Lab on a Contact Lens Can Measure Stress Through Serotonin

Researchers fabricated soft hydrogel contact lenses with graphene and silver electrodes that detect serotonin in tears at concentrations as low as 72 femtomoles per liter, below the typical 15 nanomoles per liter found in human tears. In laboratory and pig experiments, the lenses measured stress-induced serotonin decreases during public speaking and math tasks and remained functional after 28 days of repeated deformation. A prototype wireless version uses an NFC chip for battery-free, smartphone-based data transmission.