Medical Device Sub-Assemblies

Medical device sub-assemblies made from stainless steel or nitinol are critical components in a wide range of healthcare applications, leveraging the unique properties of these materials to meet stringent performance, biocompatibility, and durability requirements.

Tullamed has long standing expertise in leveraging a wide range of manufacturing and assembly processes including laser welding to build medical sub-assemblies..

Stainless Steel

Stainless steel, particularly grades like 316L (low-carbon) and 17-4 PH (precipitation-hardened), is widely used due to its excellent corrosion resistance, strength, and cost-effectiveness. It’s a go-to material for components that need to withstand sterilization processes (e.g., autoclaving) and bodily fluids without degrading.

Sub-Assembly Examples: Stainless steel is often used in hypotubes (thin-walled tubes in catheters), guidewires, or stents where durability is key. These sub-assemblies might include laser-cut patterns or welded joints.

Manufacturing: Common processes include CNC machining, laser cutting, and metal injection molding (MIM) for intricate shapes. Surface finishing (e.g., passivation) enhances biocompatibility by removing free iron and boosting the oxide layer.

Common Applications

Surgical instruments, orthopedic implants (plates, screws), catheter components, and endoscope parts.

Properties:

Corrosion Resistance: Essential for long-term implants or repeated use in saline-rich environments like the human body.
Mechanical Strength: Provides structural integrity for load-bearing applications.
Machinability: Allows for precision manufacturing of complex sub-assemblies.

Nitinol

Nitinol, a nickel-titanium alloy, is prized for its shape memory and superelasticity, making it ideal for devices that must flex, recover their shape, or adapt to dynamic conditions inside the body. It’s more expensive than stainless steel but excels in minimally invasive applications.

Applications

:Vascular stents, guidewires, orthodontic wires, and endovascular devices like heart valve frames or clot-retrieval systems.

Properties:

Shape Memory: Returns to a predefined shape when heated (e.g., above body temperature), useful for self-expanding stents.

Superelasticity: Can undergo significant deformation and snap back, perfect for navigating tortuous anatomy like blood vessels.

Biocompatibility:

Comparable to stainless steel, though nickel content requires careful surface treatment (e.g., electropolishing) to prevent leaching.
Sub-Assembly Examples: Nitinol stents are often laser-cut from tubes and paired with delivery systems (e.g., catheters). Guidewires might combine a nitinol core with a stainless steel coil for added stiffness.

Manufacturing

Laser cutting dominates due to nitinol’s toughness, followed by heat-setting to “train” the shape memory. Electropolishing or coating smooths surfaces and improves fatigue life.

Both nitinol and stainless steel are often part of sub-assemblies that integrate with polymers (e.g., catheter shafts) or coatings (e.g., PTFE, parylene or other hydrophilic layers) to enhance functionality.