A temporary scalp tattoo can be used to record brain activity

Brainwave analysis could be made easier by printing a temporary tattoo on a person’s head.

Electroencephalography (EEG) is a method of measuring electrical activity in the brain using electrodes placed on the scalp. It can be used to test patients for neurological disorders such as epilepsy, tumors, or injuries from stroke or traumatic impacts to the head.

Because people’s skulls vary in size and shape, technicians must spend a lot of time measuring and marking the scalp to obtain accurate readings. A gel helps the electrodes detect brain signals, but stops working properly when it dries. The cables connected to the electrodes can also cause discomfort and interfere with subtle electrical signals.

Nanshu Lu from the University of Texas at Austin and her team want to avoid these problems by printing a temporary tattoo on the subject’s scalp. The ink for the tattoo is made of two polymers called poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonate (PSS). It is highly conductive and durable and does not irritate the skin.

A computer program creates a personalized design of the tattoo based on a 3D scan of the scalp. A printer controlled by a robotic arm then applies the ink directly to the scalp. There are two different formulations of the ink: one for the electrodes that pick up brain signals and one for connections that run to the back of the neck. From there, the signals are transmitted over physical lines to a small device that records the data.

“Our technology embodies the first hair-compatible temporary e-tattoo that enables high-quality brain monitoring,” says Lu.

The tattoo has been shown to work well on people who are bald and have short hairstyles. “While the method has not yet been extensively tested on long, thick, curly hair, modified nozzle designs or the incorporation of robotic fingers for hair parting could make it feasible in the future,” she says. Data transmitters embedded in the tattoos could also make the process completely wireless, according to the team.