Doctors routinely ask for urine tests for a very good reason: they just work. Xi Xie and Hui-Jiun Chen from Sun Yat-Sen University wanted to develop a wearable device that can both accurately and sensitively measure the concentration of several important health markers from urine while providing instantaneous feedback. As a caveat, the researchers acknowledge that in a real-world setting, such ‘smart’ diapers would become slowly saturated with urine due to prolonged use, so the sensors would probably have to take multiple measurements to record stable readings