The invented diaper-embedded system is comprised of a flexible urine-activated paper battery, a colorimetric detection unit (LED/strip/photodiode), associated circuitry, wireless transmitter, and metallic traces integrated on a hydrophobic flexible substrate. It provides a fully autonomous (stays dormant before urination) and wireless monitoring of UTI upon the urination, which does not require any operation/intervention from the patient/caregiver. The entire detection and data transmission process completes within 30 minute from the beginning of the urination.