Patients frequently conceal their actual feelings from their caregivers or even from their own aware selves. To help health care providers tell the difference, a team led by scientists at Penn State has created a stretchable, rechargeable sticker that can detect real emotions — by measuring things like skin temperature and heart rate — even when users put on a brave face.

Other components include a printed circuit board, wireless charging coil, 5-volt battery and Bluetooth chip. All of these bits and pieces are encapsulated within a waterproof silicone covering, with the whole device measuring about 6 cm (2.4 inches) in length, reports New Atlas.

The strain sensor on the sticker tracks the patient's skin motions along two axes while it is briefly attached to their face. It then wirelessly transmits this information to an app on a nearby cloud-connected smartphone or tablet.

The software's AI-based algorithms can then infer the user's current facial expression, which is undoubtedly connected to their mood. The technology's accuracy in recognizing six common facial expressions—happiness, surprise, fear, sorrow, rage, and disgust—has been over 96% in lab tests.

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Nevertheless, people can fake facial expressions, frequently even unconsciously. Because of this, the app also makes use of real-time data from the blood oxygen, temperature, and humidity sensors.  The system is already nearly 89% accurate at detecting genuine emotions elicited by watching different video snippets using this combination of data.

The technology may enable doctors to remotely monitor their patients' psychological health through the internet, as the data is processed in the cloud.

"This is a new and improved way to understand our emotions by looking at multiple body signals at once," says Cheng. "People often don't visibly show how they truly feel, so that’s why we’re combining facial expression analysis with other important physiological signals, which will ultimately lead to better mental health monitoring and support."