For over a decade, scientists have been working on electronic tattoos, or e-tattoos, which stick to the skin. These tattoos help measure heart activity, check for pneumonia, and gauge stress levels. But applying them on hairy skin has been tricky because they don’t work as well.

Researchers from The University of Texas at Austin and UCLA came up with a solution by looking at regular tattoos. They created a special ink that can print directly onto a patient’s scalp to measure brainwaves.

This e-tattoo acts as a sensor for electroencephalography (EEG). EEG can diagnose brain tumors, sleep issues, and other brain problems. Nanshu Lu, who leads the project, says the goal is to make EEG sensors that people can wear comfortably for a long time, even outside hospitals.

Current EEG gear includes caps with rigid or soft electrodes and lots of wires, which can take hours to set up and maintain. The new method involves using a camera to map the shape of a person’s head. Then, a computer algorithm designs the EEG sensors for that specific head, and a robot printer places the conductive ink. This printer shoots the ink through hair without touching the patient, though it works best with short hair.

The e-tattoo design is thin and barely noticeable, making it possible to wear under hats or helmets. This means longer, less invasive monitoring. The researchers will try to make the e-tattoo work on people with longer hair and to make the ink tougher. This would be crucial for monitoring conditions like epilepsy or sleep disorders in real-life settings.

Applications to brain-computer interfaces

The researchers have described the methods and results of their study in a paper published in Cell Biomaterials.

José del R. Millán, another key researcher, notes that these e-tattoos could change brain-computer interfaces (BCI), where people control devices using their thoughts. This could greatly help those with brain impairments. Millán has already used this tech for a wheelchair and a decision-making game controlled by the mind.

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