How RFID labels are integrated into plastics

New possibilities now exist in the realm of seamless traceability, especially in lab automation and diagnostics.

In automated storage systems, it is necessary to give a sample more identification than a simple number. In the future, data matrix- or barcodes will not be able to cover applications where more data and adding/modifying data are required, and where traceability over the entire life cycle of the item must fulfil stricter quality standards.

New RFID tags can establish, for instance, the point when a sample was in a certain room and the environment in that room. These abilities make a replacement of data matrix- and barcodes with RFID quite interesting. RFID tags can also be positioned at any place on an article, or partially or fully integrated in plastics.

The most common process to produce plastic disposable diagnostic and labware items is injection moulding. There are several options for integrating RFIDs into moulded parts. Wet labels are the simplest; these are tags on an adhesive foil, handled as common labels. However, this quickly reaches its feasibility limits regarding positioning, size and protection from manipulation; it is difficult to apply labels on uneven surfaces, radii or curves, and they are exposed and can be damaged by mechanical, environmental or other influences. These problems are eliminated if the tag becomes integrated into plastic during the manufacturing process. Based on a process developed at Wedimann Plastics Technology, these tags can now be partially or fully integrated into plastic.

If RFID-inlays are used (a tag on dry foil), the material properties of the foil as well as of the processed plastic must be considered, and the foil possibly plasma-treated or coated. For a cost-effective integration of RFID-tags, however, additional process steps should be avoided; whenever possible, tags should be used as delivered by their manufacturer. Therefore, the requirements for the tags must be carefully analysed and established, and a decision made as to whether the tag is to be fully or only partially integrated in plastic.

For partial integration, the Weidmann Inmold Process is similar to the commonly used ‘in-mould labelling’ (IML). For RFID, however, the sensitive electronics are protected by a melt-flow system specially conceived for this purpose. For tags to be completely integrated into plastic, the process becomes two-staged. Once a first layer is injected over the tag, a second layer must be injected on the opposite side.

A clear distinction must therefore be drawn between completely or partially embedded tags, and the decision on which to use must be carefully evaluated. The more complex process can only be justified for articles with a long life cycle, for example items that must be autoclaved or are exposed to aggressive environments. For more common usage, the properties of partially integrated tags may be entirely adequate, since a certain level of manipulation protection is assured. 

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