A passive smart tag is described that responds to dampness in diapers once a pre-defined threshold value is reached. A high-frequency (HF) system at 13.56 MHz is used as this allows operation through water or human tissues with less absorption that would occur for an ultra-HF signal. A circular spiral coil and swelling substrate facilitate a reaction to dampness that can be detected without contact to the diaper wearer. A prototype design is simulated and measured results are provided together with a demonstration of a tag integrated into a worn diaper.
Keywords: biomedical equipment; body sensor networks; circular spiral coil; coils; diaper dampness; diaper moisture detection; frequency 13.56 MHz; high-frequency system; human tissues; intelligent sensors; moisture measurement; passive smart tag; predefined threshold value; prototype design; radiofrequency identification; skin; smart radiofrequency identification tag; swelling substrate; ultraHF signal; water.