By Matthias Hartmann, head of Sales Americas, Business Unit Adhesive Systems, Hoenle AG
Adhesives remain at the heart of medical device production, securing everything from housings and tubing to sensitive electronics and sensors. UV-curable adhesives have become industry favorites because of their precision, speed and versatility in diverse assembly applications. Yet, evolving regulatory frameworks – especially in the European Union – are driving unprecedented changes in material selection. The latest focus targets raw materials labeled “CMR” (carcinogenic, mutagenic or toxic to reproduction), most notably the photoinitiator TPO. While no TPO remains after full cure, the scrutiny of its presence in uncured adhesives has intensified regulatory pressures across the continent.
This regulatory environment has global repercussions: Many US-based medical device companies operate production facilities in Europe, binding them to EU chemical legislation and compelling a thorough evaluation of TPO-free options. As a result, the drive to develop alternative adhesive formulations is no longer just a regional necessity but a strategic imperative for all internationally operating manufacturers.
This article focuses on the next wave of UV-curable medical-grade adhesives – those free from TPO and IBOA. These cutting-edge formulations not only circumvent potential regulatory pitfalls but often surpass their predecessors in both process reliability and performance.
Regulation as a Catalyst for Innovation
The evolving regulation of adhesive raw materials – most notably the potential CMR classification of TPO by the European Union – illustrates just how dynamic and rigorous the global medical device landscape has become. For manufacturers and suppliers, the consequences extend well beyond Europe, as multinational companies with facilities on both sides of the Atlantic must treat EU rules as the benchmark for safe operations everywhere.
Responding to these impending restrictions, forward-thinking suppliers have proactively reformulated their adhesives to eliminate TPO and IBOA, future-proofing product lines and ensuring uninterrupted compliance. This approach transforms regulatory constraints into a springboard for innovation – stimulating the development of adhesives that are not only safer but also frequently outperform legacy products in terms of curing speed, bond strength and process reliability.
Such advances are more than just a reaction to shifting compliance standards; they deliver real, measurable improvements. Enhanced adhesion, more stable processes and broader substrate compatibility have become tangible benefits, demonstrating how regulatory adaptation can directly elevate the reliability and functionality of modern medical device assembly across continents.
Why UV-Curable Adhesives are Shaping the Future of Medical Device Assembly
As medical device designs evolve toward ever-greater miniaturization and automation – and as the industry’s performance and regulatory standards rise – UV-curable adhesives have become instrumental in enabling next-generation solutions. Their rapid curing under UV LEDs at 365 nm or 405 nm allows seamless integration into high-speed, automated production lines. Because these adhesives impart minimal thermal load, they safeguard thermally sensitive substrates, such as delicate plastics and electronic components.
Modern dispensing solutions, including jetting technologies, ensure pinpoint precision, making reliable adhesive placement possible even at the microscale. To further guarantee process reliability, many UV-curable adhesives are engineered with built-in fluorescence markers. Under 365 nm inspection LEDs, these features allow immediate confirmation of bond placement and complete cure status, supporting real-time, inline quality assurance.
Together, these attributes explain why UV-curable adhesives have become indispensable where medical manufacturers demand cleanliness, efficiency and uncompromised bond integrity – underpinning the performance of the world’s most advanced medical devices.
Application Fields in Medical Devices
Wearable Medical Devices
Wearable health technology – including glucose sensors (see Figure 1), oxygen monitors and insulin pumps – demands strong, reliable and skin-friendly bonds. Rapid curing and enhanced adhesion help make mass production viable for designs that must withstand skin contact and movement. TPO- and IBOA-free adhesives have demonstrated superior bond strength and process consistency in these applications, ensuring user safety while meeting regulatory expectations.
Tubes, Connectors and Drug Delivery
Infusion systems, blood bags and airway management devices require leak-proof seals between flexible and rigid materials. UV adhesives, with solvent-free and low-migration properties, deliver biocompatibility and reduced contamination risk. The dual-curing options – where shadowed regions cure via moisture or heat – ensure that every joint is reliably sealed.
Needle Bonding
Precision and reliability are critical when bonding needles to hubs for syringes and catheters. Defects can pose severe risks. Modern TPO- and IBOA-free UV adhesives now match or exceed legacy performance, offering ultra-fast cure and higher bond strength on glass, metal and plastic interfaces.
How TPO-Free Formulations Are Setting New Standards
Initial skepticism surrounded the transition away from proven TPO-based UV adhesives, given TPO’s reputation for reliable, ultrafast curing. Yet chemistry innovation has rewritten expectations. Recent developments – even those stepping further by omitting IBOA – are redefining the landscape.
Extensive scientific testing reveals that modern photoinitiator-free adhesives, such as advanced formulations with tailored viscosity profiles, match the curing speeds of legacy TPO-based systems. More notably, some new-generation adhesives deliver up to 200% higher bond strength on challenging substrate pairs, with expanded versatility spanning metals, glass and even traditionally hard-to-bond, low-surface-energy polymers.
This evolution is no longer about compromise. The newest TPO-free UV adhesives deliver stronger, faster and more reliable bonds, keeping manufacturers ahead of regulatory shifts while unlocking fresh performance benchmarks for medical device assembly.
UV Curing Systems and Process Control
Achieving reliable bonds in medical device assemblies demands more than innovative adhesive formulas; it requires curing technology carefully matched to the physical properties of every component. The wavelength of UV light – either 365 nm or 405 nm – is chosen based on optimal transmission through the substrate materials, ensuring energy reaches the adhesive layer for a complete and robust cure.
