Palm e-Tattoo can recognize when you are under stress

Abstract: A newly developed “e-tattoo” monitors electrodermal activity, detecting when a person is experiencing elevated levels of stress. The “tattoo” is attached to the user’s palm and connected to the smart watch.

Source: UT Austin

Our palms tell us a lot about our emotional state, they tend to get wet when people are excited or nervous. This response is used to measure emotional stress and help people with mental health problems, but devices that do this are now bulky, unreliable and can perpetuate social stigma by affixing highly visible sensors to prominent parts of the body.

Researchers at the University of Texas at Austin and Texas A&M University have applied new electronic tattoo (e-tattoo) technology to this type of tracking, known as an electrodermal activity or EDA sensor.

In a new paper published recently in Nature Communicationsresearchers have created a graphene-based e-tattoo that attaches to the palm of the hand, is nearly invisible, and connects to a smartwatch.

“It’s so unobtrusive that people sometimes forget they’re wearing it, and it also reduces the social stigma of wearing these devices in such prominent places on the body,” said Nanshu Lu, a professor in the Department of Aerospace Engineering and Engineering Mechanics and project leader.

Lu and her colleagues have been advancing wearable e-tattoo technology for years. Graphene has been a favored material because of how thin it is and how well it measures the electrical potential of the human body, leading to very accurate readings.

But such ultra-thin materials cannot handle much, if any, strain. This makes applying them to parts of the body that involve a lot of movement, such as the palm/wrist, challenging.

The secret sauce of this discovery is how an e-tattoo on the palm can successfully transmit data to a rigid circuit – in this case, a commercially available smartwatch, in a non-laboratory, ambulatory setting. They used a serpentine ribbon that has two partially overlapping layers of graphene and gold.

By moving the band back and forth, it can handle the effort that comes with arm movements for everyday activities like holding the steering wheel while driving, opening doors, running, etc.

Current palm tracking technology uses bulky electrodes that fall off and are highly visible or EDA sensors that are placed on other parts of the body, giving less accurate readings.

Other researchers tried similar methods using nanometer-thick ribbons with a straight line to connect the tattoo to the reader, but they couldn’t handle the strain of constant motion.

Lu said that the researchers for this research were inspired by virtual reality (VR), games and the upcoming metaverse. VR is used in some cases to treat mental illness; however, the ability to be aware of people in VR is still lacking in many ways.

“You want to know if people are responding to this treatment,” Lu said. “Does it help them? It’s hard to say at the moment.”

About this neurotechnology research news

Author: Press office
Source: UT Austin
Contact: Press Office – UT Austin
Picture: Image credited to UT Austin

Original research: Open access.
“Graphene e-tattoos for smooth ambulatory detection of electrodermal activity on the palm enabled by heterogeneous serpentine ribbons” Hongwoo Jang et al. Nature Communications

---

Abstract

Graphene e-tattoos for smooth ambulatory detection of electrodermal activity on the palm enabled by heterogeneous serpentine ribbons

Electrodermal activity (EDA) is a popular indicator of mental stress. High-end EDA sensors suffer from palm obstruction or low signal fidelity outside the palm. Our previous invention of submicron thin imperceptible graphene e-tattoos (GET) is ideal for seamless palm EDA sensing.

However, a robust electrical connection between ultrathin devices and rigid printed circuit boards is a long-missing component for ambulatory use.

To reduce the well-known stress concentration at their interfaces, we propose heterogeneous serpentine ribbons (HSPR), which refer to GET serpentine partially overlapping with gold serpentine without added adhesive.

A fifty-fold reduction in stress in HSPR compared to heterogeneous straight ribbons (HSTR) was discovered and understood. The combination of HSPR and a soft interface between the GET and the EDA wristband enabled ambulatory EDA monitoring on the palm in free-living conditions.

A newly developed EDA event selection policy exploiting unbiased phase event selection validated our GET EDA sensor against gold standards.