Ongoing advances in medical device design are meeting patients’ demands for more portable and wearable technology. Bulky external health devices, like ECG monitors, spinal stimulators, and insulin pumps, are now slim and discrete. The patient benefits of these advances can be life-changing with improved physical comfort and mental well-being. However, for manufacturers, it is a challenge to design and build these new miniaturized complex devices.

Cleaning — A Critical Production Step for Wearables

Effective design practices are critical to deliver a device that performs as intended. When designing wearables, there are many factors an engineer must consider and plan for before any prototyping or production starts. However, cleaning is a critical aspect of medical device design that is often overlooked during initial planning.

Medical devices must be cleaned and dried to the highest standards to ensure their readiness for the next step in the manufacturing process. Production debris like machining, stamping, or cooling oils, dust, metal filings, marking inks, fingerprints, and other soils must be removed prior to assembly, packaging, sterilization, or coating. Any remaining particulate or residue can lead to inconsistent outcomes and impact the devices’ performance.

Smaller medical devices often have tiny spaces that are more difficult to clean and dry during manufacturing. They often include tight crevices, blind holes, or intricately shaped openings that are particularly difficult to clean. In addition, modern devices are made with more delicate parts and varied materials. Softer plastics and lightweight metals can be easily damaged, so cleaning and drying must be done carefully to prevent harm.

As a result, medical device manufacturers require newer, better cleaning fluids and methods to get the devices clean and dry. The cleaning fluids must penetrate all areas of the complex geometries, awkward shapes, and blind holes. Plus, they cannot leave residue or damage sensitive materials such as polycarbonate and acrylic.

The Resurgence of a Tried and Tested Method

Vapor degreasing meets that demand and continues to grow in popularity for medical device cleaning and drying. A few decades ago, vapor degreasing was the preferred method for cleaning medical devices. It was easy to use and provided highly reliable cleaning performance. However, in the late 1990s, environmental concerns fueled an industry-wide trend to switch from this process to aqueous-based cleaning systems.

Although there were disadvantages to using the water cleaning systems, like high energy and water consumption, many device manufacturers were convinced it was environmentally better than vapor degreasing, which uses solvent-based cleaning fluids. However, recent advancements in solvent technology have generated more environmentally friendly fluids, which have led to renewed interest in vapor degreaser cleaning.

Future Trends in Cleaning Fluid Technology

After a vapor degreasing cycle of about 6–20 minutes, parts are clean, rinsed, dried, and ready. (Credit: MicroCare)

Nearly all of the recent advances in cleaning fluid technology are focused on developing safe chemistries that meet both cleanliness standards and environmental regulations — meaning they do not contribute to global warming and are not an ozone depleting substance. In the past, high-performing cleaning solvents used within a vapor degreaser such as trichloroethylene (TCE), perchloroethylene (perc), and n-propyl bromide (nPB) presented air and groundwater quality issues as well as health and safety concerns.

That resulted in layers of regulations established to discourage their use. Early efforts to develop cleaning solvent alternatives initially resulted in ineffective cleaning that did not meet exacting standards — especially those needed in the medical device space.

The Green Clean

Because of their improved environmental and safety profiles, modern vapor degreasing fluids make ideal long-term replacements for the less planet-friendly solvents. Importantly, they not only meet today’s environmental regulatory demands, but are also equipped to meet emerging “green” rules for the future. Today, there are a number of modern cleaning fluids available that are both very effective and environmentally progressive.

They offer excellent cleaning performance combined with a low GWP (global warming potential) and low ODP (ozone depleting potential) profile. How the fluid ingredients are combined determines the cleaning fluid’s effectiveness and its material compatibility. The vapor degreaser can use just one type of cleaning fluid or fluids can be mixed, blended, or custom formulated to remove a specific soil from a specific device, maximizing cleaning effectiveness.

These next-generation fluids maintain or even increase cleaning consistency. This reduces scrap and rework, which lessens the number of raw materials used to complete an order. They also have a lower boiling point, which reduces the amount of energy needed to heat the cleaner inside the vapor degreaser. The result is less fossil fuel consumption, a lower total carbon emission, and less greenhouse gas output. In addition, the vapor degreasing process uses zero water, helping ensure future populations will have enough of this vital non-renewable resource.

How It Works

A typical vapor degreasing system consists of two chambers, both filled with a modern cleaning fluid. In one chamber, the cleaning fluid is heated to a boil, which then generates a vapor cloud that rises to meet cooling coils. These cause the vapors to condense and return to their liquid state. This liquid is then channeled back to the rinse chamber.

Soiled parts are immersed in the continuously filtered and distilled cleaning fluid inside the vapor degreaser to dissolve or lift the soils from the parts surface. As the parts are lifted from the cleaning fluid, they undergo a brief vapor rinse and drying process. The vapor degreaser recycles and reuses the cleaning fluid for hundreds of times before it needs to be refreshed or replaced. This helps reduce the cost of hazardous waste removal. After a typical cleaning cycle of about 6–20 minutes, the parts come out clean, rinsed, dried, and ready for the next stage of production.

External health devices are becoming smaller and more discrete. (Credit: MicroCare)

Uncompromised Cleaning Effectiveness

Modern vapor degreasing fluids feature excellent materials compatibility, making them well-suited for cleaning delicate plastic parts or mixed-material devices. They also have low surface tensions and high liquid densities, meaning they penetrate parts to clean them thoroughly. Even more importantly, the cleaning fluids dry quickly without leaving any moisture inside the devices that can cause corrosion or lead to bioburden issues. Medical device designers find this benefit of modern fluid cleaning to be of utmost importance because it doesn’t limit the complexity of the product design.

Also, vapor degreasing systems are not geometry-sensitive, meaning that if the component fits in the machine, the machine will clean it, without the need for extra fixtures or equipment. This is beneficial because it maximizes valuable production floorspace, especially in cleanrooms. Vapor degreaser cleaning is a well-engineered process that is simple, predictable, and repeatable, making it easy to qualify and validate for cleanroom medical device manufacturing.

Vapor Degreasing Does More Than Clean

Using a vapor degreaser not only cleans effectively, but also creates the opportunity for manufacturing efficiencies. For example, it is possible to combine the vapor degreasing cleaning process with a second-step surface treatment for the application of medical-grade lubrication or a specialty film. The versatility of the vapor degreasing cleaning process means parts are cleaned and coated in seconds, streamlining the overall process significantly.

A Trend Setter

As the trend toward miniature external medical devices continues, designing and manufacturing them becomes more challenging. Devices continue to shrink in size and weight, while growing in complexity. Elaborate geometries, awkward shapes, and internal blind holes are now common features of the designs. These intricacies can affect long-term performance and functionality.

Cleaning is an effective step in which to ensure reliability; however, achieving thorough cleaning is more difficult. Therefore, medical device manufacturers are opting for new methods and tools. Modern cleaning fluids and vapor degreasing equipment offer better cleaning flexibility. They provide effective and consistent cleaning to meet cleanliness standards and strict performance guidelines, both now and in the future.

This article was written by Jay Tourigny, Senior Vice President at MicroCare Medical, New Britain, CT. For more information, visit here .