A Hairy Situation

The function of the human brain may still be poorly understood, but it is no longer a complete mystery. Thanks to technological innovations like electroencephalography (EEG), we can take a glimpse at the patterns of electrical signals that fire throughout this most complex of organs. This electrical activity gives us important insights into how the brain works, and can even be useful in diagnosing neurological conditions and sleep disorders. A number of research efforts have further shown that these signals can be leveraged to control computers and other electronic devices with our minds.

This may sound like science fiction, but these types of applications are actively under development and are progressing rapidly. But once we do have the ability to accurately decipher the brain’s electrical activity, another hurdle will still stand in the way of the wide availability of such technologies — a practical sensing system. Traditional EEG electrodes must be glued to the skin, and that skin must be free of hair for effective sensing. Interested in controlling your computer with your thoughts? Great! Remember to shave your head perfectly smooth every morning.

Needless to say, some people would rather keep their hair than scroll through their social media feeds with their thoughts. Recognizing that a more practical solution is needed, a team led by researchers at The University of Texas at Austin has developed an innovative solution. They have developed a method that does away with traditional electrodes and is instead printed onto the head. It still may not be for everyone, but if you happen to have short hair, it will not hinder the system’s sensing performance.

The liquid ink used in this approach, composed of conductive polymers, flows through hair and dries into a thin, flexible film that functions as an electronic sensor, or "e-tattoo." Using a computer algorithm, researchers can design precise electrode placement for an EEG and apply the ink with a high-speed inkjet printer, ensuring a quick, contactless, and comfortable process.

The e-tattoo system has proven to be effective in human trials, where it was tested against conventional EEG electrodes. It demonstrated superior stability, maintaining signal quality for at least 24 hours, while traditional electrodes began to fail after six hours due to drying gel. Furthermore, the ink’s formula can be modified to create conductive lines that run down the back of the neck, replacing standard EEG wires while reducing interference and allowing for a more compact data collection setup. Future iterations aim to integrate wireless data transmission into the e-tattoos, potentially enabling entirely wire-free EEG monitoring.

Further work is needed on this platform before it is ready for real-world use. Those with long, flowing locks or unusually thick hair will find that the performance of the electrodes is significantly degraded. Better methods of adhesion are also needed in some cases, especially for sleep studies where the electrodes are likely to experience a lot of abrasion. But if the researchers can overcome issues such as these, biological research and human-computer interfaces could benefit greatly.