As medical devices become smaller and more functionally complex, seamless integration of precision components is critical. Designers must maximize portability and usability, while manufacturers need efficient assembly methods that meet stringent quality standards and productivity goals. Establishing this vital link between ambitious design and streamlined manufacturing is essential.

There are significant obstacles in the incorporation of advanced tubing components into modern medical devices. While offering immense potential for enabling new device capabilities, these advanced tubing designs present unique integration challenges.

Engineered silicone swelling fluids are an innovative solution to overcome these hurdles. By easing the assembly of compact, intricate tubing, swelling fluids allow designers to push design boundaries while enhancing manufacturing outputs and enabling successful outsourcing partnerships.

Manufacturers can outsource production of complex tube fitting assemblies to specialized suppliers who use engineered swelling fluids to boost throughput, as design intricacy is no longer a limiting factor. [Photo courtesy of MicroCare]

 Design challenges in modern medical devices

Many medical devices rely on tubing that make reliable, leak-proof connections to device fittings and components. [Photo courtesy of MicroCare]

Many of today’s medical devices — ranging from IV tubes and bags to drainage catheters and dialysis machines — rely on tubing that must meet stringent tolerances in inner/outer diameter and wall thickness. These devices often need intricate multi-lumen tube construction, featuring multiple channels within a single tube for the delivery of fluids, gases, guidewires or miniature cameras. As demand for next-generation medical technologies continues to rise, the complexity of these tubing designs presents significant challenges in assembly.

The precise manufacturing needed for these advanced tubing designs means making reliable, leak-proof connections to device fittings and components is paramount. However, this task becomes increasingly difficult due to the delicate nature of the tubing and the need to accommodate diverse functionalities within a single conduit.

Silicone is still the preferred elastomer for medical tubing due to its biocompatibility, durability and flexibility. But unlike some materials, silicone does not naturally expand or stretch over connector barbs and textured surfaces, needing careful handling during assembly. Furthermore, silicone exhibits a high coefficient of friction, which can impede smooth assembly processes.

The delicate nature of these advanced thin-wall and multi-lumen tubes means that physically forcing them onto rigid fittings risks material damage, stress cracks and assembly failure. Such issues compromise the integrity and performance of the medical device and pose potential risks to patient safety.

To address these challenges, manufacturers must employ innovative solutions that ensure seamless assembly while keeping the integrity of the tubing and the overall device. This may involve the development of specialized connectors, lubricants or assembly techniques tailored to the unique properties of silicone and the specific requirements of advanced medical tubing.

Swelling fluids explained

Engineered silicone swelling fluids temporarily enlarge tubing diameters, allowing them to easily slide over connectors before returning to their original dimensions for a tight, secure fit. [Photo courtesy of MicroCare]

Swelling fluids offer a practical solution by temporarily enlarging tubing diameters, allowing tubes to easily slide over connectors with complex geometries before returning to their original dimensions for a tight, secure fit.

Three primary swelling fluids are commonly used in the medical device industry:

1. Silicone oils: Silicone oils function as effective lubricants, easing tubing assembly. However, they can be messy, potentially transferring residues to equipment and surfaces and attracting contaminants. Furthermore, medical grade silicone oils are expensive and offer limited swelling capabilities, making them less suitable for complex shapes and delicate tubing.
2. Isopropyl alcohol (IPA): As a cost-effective solvent, IPA swells tubing, aiding assembly. However, its slow drying time prolongs assembly cycles, affecting productivity. Additionally, IPA may not provide sufficient expansion for fragile, thin-walled tubes, leading to potential collapse or folding during assembly.
3. Engineered silicone swelling fluids: These formulations are specifically engineered to maximize and control uniform tubing expansion through short-term immersion before allowing the tubing to fully recover to its original dimensions. This temporary swelling action enables precise fitting over connectors with intricate geometries.

The engineered solution: silicone swelling fluids

While silicone oils and IPA have been widely used to aid in tubing assembly, their limitations can negatively impact productivity and design execution when manufacturing advanced medical devices.

These traditional fluids struggle to provide sufficient, uniform expansion for fragile multi-lumen tubing that must conform to detailed, intricate connector geometries, limiting design possibilities.

Silicone swelling fluids, however, are specifically engineered to maximize design flexibility and streamline manufacturing processes. One end of the silicone tube is immersed in the fluid, allowing the walls to swell and expand in a controlled, predictable manner. Often, just 1-2% expansion is needed for assembly. The exposure or soaking time determines the amount of swelling, enabling precise control over the expansion.

After the expanded tube slides over the fitting, the swelling fluid quickly evaporates, allowing the tube to return to its original molded size, resolute durometer, compression set, and strength, creating a tight, locked connection regardless of the connector’s geometric complexity.

This temporary swelling action does not degrade, weld or change the tubing material’s chemical composition or physical properties. It enables assemblies to be nonpermanent, easing field serviceability and modular designs. Manufacturers can outsource production of complex tube fitting assemblies to specialized suppliers who use engineered swelling fluids to boost throughput, as design intricacy is no longer a limiting factor.

Compliance, sustainability and operational efficiency

Unlike hazardous solutions like hexane and toluene which were commonly used as swelling fluids, engineered silicone swelling fluids are sustainable, environmentally friendly formulations that meet stringent medical and quality standards:

• Biocompatible and safe for use in medical device manufacturing
• Low global warming potential (GWP)
• Zero ozone depletion potential (ODP)
• Not classified as hazardous air pollutants (HAPs)
• Do not produce residues that impact cleanroom validation processes

Their excellent materials compatibility prevents damage to tubing, inks/coatings, connectors, and finished devices, reducing scrap rates and associated costs.

Furthermore, engineered swelling fluids enhance operational efficiency by reducing the force required for assembly, minimizing the risk of workplace injuries caused by repetitive strain. This ergonomic benefit contributes to a safer working environment and increased productivity.

Driving innovation through outsourcing in medical design

Outsourcing complex assemblies to specialized suppliers that use swelling fluids not only grants OEMs access to expertise and the latest advancements, but also offers potential cost savings and efficiency improvements.

Swelling fluids facilitate greater design creativity, supporting advanced medical solutions that meet the evolving needs of patients and healthcare providers. By adopting swelling fluid technology, device developers can gain a competitive edge, fostering collaboration, agility and cost-effective innovation.

Elizabeth Norwood [Photo courtesy of MicroCare]

Elizabeth Norwood is a senior chemist at MicroCare, which offers precision cleaning solutions. She has been in the industry more than 25 years and holds a B.S. in chemistry from the University of St. Joseph. Norwood researches, develops and tests cleaning-related products and has one patent issued and two pending for her work.

Article Source: MDO