The app makes smartphones accurate thermometers.

A fever above 100.4 °F (38 °C) may suggest a viral or bacterial infection.

 Low-grade fever is 99.5°F (37.5°C). Checking your temperature requires a thermometer, which may be unavailable. FeverPhone converts your phone into a thermometer without hardware.

Mercury thermometers are rare and expensive. Standard smartphones were used to test batteries and other internal components with thermistors.

Thermistors measure body temperature with clinical thermometers. These sensors detected phone-to-person heat transfer.

Researchers measured air temperature and heat rise when the phone touched a human using the touchscreen and thermistors.

First, they heated a plastic bag to simulate a warm forehead. Google Pixel 6, Pixel 3, and Huawei P20 phones collected data.

They used touchscreen data & phone heat rate to train a machine-learning algorithm to estimate body temperature.

The team optimized the system for phone accessories like screen protectors and cases after collecting enough data.

Researchers tested their program on humans. 16 of 37 had low-grade fevers. Pre-FeverPhone oral temperatures were obtained.

Researchers found that 90 seconds was ideal for phone-to-body heat transfer.

The researchers chose the forehead over hands, ears, and armpits because it is less susceptible to ambient air temperature and large enough to touch the phone screen.

The average FeverPhone core body temperature estimate was 0.41 °F (0.23 °C), within therapeutic limits. Researchers will optimize their app for many smartphones and smartwatches.

“We started with smartphones since they’re ubiquitous and easy to get data from,” said study lead author Joseph Breda.

 Testing smartwatch signals. Smaller watches heat faster. A Fitbit user may measure their fever in 10 seconds by touching their forehead.

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