Choosing the right bonding solutions in diagnostics

Melissa Jaime, product technology leader, Aurorium, explains the importance of choosing the right bonding solutions in diagnostic catheters.

Electrophysiology catheters and sheaths are used to treat and diagnose disorders in cardiac interventions – heart ablation to treat cardiac arrhythmia, replacement of calcified or leaking heart valves or obtaining samples of heart tissue.  These multiple-electrode electrogram recording devices are steerable inside the vascular system and provide a high degree of dexterity to reach the target site in the pathway. 

The materials used in the construction of these catheters are carefully chosen and their electrical and mechanical properties tested to verify compliance with certain critical requirements for the catheter, such as: 

  1. Appropriate stiffness to resist force from the navigation pathway, yet not so high as to provoke injuries 
  2. Flexibility and manoeuvrability to navigate the vascular pathways 
  3. Biocompatible and sterilisable for patient safety 
  4. Compatibility with various materials, especially electronic components, to enable precise design functionality 
  5. Secure adhesion and mechanical coupling between various device components and material transition joints for a reliable performance     

Biothane 90-M1 and Biothane 228 are some exmaples of the choices for biocompatible adhesive. These materials have earned a reputation and continue to be used in clinically-proven, diagnostic catheters for critical life-saving procedures. 

Proven Bonding Solutions for Diagnostic Catheters 

Each Biothane system consists of two liquid components – the Vorite prepolymer and the Polycin polyol, which when mixed together cure at room temperature to yield a cross-linked polyurethane. Once combined, adhesive viscosity begins to increase as the chemical reaction develops a cross-linked network and the material cures into a flexible solid. The rate of viscosity increase is a critical factor to consider in the design of a catheter assembly process, which can be optimised by leveraging the relationship between time, temperature, and viscosity. 

Catheter assembly typically requires multiple precise applications of small quantities of sealant to adhere tubing, seal ends, and coat sensors. Adhesives having longer pot life are often preferred in these situations, as it allows for maximum utilisation of the material before it thickens too much for proper dispensing. Once the adhesive is applied, the assembly can either be allowed to cure at room temperature or cured more quickly at elevated temperatures. Production efficiency is guided by cure behaviour, as the delicate assemblies cannot move on to the next stage of the production process until the adhesive has set. 

Out of the Biothane portfolio, Biothane 90-M1 is recognised as the choice for diagnostic catheter assemblies, due to its high strength and toughness. Whereas the faster reactivity of Biothane 228 allows for higher assembly throughput, and its greater flexibility provides an additional benefit in certain applications. 

As a modular solution, two-part Biothane Systems are formulated to meet adhesive design criteria, as well as provide suitable processability for the application at hand. It is possible for Aurorium to match different combinations of Vorite and Polycin components to customise a Biothane System.  

Biothane system reactivity may be characterised by properties such as: 

  • Pot-life - time until viscosity surpasses a usable value for a given application method 
  • Gel point - time at which the fluid polymer mixture behaves as a solid 
  • Work cure - time when sufficient strength is achieved to advance the assembly to the next processing stage 

These can be determined via oscillatory rotational rheology measurements. 

Choosing the right materials partner can help manufacturers enhance quality of life, support health and wellness, and enable customers to deliver value-added solutions.