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Forget coatings: these enclosures are inherently antimicrobial

05 October 2014

A silver-based antimicrobial additive that gives life-long antimicrobial properties to both plastic and metal enclosures won the Health category for Vero Technologies at this year's e-Legacy Awards. We take a closer look at this innovation and its many potential applications.

Hospital acquired infections have become a serious problem in recent years. While improved housekeeping and new guidelines for staff have reduced the problem to a certain extent, the underlying problem of bacterial growth on surfaces remains.

To help address the issue, Vero Technologies is now able to offer its ranges of plastic and metal enclosures and panels with Biomaster, a silver-based antimicrobial additive in the material, which provides an effective means of reducing bacteria by up to 99.99 percent for the active life of the product.

Vero Technologies has entered into a technology partnership with Addmaster, a leading supplier of technically innovative additive formulations for plastics, textiles, papers, paints and coatings. The antimicrobial additive is sparingly soluble, providing a slow release of silver ions, safely inhibiting bacterial growth for an extended period, typically in excess of the product lifetime.

The key benefit is that the silver ion material is added to the raw ABS before the moulding process in the case of plastic enclosures. As the additive becomes an integral part of the material, the efficacy of the protection does not diminish over time, giving far superior protection to external coatings that will inevitably degrade through normal wear and tear, routine cleaning and accidental damage.

For front panels and extruded aluminium enclosures, trials (in which the antimicrobial material is added to the anodising process) are currently being conducted; preliminary results show similar reductions in bacterial growth rates to those found in plastic enclosures.

Biomaster has been tested on over 50 different species of bacteria, including the commonly encountered MRSA, E.Coli, Listeria, Salmonella and Campylobacter species. Independent testing to ISO 22196:2011, using MRSA and E.Coli, has confirmed the effectiveness of the additive.

In essence, the test procedure consists of inoculating test samples with a nutrient mix containing a known amount of bacteria. The samples are maintained at 37°C for 24 hours with the amount of viable bacteria colonies being measured. 

The European test laboratory is the only one outside Japan to have SIAA, Society of Industrial technology for Antimicrobial Articles accreditation. The SIAA is a cross industry-academic group for supervising antimicrobial technology.

Vero Technologies manufactures a wide range of plastic enclosures suitable for hand-held, portable instruments and desktop applications, including such well-known brands as Veronex, IDAS, Apollo, General Purpose Box, Patina and many others.

All sizes and colours of this family of products can be supplied with the antimicrobial additive in the plastic, which does not alter the external appearance of the housings.

Also available are extruded aluminium cases and a large number of different front panel designs for cases and subracks. For OEMs involved in the medical equipment and instrumentation markets, specifying the antimicrobial versions of the products (which can be machined to suit the application without reducing the effectiveness of the antimicrobial protection) will reduce time to market and offer a demonstrable benefit in terms of enhanced performance. 

Antimicrobial moulded enclosures can also be protected against EMC if required. When EMC screening is required, three alternative internal coatings are offered that provide varying levels of attenuation at different price points to suit more than 95 percent of possible applications; for highly specialised applications, other coatings are available.

For less demanding commercial applications, the lowest cost 50-micron nickel coating provides attenuation of 50dB at 1GHz. The default coating is a 10- or 20-micron silver-coated copper particle coating, which typically attenuates by 78dB at 10 GHz.

The highest attenuation is achieved using a 22.5 micron silver coating, which gives in excess of 80dB at 1.5GHz. It provides an effective shield against RFI and EMI and can act as a ground plane to protect against electrostatic discharge (ESD).

Electronic equipment used in the food processing industry is another obvious sector for antimicrobial enclosures. In one application for portable test instruments, Veronex IP64 UL94-V0 flameproof moulded enclosures are supplied in special corporate colours and are RFI screened by means of an internal coating of silver/copper conductive material on the body of the enclosure.

The separate end panels, one of which is transparent, maintain the integrity of the RFI screen thanks to the application of a transparent conductive finish originally developed for military applications.

Apertures are provided in the top and side of the enclosure to accept data and battery recharge connectors, displays and operator controls. The coatings and finishes chosen achieve an attenuation level of 200dB at 100MHz for the completed enclosure.

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