Can Your Medical Device Survive Repeat Sterilization?
Autoclave Resistant Adhesives May Be the Answer
High heat, humidity, chemicals, and other environmental factors can cause challenges for medical tools like scopes, surgical instruments, dental equipment, general-use medical devices, and housing assemblies, as well as sensors and RFID tags adhered to medical tools. The materials that bond, coat, and encapsulate the components of such devices can be negatively impacted by these forces which can potentially lead to device failure, lost or misplaced instruments, or harm to a patient. That’s why it’s critical the products used to protect and bond the parts together be capable of tolerating a variety of stresses.
Along with the rigorous types of physical testing, standards, and approvals that medical device formulations are subjected to, including ISO 10993, many must also be able to withstand repeat cycles of sterilization.
Two categories of sterilization used in the medical device industry are classified as either physical or chemical. Physical sterilization methods include filtration, heat, radiation, and ultrasonic/vibration, whereas chemical sterilization requires a gas or liquid process. There is a large subset of techniques that fall under these main classes, such as EtO, gamma ray, E-beam, cathode ray, and oxidants, as well as autoclave and STERRAD™ Hydrogen Peroxide-Plasma.
There are pros and cons to using many of these processes. Positive attributes and outcomes depending on the method selected include high penetration capability, very rapid action against microorganisms, and the elimination of potential residues. Some of the negative factors can include long sterilization cycles, flammability, the use of hazardous materials or chemicals, yellowing of polymers, and corrosion of various metal substrates.
Considerations as to the kind of sterilization to employ are dependent upon the end-use product, its function, the substrate components, and the pressures and environments the device will be subjected to. Autoclave (steam) and Hydrogen Peroxide Gas Plasma (HPGP) are two methods often utilized in the medical device industry.
Autoclaving uses highly pressurized steam to sterilize instruments from microorganisms and bacteria that can potentially contaminate substrate surfaces by killing and rendering them ineffective. However, there are critical issues to keep in mind. Many metals have the potential to corrode or rust after repeated exposure to steam. Some plastics may lose their structural integrity, be sensitive to elevated levels of heat, be susceptible to migration of plasticizers to the substrate surface, or negatively react or break down when exposed to water.
Sterilization by autoclaving is limited to certain applications. Many medical device adhesives, for instance, have a difficult time holding up to autoclaving because of the high temperature, humidity, and pressure involved in the process. Due to these factors, there can be a weakened bond joint that fails. Alternatives to steam sterilization for heat and moisture-sensitive instruments and devices are being considered more regularly, although autoclave remains one of the most accessible options for hospitals, laboratories, research facilities, etc.
STERRAD™ Sterilization is an ideal method for heat and moisture-sensitive devices as temperatures do not exceed ~56°C (133°F) during processing. A solution of hydrogen peroxide and water is delivered to the sterilizer, then vaporized into the chamber. The solution surrounds and interacts with devices and creates a biocidal environment that inactivates microorganisms. A strong electrical field is applied to the chamber and creates a hydrogen peroxide gas plasma that dissociates hydrogen peroxide molecules into energized species. Once the electrical field is turned off, the energized species recombine, which turns the hydrogen peroxide into water and oxygen. This ensures the instruments are rapidly sterilized without any toxic residue remaining.
Many types of medical scopes and devices require repeat sterilization cycles or multiple instances of autoclaving or alternative sterilization methods like Hydrogen Peroxide-Plasma Sterilization.
Although there are formulated one- and two-part epoxies on the market for bonding, coating, and encapsulating medical devices and RFIDs, these products may not be the best choice. When compared to light-curable materials, epoxies pose numerous disadvantages such as specialized mixing systems, long cure times of up to 60 minutes, short pot life, the use of heat-curing ovens (in some instances), lower flexibility and impact resistance, and the need for purge cycles which can result in hazardous waste. One-component light-curable adhesives provide an alternative to these solutions by offering manufacturers fast cure times, from 1-30 seconds, no mixing or purging, a range of grades from rigid to flexible, and solvent-free, RoHS-compliant formulations for easier handling and disposal. The positive benefits of light-curable materials can help enhance manufacturing efficiency, decrease costs, and increase throughput.
To fulfill the need for a product capable of surviving frequent sterilization sequences, a new versatile UV/LED curable adhesive was developed that exhibits extremely low water absorption (0.5%) and is resistant to 100+ cycles of autoclave and plasma processes. This material is recommended for use as a coating or encapsulant for housing assemblies, single-use or multiple-use medical instruments, and a variety of medical scopes and dental equipment. It is especially suited for encapsulating RFID chips, sensors, and other electronic components found on medical devices, tools, and vials where moisture ingression may be of concern. Bondable substrates include stainless steel, aluminum, glass, PP/PE, and printed circuit boards.
LINK:https://dymax.com/resources/news-and-media/blog/medical/can-your-medical-device-survive-repeat-sterilization
