February 19, 2009 Sara Carr, Carl Hoge, Keith Lesser, Robert MacGregor, Oxana Petritchenko

Left Ventricular Assist Devices (LVAD) Typically LVADs are used while a patient is awaiting for heart transplant They help the LVAD to pump blood throughout the body Depending on patient, they can be implanted for months or years Eventually will have ability to become a permanent solution

Dangers of Wired Systems Wired systems pose a danger to heart pump patients Around 40% deaths in patients come from infection Most susceptible to infection after surgery or traumatic event Wired systems also limit mobility, and may cause discomfort

Customer Needs The cable entering the body is more flexible. The cable entering the body is smaller in diameter. Eliminate as many wires as possible from XPC Control Target to the LVAD, position sensors, and Active Magnetic Bearings Wireless Power System to eliminate power wires (15V and Ground) through the human skin and biological tissues. The cable, packaging, and connections are safe to human tissue. Heat generated by the inner transceiver does not cause tissue damage. The heat created by a body does not damage the electronics. Inner and outer transceivers must be protected from the outside forces. The device must function continuously, without user intervention, and be reliable with the currently established system components. The interior transceiver must fit within the human chest cavity. The exterior transceiver must be small and light enough to wear on a belt.

System Architecture

Heat Shrink Boots Power Cable Outside case DisplayPort Connector Signal cable (Through Skin) Final Product: Signal Transmission Grommet s PIC DAC Outside PCB Inner Case PIC Voltage Dividers Voltage Regulator Relay Switch Inner PCB PIC Programming Wires

Final Product: Wireless Power Pulse Generator H-Bridge Rectifier Voltage Regulator Powered LED Primary CoilSecondary Coil

Testing: Cable Cables measured at multiple locations 300% thinner Weights applied to wire between supports spaced at a fixed distance 370% more flexible Old Cable: Diameter = 8 mm New Cable: Diameter = 2.7 mm

Testing: Signals Testing Position monitor signals: Hz 0-3.3V PWM control signals: 20kHz 0-100% Duty Cycle Motor Controller signal: 50Hz 0-100% Duty Cycle Results Position monitor and PWM control signals were accurately transmitted with delay of 32μsec Method used to transmit motor controller signal was not sufficient HESA Signal In HESA Signal Out PWM Signal Out PWM Signal InMotor Controller Signal In Motor Controller Signal Out

Testing: Power Efficiency Testing Coils were set at different distances between 0.5cm – 2cm Different loads were placed at the output to measure output power Results Efficiency over full system was between 10-36% Efficiency over coils was between 16-28% at 0.5 cm

Testing Power Efficiency Various materials were placed between the coils to study performance over a 15Ω load and spacing of 0.75cm Materials Used Paper Cardboard Aluminum Foil Magnet MaterialVin (V)Vout (V) Air102.4 Paper Cardboard102.0 Aluminum100.6 Magnet101.0

Project Status Size and flexibility needs met Wireless power concept proven to work 10% efficiency over system 35% over the coils 12 of 13 signals met performance requirements Motor control signal duty cycle not within 5% of target value Sampling rate of some signals is too slow

Meeting Customer Needs Description Specification (Ideal/Marginal) Test ResultsStatus Cable Flexibility200% / 150%370%Achieved Cable Diameter2mm / 3 mm2.7 mm (300% decrease)Achieved Wires EliminationAll / 15 wires 15 wires eliminated using SPI protocol 7 wires remain Achieved Wireless PowerOptionalDelivers power with 15 – 30% efficiencyAchieved Safety Approved for medical applications Medical grade LOCTITE 5248 silicone. Achieved Heat damage to tissue Surface temperature of the case does not exceed 50ºC. Not verified because prototype was not functional. Not verified Heat damage to electronics Temperature of electronics does not exceed 120ºC. Functional at 120ºC.Not verified Shock Protection5 drops from 1.5 m heightPassedAchieved Water proof/ Pressure1m under water Did not pass – the silicone layer was too thin, no time to re-coat Will be achieved Function: continuous, no user intervention, and reliable 13 signals Final prototype – not functional Partial functionality : 12/13 signals Need not met Available space in body cabvity Less than 650 cm 3 Inner case: 90 cm 3 Achieved Dimensions and Weight Less than 900g Inner case: 9 x 5 x 2 cm, 125g Outer case: 11 x 3.5 x 2 cm, 125g Achieved Budget$2750/ $3500$2550Achieved

Future Improvements Modify PIC firmware to be capable of sampling all signals at the correct rate Implement PCBs without jumper wires Modify circuitry to transmit motor control signal with more accuracy. TET efficiency Alternative H-Bridge to dissipate less heat Alternative H-Bridge/driver circuit to run at ~170 Hz Packaging

Questions