Advanced, high-power UV LED modules, like those manufactured by the author’s company, set the industry standard thanks to fast response, low maintenance and seamless integration into automated production lines. These systems allow precise control of intensity and exposure duration, safeguarding sensitive polymers and electronics from heat and guaranteeing full polymerization for every formulation.
Validation is equally vital to maintaining quality at scale. Inline inspection with fluorescence markers – readily activated by dedicated 365 nm LEDs – enables real-time confirmation of adhesive placement. Complemented by periodic UV intensity monitoring, these measures establish a closed and traceable process loop. The result is absolute process stability, reproducible quality across millions of assemblies and rigorous compliance with medical manufacturing standards.
Regulation as a Strategic Advantage
The industry shift away from TPO, prompted by its potential CMR classification, exemplifies how regulatory action can drive progress. Suppliers that reformulate ahead of official bans keep their customers competitive and compliant. Far from being a sacrifice, the change delivers adhesives with enhanced performance attributes and greater reliability.
Manufacturers using TPO-free systems benefit not only from regulatory foresight but also from persistent improvements in bond strength, process precision and long-term stability.
Detailed Performance Comparisons
Empirical testing, as illustrated in the two graphs, underscores the advantages of next-generation, TPO-free formulations compared to TPO containing adhesives in demanding medical applications.
Comparison of TPO-Containing and TPO-Free Formulations
Figure 2 analyzes lap-shear bond strength across six substrate combinations.
- No surface pretreatment was conducted for these measurements. Especially on low-surface-energy plastics, such treatment could increase bond strengths remarkably.
- PC/PC: The higher-viscosity TPO- and IBOA-free solution shows a modest improvement (+9%) over the legacy adhesive, while the TPO-/IBOA-free formulation matches baseline performance.
- Glass/Stainless Steel: Both alternatives demonstrate significant gains – the higher-viscosity TPO-/IBOA-free adhesive doubles the bond (+100%) and the standard TPO-/IBOA-free formulation increases strength by 60%.
- PMMA/PMMA: The TPO-/IBOA-free version is slightly reduced (-12%) vs. the legacy adhesive, while the higher-viscosity variant achieves a +56% improvement, underscoring the impact of viscosity tuning for acrylics.
- PP/PP: Both newer formulations comfortably outperform the legacy product, with the higher-viscosity option reaching a +200% gain.
- PP/Stainless Steel: Both alternatives double the bond (+100%), confirming robust adhesion on mixed polymer-metal interfaces.
- PC/Stainless Steel: The TPO-/IBOA-free adhesive records a small dip (-15%), while the higher-viscosity alternative is essentially on par (-2%) with the legacy material.
These results highlight how modern TPO- and IBOA-free adhesives, available in varying viscosities, not only comply with regulatory standards but also deliver outstanding bond strength – especially on glass, metal and PC – essential for medical devices.
Performance of TPO-Free vs. Conventional UV Adhesives
Figure 3 shows the results of testing that includes seven material pairs:
- PC/PC: The TPO-free reformulation exhibits a 30% reduction compared to the conventional material, suggesting targeted selection for engineering plastics.
- Glass/Stainless Steel: A significant gain (+320%) for the TPO-free adhesive underlines its utility on glass-to-metal designs, such as syringe components.
- PMMA/PMMA: Modest reduction (-5.6%) versus the conventional formulation, but still in the same performance range for acrylic substrates.
- PP/PP: A 17% improvement suggests enhanced bonding to low-energy polypropylene.
- PP/Stainless Steel: An increase of 15% provides robust adhesion under mechanical load.
- PC/Stainless Steel: Performance is identical (±0%), ensuring flexibility in design.
- PC/Glass: The TPO-free solution sees a 25% decrease, indicating that portfolio consultation is advised for demanding applications.
In summary, the adhesive innovations highlighted in these graphs – particularly the TPO- and IBOA-free formulations with variable viscosities – not only meet regulatory demands but also frequently match or outperform the established standards. Crucially, the optimal adhesive always is determined by the specific bonding pair in question, as the chemistry of both parts can dictate final bond strength and durability. By carefully choosing the adhesive in close consultation with an experienced specialist, manufacturers can ensure the most effective match for each application, maximizing the performance and reliability of every medical device assembly.
Conclusion
The medical adhesive sector is undergoing rapid transformation as regulatory scrutiny increases, especially in Europe. Rather than impede innovation, these changes have catalyzed credible scientific and commercial advances. Today’s leading TPO- and/ or IBO-free UV-curable adhesives achieve faster cures, greater bond strength and proven biocompatibility. Supported by advanced curing systems and stringent process control, these materials meet the demands of high-volume, automated medical device production while keeping manufacturers ahead of the regulatory curve.
Crucially, the march toward TPO- and IBOA-free formulations demonstrates that compliance and competitiveness are not mutually exclusive. On the contrary, proactive adaptation has delivered adhesives that bridge regulatory gaps and elevate performance – a future-ready solution for modern medical device manufacturing.
Matthias Hartmann is the head of Sales Americas for the Business Unit Adhesive Systems at Hoenle AG. He began his career with Hoenle AG in 2012 as a regional Sales Engineer focusing on UV curing equipment. Since 2024, he has managed sales for both adhesives and curing equipment across the Americas, leveraging his extensive experience in technical sales and UV curing technology. Hartmann can be reached at email: Matthias.hartmann@hoenle.com, www.hoenle.com.
