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Transcript of Www.c 2 s 2.org 2007 Technology in Medicine U NIVERSITY of V IRGINIA Portable, Unobtrusive Medical...
www.c2s2.org
2007 Technology in Medicine UNIVERSITY of VIRGINIA
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
Circuit Design in a Power-Limited Era
Micro-sensor networks
Ambient Intelligence
Medical devicesPortable Electronics
High Performance Applications(Power Density)
Power
Perf
orm
ance
Applications are Limited by Power
1.89mm256kb SRAM Array
32k
b
Blo
ck
Sub-threshold SRAM
Sub-VT Filters Ultra-Dynamic Voltage Scaling
Sub-threshold Operation of Digital Circuits
Sub-threshold logic operates with VDD < VT
Both on and off current are sub-threshold “leakage”
Leads to MINIMUM ENERGY/OPERATION
Gate Leakage Energy
90nm simulationfor 32-bit CLA addershowing minimum energy per operation
Total Leakage Energy
Total EnergyActive Energy
Eleak = VDD ● I ● TD
Sensor
Front End: Detect & digitize sensor data
u-Processor Bluetooth
Wireless “Patch”
Phase 1: Integrate onto printed circuit boardPhase 2: Build custom Integrated Circuit (i.e. chip)
RF transceiver
Sensor(s)A/D(s)
Radio Interface
Sensor Interface
HW Processing
HW ProcessingProgrammable Control Unit
Memory
Sh
are d
Bu s
Integrated Circuit
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
Low Energy Operation Essential
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Automation of Test Animal Monitoring via Non-Contacting Bio-Telemetry
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
Actual photo of dummy chipglued to flea (yes, it jumped
around with the chip)
Low Energy Consumption Enables New Applications:
Ultra-Low Energy Circuits for Energy Constrained Applications
Example: Wireless 1-Lead EKG “Patch”
What can Ultra-Low Energy Circuits Do for YOU?
Wireless transmissionto PDA, laptop, etc.
Circuit Techniques Proven in Silicon
Example: A wireless patch to capture and transmit EKG waveforms
Phase 1 Initial Implementation working:
Advantages of Ultra-Low Energy Hardware
Smaller Form Factor e.g. 1-Lead wireless EKG on 1-2 chips (<1cm3)
Lower Cost Smaller size and fewer parts lower cost
Built-in flexibility allows for reuse in different applications
Unobtrusive Wireless connectivity is easy on the user
Wear it home; put on and off like a BandAid
Longer Lifetime Modern Holter monitors (EKG recorders) record for ~24 hours
1 month lifetimes now possible but only with clunky, costly systems
Our approach: Lifetimes of months or years are possible
With Energy Scavenging, lifetime is unlimited by energy concerns
Phase 2: Integrate onto a chip
Sub-threshold logic for low energy
Energy scalability to adapt to requirements
Programmability for hardware reuse
Uses for Wireless EKG:
Detect Atrial Fibrillation Goal: Detect and record paroxysmal AFib
events based on heartrate statistics 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
Low Energy Operation Essential to enable required Lifetime of the patch
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
Triage ManagementRural HealthcareIn-home monitoring of the elderly…
Data security Goal: Protect Mobile Data Ensure continuous link with user after
authentication Place data in safe state if link is lost
Low Heart Rate EventSafe Mode Entered
Connect to Patch Simulator Policy Control EngineInitial Authentication
Other Applications for Low Energy Sensing Platforms:
<Your Data Sensing Application Here!> What data would help you …
… to diagnose problems?
… to treat patients?
… to see the impact of medication?
Cutting edge low power sensors are …
… unobtrusive.
… smaller.
… cheaper.
… much longer lasting.