As medical devices that directly contact human tissues—such as blood vessels, airways, or the urogenital tract—catheters must meet three core standards:

Biocompatibility (non-toxic, non-immunogenic),

Mechanical compatibility (matching the target tissue’s mechanical properties),

Clinical adaptability (resistance to sterilization, disinfection, and body fluids).

Currently, the most commonly used materials include:

Thermoplastic Polyurethane (TPU)

Polyether Block Amide (PEBAX)

Polyamide (PA, e.g., Nylon 12)

Each material serves different applications and must be selected based on specific clinical needs.

1. TPU: Balancing Biocompatibility and Processability

TPU is a segmented copolymer composed of alternating hard (isocyanate) and soft (polyether or polyester) segments. Its tunable molecular structure makes it widely used in medical catheters.

✅ Advantages:

Excellent Biocompatibility: Passes ISO 10993-4/5 tests, suitable for long-term contact with human tissue.

Superior Flexibility and Clarity: Shore hardness range 60A–90A provides adaptability in flexibility; high transparency aids in visual catheter tracking during procedures.

Chemical Resistance: Tolerates common disinfectants such as alcohol and iodine; better hydrolysis resistance than standard polyurethane.

Good Processability: Compatible with extrusion and injection molding; supports multilayer co-extrusion for complex catheter structures.

❌ Limitations:

Limited High-Temperature Resistance: Degradation of ester bonds above 80°C limits high-temperature sterilization use.

Insufficient Kink Resistance: Prone to permanent deformation at bending angles >90°; may require braided reinforcement (e.g., metal wire), increasing processing complexity.

Relatively High Cost: Medical-grade TPU is 3–5 times more expensive than PVC.

2. PEBAX: The “Anti-Kink Expert” for Interventional Devices

PEBAX is a block copolymer of polyamide (hard segment) and polyether (soft segment), making it ideal for minimally invasive applications—especially in cardiovascular and neurovascular interventions.

✅ Advantages:

Excellent Mechanical Balance: Top-tier kink resistance with >95% elastic recovery after 180° bending. Enables smooth navigation through tortuous vessels without trauma.

Outstanding Fatigue Resistance: Ideal for high-frequency operations like cardiac ablation and neuro microcatheters.

Sterilization Compatibility: Maintains >90% of tensile strength and kink resistance after sterilization.

Adjustable Radiopacity: Uniform dispersion of barium sulfate or tungsten powder allows clear X-ray visibility.

❌ Limitations:

Tight Processing Window: Requires precise temperature control and specialized extrusion equipment.

High Material Cost: Medical-grade PEBAX (e.g., Arkema PEBAX® MED) costs 2–3 times more than TPU.

3. PA (e.g., Nylon 12): The “Structural Backbone” for Rigid Sections

PA materials, particularly Nylon 12, feature high crystallinity and rigidity, making them suitable for structural components within catheters.

✅ Advantages:

High Rigidity and Dimensional Stability: Ideal for components requiring structural support (e.g., PTCA catheter shafts).

Excellent Wear Resistance: High surface hardness (Shore D 70–80) and low friction coefficient support long-term or repeated use.

High-Temperature Resistance: Short-term resistance up to 150°C enables high-temperature sterilization.

❌ Limitations:

Moisture Absorption: ~1.5% water absorption can cause dimensional changes in long-term implants; requires modification to reduce moisture impact.

Limited Flexibility: High rigidity can damage vessel endothelium during insertion; often requires a TPU coating for softness.

Biocompatibility Concerns: Degradation by-products may trigger inflammation; controlled degradation rates via molecular modification are required.

4. Emerging Trends and Innovations in Catheter Materials

TPU + PEBAX Blending:
Blending 50% TPU (biocompatibility) with 50% PEBAX (kink resistance) creates an interpenetrating soft-segment network. Widely used in cardiac ablation catheter tips, this approach balances fatigue resistance with myocardial compatibility.

Nano-Reinforced PA:
Adding 1–3% carbon nanotubes improves Nylon 12’s tensile modulus and reduces water uptake. Applied in bioresorbable scaffold frameworks.

Biodegradable TPU:
Polyester-based biodegradable TPU, such as polybutylene succinate segments, degrades in 6–12 months into CO₂ and water. Suitable for temporary implant devices.

5. The “Three-Dimensional” Selection Framework

Performance Fit: Choose based on clinical priorities (e.g., kink resistance for cardiovascular catheters → PEBAX; long-term indwelling → TPU).

Cost Balance: Combine materials for cost-effective solutions (e.g., PA+TPU for urinary catheters); prioritize high-performance PEBAX for premium devices.

Manufacturing Feasibility: Consider processing complexity, equipment, and supply chain support.

Conclusion

Optimal catheter material selection lies at the intersection of safety, performance, and cost. Material blending and modification techniques continue to expand the design window, enabling safer, more precise, and cost-effective interventional devices.