Compounding Solutions, a specialist in medical extrusions, highlights technologies such as ReZilok which it believes address some of the current needs of the medtech sector.
supply versus demand
In the medical device industry, the trend towards minimally invasive surgical techniques is the driving force for smaller, more innovative medical devices. Devices for vascular and other applications continue to reach deeper into the anatomy with more therapeutic technology, whilst medical device manufacturers are demanding polymeric tubing that boasts greater precision, tighter tolerances and increased functionality.
In catheter design, the designer must not only consider the functional requirements of the application but also be cognizant of the manufacturing process required to produce the device. The designer must identify the key performance requirements of the medical tubing properties such as flexibility, lubricity, clarity, kink resistance, push strength, torque transfer characteristics, hoop strength, radiopacity and bondability.
The ability to hold tight tolerances is critical when selecting the ideal design for a particular medical application. Generally, a single polymer material will not meet all of the performance requirements adequately. As a result, designs have become very complex, with different materials required in different areas of the catheter.
An example is a typical balloon catheter, where the inner diameter of the catheter needs to be very smooth and lubricious to slide with minimal effort over a guidewire along the tortuous bath of the anatomy to the treatment site. Typical materials used are fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE) and high-density polyethylene (HDPE). Fluoropolymers provide the best lubricity, however, they present bonding and processing challenges. An example is HDPE loaded with Compounding Solutions’ Mobilize technology, a lubricious additive that can be incorporated with the inner layer material to reduce the coefficient of friction.
The material in the outer layer of the shaft is generally a coloured nylon 11, nylon 12 or poly-ether block amide (PEBA) compound. Often various durometers are required along the length of the shaft to ensure the correct combination of pushability at the proximal end and flexibility at the distal tip end. The designer should consult with the compound supplier as very often these compounds will need to be stabilised so that the material is not degraded during the assembly process. This process often involves heat, exposure to ultraviolet light and high stresses. Special compounding techniques need to be employed to ensure optimal dispersion of the pigments and stabilisers as the tubing wall can often be as low as 0.002”.
If a HDPE is used on the inner layer and a nylon or PEBA on the outer layer as described above, then a bonding or tie layer must be employed to bond these dissimilar materials during the extrusion process. ReZilok Rx 101, is a new linear low-density polyethylene with grafted maleic anhydride tie layer resin developed by Compounding Solutions. ReZilok meets the requirements of the medical device industry, complies with ISO 10993-5 cytotoxicity, whilst claiming to offer superior bondability.
In order for the medical practitioner to detect the distal end of the device when it is deep within the anatomy, metal marker bands of the platinum iridium type are often used. These marker bands show up much brighter than other parts of the device under fluoroscope, ensuring the balloon is correctly located before inflation occurs. Polymer marker bands can be used instead of metal ones in many situations. The polymer marker band is advantageous in that it does not impede the flexibility of the distal end, which a rigid metal marker band may do. In order to compete with the radiopacity of platinum iridium, tungsten metal powder is compounded with a similar base resin to the shaft resin, usually at very high loadings, even as high as 90% in some applications. Compounding Solutions have developed a proprietary tungsten powder with an average particle size of less than 1 micron and low oxygen surface defect concentration that is well suited to this application.
Typically, on the injection moulded hub at the proximal end of the device, devices are labelled with critical product information. Due to recent FDA regulations going into effect, specifically the unique device identification (UDI) system, Original equipment manufacturers are now exploring laser marking options in medical compounds. Not all thermoplastics are easily laser markable, therefore additives have to be used to highlight the contrast and make laser marks more visible. MasterMark technology is a laser marking additive developed by Compounding Solutions to offer a high quality, versatile and efficient solution for direct marking with the most commonly used types of laser sources. Laser marking is the preferred method for product identification in the healthcare industry. It provides a solvent-free, permanent, and cost-effective solution for the identification of plastic medical device components.
The current transition of the healthcare market demand produces devices designed to diagnose and treat patients with innovative layout. The medical device manufacturing industry requires new compounds to meet reforms, technology, and law requirements. The medical device manufacturing companies need new compounds and material technologies to support the urgency of changes in the MedTech industry.