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A contact lens reads serotonin in tears to track stress

A gloved hand holds a soft, clear smart contact lens printed with a serpentine graphene-and-silver sensor trace around its rim, the Terasaki Institute logo in the corner.

Terasaki Institute for Biomedical InnovationPress kit

Researchers at the Terasaki Institute for Biomedical Innovation in Los Angeles described a contact lens that measures serotonin in tears, in a paper published in Science Translational Medicine on 16 September 2026. The team, led by Yangzhi Zhu, tested it on pig and human tears.

The soft, reusable hydrogel lens carries flexible graphene and silver electrodes laid out in serpentine patterns, with a ferrocene compound bonded to the graphene to pick up serotonin. It detects the molecule down to 72 picomolar, according to IEEE Spectrum, well below the roughly 15 nanomolar found on average in human tears. The electrodes kept working through more than 28 days of repeated flipping, folding, stretching and twisting.

In a pilot with 10 volunteers, the lens tracked serotonin before, immediately after and about 30 minutes after stress tasks such as public speaking and mental arithmetic. Serotonin is usually measured in blood samples. The study is an early human pilot, not a cleared device.

Sources

  1. [1]Serotonin measurement by lab-on-a–contact lens in porcine and human tearsScience Translational Medicine··Paper
  2. [2]Lab on a Contact Lens Can Measure Stress Through SerotoninIEEE Spectrum··Article