When assembling medical devices, ultrasonic welding and solvent welding are popular joining methods for plastic parts. Although they offer fast processing and strong bonding, each method has its own set of challenges that can impact the manufacturing process. This article provides a breakdown of the challenges associated with these two methods and explores adhesive technology as an alternative.

Solutions for Medical Devices Assembly

Challenges of common plastic joining methods 

Challenges of Ultrasonic welding in Medical Devices Assembly 

Ultrasonic plastic welding, also referred to as fusion bonding, is a process used to join plastic components by applying high-frequency ultrasonic acoustic vibrations to the workpieces being held together under pressure. The vibrations cause localized heating due to friction and intermolecular motion, which melts the plastic at the interface of the parts.

While offering many advantages, it also has several disadvantages and limitations such as: 

• Limited joint size due to bond gap variances. 
• Requires well-considered part design a variances and material choice. 
• May not be effective for certain materials like polyolefins (polypropylene and polyethylene). 

Challenges of Solvent welding in Medical Devices Assembly 

Solvent welding is a process used to join plastic parts by applying a chemical solvent that temporarily dissolves the surfaces of the plastics. This allows the parts to fuse together as the solvent evaporates and the plastic re-solidifies.

However, solvent welding presents unique challenges in medical device assembly due to stringent requirements for biocompatibility, sterility, and durability.

• Effective for certain plastics (e.g PVC) but not suitable for all materials (e.g., polyolefins). 
• Requires careful material compatibility. 
• May release toxic fumes during the process.

Adhesive Technology: Revolutionizing Plastic Joining in Medical Devices Assembly 

Advantages of Adhesive in Medical Devices Assembly 

Adhesive technology offers a superior approach to overcoming the challenges associated with plastic joining methods such as ultrasonic and solvent welding by offering a versatile, robust, and aesthetically superior bonding solution.

• Enhanced Material Compatibility: Medical device adhesives are formulated to effectively bond a diverse range of plastics, including those resistant to other joining techniques. Manufacturers can select from a variety of adhesives, such as epoxies, polyurethanes, silicones, and cyanoacrylates, each offering unique properties to suit specific application needs. 

• Improved Aesthetic and Structural Integrity: Unlike welding, which can alter the appearance of plastics and create visible joint lines, medical device adhesives provide a clean and seamless bond. This is particularly valuable in consumer-facing products where aesthetic integrity is crucial. Additionally, adhesives distribute stress evenly across the joint, reducing the risk of failure and enhancing the durability of the bond. For example, UV adhesive is a popular choice for creating a transparent bonds in applications within the industry.

Read more at: What is UV Adhesive? Applications of UV Adhesive in Medical Industry

• High strength bonding, sealing, gap filling: Adhesives are engineered to form strong, durable bonds that can often surpass the strength of the materials being joined. This is particularly valuable in medical devices where structural integrity is paramount. High-performance medical device adhesives such as epoxies, acrylics, and polyurethanes are designed to withstand extreme conditions including high temperatures, mechanical stress, and environmental exposure.

• Easy in-line processing: Adhesives can be applied using automated dispensing systems that ensure precise application, reducing waste and increasing the consistency and reliability of the bonding process. This automation is critical in high-volume production environments where speed and repeatability are key.

• Biocompatibility ensuring the safety for human use: Adhesives intended for medical use must comply with stringent regulatory standards, such as ISO 10993 and USP Class VI, which outline a series of tests to evaluate biocompatibility based on the nature and duration of body contact with the material. Manufacturers can ensure that medical devices meet the necessary safety standards required for human use while providing strong, reliable performance.

Medical Adhesive and Typical Application

Adhesive Selection in Medical Devices Assembly 

Among the most popular choices in the industry are light-curable adhesives, cyanoacrylates, light-curing cyanoacrylates, and two-part epoxies. Each of these medical devices adhesives offers unique advantages and limitations suitable for various applications. 

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In navigating the complexities of medical device assembly, selecting the right adhesive plays an important role in ensuring product performance, safety, and regulatory compliance. Prostech stands ready to provide expert consultation and support in choosing the optimal adhesive solution for your specific application needs. With our experience in medical device manufacturing and deep understanding of adhesive technologies, we offer tailored guidance to address challenges and optimize processes. Contact us today to get free consultations!