Are there any known materials that can help insulate RFID tags from the detuning effects of metal and water?
Any material with a dielectric constant of zero (that is, any material that does not conduct electricity) can be used to mitigate the detuning of an RFID tag's antenna by water or metal. Styrofoam, for example, can be used as a spacer to keep a tag away from metal or water, and can prevent the antenna from being detuned. Keep in mind that water also absorbs RF energy, which can reduce a tag's read range. Most users try to place tags in air gaps (at the neck of a water bottle, for instance). Tag antennas can be tuned to work around certain materials—the right tag depends on precisely what you are trying to track.
—Mark Roberti, Founder and Editor, RFID Journal
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