An electroencephalography (EEG) is a non-invasive exam that records electrical activity in the brain. Brain cells communicate through electrical impulses. An EEG records the brain’s electrical behavior, which can then be used to detect any abnormalities in the brain that may result from brain tumors, disease, injuries, etc. It is often used to diagnose sleep disorders, epilepsy, and brain injuries.
The exam uses small metal discs called electrodes that are attached to the scalp using a wet gel. While the exam is widely used, there are some challenges faced with its current setup.
For one, a general standard is that each electrode must be placed anywhere from 10 to 20 percent of the skull’s distance away from each other. While EEG caps — caps with suggested electrode placement — can eliminate some of the issues that arise with imprecise electrode placement, head shapes vary from individual to individual, thus leading to further misplacement. Here is where EEG technicians come to the rescue, as they are trained to manually mark electrode positions on a patient’s head before adding the wet-gel to the scalp, attaching the electrodes, and finally connecting the cables. While EEG technicians help, the process can be time-consuming and is susceptible to human error.
Issues don’t stop there, as once electrodes and cables are attached to the patient, the patient’s movements are drastically restricted to prevent electrode detachment. Even if a patient restricts their movements for the duration of the exam, the wet-gel used to attach electrodes to the scalp can dry and thus lose its conductivity.
When diagnosing epilepsy, an EEG test may run anywhere from hours to days. If electrodes are to be used for prolonged periods of time, an adhesive paste or collodion glue is used instead of the wet-gel, but requires periodic maintenance.
But new EEG e-tattoos can eliminate some of these downsides. These new e-tattoos will provide on-scalp digital printing that can eliminate manual inconsistencies in the installation of electrodes, which is achieved through the 3-D scanning of an individual’s head and a 5-axis microjet printing robot.
A conductive polymer biocompatible ink for bio-interfacing was developed. The ink is jetted through the hair where it dries and converts into a stretchable, soft film. This ink prints out disc-shaped circles on the scalp and then draws curved lines from these discs to the base of the skull where cables would then be attached.
The e-tattoos, upon testing, demonstrated good skin adhesion, breathability, and stability against sweat and oxidation. Additionally, e-tattoos last longer on the skin than traditional electrodes. They might even be able to provide better EEG exams for individuals with curly hair, a hair type on which electrodes don’t always stick well. But don’t worry, these tattoos aren’t permanent and can be removed with soapy water.
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