1. www.c 2 s 2.org 2007 Technology in Medicine U NIVERSITY of V IRGINIA 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 devices Portable Electronics High Performance Applications (Power Density) Power Performance Applications are Limited by Power 1.89mm 256kb SRAM Array 32kb Block Sub-threshold SRAM Sub-V T Filters Ultra-Dynamic Voltage Scaling Sub-threshold Operation of Digital Circuits  Sub-threshold logic operates with V DD < V T  Both on and off current are sub-threshold “ leakage ”  Leads to MINIMUM ENERGY/OPERATION Gate Leakage Energy 90nm simulation for 32-bit CLA adder showing minimum energy per operation Total Leakage Energy Total Energy Active Energy Eleak = V DD ● I ● T D Sensor Front End: Detect & digitize sensor data u-ProcessorBluetooth Wireless “Patch” Phase 1: Integrate onto printed circuit board Phase 2: Build custom Integrated Circuit (i.e. chip) RF transceiver Sensor(s)A/D(s) Radio Interface Sensor Interface HW Processing Programmable 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 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 chip glued 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 transmission to 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 (<1cm 3 )  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 TechnologyPower Density (µW/cm 2 ) Vibration – electromagnetic [Khulah, MEMS04]4.0 Vibration – piezoelectric [Roundy, CComm03]500 Vibration – electrostatic [Meninger, TVLSI01]3.8 Thermoelectric (5 o C difference) [Bottner, JMES04]60 Solar – direct sunlight [Panasonic98]3700 Solar – indoor [Panasonic98]3.2 Triage Management Rural Healthcare In-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 Other Applications for Low Energy Sensing Platforms:  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.