Smiha Sayal Left Ventricular Assist Device (LVAD) Mechanical device that helps pump blood from the...

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 Left Ventricular Assist Device (LVAD)  Mechanical device that helps pump blood from the heart to the rest of the body.  Implanted in patients with heart diseases or poor heart function.

Transcript of Smiha Sayal Left Ventricular Assist Device (LVAD) Mechanical device that helps pump blood from the...

Smiha Sayal Left Ventricular Assist Device (LVAD) Mechanical device that helps pump blood from the heart to the rest of the body. Implanted in patients with heart diseases or poor heart function. Miniaturize the existing LVAD system to achieve portability while retaining its safety and reliability. All team members Safe Robust Affordable Easy to wear and use Interactive with user Controllable by skilled technician Comparable performance Compatible with existing pump CorAide (NASA) Black box architecture used during development Large, not portable Runs on AC power Has both internal / external components Equivalent to our Option 2 Unfinished implementation All electronics external ADC internal only Pump and motor control internal All electronics and battery internal Option 1 Smallest internal volume Feasible within timeline Easiest to maintain Minimum 20 wires Option 2 Relatively small internal volume Slightly higher risk of internal failure Minimum 10 wires Option 3 Large internal volume Difficult to design Electronics failure is fatal Minimum 3 wires Option 4 Large internal volume Difficult to design Electronics failure is fatal Minimum 3 wires Best Option Nicole Varble and Jason Walzer Needs The external package should be lightweight/ robust/ water resistant The devices should be competitive with current devices The device should fit into a small pouch and be comfortable for user Specification Optimum weight of 5 lbs Optimum dimensions of ~6 x 2 x 2 Risks Housing for the electronics is too heavy/large/uncomfortable Preventative measures Eliminate heavy weight materials Eliminate weak, flexible materials Material is ideally machinable +Extremely lightweight -Not robust -Long machining and processing time External mold to create silicon/plastic housing +Extremely lightweight +Relatively robust +Extremely fast machining time Rapid Prototyping +Lightweight +Robust -long machining and processing time Aluminum housing +Relatively lightweight +Extremely robust -long machining and processing time Titanium housing Dimension System ABSplus Industrial thermoplastic Typically used for product development Machinable Material can be dilled (carefully) and tapped Accepts CAD drawings Obscure geometries can be created easily Ideal for proposed ergonomic shape Lightweight Specific gravity of 1.04 Porous Does not address water resistant need 0.007 material/layer Capable of building thin geometries Builds with support layer Models can be built with working/moving hinges without having to worry about pins Mechanical Property Test Method ImperialMetric Tensile StrengthASTM D6385,300 psi37 MPa Tensile ModulusASTM D638330,000 psi2,320 MPa Tensile ElongationASTM D6383% Heat DeflectionASTM D648204F96C Glass TransitionDMA (SSYS)226F108C Specific GravityASTM D Coefficient of Thermal Expansion ASTM E E-5 in/in/F Important Notes Relatively high tensile strength Glass Transition well above body temperature Specific Gravity indicates lightweight material Need: The external package should resist minor splashing Specification: Water Ingress Tests Once model is constructed, (user interface, connectors sealed, lid in place) exclude internal electronics and perform test Monitor flow rate (length of time and volume) of water Asses the quality to which water is prevented from entering case Risk: Water can enter the external package and harm the electronics Preventative measures: Spray on Rubber Coating or adhesive O-rings around each screw well and around the lid Loctite at connectors Need: The device should survive a fall from the hip Specification: Drop Test Drop external housing 3-5 times from hip height, device should remain fully intact Specify and build internal electrical components Identify the most venerable electrical component(s) which may be susceptible to breaking upon a drop Mimic those components using comparable (but inexpensive and replaceable) electrical components Goal Show the housing will not fail Show electronics package will not fail, when subjected to multiple drop tests Risks The housing fails before the electronic components in drop tests The electronic components can not survive multiple drop tests Preventative Measures Eliminate snap hinges from housing (screw wells to secure lid) Test the housing first Take careful consideration when developing a thickness of the geometry Design a tight electronics package Need: Internal Enclosure dissipates a safe amount of heat to the body Risk: Internal electronics emit unsafe amounts of heat to body Benchmarking: Series of tests studied constant power density heat sources related to artificial hearts 60-mW sources altered surface temperatures 4.5, 3.4, 1.8 C above normal at 2, 4, 7 weeks 40mW/cm 2 source increased to upper limit of 1.8 C Specifications: Internal devices must not increase surrounding tissue by more than 2C Wolf, Patrick D. "Thermal Considerations for the Design of an Implanted Cortical BrainMachine Interface (BMI)." Ncib.gov. National Center for Biotechnology Information, Web. 30 Sept Need: Device should be comfortable for user ANSUR Database Exhaustive military database outlining body dimensions Waist Circumference (114) Males: mm Females: mm Waist Depth (115) Males: mm Females: 102 mm Calculated average radius of hip Males: mm Females: mm Acceptable Avg. Radius of hip ~120 mm CAD model is can be easily resized Removable top panel for electronics access Andrew Hoag and Zack Shivers Requirements Selecting suitable embedded control system Designing port of control logic to embedded system architecture Customer Needs Device is compatible with current LVAD Device is portable/small Allows debug access Impeller must be levitating or floating Electromagnets control force exerted on impeller Keeps impeller stabilized in the center Position error measured by Hall Effect sensors Algorithm complexity influences microcontroller choice Electronics choices affect volume / weight Proportional Integral Derivative (PID) Very common, low complexity control scheme Requirements: Can handle PID calculations Has at least 8x 12-bit ADC for sensors at 2000 samples/sec Multiple PWM outputs to motor controller(s) Same control logic as current LVAD system Reprogrammable Custom Embedded dsPIC Microcontroller Blocks for Simulink Small Inexpensive (