Urine-powered (galvanic) electric cell and sensor on paper substrate

A self-powered urinalysis platform for point of care utility is reported consisting of an electrochemical sensor fabricated on paper substrate and powered by urine. A galvanic cell activates upon addition of urine, with the REDOX reaction between urine and electrode–electrolyte pair Al|NaOH|NaCl|CuSO4|Cu generating power. Owing to presence of many ionic species in urine, electrical conductivity (EC) is positively related to osmolality, Na+ concentration, and uric acid concentration. Urine EC dependence on osmolality and Na+ concentration contribute to cell electrical property. The cell consists of several layers: the base paper layer (impregnated with NaOH), hydrophobic and hydrophilic layers, CuSO4 and NaCl strips, and Cu and Al electrodes. A single cell device upon exposure to urine generates an open circuit voltage of 1.15 V and a short circuit current of 1.6 mA. A series twin cell device can power an LED for ~40 min. The device also selectively responds to K+ ion discharged in urine within the physiological range (25–125 mEq l−1). A single cell device generates short circuit current in range of 2.4–3.3 mA for concentrations of K+ from 50 to 130 mEq l−1 in urine.