The Green Revolution in Medical Device Coating

As manufacturers of catheters and guidewires, you're well aware of the importance of hydrophilic coatings in ensuring these devices glide smoothly through blood vessels. But have you ever stopped to think about how these coatings are applied? Recent advancements in coating technology are not only improving the efficiency of this process but also making it more environmentally friendly. Let's explore how these innovations are transforming the manufacturing landscape.

The Old Way: Energy-hungry and Inefficient

Traditionally, coating medical devices has been a bit of an energy hog. The machines used to apply and cure these coatings have typically relied on mercury vapor lamps, which are about as efficient as leaving your oven on all day to make toast. These old-school systems can burn up to 2000W of power, and they often stay on all day long due to their long warm-up times.

The coating process itself is quite simple, but must be very carefully controlled. As you know, many catheters, guidewires, and guide sheaths are coated with a hydrophilic coating; a polymer that readily absorbs water. This coating lubricates the device, allowing it to glide smoothly through blood vessels. The application process usually involves dipping the device into a bath of coating solution and extracting it at a controlled speed to ensure uniform coverage.

After application, the coating needs to be cured. While some coatings cure with heat, many require UV light. This is where those energy-hungry lamps come into play. Traditional machines might use fluorescent, mercury vapor, or even microwave lamps to generate the necessary UV light. These light sources have several drawbacks: they take time to warm up, lose power over time, and often emit a broad spectrum of light, including unwanted heat.

The LED Revolution: Efficient and Eco-Friendly

But here's where things get interesting. New coating machines are hitting the market that use LED technology instead. These aren't your average LEDs, though. We're talking about specialized UV LEDs that emit light deep into the UV spectrum as low as UVC – perfect for curing those hydrophilic coatings that make medical devices so slippery and easy to use.

The benefits of these new LED-based coating machines are numerous:

LED UV Curing Chamber

• Energy efficiency: They use only about 70W of power while running, compared to 2000W for traditional systems.

• Instant start-up: Unlike old lamps that needed

  warm-up time, LEDs are ready to go instantly.

• Mercury-free: LED systems don't contain mercury, making disposal simpler and far more environmentally friendly.

• Consistent output: LEDs maintain their light output over time, unlike traditional bulbs that degrade.

• Targeted wavelength: LEDs emit light at specific wavelengths, reducing wasted energy on unnecessary parts of the spectrum.

Our own Automatic Coating Machine ticks all of these boxes, and is nearly 100x more power efficient than older models. 

Precision and Consistency: The Future of Coating Technology

This new generation of coating machines is changing the game when it comes to the coating process itself. Many now feature dual dipping stations, allowing for the application of both primer and top coats in a single automated process. The level of control is impressive. Some machines allow operators to set two distinct retraction speeds along the device length, enabling variable coating thickness where needed. After dipping, the coating can be dried using heated forced convection before being cured in the UV chamber.

Hydrophilic Coating Machine, with LED curing chamber opened

These processes are automated and programmable, which means more consistent results and less human error. Many systems even allow for multiple user-defined recipes to be stored, ensuring repeatability across production runs. All of this adds up to coating techniques that are quicker, cleaner, and far more energy-efficient.

We at Pilot Line believe the future of medical device coating encompasses both creating better products and doing so in a way that's kinder to our planet. And as medical device manufacturing continues to evolve, we are proud to contribute innovations that improve product quality while simultaneously reducing environmental impact. By dramatically reducing energy consumption, eliminating hazardous materials, and improving process control, these new coating machines are a perfect example of how technology can help us work smarter and greener.

Click here to learn more about Pilot Line's coating machine

INTRODUCING OUR NEW AUTOMATED DIP COATING MACHINE

We're proud to announce the launch of our new Single-Device Dip Coating Machine. The Coating Machine was developed in partnership with ISurTec and is designed to work with their Hydrophilic Medical Device Coatings and any other UV curable coating. Now you can coat your devices on your schedule, in your lab. No more minimum lot sizes or waiting for days. In fact you can buy this machine and ISurTec coatings faster than you can get a lot coated!

