Northwestern University engineers develop wireless polygraph to detect stress
Engineers at Northwestern University have created a wireless polygraph.
The innovation falls into the same category as devices seen during police interrogation scenes in movies, but it is not a lie detector. It measures stress hidden deep within the body by tracking physiological signals such as heart activity, breathing patterns, and sweat response.
Northwestern said the device was designed especially for patients who cannot verbalize or otherwise communicate discomfort from stress, such as infants and some elderly patients. The device could also diagnose sleep disorders without bulky la equipment, monitor mental health conditions over time, and sense early signs of medical complications, the university said.
"Sometimes, the body manifests signs of stress before a person is consciously aware of it," Northwestern's John A. Rogers, who led the device development, said in a news release. "Even if people don't realize how much pressure they are under, stress is quietly affecting their health. Prolonged stress can have adverse consequences, especially for pregnant mothers, children and critically ill patients. An ability to track stress based on quantitative measurements could empower people to take stress-relieving actions with direct benefits to their health."
Development of the polygraph started with a request from pediatricians at Lurie Children's Hospital.
Rogers' team has already developed numerous wearable electronic devices for infants and children, which can track vital signs, treat congenital conditions, and diagnose and monitor disease, Northwestern said. Lurie asked his team to create a soft and non-invasive device that could track babies' stress levels during hospital stays without having to take blood or saliva samples.
Right now, finding out information about babies' stress levels is dependent on casual observation of crying, facial expressions, and movement, as well as basic vital signs, Northwestern said. But such observations can be subtle or inconsistent, and may not be present at all, Northwestern said.
"Stress is often scored using survey sheets and nursing assessments," Rogers said in the release. "The entries include things like tonality and volume of crying. Infants obviously cannot describe their own pain levels. So, unlike with adults, determining stress in babies can be incredibly challenging. We wanted to take subjectivity out of these assessments."
The new polygraph tracks the body's stress signals around the clock, and can quantify how stressed someone is each day and the intensity levels of the stress, Rogers' longtime collaborator, Dr. Debra Weese-Mayer, explained in the release.
The polygraph is composed of several minuscule sensors in one soft device. They track physiological stress signals in different ways — a microphone and motion sensor to capture mechanical and sound signals from the heart and lungs, other sensors to detect skin temperature and heat flow associated with blood circulation near the surface, and another sensor still that measures the documented stress marker of changes in the skin's electrical conductivity brought on by sweat gland activity.
All these signals go to a cellphone, smart watch, or tablet, and area analyzed by machine learning, Northwestern said.
The device weighs less than 8 grams — or eight paperclips — and moves with the skin. It can operate nonstop for more than 24 hours, Northwestern said.