10 FAQ: ePTFE Coating for Medical Devices

1. What is ePTFE and why is it important in medical devices?

Expanded Polytetrafluoroethylene (ePTFE) is a biocompatible fluoropolymer with a microporous structure. It offers excellent chemical resistance, flexibility, and controlled porosity, making it ideal for vascular and neurovascular implants. Its ability to minimize thrombogenicity and allow tissue ingrowth while maintaining structural integrity is why it’s widely used in stent-grafts, heart valves, and endovascular covers.

2. How is the sintering process for ePTFE performed?

Sintering involves heating ePTFE under controlled conditions to fuse nodes and fibrils without collapsing the porous structure. This process stabilizes internodal distance (IND), improves mechanical strength, and ensures dimensional consistency. Typical parameters include precise temperature profiles and dwell times validated through SEM imaging and permeability testing.

3. What is the difference between lamination and sintering?

Lamination bonds ePTFE layers to other substrates (e.g., nitinol, stainless steel, or polymer membranes) using heat, pressure, and sometimes adhesive primers. Sintering, on the other hand, modifies the ePTFE itself to enhance structural integrity. Lamination focuses on adhesion between layers, while sintering optimizes the material’s internal microstructure.

4. How do you achieve strong adhesion between ePTFE and nitinol?

Strong bonding requires surface activation of nitinol (via plasma treatment or chemical etching) combined with optimized primers and controlled lamination conditions. Peel strength tests (ASTM F88) are used to validate adhesion. Advanced methods include selective bonding zones to maintain flexibility while ensuring secure attachment.

5. What is a low crimping profile and why does it matter?

A low crimping profile means the device can be compressed to a smaller diameter without damaging the cover. This is critical for minimally invasive delivery systems, as it reduces sheath size and improves navigation through tortuous anatomy. ePTFE’s thin, flexible structure helps achieve low profiles while maintaining durability.

6. Is ePTFE resistant to delamination?

Yes, when processed correctly. Delamination risk is minimized through proper lamination techniques, validated peel strength, and quality control measures such as SEM analysis and cyclic fatigue testing. Medibrane’s processes are designed to ensure repeatable adhesion and long-term integrity under physiological conditions.

7. How is peel strength tested for ePTFE coatings?

Peel strength is measured using standardized tensile tests (e.g., ASTM F88) where bonded samples are pulled apart at a controlled rate. Results are expressed in Newtons or pounds per inch. High peel strength indicates robust adhesion, which is essential for device reliability during deployment and long-term use.

8. What is the difference between ePTFE and Dacron?

ePTFE is a microporous fluoropolymer offering flexibility, low thrombogenicity, and controlled porosity. Dacron (polyester) is woven, providing higher tensile strength but less flexibility and ingrowth potential. ePTFE is preferred for low-profile, compliant covers, while Dacron suits applications requiring structural reinforcement.

9. What standards apply to ePTFE coatings?

ISO 13485 governs quality management for medical devices. Additional standards include ISO 25539-2 for endovascular devices and ASTM methods for peel strength and permeability. Compliance ensures safety, repeatability, and regulatory acceptance for implantable products.

10. Can ePTFE be combined with TPU membranes?

Yes. Composite membranes of ePTFE and TPU (thermoplastic polyurethane) are used to balance flexibility, sealing, and mechanical strength. TPU adds elasticity and bonding capability, while ePTFE provides biocompatibility and porosity. These hybrids are common in advanced stent-graft and structural heart applications.