In light of our specialization in medical device development and manufacturing, it’s essential for us to consistently stay updated on and adapt to the dynamic shifts within the industry. The medical device sector has seen a significant transformation over the past two decades. As devices become smaller and more intricate, the materials and components used in their construction face increasing demands. One of the critical components that have gained prominence in this evolution is medical-grade adhesives.
Market Trend
In 2001, the global market for medical-grade adhesives stood at a modest $540 million. Fast forward to 2020, and this figure has skyrocketed to over $15 billion, with the United States leading the charge. This exponential growth underscores the increasing reliance on adhesives in medical device manufacturing. As the U.S. exports more medical devices to emerging markets in South America and the Asia-Pacific region, there’s a pressing need for devices that are both cost-effective and durable.
Types of Medical Adhesives
- Synthetic Adhesives:
- Structural Adhesives: These include Cyanoacrylates (CA), Polyurethanes, and Epoxy adhesives (single or dual-component).
- Non-structural Adhesives: Examples are Silicones, Hot-melt adhesives, and Coating sprays.
- Pressure-sensitive adhesives, like cohesive tape falls under this category.
- Biological Adhesives: Notably, these aren’t used in medical device manufacturing.
Both Cyanoacrylate and Epoxy adhesives play pivotal roles in the medical device manufacturing sector. Cyanoacrylates, known for their rapid curing and versatility, offer quick bonding solutions without the need for specialized equipment. On the other hand, Epoxy adhesives, celebrated for their robust bonding and resistance to environmental stresses, can bond a diverse range of substrates, making them invaluable for intricate medical device challenges. Given their combined significance and the advancements in their respective formulations, a deeper understanding of these adhesives is crucial for optimal application in the ever-evolving medical device landscape.
Deep Dive into Cyanoacrylate Adhesives
Cyanoacrylate, an acrylic monomer, hardens into a “plastic” form. Often referred to as “instant glues” or “super glues,” they cure by reacting with a minimal amount of moisture on the surfaces to be bonded. They don’t require drying ovens or special cross-linking equipment. (However, it’s essential to ensure proper ventilation when using them.)
Their gap-filling range is between 0.015 mm and 0.5 mm. While they have a fixation time of around 90 seconds, complete drying can take between 1 to 24 hours, influenced by humidity and temperature. The optimal humidity level for curing is between 40-60%, and the drying temperature is 80-120°C for metal components. For plastic components, especially ABS, the temperature should be below 80°C.
Light-curing Cyanoacrylate Adhesives
Designed for high-speed drying, these adhesives are solvent-free with minimal outgassing. They offer a wide range of viscosities suitable for automated dispensing and typically cure within 5-15 seconds under 80-100 mW/cm2 at wavelengths between 405-265nm.
Epoxy Adhesives in Details
Epoxy-based adhesives are versatile in industrial applications. They generally consist of resin and hardeners. Their curing can occur at room temperature, elevated temperatures, or with UV light (though very few are medical-grade). Epoxies offer excellent resistance to environmental and media effects, can be used at higher temperatures, and provide a dry, non-tacky surface once cured.
Advantages of Adhesion
- Quick, simple, cost-effective (at about $0.1 per adhesion), and convenient.
- Allows for the combination of different materials.
- Doesn’t require specialized knowledge for the operator.
- The adhesive layer seals and protects against corrosion.
- Thin bonding lines offer aesthetic appeal.
- Provides vibration damping.
- Can offer conductive or insulating properties.
- Easily automated.
Challenges with Adhesion
- Time-consuming, with adhesive curing taking up to 24 hours, so we often use rapid-curing or UV-curable formulations.
- Surface preparation quality affects adhesive bonding, hence we apply standardized surface treatments such as sandblasting, degreasing with IPA, and applying bonding primers.
- Sensitive to environmental factors like humidity and temperature, therefore, they are stored in controlled environments and specially formulated adhesives are employed.
- Some adhesives can be harmful, therefore we prioritize non-toxic or low-VOC adhesives and ensure proper ventilation.
- Certain adhesives, like cyanoacrylate, can age seals due to outgassing. This issue can be addressed by using resistant sealants or alternative adhesives.
- Process validation is essential, so regular quality checks and validation tests are conducted.
Comparison of Adhesives
| UV Light-Curing Cyanoacrylate Adhesive | Epoxy Mixture 2-Component | Humidity-Curing Cyanoacrylate Adhesive | Silicones 1 & 2-Component | |
| Application | Bonding, Sealing, Coating Formation | Bonding, Sealing, Coating Formation | Bonding, Sealing, Coating Formation | Bonding, Sealing, Coating Formation, Seal Casting |
| Typical Operational Temperature Range | -51°C to 205°C | -40°C to 205°C | -51°C to 120°C | -60°C to 205°C |
| Cross-linking Condition | UV Light Source 265-405nm | Room Temperature, Drying Oven | Room Temperature & Humidity, Can be accelerated in a drying oven or using an activator | Room Temperature / Heat Cross-linking |
| Key Property | Fast bonding time, good mechanical properties, excellent chemical resistance | Toughness, good vibration damping capability, high mechanical properties, excellent chemical resistance | Good mechanical properties, fast bonding for small parts, wide viscosity range, poor chemical resistance | Excellent flexibility, hardens on thick sections, poor chemical resistance |
| Bond Strength – Metal | Good | Excellent | Excellent | Good (with primer) |
| Bond Strength – Plastic | Very Good | Excellent | Very Good | Weak |
| Bond Strength – Rubber | Very Good | Very Good | Good | Weak |
| Repeated Autoclaving Resistance | Very Good | Excellent | Weak | Weak |
| Repeated Chemical Sterilization Resistance | Very Good | Excellent | Weak | Weak |
| Gamma (15-45kGy) & EtO (ethylene oxide) Resistance | Excellent | Excellent | Excellent | Excellent |
Biocompatibility of Adhesives in Medical Devices
Manufacturers traditionally focus on two types of medical devices: disposable sterile devices and sterilizable, reusable devices. The first, disposable sterile devices, includes instruments such as syringes, catheters, and infusion assemblies. These are designed for a single use and often have prolonged and direct contact with bodily fluids. This makes the biocompatibility of the adhesive used in these devices absolutely crucial, as any adverse reaction can pose immediate and severe health risks to the patient.
The second category is sterilizable, reusable devices. Crafted for multiple uses, these devices undergo sterilization processes between each application. Even though they might not always be in direct contact with internal body fluids, the nature of their repeated use necessitates that the adhesives remain stable and non-reactive over extended periods.
Given the critical roles these devices play, the adhesives selected must adhere to strict criteria. They should not release any harmful substances that the body might absorb, must remain stable and not degrade when in contact with blood or other bodily fluids, and importantly, they shouldn’t trigger any immune responses or cause allergic reactions in the patient.
To ensure these standards are consistently met, the industry employs rigorous testing protocols. Two of the most prominent standards guiding these tests are the US Pharmacopeia (USP) Class VI-FDA Regulation and ISO 10993:2018. These benchmarks not only ensure the safety of the patient but also guarantee the effective performance of the medical device, underscoring the significance of adhesive biocompatibility in the medical device industry.
Conclusion
The medical device manufacturing industry’s shift towards smaller, more intricate devices has placed adhesives at the forefront of innovation. As engineers and technical professionals involved in production, understanding the nuances of these adhesives is crucial. Our expertise in this domain ensures that when you outsource your manufacturing to us, you’re partnering with a team that understands the intricacies of medical-grade adhesives. Together, we can drive the next wave of medical device innovations.