP
Force Sensitive Resistors
•  Composite structure
–  Top, ink, electrodes
•  Flat, but can be fragile to shear force (delamination) and sensitive to bend
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JAP
The FlexiForce (from TekScan)
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JAP
FSR Bendy Sensors
Available from the Images Co. (for PowerGlove - made by “Abrams-Gentile)
High-end versions made by Immersion for their CyberGlove
- 0.5° resolution, 1° repeatability, 0.6% max nonlinearity, 2-cm min bend radius
These only measure bend in one dimension (expanding the FSR’s on surface)
- Conduction saturates quickly when contracted
- Can measure bidirectional bend with 2 FSR’s back-to-back (and diff amp)
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JAP
Data Glove by Tom Zimmerman (VPL)
•  Cladding of a Graded Index
Optical Fiber is abraded at point
where sensitivity is desired
•  When fiber bent, light leaks out as
a function of bend angle
–  Drop in signal at detector
Emitter
Detector
•  Patented by Tom Zimmerman (lab
alum) at VPL in 1985 & 1990.
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JAP
Measurand’s Shape Tape
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JAP
How ShapeTape Measures Twist
Bend fibers near center of strip
Twist fibers near edges
Can also wrap fibers around center?
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JAP
Strain Gauges
Many manufacturers (e.g., JP Technologies), many patterns...
Simple strain gauge
Torsional strain gauge
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JAP
Strain Gauge Patterns
Strain Gauges want to be bonded onto a hard surface, so they can be forced into
strain when the surface is deflected. Soft materials won’t strain the gauge enough
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JAP
Load Cells
20 Ton load cell for truck weight
Simple, “naked” load cell from Ohio State
•  Bond strain gauge to cantilevered beam
–  Force deflects beam, bends strain gauge, creates
signal
•  Can be quite accurate
–  Compensate temperature effects
Load Cell assortment from DHS
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JAP
Silicon Pressure Sensors
• 
Piezoresistors diffused onto silicon at R1, R2
–  Boron doping typical…
• 
Piezoresistors couple into longitudinal &
transverse stress
–  Coupling is opposite for each mode
• 
R1 and R2 essentially subtract in a half-bridge
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JAP
Piezo Foil (PVDF)
http://www.meas-spec.com/myMeas/sensors/piezo.asp
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JAP
Compound Eyes
Great for detecting motion – see transitions from one eyelet to the other, large FOV
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JAP
The Ommatidia
Collimated – narrow FOV – up to 30,000 per eye in some insects
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JAP
Not a light-field camera!
•  http://askabiologist.asu.edu/content/
hollywood-misconception
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JAP
Ants also have simple eyes atop their head
•  The Ocelli – sense light levels & polarization,
UV on some insects (e.g., bees)
•  Ants can have 3
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JAP
Compound Eye Research Prototypes
•  John Rogers & group, University of Illinois UC
•  Uses stretchy interconnects
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JAP
Photodetectors
http://www.engr.udayton.edu/faculty/jloomis/ece445/topics/egginc/tp4.html
Speed
Ex Vg/Ex
G
Poor G/Pr
G
?
?
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Photoresistors
CdS tends to like Yellow...
Photons knock electrons into conduction band
1 photon can release 900 electrons Acceptor band keeps electron lifetime high
-> Lower Resistance with increasing light
Slow response...
Goes from MΩ to Ohms
•  CdS (Cadmium Sulfide) and CdSe (Cadmium Selenide) cells are common
( I ) Directly beneath the conduction band of the CdS crystal is a donor level and there is an acceptor level above the
valence band. In darkness, the electrons and holes in each level are almost crammed in place in the crystal and the
photoconductor is at high resistance.!
( II ) When light illuminates the CdS crystal and is absorbed by the crystal, the electrons in the valence band are excited
into the conduction band. This creates pairs of free holes in the valence band and free electrons in the conduction band,
increasing the conductance.!
( III ) Furthermore, near the valence band is a separate acceptor level that can capture free electrons only with difficulty,
but captures free holes easily. This lowers the recombination probability of the electrons and holes and increases the
number for electrons in the conduction band for N-type conductance
Condition like FSR’s (voltage divider, transimpedance amp, etc.)
2/04
JAP
Photodiodes
Solar Cells
- Big (optimized) versions
Photodiodes
- (Smaller)
•  Photons interacting in the depletion region produce electron-hole pairs
–  Electrons diffuse through depletion region, driven by the E-field, to arrive
at the N layer and electrode, producing current.
–  Make depletion region bigger (more reverse bias)
•  More efficient (higher probability of photon interaction)
•  Faster (charge doesn’t have to diffuse across longer lengths before it hits Efield, hence less charge stored, hence smaller capacitance)
•  PIN diodes increase the collection area - faster response
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JAP
Photodiode IC’s
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JAP
The Phototransistor
•  Like diodes, all transistors are light-sensitive. Phototransistors are
designed specifically to take advantage of this fact. The most-common
variant is an NPN bipolar transistor with an exposed base region. Here,
light striking the base replaces what would ordinarily be voltage
applied to the base -- so, a phototransistor amplifies variations in the
light striking it. Note that phototransistors may or may not have a base
lead (if they do, the base lead allows you to bias the phototransistor's
light response).
•  Phototransistors run in the photoconductive mode
•  They’re pretty slow, on average (e.g., Khz response)
•  …But give a fair amount of gain and are very easy to use.
–  Generally ground emitter and provide a collector resistor to set gain
•  Photodarlingtons give more gain, but can be slower…
http://encyclobeamia.solarbotics.net/articles/phototransistor.html
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Phoresis
Parasitic Mobility in Mobile Sensor Networks
Best Paper Award
Active
Innovations and Architecture
Passive
-  Interpretation of Energy Harvesting in mobile networks
-  Three flavors:
-  The Tick (e.g., jumps onto a host, attaches, then disengages)
-  The Bur (e.g., sticks to passing object, then shakes off)
-  The Symbiote (an appliance you want to carry while it works)
-  Contains GPS, RF, basic sensor suite
Paradiso & Laibowitz 2005
Symbiotic