A Step-by-Step Guide to Constructing a Catheter with Filmcast PTFE

Filmcast PTFE liners are renowned for their lubricious properties, making them essential for high-performance catheter construction and advanced delivery systems. With Confluent’s thin-walled PTFE liners, supplied with a core mandrel, engineers can streamline catheter assembly and achieve precision and durability in their designs. Below, we outline the key steps for constructing a catheter using Filmcast PTFE liners.

Step 1: Preparing the PTFE Liner

Confluent supplies PTFE liners cut to discrete lengths, packaged in protective bags and tubes to ensure safe transport.

1. Inspect the Liner: Before beginning, carefully examine the liner to ensure it is free of bends or damage.
2. Straighten the Liner if Needed: If the liner is slightly bent, gently straighten it without overstretching. This ensures a straight mandrel during reflow, minimizing the risk of bends or thin spots in the finished catheter shaft.

Once the liner is straightened and inspected, you’re ready to start building the catheter shaft.

Step 2: Adding Braiding or Coiling for Enhanced Performance

The addition of braiding or coiling over the PTFE liner allows for precise control over catheter flexibility, stiffness, pushability, and kink resistance. There are two common methods to incorporate braiding or coiling:

1. Direct Braiding or Coiling: Perform the braiding or coiling directly over the PTFE liner, either continuously onto a spool or in discrete lengths.
2. Pre-Formed Braiding: Use pre-formed braiding as a sleeve, sliding it over the PTFE liner.

For pre-formed braiding, follow these steps:

• Tension the Braid: Secure one end of the braid by twisting it tightly to lock it in place.
• Tension the Length: Pull the braid taut along the entire length of the liner and twist the opposite end to prevent springing.
• Trim Excess: Use side cutters to trim any excess braid for easier loading of the outer jackets and heat shrink.

Step 3: Loading the Outer Jackets and Heat Shrink

With the braid in place, proceed to assemble the outer components:

1. Slide on the Outer Jackets: Place the outer jackets over the braided layer.
2. Apply Heat Shrink Tubing: Slide heat shrink tubing over the outer jackets to secure them for the reflow process.

Step 4: Reflowing the Shaft

Reflowing laminates the layers together, creating a robust catheter shaft.

1. Reflow Process: Use a vertical laminator or an oven to reflow the assembly.
2. Remove Heat Shrink: Once the reflow process is complete, carefully remove the heat shrink tubing, revealing a fully laminated shaft.

Step 5: Removing the Core Mandrel

The next step is to remove the core mandrel while preserving the integrity of the PTFE liner.

1. Trim Excess Material: Roll cut both ends of the catheter shaft to remove excess material, ensuring minimal scoring of the core mandrel.
2. Elongate and Release: Secure one end of the mandrel in a stationary fixture. Using pliers, grasp the other end and slowly elongate the mandrel. This will cause the mandrel to neck and release from the shaft.
3. Clean Removal: Use side cutters to make a clean cut at one end of the mandrel. Remove it by sliding it carefully through the interior of the shaft to avoid damaging the PTFE liner.

Step 6: Final Cut and Inspection

With the core mandrel removed, roll cut the finished catheter shaft to the desired length. Perform a final inspection to ensure the shaft meets all specifications and performance requirements.

Innovative PTFE Solutions for Medical Excellence

Confluent’s Filmcast PTFE liners offer industry-leading specifications, with inner diameters up to 0.155” and rapid lead times of three weeks or less. Their advanced design capabilities and skilled development teams are equipped to tackle the most complex catheter challenges, transforming innovative concepts into life-saving medical solutions.

Whether you’re designing for pushability, flexibility, or kink resistance, Filmcast PTFE provides the foundation for durable, high-performance catheter construction.