Transcript Poster - University of Virginia

www.c2s2.org
Portable, Unobtrusive Medical Sensors using
Ultra-Low Power Electronics
Benton Calhoun (ECE)
, Travis Blalock (ECE) , and Alf Weaver (CS) .
School of Engineering and Applied Science
Ultra-Low Energy Circuits for Energy Constrained Applications
Circuit Design in a Power-Limited Era
Sub-threshold Operation of Digital Circuits
High Performance Applications
(Power Density)
Applications are Limited by Power
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Circuit Techniques Proven in Silicon
Sub-threshold logic operates with VDD < VT
Both on and off current are sub-threshold “leakage”
Ultra-Dynamic Voltage Scaling
Sub-VT Filters
Leads to MINIMUM ENERGY/OPERATION
Active Energy Total Energy
90nm simulation
for 32-bit CLA adder
showing minimum
energy per operation
Medical devices
Portable Electronics
Micro-sensor networks
Sub-threshold SRAM
Total Leakage
Energy
32kb Block
Performance
Ambient Intelligence
Eleak = VDD ● I ● TD
256kb SRAM Array
1.89mm
Gate Leakage Energy
Power
Example: Wireless 1-Lead EKG “Patch”
Example: A wireless patch to capture and transmit EKG waveforms
Advantages of Ultra-Low Energy Hardware
 Smaller Form Factor
u-Processor
Bluetooth
e.g. 1-Lead wireless EKG on 1-2 chips (<1cm3)
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Smaller size and fewer parts lower cost
Built-in flexibility allows for reuse in different applications
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Wireless connectivity is easy on the user
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Modern Holter monitors (EKG recorders) record for ~24 hours
1 month lifetimes now possible but only with clunky, costly
systems
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Our approach: Lifetimes of months or years are possible
With Energy Scavenging, lifetime is unlimited by energy concerns
 Lower Cost
Wireless “Patch”
Sensor
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Wireless transmission
to PDA, laptop, etc.
 Unobtrusive
Front End: Detect & digitize sensor data
Phase 1: Integrate onto printed circuit board
Phase 2: Build custom Integrated Circuit (i.e. chip)
Phase 1 Initial Implementation working:
Phase 2: Integrate onto a chip
Programmable
Control Unit
Memory
Sh
are
d
Bu
s
HW Processing
 Longer Lifetime
Integrated
Circuit
HW Processing
Radio Interface
RF transceiver
Sensor Interface
A/D(s)
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Wear it home; put on and off like a BandAid
Sensor(s)
Sub-threshold logic for low energy
Energy scalability to adapt to requirements
Programmability for hardware reuse
Energy Scavenging Technology
Power Density (µW/cm2)
Vibration – electromagnetic [Khulah, MEMS04]
4.0
Vibration – piezoelectric [Roundy, CComm03]
500
Vibration – electrostatic [Meninger, TVLSI01]
3.8
Thermoelectric (5oC difference) [Bottner, JMES04]
60
Solar – direct sunlight [Panasonic98]
3700
Solar – indoor [Panasonic98]
3.2
What can Ultra-Low Energy Circuits Do for YOU?
Other Applications for Low Energy
Sensing Platforms:
Uses for Wireless EKG:
Detect Atrial Fibrillation
 Goal: Detect and record paroxysmal AFib
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<Your Data Sensing Application Here!>
events based on heartrate statistics
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Collaboration with Ben Calhoun and Travis Blalock – ECE,
Randall Moorman - Cardiovascular Medicine
Use a later version of the EKG patch
Monitor statistical distribution of R-R intervals and record AFib
events
 What data would help you …
 … to diagnose problems?
 … to treat patients?
 … to see the impact of medication?
Low Energy Operation Essential to enable
required Lifetime of the patch
Data security
 Goal: Protect Mobile Data
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Ensure continuous link with user after
authentication
Place data in safe state if link is lost
Initial Authentication
Triage Management
Rural Healthcare
In-home monitoring of the elderly
…
Safe Mode Entered
Low Energy Consumption Enables New Applications:
Connect to Patch Simulator
Policy Control Engine
Low Heart Rate Event
2007 Technology in Medicine
 Cutting edge low power sensors are …
 … unobtrusive.
 … smaller.
 … cheaper.
 … much longer lasting.
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Plague Tracking via Flea Telemetry
Goal: Study propagation of plague in Utah
prairie dog population
Collaboration with Jeff Wimsatt - Biology, Ben Calhoun and
Travis Blalock - ECE
Chip communication and power through magnetic field
coupling to on-chip coil
Flea chip communicates with collar transceiver - collar
communicates with base station
Each chip has unique code and reports temperature to
indicate flea status
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Low Energy Operation Essential
Actual photo of dummy chip
glued to flea (yes, it jumped
around with the chip)
Automation of Test Animal Monitoring via Non-Contacting BioTelemetry
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Remotely powered, internal chip-based monitoring of animal status
Temperature, hydration, location, activity level, and other physiologic
indicators
Allows real-time monitoring of large populations of test animals with
dramatically improved disease status information
Non-contact monitoring reduces stressful handling events and allows for
better control of pain management
Collaboration with Jeff Wimsatt - Biology, Travis Blalock, Ben Calhoun
and Ron Williams – ECE
Low Energy Operation Essential
UNIVERSITY of VIRGINIA