Disclosed is a non-therapeutic use of a sensor for detecting biological fluids in vitro, the sensor comprising a substrate coated with conductive ink, the substrate being inert relative to the conductive ink, the sensor comprising means for measuring conductivity or resistivity of the conductive ink, wherein the conductive ink comprises a carbon substrate and a surfactant. The sensor may also comprise a polymer such as a gum. Also disclosed are methods of detecting biological fluids and uses of the sensor.
