Objective: To develop a system that transmits signals to and from a Left Ventricular Assist Device (LVAD) with a decreased amount of physical wiring through the skin. Motivation: The RIT LVAD blood pump used a large signal and power cable entering through the skin. The lack of flexibility in this cable caused discomfort, limited range of motion, and was associated with many health risks to the patient because of the exposure of the tissue to the cable, which caused approximately 40% of LVAD patient fatalities. In order to power the LVAD system located inside the body four percutaneous 26AWG wires are required. A TET system was designed to eliminate this required connection. Using inductive coupling, a primary coil located on the outside of the body ideally would transfer the required energy to a secondary coil located inside the body. Efficiency of the TET was measured over the coil at varying air gap distances. Power efficiency was between 15-30% at 0.5 cm spacing and between 4-6% at 2 cm. DESIGN IMPROVEMENT: The cable was decreased to a diameter of 2.7 mm with only 7 wires. This provided a 300% decrease in diameter and a 370% improvement in flexibility. The reduced diameter was accomplished by changing the placement of electronic components as well as implementing Serial Peripheral Interface (SPI) protocol. This method was capable of transferring all of the required sensor and control signals over fewer wires. ORIGINAL DESIGN: The original design of the percutaneous LVAD cable consisted of 23 wires with a diameter of 8mm. Project: Dates: 09/02/2009 – 02/20/2010 Advisor: Dr. Rick Lux Funding: National Heart, Lung and Blood Institute (NIH) Old Cable: Diameter = 8 mm Flexibility: The cable was tested for flexibility measuring its deflection under various weights, applied to the center of a cable section. Power cable: The cables current capabilities were tested using a load resistance to ensure it could safely carry 3 Amps over a sustained period of time. Shock: The cases were drop tested for their ability to protect electronics from mechanical shock in case of impact Signals: The integrity of SPI was tested to ensure continuity of signal processing of PWM and HESA sensors by measuring the input signal in comparison to the output signal Pulse Generator H-Bridge Rectifier Voltage Regulator Powered LED Primary CoilSecondary Coil Carl Hoge (ME)Sara Carr (EE) Lead Engineer Robert MacGregor (ISE) New Cable: Diameter = 2.7 mm Interior Electronics Exterior Electronics ORIGINAL DESIGN Interior ElectronicsExterior Electronics PROPOSED DESIGN TETS Customer Needs Importance DescriptionTest Results & Future Work 14The cable entering the body is more flexible.Improvement of 370% over the old cable 25The cable entering the body is smaller in diameter.Cable diameter: 2.7 mm (300% decrease) Eliminate as many wires as possible from XPC Control Target to the LVAD, position sensors, and Active Magnetic Bearings 15 wires eliminated using SPI protocol 7 wires remain 6, 83 Wireless Power System to eliminate power wires (15V and Ground) through the human skin and biological tissues. The TET system demonstrates feasibility of eliminating the 4 power wires by delivering power with 15 – 30% efficiency. 9, 10, 145 The cable, packaging, and connections are safe to human tissue. The cable and case are covered by medical grade LOCTITE 5248 silicone. All components and materials are IEEE and FDA approved, as applicable. 115 Heat generated by the inner transceiver does not cause tissue damage. Heat test will verify that the surface temperature of the case does not exceed 50ºC. 125The heat created by a body does not damage the electronics. Heat test will verify that the ambient temperature of electronics does not exceed 120ºC. 135 Inner and outer transceivers must be protected from the outside forces. A drop test proved durability of the case and proper protection of electronics The device must function continuously, without user intervention, and be reliable with the currently established system components. Input and output of PCB signals were tested using wave generator and oscilloscope. It will be tested with the current LVAD system in order to demonstrate these functions. 205The interior transceiver must fit within the human chest cavity. Available cavity volume: 650 cm 3 Inner case volume: 90 cm 3 21, 225 The exterior transceiver must be small and light enough to wear on a belt. Inner case: 9 x 5 x 2 cm, 125g Outer case: 11 x 3.5 x 2 cm, 125g Importance scale (5=must have, 3=nice to have, 1=preference only). CONCEPT SELECTION: Wireless communication was considered, but due to the time frame and complexity of the human body, a hardwired design was chosen. Oxana Petritchenko (ME) Project Manager Keith Lesser (CE) Heat Shrink Boots Power Cable Outside case DisplayPort Connector Signal cable (Through Skin) Inner Case PIC Voltage Dividers Voltage Regulator Relay Switch Inner Case Grommets PIC DAC Outer Case Dr. Steven Day Faculty Guide Dr. Cheng Shanbao Customer