Electronic tattoos could help measure stress
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Researchers at The University of Texas at Austin and Texas A&M University have used e-tattoos to detect electrodermal activity and measure patients' emotional stress levels.
Electronic tattoo (e-tattoo) technology could be the key to tracking a natural body response which makes the palms of someone's hands wet when they are excited or nervous, and helping people that suffer from mental health conditions.
Although this bodily response - called electrodermal activity - has been known for a long time, devices used to track it have traditionally been bulky, unreliable and highly visible, which perpetuates social stigma.
Instead, the team at the University of Texas at Austin and Texas A&M University have created a graphene-based e-tattoo for electrodermal activity (EDA sensing) that is nearly invisible. The new device attaches to the palm of the hand and connects to a smartwatch.
"It's so unobstructive that people sometimes forget they had them on, and it also reduces the social stigma of wearing these devices in such prominent places on the body," said Nanshu Lu, professor in the Department of Aerospace Engineering and Engineering Mechanics and leader of the project.
Lu and her collaborators have been advancing wearable e-tattoo technology for many years. In this journey, graphene has been a favourite material because of how thin it is and how well it measures electrical potential from the human body, leading to very accurate readings.
However, such ultra-thin materials can't handle much, if any strain, making the process of applying them to parts of the body that include a lot of movement, such as the palm or wrist, quite challenging. Eventually, e-tattoo technology proved to be the puzzle's missing piece.
Another key aspect of the research is the process by which the e-tattoo on the palm is able to successfully transfer data to a rigid circuit - in this case, a commercially available smartwatch - in out-of-lab, ambulatory settings.
To achieve this, the team used a serpentine ribbon that has two layers of graphene and gold partially overlapped. By snaking the ribbon back and forth, it can handle the strain that comes with movements of the hand for everyday activities like holding the steering wheel while driving, opening doors, running etc.
In the past, other researchers have tried similar methods using nanometre-thick straight-line ribbons to connect the tattoo to a reader, but these were not able to handle the strain of constant movement.
Lu said the researchers were inspired by virtual reality (VR), gaming and the incoming metaverse for this research. VR is used in some cases to treat mental illness; however, the human-aware capability in VR remains lacking in many ways.
"You want to know whether people are responding to this treatment," Lu said. "Is it helping them? Right now, that's hard to tell."
Lu's team is not the only one that has utilised e-tattoo technology for health-related applications. Last year, scientists in Germany developed an implantable sensor made of gold nanoparticles that could reveal concentration changes of substances in the body.
In California, engineers designed a flexible alcohol-detecting wearable sensor that accurately measures blood alcohol levels from sweat and transmitted the data wirelessly to a smartphone app.
The scientists' research was recently published in the journal Nature Communications.
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