People being monitored for chronic kidney disease or heart failure often have high levels of potassium in their blood (hyperkalemia) due to impaired renal potassium excretion caused by kidney damage or by medications. But such medications interfere with urinary potassium excretion. This electrolyte imbalance can be life-threatening and thus must be closely monitored. In collaboration with French start-up Ki'tech, researchers at the Fraunhofer Institute for Microengineering and Microsystems IMM want to revolutionize patient monitoring with a minimally invasive solution that measures biomarkers, including potassium, in the subcutaneous interstitial fluid.