Engineers at Northwestern University have created a small wearable device that can detect stress hidden deep inside the body, even before a person may realize they are under pressure.
The soft, lightweight device works a bit like a modern version of a polygraph, often called a lie detector, but instead of trying to catch dishonesty, it is designed to monitor physical signs of stress.
The researchers hope it could eventually help doctors track stress, pain, sleep problems and other health conditions in a simple and non-invasive way.
The study was published in Science Advances.
The wearable device is about the size of a small bandage and sticks gently to the chest. Even though it is tiny and weighs less than eight grams, it contains several sensors that work together to continuously monitor the body.
It measures heart activity, breathing patterns, sweating, blood flow, skin temperature and other signals linked to stress.
These measurements are combined to create a detailed picture of how the body is responding in real time.
Research leader John A. Rogers said stress often affects the body long before people consciously notice it.
Chronic stress can quietly damage health over time, especially in vulnerable groups such as pregnant women, children and critically ill patients.
The project originally began after doctors at Ann & Robert H. Lurie Children’s Hospital of Chicago asked Rogers and his team to develop a better way to monitor stress in babies staying in hospital.
Currently, doctors and nurses often rely on crying, facial expressions and movement to judge whether babies are stressed or uncomfortable. But these signs can be difficult to interpret and are sometimes completely absent.
The new wearable system aims to remove some of that guesswork by providing objective measurements of stress around the clock.
The researchers drew inspiration from traditional polygraph machines, which measure physical reactions linked to stress. However, regular polygraphs use large wired systems with separate sensors attached to different parts of the body. The Northwestern team wanted to create something much smaller, softer and easier to wear.
The resulting device combines many sensors into a single flexible patch. One sensor tracks tiny mechanical and sound signals from the heart and lungs. Others measure skin temperature, blood circulation and sweat-related electrical changes in the skin.
The system wirelessly sends data to a smartphone, smartwatch or tablet, where machine learning software analyzes the patterns and estimates stress levels in real time.
The researchers tested the device in several different situations.
During simulated lie detector tests, it successfully tracked stress responses that closely matched commercial polygraph systems. In experiments where participants completed difficult listening tasks in noisy environments, the wearable detected rising stress levels as the tasks became harder.
The device also monitored stress reactions when volunteers placed their hands in ice-cold water. In sleep studies involving children, it identified breathing problems and nighttime awakenings with accuracy similar to hospital sleep tests, but with much less discomfort.
In another experiment involving medical students in emergency room training exercises, people with stronger stress responses tended to perform worse under pressure.
The researchers now hope to test the technology in larger groups of patients and eventually use it both in hospitals and at home. Future versions may even include sensors that measure brain activity, helping scientists better understand the difference between stress and pain.
The team believes the technology could one day warn people when stress levels become dangerously high, allowing earlier intervention before long-term health problems develop.
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