Researchers have designed a new type of ink that can be painted onto a patient’s scalp to allow measurement of brain activity, potentially replacing electrodes with long wires.
The current method for measuring brain activity - electroencephalography (EEG) – requires technicians to measure the patient’s scalp with rulers and pencils and mark over a dozen spots where they will glue on the electrodes connected to a machine.
“Our study can potentially revolutionize the way non-invasive brain-computer interface devices are designed,” Jose Millan of the University of Texas at Austin, who worked on the project, said in a statement.
With a computer algorithm, researchers identify the spots on the scalp for measuring brain activity. They used a digitally controlled inkjet printer to spray a thin layer of the ink onto those spots. Once dried, the ink works as a thin-film sensor, picking up brain activity through the scalp.
Electronic tattoos have already been used on hairless skin for measuring heart activities, but designing e-tattoos for hairy skin has been a persistent challenge, the researchers noted in a report published in Cell Biomaterials.
To overcome this, they designed an ink that can flow through hair to reach the scalp.
When the team printed e-tattoo electrodes onto the scalps of five short-haired volunteers and attached conventional electrodes next to the e-tattoos, the e-tattoos detected brainwaves as efficiently as the electrodes.
The e-tattoo electrodes showed stable connectivity for at least 24 hours, while gel used on the conventional electrodes started to dry out after six hours. Beyond six hours, over a third of the conventional electrodes were failing to pick up any signal, and most of the others had reduced contact with the skin, resulting in less accurate signal detection.
“The broader significance of this technology lies in its potential applications beyond traditional EEG use,” the researchers said in their report.
“On-scalp printed ultrathin e-tattoos could play a pivotal role in developing brain-computer interfaces for... prosthetics, virtual reality, and human-robot teaming,” they said.
