March 4, 2024

Since the emergence of COVID-19, people have become more sensitive to checking for signs of fever. Now, researchers at the University of Washington have developed an app that turns an ordinary smartphone into an accurate, easy-to-use thermometer.

A fever is generally considered to be a temperature of 38°C (100.4°F) or higher and may be a symptom of a viral or bacterial infection. The lower limit for a low-grade fever is 99.5 °F (37.5 °C). But to measure body temperature, you need a thermometer, which may not be readily available.

Old-fashioned mercury thermometers are virtually extinct, and digital versions can be pricey, but the FeverPhone app turns your smartphone into a thermometer without any additional hardware.

The researchers used thermistors embedded in common smartphones, which are often used to monitor the integrity of the device’s internal components, especially the battery. These thermistors are the same thermistors used in clinical-grade thermometers, which measure the change in temperature when the thermistor comes into contact with the body.

They realized that these sensors could track the heat transfer between the person and the phone. The researchers began experiments using the phone’s touchscreen to sense contact with the skin and a thermistor to measure air temperature and heat rise when the phone touched the body.

They first used a plastic bag filled with hot water to simulate a warm forehead, pressing a mobile phone screen against the bag. They collected data using three phone models: Google Pixel 6, Google Pixel 3, and Huawei P20. The data they collected was used to train a machine-learning model that estimates body temperature by tracking how quickly the phone heats up and using data from the touchscreen to calculate how much heat is generated when someone touches the phone. Once enough data has been collected, the researchers can calibrate the model to account for changes caused by phone accessories such as screen protectors and cases.

In the completed initial tests, the researchers started using human subjects to test their application. They recruited 37 participants, 16 of whom had at least low-grade fever. Before testing with the FeverPhone, participants took their body temperature using an oral thermometer.

Participants pressed the phone’s touchscreen to their forehead for about 90 seconds, which the researchers found was the best time to perceive body heat transfer to the phone. The researchers chose the forehead over other body parts (hands, ears, armpits) because it is less susceptible to drastic temperature changes in the temperature of the surrounding air and is large enough to make contact with the phone screen.

They found that the average error in FeverPhone’s estimated core body temperature was about 0.41 °F (0.23 °C), well within the clinically acceptable margin of error.

The researchers will continue to fine-tune their app, aiming to make it available on a wide range of smartphones and smartwatches.

“We started with smartphones because of their ubiquity and easy access to data,” said Joseph Breda, the study’s lead author. , so their temperature changes faster. So you can imagine a user putting a Fitbit on their forehead and measuring within 10 seconds if they have a fever.”

The FeverPhone application is not yet available for download.

The study was published in Proceedings of the ACM Conference on Interactive, Mobile, Wearable and Ubiquitous Technologies.

source: Washington University