The fundamentals of radiofrequency communication still apply to Wiliot Tags. If a tag is covered with a material that is an RF blocker, the tag will not operate. Since we harvest and broadcast at 2.4GHz/Bluetooth, the behaviors can differ from RFID in that signals can bounce around more, which can be positive or negative depending on the application. Since Wiliot tags are constantly harvesting, and the infrastructure to energize and read is low cost and more pervasive, time is on our side, a signal may eventually get through. With RFID, using an expensive handheld reader, a signal might not be received when read over a 1-second interval. With more low-cost readers, more angles of transmission can be used.
As with RFID, different inlay, antenna designs, and special gap fillers may be required to support on-metal/skin/liquid/glass applications. Metal and liquids are the most challenging materials that affect RF environments in both the harvesting and transmission path.