Hydrophilic coatings are “water-loving” surface modifications. They attract water molecules from their surroundings to create hydrogels. The resulting surface has high lubricity and a low coefficient of friction. As a result, these coatings have a wide range of uses. These include improved wettability, reduced friction, high lubricity, anti-fog and condensation, and more. Such properties have benefits in many areas, including medical devices. For example, they can reduce pain and tissue damage. This is critical during invasive diagnosis and treatment procedures.
These coatings can be custom formulated to meet very specific performance needs. For example, Hydromer®, Inc. offers a wide range of customizable hydrophilic coatings. But how do you ensure their performance meets your product requirements? They can be evaluated using a variety of tests. So understanding how to test the effectiveness of hydrophilic coatings is critical. It ensures the coating you use meets your needs.
In this article, we discuss how to test the performance of hydrophilic coatings. The use of specialized tools and analytical testing expertise is mandatory. They allow you to get accurate data and make informed decisions.
How To Evaluate Hydrophilic Coatings
The specific testing needed will vary depending on what your performance requirements are. Below are a few of the most common tests for evaluating the performance of these coatings.
Note that the following tests may vary based on the functional requirements.
1. Lubricity Testing
Hydrophilic coatings’ ability to reduce friction is one of their most beneficial properties. These coatings become “slippery-when-wet”, increasing lubricity and reducing friction. For example, they reduce friction between medical devices and human tissue. This helps reduce pain and improve outcomes during operational procedures.
Testing the lubricity of a coating is critical. It ensures the coating meets product performance requirements. This is done by measuring the coefficient of friction.
A pinch test is usually used to measure the lubricity of hydrophilic coatings. A hydrophilic coated device is clamped. Then the force required to pull it through the clamp is measured. The coefficient of friction is calculated as well.
The hydrophilic coatings developed by Hydromer®, Inc. offer excellent wettability and lubricity. Reduced friction prevents blood clotting, which can lead to atrial fibrillation, strokes, or even heart attacks. Our coatings are medically proven to be safe for human interventional procedures.
2. Contact Angle Measurements
Contact angle measurements serve to quantify the contact angle of a surface. The contact angle of a surface represents its wettability and level of hydrophilicity. This measurement should be as small as possible for greater wettability. Hydrophilic coatings exhibit minimal or even zero contact angles. This makes them a perfect choice when water droplets need to be spread equally across a surface.
The contact angle must be consistent across the coatings in medical device applications. This consistency helps to avoid patient discomfort, pain, and tissue damage. In industrial applications, inconsistency may cause a lapse of performance across a surface, such as with anti-fog or marine coatings. Inconsistent contact angles across the surface may be a result of different things. Examples would be uneven coating application, inadequate mixing, etc.
3. Durability Tests
Durability is a critical performance attribute for all coatings, hydrophilic ones included. This is true for hydrophilic coatings used for medical and industrial applications.
The pinch test used for lubricity can also measure the durability of the coating.
The product coated with hydrophilic coatings is clamped and pulled many times through silicone pads. This test measures the coating’s durability. The friction force should remain constant throughout the test. This shows a strong bonding of the hydrophilic coating with the product’s surface.
Durability is critical with medical device coatings used in the human body. Reduced durability of the coating may lead to loose bonding and/or worn coatings. Low coating durability can result in many adverse effects. These include performance changes, excessive discomfort, and patient pain. Testing of the coatings helps ensure the product meets the specific requirements.
4. Fibrinogen Assay (Thrombogenicity Testing)
The liver produces fibrinogens responsible for blood clotting. Improper hydrophilic coating lubrication leads to fibrinogen sticking to the medical device surface. This leads to blood coagulation. As a result, it is important to test the thrombogenicity of a coating.
This test determines the anti-thrombogenic nature of hydrophilic coatings. It aims to measure the number of fibrinogens that will stick to the surface of the medical device. The test aims to be representative of when a device is inserted into a human body. It is similar to the natural blood coagulation mechanism.
The test exposes a hydrophilic coating to radioactive fibrinogens. This determines how radioactive the hydrophilic surface becomes. The count of adhered radioactive substances should be below the baseline. A high count shows that the coated surface adsorbed a high amount of the fibrinogens. This indicates a surface that would allow for blood coagulation that leads to strokes and heart attacks.
This is a specialized test. Contact our team at Hydromer with any questions.
Hydromer Specialized Analytical Services
Hydromer, Inc. is a leading hydrophilic coatings manufacturer. We have an in-house team of Ph.D. chemists, engineers, machinists, and regulatory experts. Our company also has best-in-class laboratories to conduct product analysis and testing.
If you need specialized testing for your hydrophilic coated products we can help. Below we give a brief overview of our hydrophilic coating testing services.
Our testing capabilities fall into three categories:
1. Analytical
Analytical testing focuses on the chemical composition and molecular structure of hydrophilic coatings. Our team uses sophisticated techniques and advanced tools to obtain accurate measurements.
Here are some of the analytical tests we can perform:
- FTIR (Fourier Transform Infrared Spectroscopy): Specialized equipment is used to identify chemical bonds and functional groups by measuring infrared absorption.
- GC/Mass Spec (Gas Chromatography/Mass Spectrometry): This test separates and analyzes volatile compounds by interacting with the polar molecules in the sample.
- HPLC (High-Performance Liquid Chromatography): Used to determine how well polar (water-loving) molecules will interact with the substrate surface. It separates and quantifies chemical mixtures, ensuring consistent formulation.
- UV/Visible Spectroscopy: We measure optical properties of the hydrophilic coatings in this test to determine chemical concentration and stability.
2. Chemistry
Our chemistry testing services examine properties such as viscosity, biocompatibility, and friction. Some of our chemistry tests include:
- Collagen Analysis: This test determines the collagen integrity and interaction properties. The measurements play a crucial role in wound healing or tissue engineering.
- Cytokine Qualification: Used to identify the effect on cytokine production for better biocompatibility and non-inflammatory responses.
- Free Radical Polymerization: Analyzes how well a hydrophilic coating can attract water based on the curing process.
- Coefficient of Friction
- Viscosity
3. Microbiology
To comply with regulations, you must test the biological safety and effectiveness of hydrophilic coatings. Our team understands the importance of antimicrobial testing and cytotoxicity assays in the successful launch of medical products.
- Antimicrobial Testing: Measures the ability of a hydrophilic coating to kill bacteria and fungi.
- Minimum Inhibitory Concentration (MIC): This test determines the lowest concentration of the antimicrobial agent preventing microbial growth.
- Zone of Inhibition
Get Help with Hydrophilic Coating Development and Testing
Do you need to develop a custom hydrophilic coating? Or do you need to test your product’s coating performance. Either way, the team at Hydromer, Inc. can help you.
We are a hydrophilic coatings manufacturer. But we do not just develop custom coatings. As a client you will have access to a full-range of services, no matter where you are in the product lifecycle. We can help you with your product analysis, testing, and development processes:
- In-house contract coating services
- Contract Research and Development (R&D) services
- Specialized Analytical Testing
- Custom Machine Building
- Turn-key Operations
- Technology Transfer Services
- Technical consulting and support services
Get in touch with the Hydromer team by clicking here.