The Coating Machine is designed to precisely apply coatings on medical devices. It features two dipping stations, one for a primer coat and one for a top coat, allowing for a fully automated coating process. Devices are dipped and retracted at controlled speeds, with the ability to set two distinct retraction speeds along the device length for optimal coating thickness. After retraction, the coating goes through a controlled drying process with heated forced convection. It's then cured with UVC LEDs in the curing chamber. An iris mechanism minimizes UV radiation exposure by sealing the chamber during curing. The entire process is fully automatic and programmable, with the option to lock settings to prevent unauthorized changes.

Technical Specifications:

Coating Length: up to 100 cm

Device Length: up to 125 cm

Device Diameter: up to 27 fr

LED Wavelength: 275nm

User-programmable Recipes: 25

Power Input: 110 - 240 VAC 400W         

Learn more about the new Pilot Line Dip Coating Machine

Learn more about the ISurTec Hydrophilic Medical Device Coating

Coiled Catheter OD Calculation for Designers

Want to save time when ordering extrusions for your next catheter project? This article will help you calculate the diameter of your next coiled catheter.

Background

Many neuro and peripheral catheters are made by a process of reflowing or laminating polymers and reinforcement materials over a mandrel. The reinforcement material we'll consider in this article is a coil. A coil winder is used to wind a wire over a catheter mandrel. Then a polymer jacket is sized to slide over the coil during assembly. Heat shrink tubing is then slid over the jacket. During the catheter reflow process, the jacket melts and is compressed by the heat-shrink. This causes the jacket to reduce in diameter and increase in wall thickness.

Conservation of Area

For starters, let's think of the cross section of a reflowed catheter without a coil. There's a mandrel, liner, and polymer jacket. During the catheter reflow process the jacket melts and is compressed by the heat shrink tubing. This reduces inner and outer diameter of the jacket. Since no material is lost during the catheter reflowing process, the cross-sectional area of the jacket must be the same before and after reflowing. We can use this to calculate the relationship between the pre and post reflowed jacket diameters.

Keep in mind that the final ID of the jacket would be the liner OD, or the diameter of the mandrel plus twice the liner thickness.

Enter the coil

Now let's add a coil. The conservation of

area method is invalidated because the coil is not a uniform tube. In fact, the jacket is no longer a uniform tube.

The reflowed jacket has a helical void in it because of the space the coil takes up inside of it. Instead of thinking of a conservation of area, we can use a conservation of volume to equate the pre and post lamination conditions. Again, we assume that we're not losing any material during catheter reflow. Let's cut a section of coiled catheter into a unit length and work out the volumes of each component. We'll use 1 inch for the length unit and use inches for all the diameter and volume calculations too.

Finding the volume of the jacket is straightforward. We just multiply the cross-sectional area of the jacket (first equation) by the length. Since the length is 1, it's unchanged. For the coil volume it's the same plan. We'll multiply the area of the coil wire by the length of the coil wire in a unit length of catheter. Visualize un-wrapping the coil wire along the coiled length. The result forms a right triangle.

The height of the triangle (a) is 1 unit (the same unit as the rest of your calculations). For the base of the triangle (b), think of how many times the cylinder would turn if you unwrapped the coil. The number of turns can be represented by the length of the cylinder (1 unit) divided by the pitch of the coil. We multiply the number of turns by the coil mean diameter and Pi to find this leg of the triangle.

Great, we have the length of each leg, now we just apply the Pythagorean theorem to get the wire length. Note that this number expresses how much coil wire is required per length of catheter. So, if you wanted to know how much total wire a catheter would take, you just multiply this number by the length of the catheter.

To find the volume of coil wire in a unit length, we now multiply the cross-sectional area of the wire by the length of the wire. If using a round wire you'd use the equation for the area of a circle. If you're using flat wire, you'd multiply the wire width by the thickness. Add the volume of the coil to the volume of the jacket and that gets us the total volume before and after reflowing! Let's remember the equation for the area of a pipe and assume that the area is equal to the volume since the length is 1. Solving for OD we get:

Conclusion

Using this method, you can calculate the OD and wall thickness of polymer jackets for reflow. It should save you a few prototype iterations when designing a new catheter. Additionally, you can fine-tune the OD of the device by varying the coil pitch. If reflowing a braided shaft, the volume of the braid can be calculated similarly based on the braid angle, number of wires, and cross section of the wire. Of course, these calculations should only be used as a starting point. Fine-tune your catheter OD with prototypes and testing. Good luck!