Medical devices are coated for numerous reasons. All coatings applied to them are designed to seamlessly integrate with the biological environment and enhance the device’s functionality. One of the key considerations while designing such a coating is material selection, coating equipment type, and application method. The coating method ensures a uniform, thin layer on the medical devices. There are many application (coating) methods. However, not all of them are supported by fully automated coating systems, which are becoming more prevalent in the industry.
Enterprise device manufacturers use automated coating systems to improve processing times and support high-volume production. These systems have become popular for their precision and consistency, which manual coating systems cannot match.
In this article, we will take a quick look at different coating methods supported by a fully-automated medical coating system. Our goal is to understand available options and potential considerations while incorporating different coating application modules across an automated medical coating line. If you are a Plant Manager, Operations Manager, Plant Engineering Manager, Coating Department Manager, VP Operations, Facilities Manager or Director, COO, etc. then this article is for you.
What is a Fully-Automated Coating System?
A fully automated coating system supports high-volume production and improves efficiency. It minimizes variations common in semi-automated or manual systems. This ensures consistent adhesion and uniform thickness, even at high throughput.
Nearly all manufacturers are implementing automated machines for full-scale production. Automation not only reduces labor requirements but also significantly improves speed, accuracy, and efficiency. These systems are proven to improve processing times and ensure consistent quality across all batches. Companies like Hydromer®, Inc., a leading manufacturer and supplier of advanced hydrophilic coatings, with over 40 years of industry experience, sell fully automated coating equipment that can coat millions of units per year.
Medical Coating Application Methods
Different medical coatings are applied to enhance the device’s functionality and durability in biological environments. These formulations are composed of chemistry, polymers, glass, metals, or ceramics, with selection based on specific application requirements. The most commonly used type is Medical Device Hydrophilic Coatings.
There are several ways to apply medical coatings to the surface of the device substrates. These various processes are known as the application methods or coating methods.
Here is a quick list of medical coating application methods:
- Dip
- Spray
- Spin
- Flow
- Meniscus
5 Compatible Coating Methods for Automated Coating Systems
One of the key components of a fully-automated coating system is the coating application module. Medical devices are coated using a wide range of processes or methods. However, a few of them are complex and cannot be included in semi- or fully-automated coating lines.
Below, we discuss the hydrophilic coating application methods that are used across automated coating lines:
1. Dip Coating Methods for Medical Devices
Dip coating modules integrate easily with automated lines. They are ideal for high-volume, fast throughput. This coating method produces parts that meet the rigorous demands of modern healthcare applications.
Process
In dip coating, parts or entire devices are immersed in a coating solution. Mechanized processes control the immersion and withdrawal rates to ensure uniform and consistent coatings.
Advantages
- The dip coating method is an excellent choice for complex geometries.
- It can be easily scaled up for high-volume applications as per the production requirements and the complexity of medical devices.
2. Spray Coating
The spray coating method is another good choice to be included in an automated coating line. It prevents the continuous or excessive deposition problems associated with other coating application techniques, such as the spin and dip methods.
Process
A liquid coating solution is atomized into a mist and sprayed onto the substrate. The spray coating modules include high-precision nozzles, heated spray headers, and advanced motion control systems. These evenly deposit an ultra-thin layer of coatings onto the medical device surfaces.
Most modern spray coating modules use ultrasonic nozzles, which provide pressure-less atomization and precise droplet control.
Advantages
- Nozzle size and configuration can be adjusted for fine atomization and controlled droplet distribution.
- This method improves material utilization and efficiency by reducing overspray.
- Spray coating is particularly effective for applying medical hydrophilic coatings for drug-eluting devices.
3. Spin Coating
The spin coating method is potentially the quickest way to apply coatings to device substrates. The thickness or uniformity of the applied coating is controlled using the speed and duration of spinning.
Process
The spin coater uses centrifugal force to apply a thin film coating onto the surfaces of the medical device. It spins both the liquid coating solution and parts at high speeds for even covering.
The process starts by applying an excess amount of coating solution to the substrate, then the substrate is rotated at high speeds to let the centrifugal force spread the solution evenly across the entire surface.
Advantages
- Spin coating is one of the simplest and easiest techniques for applying medical coatings.
- Centrifugal force provides excellent uniformity and thickness control.
- Excess coating solution evaporates quickly during spinning or drying.
- This method is ideal for applying ultra-thin coatings in automated coating systems
4. Meniscus Coating
Hydromer®, Inc. offers a proprietary meniscus coating technology. It is well suited for precisely applying thin, uniform coatings to devices, such as catheters and guidewires. This method relies on surface tension and capillary forces.
The meniscus method is popular as the meniscus-guided coating application technique. It is best suited for devices that are long (100+ cm) and have a small diameter.
