There’s no question that being intentional and attentive to processes is beneficial. Parts cleaning falls high on the process priority list, yet there can be gray areas about what is required. This article offers guidance to help you determine your cleaning operation and optimize processes.
What is your medical device cleaning process and how does your team provide samples to a validation testing facility? Parts frequently arrive at our lab in varying states of “pre-cleaned.” These parts must then be validated to the predetermined criteria required to pass the approval process. Your validation partner should be informed up front as to what (if any) cleaning process has been done.
If you have data that supports any pre-cleaning processes (i.e. where parts or devices have been cleaned prior to arriving at the final packaging location), it is helpful to share. Any data can help us find your best path, but if not, we can still get you to the finish line. Below you’ll see the most common final cleaning methods that are used and validated within our facility, prior to the packaging process.
ALCOHOL CLEANING
IPA Alcohol wipes
Disposable, saturated wipes may use Isopropyl Alcohol (IPA) strengths of 70 percent, 90 percent, or 99 percent. They are appropriate for cleaning small, specific areas and should be used on fully accessible surfaces where rinses would be impractical.
Fun Fact for Parts Cleaning Trivia Night
Did you know that 70-percent IPA concentration provides better disinfection than 90 percent or 99 percent concentrations? The water content of the 70% IPA acts as a trojan horse to soak into the bacteria, allowing it to be killed more effectively. Applying 90 percent or 99 percent can evaporate too quickly to kill some pathogens.
IPA Alcohol Dip
Also self-explanatory, IPA dipping uses the same strengths as wipes in a more thorough cleaning process to decontaminate parts. The dip method may be poured or sprayed, which provides a more thorough result for parts with complex geometries and more surface areas (compared to IPA wipe process). In addition, this method can be used for parts that are sensitive to ultrasonic methods described below – whether that’s the specific detergent or the exposure to the cavitation process and other drying methods.
ULTRASONIC CLEANING
An ultrasonic process typically uses a cleaning solution dispersed through the tank by high-frequency sound waves. The process, called cavitation, creates a microscopic bubbling action that results in powerful agitation for thorough cleaning of parts placed in baskets stacked within the unit. Wire baskets stack in the unit so that all pieces are uniformly treated during the process. The device, parts, or representative samples are validated according to what we know about the manufacturing process. A customer may choose to make a special sample with unique geometry that has more complexity and/or previous manufacturing steps than the actual part to be manufactured. This provides an added level of assurance that the cleaning process recommended will meet requirements. Based on the number of samples available for validation and manufacturing output goals, multiple lots (i.e., multiple sizes of the same part) can be combined to improve manufacturing efficiencies.
Frequency settings within an ultrasonic process alters bubble sizes to accommodate different geometries. Temperature settings are set based on materials and types of manufacturing contaminants we want to remove (i.e., greases). Lastly, the duration or time of exposure in the unit determines the level of cleanliness. However, all settings must be carefully calibrated to avoid damaging sensitive plastics or coatings.
Ultrasonic with IPA
One factor to be considered when choosing a solution: If minimal residue and fast drying are essential for the parts, IPA (Isopropyl Alcohol) is a good choice. For applications involving certain coatings or softer plastics that may degrade under higher temperatures, adjustments might be necessary. Identifying these coatings upfront with your validation partner ensures the optimal process and product can be selected with confidence, helping to determine the operation for the best results.
In some instances, ethanol may be preferable to IPA. Ethanol may be indicated when certain coatings or plastics are present on parts. That said, ethanol evaporates more slowly than IPA, so moisture concerns must be considered. Lastly, specific equipment is typically required to be used with this process, as alcohols can be flammable when exposed to ultrasonic settings or higher temperatures.
Ultrasonic with Detergents
Ultrasonic process can also incorporate detergents other than alcohol. Remember to confirm the compatibility of any detergents when a medical device contains titanium coatings or bonding agents. When choosing, we use all available history and data to determine whether an alkaline detergent (commonly used for single-use devices) or an enzymatic detergent (primarily used in the U.S.) is more suitable for reprocessing devices, considering their interaction with the human body. One thing to consider with enzymatic detergents is that they are not as harsh and can break down at lower temperatures. The bottom line is that the detergent must match product characteristics and regulatory requirements.
Summary of Ultrasonic Cleaning
Once production begins, you can’t exceed what the device was validated to, so the quantities must be carefully thought through. If only 50 parts are available for testing and we can load five parts into each basket for validation, but the production goal is 1,000 parts, only five parts can be produced at a time due to the validated process. This significantly impacts throughput, leading to increased piece prices. Discussing options and projected volumes upfront can help prevent bottlenecks in production later on.
By identifying the part with the most demanding, largest, and most complex surface area to validate, we have an effective cleaning process that brings confidence to the smaller and less complex areas of the medical device. By verifying that all product materials can tolerate the planned cleaning process (i.e., higher drying temperatures), risks can be mitigated. Similarly, assessing all cannulations, fenestrations, blind holes, threads, and 3D-printed features that may present cleaning challenges are equally as important.
Speaking of drying, the next critical decision in the cleaning process involves selecting the appropriate method—whether air drying, forced air, or vacuum drying. It’s important to analyze the geometries and surface areas to identify features that may retain moisture. Additionally, if forced air is chosen, there may be requirements regarding the source of the air due to quality concerns related to contaminants. We have previously discussed that certain materials have lower temperature tolerances, which remains relevant during the drying process.
The key role of an engineer is to identify the client’s worst-case device scenario. This often involves extensive discussion and validation during the design phase. Asking questions like those in the Q&A below ensures all key considerations are addressed, leading to a more efficient process. It also provides your validation partner with the necessary information to determine the parameters and goals for your validation.