Wearable sweat patch tracks oestradiol and progesterone to estimate ovulation

# What the patch does A wearable skin patch collects a tiny amount of sweat and reports estimated levels of two reproductive hormones: oestradiol (the main ovarian oestrogen) and progesterone. The aim is to give wearers a continuous view of hormonal changes across the menstrual cycle and potentially predict ovulation without blood draws or clinic scans.

# How it works The patch uses a mild electrical current to induce sweating. Inside the sensor are two engineered DNA molecules that bind selectively to oestradiol or progesterone. Each binding event produces a distinct electrical signal that the patch converts into an estimated hormone level and transmits to a smartphone app.

Sweat composition varies across people and time, which can distort measurements. The research team included a dried buffer on the sensor that rehydrates when sweat arrives, standardising pH and salt concentration so the hormone readouts are more consistent.

• Sample volume and timing: The sensor needs about 9 microlitres of sweat and takes around 90 minutes to produce a reading.

• Participant testing: The device was evaluated on nine women (a mix of reproductive-age and postmenopausal participants). A separate 28-day monitoring run involved three women — one reproductive-age, one perimenopausal, and one postmenopausal — where the patch captured hormone patterns consistent with expectations for those stages.

# What the early results show The patch tracked hormone fluctuations that broadly matched blood samples and the expected cycle-related patterns. For the reproductive-age participant in the 28-day test, oestradiol and progesterone rose and fell in ways consistent with ovulatory cycling. The postmenopausal participant showed consistently low levels on the patch and in blood.

# Open questions and next steps The researchers identify several unknowns that need addressing before this becomes a practical ovulation tool:

• Larger and more diverse trials to confirm how reliably sweat hormone levels track blood across ages and reproductive stages.
• Direct comparisons with standard ovulation measures, such as urine luteinising hormone tests and transvaginal ultrasound, to assess timing accuracy and clinical usefulness.
• Determining whether the patch can detect hormonal changes early enough and consistently enough to predict ovulation for people trying to conceive.

Gillian Goddard of NYU, who was not involved in the work, said the patch could be less invasive than blood tests and sonograms and potentially more informative than current wearable signals, but emphasised the need to verify prediction timing given individual variation in hormone trajectories.

# Practical implications for readers If subsequent studies confirm these findings, the patch could offer a noninvasive option to monitor cycle hormones at home and give more direct hormonal information than temperature-based trackers. At present, evidence is preliminary: the device showed promising correlations in a small sample but requires broader validation before being relied on for fertility decisions.

# Publication detail The device study is reported in the journal Device (DOI: 10.1016/j.device.2026.101299).