Researchers have developed a lab on a contact lens capable of detecting serotonin in tears, potentially enabling continuous, noninvasive monitoring of stress and other physiological changes. The soft, reusable hydrogel lens incorporates flexible graphene and silver electrodes, with ferrocene helping it selectively detect extremely low serotonin concentrations. Laboratory tests showed sensitivity well below typical serotonin levels found in human tears, while experiments involving 10 volunteers found that tear serotonin decreased after stressful public-speaking and mathematics tasks. Testing on an anesthetized pig also demonstrated serotonin detection without signs of short-term irritation or infection.
The technology could eventually shift wearable health monitoring beyond physical measurements such as heart rate and temperature toward continuous biochemical sensing. Researchers have already produced a proof-of-concept wireless version using NFC for battery-free sensing and smartphone data transmission. However, substantial validation and safety testing remain necessary, particularly to understand how tear serotonin varies among individuals and relates to blood biomarkers and clinical assessments. Future versions could simultaneously measure serotonin, cortisol, and other molecules, potentially turning contact lenses into wearable platforms that provide a richer picture of stress and physiological health throughout everyday life.
More information:
https://spectrum.ieee.org/serotonin-stress-smart-contact-lens