Glass offers excellent strength, transparency, and maneuverability. It is one of the most commonly used materials for modern, high-tech medical devices, and it is critical for diagnostic and operational procedures. Examples of devices glass is used in include borosilicate microelectrodes, intraocular lenses, middle-ear prostheses, and more.
However, glass surfaces can be brittle. They are also susceptible to biofouling, which means the material is not inherently biocompatible. That’s why the surface properties of glass-based medical devices inserted or implanted are modified. In order to accomplish this surface treatments are used, such as medical coatings. There are various types of medical coatings, but medical-grade hydrophilic coatings are becoming recognized as the best choice. That is because Hydrophilic Coatings for Glass Substrates help ensure safety and biocompatibility of devices. They can also be customized to work with various types of glass, including silica and borosilicate, and they can accomplish a wide range of functionalities.
This informative guide highlights the importance of hydrophilic coatings for glass substrates. First, we will explore the different types of glass used in medical devices along with the challenges associated with applying hydrophilic medical coatings to them. This is essential reading if you need to manufacture reliable glass-based medical devices.
Types of Glass Used for Medical Devices
Glass is not a single uniform material. Many different types of glass exist based on the composition of materials like silica, boron, sodium, and more. Each different glass type offers distinct mechanical, chemical, and biological properties.
The right choice of material depends upon the underlying medical application. Below, we discuss the most popular choices for different types of medical devices.
- Silica Glass: This type of glass is known for its optical clarity. It is mostly used in medical sensors used inside the body, such as neural probes and optical fibres in catheters.
- Borosilicate Glass: This glass is composed of silica and boron trioxide. Such a composition offers excellent mechanical strength and chemical resistance. Borosilicate glass is an excellent choice for drug containers and syringes that undergo repeated sterilization.
- Glass-Ceramics: Glass-ceramics are used in aesthetic medical devices and implants, such as dental crowns and bridges. The most common example is lithium disilicate, which is prepared through a crystallisation process at a controlled temperature. Such material is known for its aesthetic appearance and mechanical strength.
- Bioactive Glass: This glass combines silica with calcium, sodium, and phosphorus oxides. Its main purpose is to form a hydroxyapatite layer and stimulate bone regeneration. It is used in applications such as middle-ear prostheses and dental bone grafts.
Challenges Associated with Coating Glass Substrates
Glass is one of the most common materials for medical instruments, laboratory equipment, and more.
Not all glass-based devices need to be treated with medical coatings. However, devices that come in contact with biological environments do need hydrophilic medical coatings or another surface treatment. The main purpose of these coatings is to ensure both the biocompatibility and effectiveness of medical procedures. They help make the devices safer and perform better.
But coating a substrate can sometimes be difficult. And coating glass substrates is no different. That is because glass substrates present some unique challenges.
Here is a quick list of challenges associated with applying medical-grade coatings to glass substrates.
1. Chemically Inert Surface
Glass, created by fusing materials such as silica and borosilicate, is chemically stable or inert and does not react easily with other materials.
Simply put, it means that due to glass’s non-reactive nature, coatings can fail to create strong bonds and may delaminate in most cases. That’s why the surface treatment is critical. For example, certain primer coats can improve adhesion, and plasma treatment is used to develop chemically reactive hydroxyl (-OH) groups on the surface of glass.
2. High-Temperature sterilization
Most coatings cannot withstand repeated sterilization methods, including gamma irradiation and autoclaving, essential for eliminating pathogens from the surface of glass-based medical devices.
To solve this problem, a few manufacturers customize their coatings to withstand repeated high-temperature sterilization. For example, Hydromer® has polymer crosslinking formulas that help the coating become thermally stable and resist swelling, hydrolysis, and mechanical abrasion.
3. Imbalance of Optical Properties
Most medical devices made of glass are intended to have excellent optical clarity. However, a bad application or a mismatched coating can significantly distort light transmission by changing the refractive index. Such scattered light reduces the effectiveness of the underlying medical devices.
The coating layer must be ultra-thin and optically transparent to avoid such complications. That’s where hydrophilic coatings become useful. They are applied in the nanometer and low-micrometre range. Such coatings are also inherently optically transparent to some extent.
4. Complex Geometries
Glass-based medical devices include microelectrodes, microneedles, pipette tubes, and capillaries. These devices are thin and have narrow channels that are hard to coat. Advanced coating chemistries and application methods are needed to ensure a uniform coating layer for these devices.
At Hydromer®, we use controlled deposition techniques to ensure uniform thickness across the entire surface of complex medical devices.
What are Hydrophilic Coatings?
