Summary: A recently developed “electronic tattoo” monitors electrodermal activity, revealing when a person is experiencing elevated levels of stress. The “tattoo” is attached to the palm of the user’s hand and connected to a smart watch.
Font: Austin Autonomous University
Our palms tell us a lot about our emotional state, tending to get wet when people are excited or nervous. This reaction is used to measure emotional stress and help people with mental health problems, but the devices to do so are now bulky, unreliable and can perpetuate social stigma by placing highly visible sensors on prominent parts of the body.
Researchers at the University of Texas at Austin and Texas A&M University have applied emerging electronic tattooing (e-tattoo) technology to this type of monitoring, known as electrodermal activity or EDA sensing.
In a new article recently published in nature communicationsResearchers created a graphene-based electronic tattoo that sticks to the palm of the hand, is nearly invisible, and connects to a smartwatch.
“It’s so discreet that people sometimes forget they were 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 Mechanical Engineering and leader of the Project.
Lu and his collaborators have been advancing portable electronic tattoo technology for many years. Graphene has long been a favorite material because of how thin it is and how well it measures the electrical potential of the human body, leading to highly accurate readings.
But these ultra-thin materials can’t withstand much stress, if any. That makes applying them to parts of the body that involve a lot of movement, like the palm of the hand or the wrist, a challenge.
The secret ingredient in this discovery is how the electronic palm tattoo can successfully transfer data to a rigid circuit, in this case, a commercially available smartwatch, in ambulatory settings outside of the laboratory. They used a serpentine ribbon that has two partially overlapping layers of graphene and gold.
By snaking the tape back and forth, you can manage the strain that comes with hand movements for everyday activities like holding the steering wheel while driving, opening doors, running, etc.
Current palm monitoring technology uses bulky electrodes that fall off and are highly visible, or EDA sensors applied to other parts of the body, giving a less accurate reading.
Other researchers have tried similar methods using nanometer-thick straight-line ribbons to connect the tattoo to a reader, but they couldn’t withstand the stress of constant movement.
Lu said the researchers drew inspiration from virtual reality (VR), gaming, and the incoming metaverse for this research. VR is used in some cases to treat mental illness; however, human capability in VR is still lacking in many ways.
“You want to know if people are responding to this treatment,” Lu said. “Are you helping them? Right now, that’s hard to say.”
About this neurotechnology research news
original research: Open access.
“Electronic graphene tattoos for detection of non-obstructive ambulatory electrodermal activity in the palm enabled by heterogeneous serpentine ribbons” by Hongwoo Jang et al. nature communications
Electronic graphene tattoos for detection of non-obstructive ambulatory electrodermal activity in the palm enabled by heterogeneous serpentine ribbons
Electrodermal activity (EDA) is a popular index of mental stress. State-of-the-art EDA sensors present obstruction in the palm of the hand or poor signal fidelity outside the palm. Our previous invention of imperceptible graphene electronic tattoos (GET) with a submicron thickness is ideal for unobstructed EDA detection in the palm of the hand.
However, the robust electrical connection between ultrathin devices and rigid circuit boards is a long-missing component for outpatient use.
To minimize the known stress concentration at their interfaces, we propose Heterogeneous Serpentine Tapes (HSPR), which refers to a GET streamer partially overlapping a gold streamer with no added adhesive.
A fifty-fold stress reduction in HSPR versus heterogeneous straight ribbons (HSTR) has been discovered and understood. The combination of HSPR and a soft interlayer between the GET and an EDA wristband allowed ambulatory EDA monitoring in the palm of the hand under free-living conditions.
A newly developed EDA event selection policy leveraging unbiased phasic event selection validated our GET EDA sensor against gold standards.