Catheters are vital tools in modern medicine. From cardiology and interventional radiology to urology and neurology, they enable minimally invasive therapies that save lives every day. But designing a catheter is a balancing act: it must remain flexible enough to navigate delicate vessels, while being strong enough to resist kinking, collapse, or torsional stress.

The solution is braided catheter reinforcement. By embedding ultra-fine stainless steel wires into the catheter wall, engineers can achieve a unique combination of torque control, kink resistance, and pressure stability.

Clinical Relevance of Braided Reinforcements

Different medical specialties place distinct requirements on catheter design:

• Cardiovascular catheters (e.g., for angioplasty or stent delivery) require excellent torque transmission and kink resistance to navigate tortuous coronary arteries.
• Neurovascular catheters must combine ultra-fine flexibility with stable pushability to reach small cerebral vessels.
• Urology and drainage catheters benefit from braided reinforcement when long-term mechanical stability and resistance to collapse are needed.
• Electrophysiology catheters rely on precise torque control to ensure accurate ablation in cardiac tissue.

In all these applications, braided fine-wire structures make the difference between a device that feels intuitive to the physician and one that struggles under clinical conditions.

Stainless Steel Wire for Catheter Reinforcement

While polymers provide flexibility, only stainless steel wire reinforcement can deliver the needed mechanical stability and durability. Stainless steel remains the industry standard for braided catheters thanks to its biocompatibility, corrosion resistance, and mechanical strength. Common stainless grades include:

• AISI 304 (EN 1.4301) – an austenitic stainless steel with excellent formability and corrosion resistance, ideal for general-purpose catheters.
• AISI 304V (EN 1.4310) – vacuum arc remelted, for increased purity and homogeneity, well suited to fine wire applications such as catheter braid reinforcement with high tensile and fatigue strength.
• AISI 316L (EN 1.4404) – “surgical stainless steel,” offering superior resistance to pitting and stress corrosion cracking, widely used in long-term implants and high-performance catheters.
• AISI 316LVM (EN 1.4441) – remelted material with excellent micro cleanliness and structural homegeneity used for surgical implants and in some catheter applications. 

These grades are well-known for meeting ASTM F138 / F139 standards for implantable stainless steels and ensuring compliance with ISO 10993 biocompatibility testing.

Wire Dimensions and Braid Designs

For catheter reinforcement, stainless steel wire must meet extreme precision standards: 

• Diameters typically range from 0.0008 in. to 0.003 in. (20–80 µm).
• The braid angle (usually between 30° and 60°) determines the balance between torqueability and flexibility.
• Wire count and pitch influence overall catheter stiffness and pushability.
• Surface quality is decisive: mirror-polished and defect-free wires reduce friction in the braid and prevent microcracks under cyclic loading.

These technical parameters directly influence catheter performance, reliability, and physician handling.

The Braiding Process in Catheter Manufacturing

The braiding process itself is a critical step in catheter manufacturing. Ultra-fine stainless steel wires are woven around a polymer tube (often PTFE or Pebax) using high-precision braiding machines. During this process, carefully controlled wire tension ensures that every strand is laid with exact pressure, which prevents irregularities in the braid structure. Equally important is maintaining a uniform braid density, as this guarantees consistent torque transmission along the entire catheter shaft. By adjusting the braid angle, engineers can fine-tune the balance between flexibility and stiffness, tailoring the catheter’s performance to specific clinical applications. After braiding, the reinforced shaft is typically encapsulated with an additional polymer layer, embedding the wire mesh and creating a smooth, biocompatible outer surface. The result is a catheter that combines the best of both worlds: polymer flexibility and stainless steel strength.

Zapp: The Trusted Partner for Medical Stainless Steel Wire

For manufacturers aiming to deliver next-generation catheter performance, Zapp is a trusted partner in the medical device industry.

Why leading device makers choose Zapp:

• Tightest tolerances – Zapp supplies precision wire with consistent diameters, ensuring uniform braiding and predictable catheter performance.
• Optimized surface finish – ultra-smooth wires reduce friction during braiding and enhance fatigue resistance inside the final device.
• Biocompatible materials – meeting ISO requirements for medical applications.
• Wide range of alloys – from standard stainless steels to high-performance specialty grades.
• Global support – with expertise in medical wire applications, supports catheter reinforcement development from concept to commercialization.

With Zapp stainless steel wire, global catheter manufacturers can deliver medical devices that meet the highest standards of performance, reliability, and patient safety.