A diaper-based printed sensing array for noninvasively and speedily detecting morphine and potassium ions

Soft, skin-mounted devices for noninvasive, on-demand biofluid analysis to track targets such as electrolytes and administered drugs are essential. Although several sensors have proven their ability to monitor biomarkers, the development of a wearable and flexible sensing array for rapidly tracking both electrolytic ions and morphine remains a significant challenge that requires exploration. Here, we present the first example of a fully integrated, soft, and flexible multiplexed device on a diaper, which combines biosensors for real-time electrochemical monitoring of morphine and potassium ions. We engineered a screen-printable ink using multi-walled carbon nanotubes (CNTs), graphite, and elastomer to make the wearable morphine sensor. Our morphine sensor with high catalytic activity toward morphine oxidation showed a response range from 1.0 x 10-7 M to 1.0 x 10-3 M morphine with a limit of detection (LOD) of 2.4 x 10-8 M. Furthermore, we designed the array to include a potentiometric sensor with an ionophore-based electrode for sensitive detection. The wearable potassium sensor exhibited a high response, reaching a low concentration down to 1.0 x 10-6 M. In addition, this wearable sensor remains impervious to common agents found in urine. Furthermore, our diaper-based flexible CNT-graphite electrodes can withstand multiple mechanical deformations. These advancements in new flexible nanocomposite CNT-based ink and diaper-based electrodes hold promise as candidates for noninvasive analysis development.