Process
A meniscus forms as a standing liquid between the coating source and substrate surface, and is drawn along the substrate to apply a thin coating. Coating thickness and uniformity depend on the speed at which the meniscus moves.
Advantages of Meniscus Coating
- It enables precise coating localization and lets the manufacturer target functional zones without any need for masking.
- Material waste is minimal or nonexistent.
- There is a low risk of bead formation at the ends.
5. Flow Coating
This is a liquid deposition method for applying coatings to medical devices. It uses gravitational force to apply coatings.
Process
In this method, a controlled stream of coating solution flows over a substrate. The flow is arranged downwards to ensure a sufficient force by gravity. This flow continues until the entire surface becomes fully wet. At last, the remaining or excess coating is drained.
Some manufacturers use continuous conveyor flow systems, where parts pass through a flowing liquid curtain.
Advantages
- Flow coating is ideal for devices with larger surface areas.
Comparison of Compatible Coating Methods
| Coating Method | Best For (Device Geometry) | Key Advantage | Material Waste / Efficiency |
| Dip Coating | Complex geometries, high-volume batches | Highly scalable and ensures consistent, uniform coverage. | Low (excess drips back into the reservoir) |
| Spray Coating | Drug-eluting devices, complex shapes | Precision droplet control and pressure-less atomization. | Moderate (minimized by ultrasonic nozzles) |
| Spin Coating | Small, flat, or symmetrical substrates | Fastest application of ultra-thin, highly uniform films. | Moderate to High (excess is spun off) |
| Meniscus Coating | Long, small-diameter (catheters, guidewires) | Precise localization without the need for masking. | Minimal (highly efficient material use) |
| Flow Coating | Devices with larger surface areas | Ideal for continuous, conveyor-based automated lines. | Low (solution is typically recirculated) |
Considerations When Choosing a Coating Application Module for automated medical manufacturing
Uniform coating coverage is essential for the safe use of medical devices in biological environments. In addition to coating uniformity, consider the following factors when selecting a coating application module for your fully automated coating line:
- Geometry: Application techniques vary based on device geometry. Complex devices are best coated using dip or spray methods, while catheters and guidewires are suited to meniscus coating.
- Performance Requirements: Coating materials, such as polymers and metals, have unique properties. For example, polymer-based hydrophilic coatings offer exceptional lubricity and low friction, and can be customized for antimicrobial, thromboresistant, or drug-eluting properties. Meniscus, dip, and spray methods are typically best for these coatings.
- Thickness: Coating thickness and uniformity are directly linked to the overall performance and long-term safety of the underlying medical devices. That’s why an uneven layer of coating onto an invasive medical device does not comply with strict regulatory guidelines. It is suggested to choose a precisely controlled coating method if the thickness tolerance is tight.
- Material Compatibility: Each coating material exhibits different surface energy, which is an important factor when it comes to proper adhesion. As such, manufacturers must choose an application method compatible with the coating material because the stability and durability of a medical coating heavily depends upon substrate adhesion.
- Drug Loading Accuracy: Coating thickness and drug holding capacity play a critical role in the success of a drug-eluting medical device. These two factors determine the release kinetics and frequency of the therapeutic dose. Spray coating is typically the most compatible coating method for drug-eluting devices.
- Scalability: Application modules should transition efficiently from R&D and pilot production to full-scale manufacturing without compromising quality. You will wan to confirm with the equipment supplier whether modules support multi-lane or parallel expansion.
The coating experts at Hydromer can help you determine the appropriate coating and application method for your specific device requirements.
Hydromer®: Hydrophilic Medical Coating Manufacturer and Coating Systems Supplier
Hydromer®, Inc. is a leading manufacturer and supplier of advanced hydrophilic coatings, with over 40 years of industry experience.
We also supply high-performance, fully automated coating systems to medical device clients, including leading OEMs and CMOs. Our team supports clients throughout product development, from R&D and coating formulation to equipment provision.
Automated Medical Coatings Systems by Hydromer®, Inc
Our two most popular automated coating lines are:
- Hydrophilic Coating System: This automated system features integrated UV curing and is designed for applying hydrophilic coatings to medical devices. It requires only one or two operators and supports an annual capacity of 200,000 to 300,000 units.
- Fully Automated Coating System: This end-to-end solution is suitable for industrial applications and compatible with various medical-grade coatings. It requires one operator and is ideal for large-scale production of complex devices such as catheters and guidewires.
To learn more about our coating systems, please contact us.
Need assistance?
Contact our team to learn more or to schedule a demonstration.
Frequently Asked Questions
Coating methods compatible with fully automated medical coating systems include dip coating, spray coating, spin coating, meniscus coating, and flow coating.
Meniscus coating method is generally the best application technique for devices like catheters and guidewires.
Spray coating is generally the best coating method for drug-eluting devices.
