Solving Medical Device Cleaning Challenges

A medical device component can look perfectly clean and still carry contamination either on the surface or hidden somewhere you can’t easily see or reach. Machining, molding, polishing, transporting, and assembly all leave something behind, including cutting oils, coolants, drawing compounds, mold release, polishing paste, fingerprints, or particulates. Some of it sits in plain sight; most of it does not. For example, the contaminant could be in a blind hole in a machined titanium part, drawing lubricant left inside a stainless needle after forming, mold release clinging to a molded polymer part, or adhesive residue picked up during catheter assembly.

None of this is immediately apparent. A part can pass every visual check and still cause a weak bond, a coating defect, an electrical short, or an assembly failure several steps later down the production line. At that point, figuring out where it went wrong is a lot harder than preventing it would have been in the first place.

Cleaning requirements vary considerably from one part to another. What works depends on what contamination is on the part, what the part is made of, its geometry, how many you’re making, and what happens to it next.

Identifying the Contamination

First, determine what contaminant you’re trying to remove. Cutting oil, grease, flux, and polishing compound don’t behave the same way. For example, a fluid that cuts through a light machining oil in seconds can struggle against a heavy wax.

Contaminant location changes the problem as much as the contaminant itself. Oil on an exposed surface is straightforward. Wipe it and you are done. The same oil three inches down a narrow bore is a different job entirely, because the cleaning fluid now has to physically reach the contamination before it can remove anything. This is why cannulated components, biopsy needles, trocars, and other parts with narrow internal passages are so hard to clean by hand. Lubricant settles into places a wipe or brush cannot reach.

The part’s material complicates things further. Stainless steel, titanium, aluminum, ceramics, silicone, polyurethane, and a long list of engineered polymers are used in device manufacturing. A cleaning fluid that’s fine on one material can stain, swell, or craze another. This gets harder with multi-material assemblies. A catheter or delivery-system part, for instance, might combine polymers, metals, coatings, and adhesives all in a footprint the size of a fingernail. The cleaning fluid that is perfectly safe on the metal housing might damage a seal or compromise an adhesive nearby. Testing representative parts under realistic production conditions can identify these compatibility issues before they reach production.

From product launches to M&A and manufacturing trends, the MPO Source delivers the medtech news you need twice a week. Subscribe here!

Manual Cleaning

For some medical device parts cleaning applications, manual cleaning is still the right call. A small batch of stainless parts with fingerprints or a light film of machining oil doesn’t need a fully automated cycle. An operator with a controlled amount of fluid and a lint-free wipe can manage it. The same logic applies to mid-assembly, where an accessible surface needs a quick cleaning before bonding, or in rework, where sending an entire printed circuit board back through production cleaning is overkill for one contaminated spot.

The challenge is keeping consistency. Two operators rarely use the same amount of fluid, let it sit for the same amount of time, or wipe it away the same way. In a validated process, fluid quantity, application method, contact time, and wiping technique all need to be defined rather than left to individual judgment.

Manual cleaning also has practical limits. A cannula, narrow lumen, blind hole, or intricate machined feature can hold contamination well past where an operator’s hand, cleaning brush, or wipe can go. Higher volume compounds the problem. Cleaning 20 parts by hand is reasonable; cleaning 2,000 a day is a different project entirely.

Vapor Degreasing for Complex Parts

For complex geometries, higher volumes or applications where repeatability is critical, closed-loop vapor degreasing may be a better fit. Cleaning fluid is heated inside a vapor degreasing machine creating a vapor zone. A cool part is put into that zone, and the vapor condenses on the surface, dissolving contamination and carrying it away as it drains. For parts with heavier contamination, the process may include immersion in the boiling fluid first before a rinse in the vapor zone. Depending on the equipment layout, spray wands, ultrasonics, or agitation can also be added ahead of the final vapor rinse.

Difficult geometries are where vapor degreasing makes the biggest difference. A low-surface-tension vapor degreasing fluid can reach and remove contaminants in spaces that aren’t practical to clean with a wipe or brush, such as particulate trapped in a recess of a titanium component or drawing lubricant inside a narrow needle. Fluid choice is not just about cleaning power. Surface tension, boiling point, vapor pressure, drying behavior, and fluid stability all affect performance inside the equipment, while material compatibility is always important for the parts being cleaned.

Choosing the Right Cleaning Process

The decision is not between manual cleaning or vapor degreasing. Many manufacturing operations use both, depending on the part and where contamination occurs.

A titanium surgical instrument, for example, might need vapor degreasing to remove oil trapped in threads, while an accessible surface on a catheter, contaminated during handling, can simply be wiped down. 

The soil and substrate also influence the decision. Molded polymer parts require a fluid that removes mold release without swelling or crazing the material. Printed circuit boards carrying flux residue need a method to remove the residue without damaging the board substrate itself or the sensitive electronic components.

The cleaning process needs to fit the part and the manufacturing operation rather than forcing every part through the same approach.

Setting Cleanliness Requirements

The most useful question is whether a part is clean enough for the next step of production. Residual oil can interfere with bonding. Contamination can undermine coating adhesion. Particulates can cause assembly problems or become trapped inside the finished device.

Cleanliness criteria should go beyond visual inspection. Depending on the application, that might mean measuring surface energy, extractable residue, or particulate count. The appropriate standard depends on the component and what the cleaning process needs to do downstream.

Process Testing and Validation

A technical data sheet is a useful starting point, but final fluid choice should be based on testing your parts and soils under conditions that resemble your production. For manual cleaning, that means working out fluid quantity, application method, contact time, and wiping technique. For vapor degreasing, variables can include immersion time, vapor exposure, ultrasonic settings, basket loading, and cycle time.

It is worth involving the fluid supplier before you lock down your cleaning process. Sharing details about the soil, substrate, part geometry, equipment, and production requirements can help narrow the options. Lab testing with contaminated sample parts can then confirm that the proposed approach works before it reaches the production floor.

The goal is a cleaning process that works consistently on the production floor. One that removes the contamination without damaging the part or causing problems at the next manufacturing step. Reaching that point usually requires testing the fluid on actual parts, with actual soils, under conditions that reflect production.

More insights from this author: The Critical Role of Outsourcing in Medical Device Cleaning

Elizabeth Norwood is a senior chemist at MicroCare LLC, which offers precision cleaning solutions. She has been in the industry for more than 25 years and holds a BS in chemistry from the University of St. Joseph. Norwood researches, develops, and tests cleaning-related products. She currently has one patent issued and two pending for her work. For more information, visit www.microcare.com.