Medical Device Link.

Originally Published EMDM October 2004

Special Report

Device manufacturers tend to be obsessive about cleanliness, and for good reason. Even a minute contaminant on an implant can have far-reaching consequences. It may cause the device to fail prematurely, put a patient at risk of serious infection, and perhaps lead to a sudden decline in the manufacturer’s financial health.

Medical devices in general need to be free of contaminants to ensure that surface treatment and sterilization processes are not compromised. Metal debris, polishing compounds, grinding fluids, and other contaminants introduced during the production stage may remain on the device surface or become lodged in holes and crevices. They must be removed.
Finally, one should not neglect the role that aesthetics plays in device acceptance. Practitioners and patients alike would reject a medical product with a less-than-perfect surface finish.

For the removal of trace elements of contamination, ultrasonic technology is among the preferred methods. To simply add lustre to a stainless-steel device, the solution might be found in crushed nutshells.

Bursting Bubbles

Ultrasonic technology achieves acceptable levels of cleanliness even in parts with complex geometries and in hollow-body instruments. The process involves immersing the workpiece in a tank filled with cleaning fluid, which is agitated by ultrasonic waves. Cavitation—the formation and collapse of microsopic bubbles—produces a scrubbing action that thoroughly cleans the device yet is so gentle that it won’t damage delicate mechanisms. While cavitation is at the heart of ultrasonic systems, users should not neglect other factors such as the type of detergent that is used, the cleaning fluid’s temperature, and the rinsing cycle, according to UK ultrasonic system developer Kerry Ultrasonics Ltd. Depending on the application, other forms of cleaning may be appropriate. Swiss supplier of contract cleaning services and equipment KKS Ultraschall AG uses vibratory bowls filled with everything from crushed nutshells to polymer pellets to burnish devices. And Layton Technologies in the UK has developed a method to clean and dry synthetic tissue culture discs using methanol.

These and other companies supplying parts-cleaning services and equipment are profiled in this section. Further sourcing opportunities await at the international parts2clean trade show, which takes place in Friedrichshafen, Germany, on 26–28 October. Information on the event can be found at www.parts2clean.de.  

UK Firm Finds Methanol Solution

When a US company failed to find a safe and effective way to use methanol to clean and dry synthetic tissue culture discs on its home turf, it turned to UK-based Layton Technologies (Weston Coyney, Staffs). “It was a tough assignment, because methanol is notoriously difficult to handle,” says managing director Phil Dale. “But it was the only chemistry suitable for the removal of forming oils and manufacturing soils from the culture discs, because of their delicate nature.” And so Layton sprang into action.

The company found a solution in what it calls low-emission solvent cleaning plant technology. The methanol first is boiled off and condensed and then routed to an immersion clean sump. The 5-mm polypropylene and nonwoven polyester culture discs are immersed in the ambient methanol, agitated via ultrasonic waves, and dried by exposure to a nitrogen-enriched warm atmosphere. The automated process is carried out under sealed conditions.

A refrigeration plate controls the diffusion of methanol vapours during the loading and unloading of the process chamber. It also serves as the cooling source for vapour condensation during the drying phase.

In addition to this project, Layton has developed a cleaning system for an orthopaedic implant manufacturer, and it has extensive experience supplying parts-cleaning technologies to aerospace and military specifications. Meeting specific customer requirements and designing flexibility into its systems are among the cornerstones of the company.

“Enough flexibility is incorporated into each machine to enable the customer to totally change the process quickly and easily,” says Dale. The company’s guiding principle, he adds, is to “design, engineer, and manufacture systems that are fit for purpose now and in the future.”

Ultrasonic Waves Can’t Do It Alone

Ultrasonic waves create microscopic bubbles, whose formation and collapse produces a gentle scrubbing action that quickly and thoroughly cleans objects inside out. The cavitation process, as it is called, removes contaminants even from difficult-to-clean crevices and tubes, yet it will not damage delicate or intricate mechanisms. Ultrasonic waves alone, however, are not sufficient to properly clean metal medical devices and implants, according to Kerry Ultrasonics Ltd., which was recently acquired by Guyson International Ltd. (Skipton, N Yorks, UK). In aqueous wash systems, for example, the detergent used, the solution temperature, and effective filtration and rinsing systems are equally important factors. A four-stage system developed by Kerry Ultrasonics integrates these features.

In the first stage, workpieces are cleaned by means of ultrasonic waves combined with a cleaning solution. Two immersion rinses follow, and the process is completed with a hot-air drying cycle. To ensure process repeatability, the company offers a two-axis programmable work transporter. Pick-and-place basket programming is a standard feature. This type of system is suited for cleaning implants made from stainless steel, titanium, and other alloys. Nitric acid passivation can be incorporated.

Kerry Ultrasonics also offers the Microsolve system that combines ultrasonic cleaning with a mixture of hydrocarbon and hydrofluoroether (HFE) solvents. The small-footprint two-stage machine safely cleans the surfaces of polished mould tools used to manufacture implants, cannulae, catheters, and contact lenses.

Parent company Guyson International has developed blast-style finishing systems that can be used to impart a keyed surface onto prosthetic implants prior to coating operations.


Polishing Kit Suited for Devices with Fibre-Optic Parts

A polishing kit incorporates all the necessary tools and consumables needed to process medical devices that integrate fibre-optic light guides. TransLab from Krell Technologies (Morganville, NJ, USA) includes an automatic polishing device, polishing films, a fibre inspection scope (with optional video hookup), and cleaning supplies. Polishing fixtures are available for standard and custom components. The kit is suited for use with catheters, endoscopes, probes, illumination bundles, image fibres, and laser delivery cables.


Solvent Is Eco-Friendly

Hydrofluoroether (HFE) materials are increasingly replacing hydrofluorocarbon HCFC-141b as a solvent in medical deposition, cleaning, and tube- swelling applications. Unlike HCFC, HFE-based materials have zero ozone depletion potential and they are exempt from the definition of a volatile organic compound. HFE-based Novec fluids, developed by 3M Specialty Materials (Zwijndrecht, Belgium), can disperse a range of coatings, feature uniform wetting and coating properties, and dry rapidly. They are suited for depositing silicone, PTFE, and heparin on needles, IV tubes, and catheters.


Swiss Firm Opens Full-Service Shop

Nestled in the postcard-perfect setting of Steinen near the Swiss Alps, KKS Ultraschall AG has set an ambitious agenda. “Our mission,” says managing director Hans-Peter Keller, “is to provide a full-service surface treatment centre for medical technology companies.” Offering both contract parts-cleaning services and associated ultrasound equipment, the company recently began building a 2400-m2 addition, 700 m2 of which has been set aside for surface treatment activities.

The company offers a range of surface treatment services depending on the material being processed and desired properties. “We use wet blasting on ceramic components to achieve a smooth surface,” explains Keller. “When the customer wants a rougher surface, to promote bone growth, for example, we can dry blast the part.” Electropolishing is available for implanted screws and related products. The company’s latest addition to its line of ultrasound machines offers dual-frequency cleaning for aggressive and gentle cleaning operations. In addition, vibratory bowls filled with everything from crushed nutshells to plastic pellets are available to polish implants and related devices.

KKS Ultraschall also designs equipment for OEMs, and it has developed in-line cleaning equipment that complies with US FDA guidelines.

Copyright ©2004 European Medical Device Manufacturer