Why is soldering or gluing polymer membranes to Nitinol scaffolds inefficient?

Soldering and gluing are manual processes that are nearly impossible to validate for medical grade production. They require thicker membranes (50+ microns), result in high scrap rates, and create bulky profiles. Sutureless lamination replaces these with an automated 15-micron process.

Can you achieve a 15-micron wall thickness on a Nitinol scaffold?

Yes. While dip coating and manual gluing often result in thicknesses over 50 microns with high variability, sutureless lamination achieves a 15-micron wall thickness with +/- 20% tolerances.

How do you bond TPU to Nitinol without glue?

Medibrane uses the Adera adhesion platform to create a covalent bond between the TPU and the Nitinol struts, eliminating the need for manual gluing or soldering while preventing delamination.

Revolutionizing Nitinol Covering: Sutureless TPU Lamination vs. Traditional Techniques

Feb 26
3 min read

When manufacturing advanced neurovascular or cardiovascular devices,such as embolic protection devices and drug delivery catheters,the quality of the polymer covering on the Nitinol scaffold can make or break the product.

Covering these intricate, shape-memory structures requires precision, reliability, and ultra-low profiles.

For years, manufacturers have relied on traditional methods like dip coating, manual gluing, or soldering to attach Thermoplastic Polyurethane (TPU) membranes to Nitinol struts.

However, as the demand for smaller, more complex delivery systems grows, these legacy methods are showing their limitations.

Enter sutureless lamination,an automated, highly controlled process that is changing the standard for medical device encapsulation.

Let's break down how sutureless lamination of TPU membranes compares to traditional dip coating and manual bonding, and why it's becoming the superior choice.

The Limitations of Traditional Covering Methods

Before we look at the solution, we have to understand the bottlenecks in traditional manufacturing.

1. Dip Coating: The Struggle for Consistency

In dip coating, the Nitinol scaffold is repeatedly submerged into a polymer solution. The membrane is essentially formed on the scaffold itself.

Thickness Control: Because the polymer cures directly on the strut geometry, achieving a uniform wall thickness is incredibly difficult. Gravity and surface tension lead to webbing and uneven distribution.
Defects: This wet-to-dry process is highly susceptible to trapping air bubbles, creating pinholes, or leaving surface defects that can compromise the device's integrity.

2. Manual Gluing & Soldering: The Validation Nightmare

Manual attachment involves operators painstakingly gluing or soldering the membrane to the Nitinol frame.

High Wall Thickness: Manual handling requires a more robust material. Because of this, manual bonding typically requires wall thicknesses of around 50 microns just to survive the assembly process.
Scrap and Touch Time: Relying on human hands for microscopic precision leads to high touch times and, inevitably, higher scrap rates.
Process Validation: In the MedTech industry, process validation is everything. Manual gluing or soldering is notoriously difficult—if not impossible—to properly validate to regulatory standards due to the inherent variability of human operators.

The Sutureless Lamination Advantage

Sutureless lamination flips the script by separating the membrane creation from the scaffold attachment.

By preparing the TPU membrane in advance and then automatically laminating it onto the scaffold, manufacturers unlock a host of critical advantages:

Precision Wall Thickness: Because the membrane is extruded or cast prior to application, manufacturers have total control over its thickness. You aren't hoping for an even coat; you are applying an exact, pre-measured film.
Defect-Free Surfaces: Pre-fabricating the membrane completely eliminates the bubbling and webbing issues associated with wet dip coating.
Ultra-Low Profiles: This is where sutureless lamination truly shines. Instead of settling for 50-micron walls, lamination allows for ultra-thin wall thicknesses of just 15 microns, with tight tolerances of +/- 20%. This is a massive advantage when designing devices that must navigate tortuous anatomies.
Automated and Validatable: Sutureless lamination is an automated process. This drastically reduces operator touch time, minimizes scrap, and—most importantly—creates a highly repeatable process that is straightforward to validate for FDA and CE mark submissions.

The Secret Sauce: Medibrane’s Adera™ Adhesion Platform

One of the historical challenges of laminating over Nitinol is ensuring the polymer actually stays attached to the smooth metal struts without peeling or delaminating.

To solve this, Medibrane utilizes the Adera™ adhesion platform.

Instead of relying purely on mechanical encapsulation or weak surface adhesion, the Adera technology alters the surface chemistry to create a covalent bond between the TPU membrane and the Nitinol struts.

This covalent bonding ensures that the ultra-thin 15-micron membrane acts as a seamless extension of the metal scaffold, offering unparalleled durability and peel resistance even when compressed into a microcatheter.

Conclusion

As medical devices get smaller and the anatomical targets get harder to reach, the manufacturing processes must evolve. Sutureless lamination of pre-formed TPU membranes offers the precision, low profile, and validation-friendly automation that traditional dip coating and manual gluing simply cannot match.

References :

Choi, S. Y., Lee, J. C., Suh, I. W., Park, C. H., & Kim, C. S. (2025). Study on Polyurethane Dipping Double-Layer Membrane Coating Method for Developing Polymer-Covered Stents. Tissue Engineering Part C: Methods, 31(9), 342-349

Raju, R. M. (2020). Joining Technologies for Cardiovascular Implants [Doctoral thesis, UCL (University College London)]. UCL Discovery