TDS Product Design Flashcards
Increase on-hand knowledge of design choices in TDS products
MP35N
Material used for cables in leads, known for ultra-high tensile strength (100-300ksi) and great corrosion resistance against saltwater, good for medical use. Made of 35 Cobalt, 35 Nickel, 20 Chromium, 10 Molybdenum
ETFE
ETHYLENE TETRAFLUOROETHYLENE. This copolymer has a melting point above 200 °C.
7x7 MP35N Cable
Used to hold together our leads without a central lumen. Breaking strength 11lbs, elongation < 1%, 13.2 max ohm/ft
Platinum-Iridium Helix
Platinum is used in medical applications for 3 reasons: it’s radio-opaque for visualizing under fluoroscopy, it doesn’t corrode or dissolve in the body, and it is very conductive
TR Spacer
Tip to Ring Spacer. Used to separate the tip electrode and the ring electrode on a lead. Typically made from polyurethane.
Polyurethane vs Silicone Use in Medical Devices
Silicone advantages are its biocompatibility (less platelet activation, more resistance to environmental stresses). However, the downsides is that it is more “sticky” for lead body use. Polyurethane is a tougher material mechanically, and can be made into a thermoplastic, which makes it easier to mold and extrude. Silicone is a thermoset.
Environmental Stress Cracking
Stress cracking does not break polymer bonds. Instead, it breaks the secondary linkages between polymers. These are broken when the mechanical stresses cause minute cracks in the polymer and they propagate rapidly under the harsh environmental conditions. The body is considered a harsh environment
TiN
Titanium Nitride coating. This is used on many Medtronic electrodes that are in contact with tissue because it creates a larger surface area, which in turn create a higher capacitance, which is better at isolating the electrode from the tissue while still passing the electrical pulses. A nitride-rich formula creates more surface area than a titanium-rich formula.