Hydrophilic coatings are commonly the best choice for modifying a medical device’s surface characteristics. They are “slippery-when-wet” surface modifications. Their primary purpose is to attract liquid molecules from the surrounding to create a thin, lubricious layer on the substrate’s surface.
The term “hydro” means water, and “philic” means affinity or love for. As such, they are also known as the water-loving (water-attracting) surface coatings. In contrast to most popular hydrophobic coatings that repel water molecules, hydrophilic coatings attract water molecules.
These coatings are formulated using a variety of hydrophilic and thermally stable polymer chemistries, such as polyvinylpyrrolidone (PVP), polyacrylamide (PAAm), and zwitterionic polymers that resist heat and biofouling.
Hydromer®, Inc., is a leading Hydrophilic Coatings manufacturer serving the medical device space. We have the technology and expertise to customize hydrophilic coatings for specific medical applications. Custom-formulated Hydromer coatings provide various beneficial properties and functionalities. These include, but are not limited to:
- Lubricity (friction reduction)
- Thromboresistance
- Antimicrobial properties that help reduce infections, and more.
- Drug-eluting capabilities
- And more
To read more about Hydromer multifunctional hydrophilic coatings, read our guide: Hydrophilic Coatings for Medical Devices: Intro, Benefits & Uses
Benefits of Coating Glass Substrates With Hydrophilic Coatings
Hydrophilic coatings create bonds at the nanoscale to produce highly functional water-attracting surfaces. These coatings help overcome many complications associated with diagnostic and operational procedures. Their unique properties, functionality, and customization have made them a critical component for modern medical devices, including those made with glass.
Below are some of the many advantages of applying hydrophilic coatings to glass substrates:
- Enhanced Anti-Fogging: Hydrophilic coatings are able to evenly spread condensed water into a transparent film. Thus, they prevent fog, condensation, and micro-beading of water droplets on glass surfaces. These coatings are custom-formulated to accomplish different goals, such as high precision visualization and reliable diagnostics.
- Improved Wettability and Lubricity: Glass surfaces are inherently smooth. However, they are not lubricious enough to be inserted and navigated through the biological environment (body). This issue becomes a notable problem whenever the glass surface is dry. Hydrophilic coatings help by forming a thin, lubricious layer with a significantly lower coefficient of friction and contact angle. Such a layer reduces tissue trauma and improves patient comfort.
- Antimicrobial Properties: Hydrophilic coatings can be custom-formulated with antimicrobial properties. An ultra-thin layer of these coatings on the surface of medical devices acts as a physical barrier to help reduce bacterial adhesion.
- Thromboresistance: Glass absorbs proteins from blood, which stick firmly to its surface. This leads to the formation of blood clots (thrombus). Hydrophilic coatings are thromboresistant, helping prevent both protein adsorption and cellular adhesion.
- Longevity: Long-term exposure of glass-based medical devices and implants to the biological environment increases the risk of leaching, ion release, or pH-driven surface degradation. The protective barrier created by hydrophilic coatings prevents direct contact of glass with the such dynamic biological environment.
Hydromer®, Inc.: A Leading Hydrophilic Coatings Manufacturer
Hydromer®, Inc. has 40+ years of experience formulating, manufacturing, and supplying clinically proven hydrophilic medical coatings to device manufacturers worldwide.
We deliver custom hydrophilic coating solutions that help OEMs bring innovative products to market. Our multifunctional hydrophilic coatings can be applied to various substrates, including glass, metals, and polymers. And they can be custom formulated to meet your product’s specific safety and performance requirements.
We understand the importance of creating safe, high performance medical devices. These products set your company apart from your competitors. And advanced medical coatings play a critical role in developing advanced devices. And we are the experts in hydrophilic medical coatings!
Hydromer® uses only the highest quality ingredients to manufacture top-notch, custom medical coatings. Our coatings can be formulated with the following properties:
- Long-lasting hydrophilicity
- High lubricity
- High wettability
- Antimicrobial
- Drug-eluting capabilities
- Biocompatibility
- Low particulate
- Enhanced adhesion
- High durability
- Thromboresistance to reduce blood clotting
Get in Touch
Among the sea of medical coating suppliers, we are more than just another company. You will get a partner to help you develop a coating to meet your specific product goals and regulatory requirements. Our team includes highly qualified PhD chemists, scientists, engineers, and regulatory experts.
But what sets us apart from our competitors is the wide range of support services we offer to our customers worldwide.
- Research and Development (R&D) services
- Contract coating services
- Specialized Analytical Testing
- Custom Machine Building
- Turn-key Operations
- Technology Transfer Services
- Technical consulting and support services
Contact our team of coating experts today to learn more about our services.
