Inkjet printed passive RFID sensor for wetness detection of diapers

Infants, the elderly, people with disabilities, and patients in hospitals are among those who use disposable diapers. Event-based alerting regarding the wetness level of diapers can improve care for this population by improving incontinence management, decreasing the risk of getting cold, rashes, and infections. Therefore, this paper presents an inkjet printed ultra-high frequency (UHF) radio frequency identification (RFID) sensor for wetness detection of diapers. The proposed sensor design consists of an L-shaped radiator, a T-shaped loop, and two small stubs. The loop is connected to Impinj R6 RFID chip and joined at the middle of L-shaped radiator. This sensor design covers a bandwidth ranging from 900–935 MHz along with a read range of 2.5 m. The tag antenna is optimized to work on water filled slab with a low conductivity value (0.05). However, the realized gain of this sensor reduced drastically after increasing conductivity. An experiment is conducted to record the difference between received signal strength indicator (RSSI) of the empty, water and urine-filled diaper. So, the proposed sensor can be useful for sensing the wetness level of both adult and baby diapers.