Electroencephalogram (EEG) monitoring has been around since the 1920s and is widely used by researchers and medical practitioners alike. However, the standard technology is outdated and can be burdensome on the patient with unprecise recordings. UT Austin Biomedical Engineering researchers aim to change that with innovative research to improve EEG technology for sleep monitoring.

Their paper, published in the journal Device, details how their findings are breaking barriers and setting a new standard for brainwave recording.

What is EEG and why it is important

EEG is a technique used to record electrical activity in the brain over a finite period of time that can range from several minutes, hours, and even days. The ability to detect abnormal brainwave patterns contributes significantly to the understanding and diagnosis of sleep patterns and neurological disorders.

Recent EEG technology advancements provide portable and wireless EEG devices, making it easier to record brainwave activity in various settings and at any time. High-quality and continuous EEG monitoring is optimal for sleep research, sleep monitoring, as well as the evaluation and treatment of sleep disorders.

How EEG can be improved

Existing, continuous EEG monitoring technology suffers from fragile connections, long-term stability, and a complex process to apply the electrodes to patients for monitoring outside of the clinical setting.

The electrodes are commonly adhered using an ether-based glue that requires a solvent such as acetone to be removed—making the process unpleasant for the patient. Additionally, the signal quality from the electrodes degrades over time as the gel dries out due to fragile connections between the conductive gel and the recording technology. Lastly, hair, dirt and other elements can obstruct a proper recording.

Researchers in the UT Austin Department of Biomedical Engineering, including graduate student Leon Hsieh of the Wang Lab, are using hydrogel electrodes where hair impedance is inconsequential and ether-based glue is a matter of the past.

About the technology

High-performance conductive hydrogels are an encouraging potential for long-term EEG applications due to their ability to penetrate through hair, strong adhesion to the surface area, excellent conformability to the skin, and stable recording over long periods of time.

As an added bonus, when used as pre-formed electrodes, the hydrogels bypass several of the complications that come with traditional EEG adhesive gels. Moreover, the preformed hydrogels are convenient for healthcare providers and patients as they do not require complex preparation prior to use.

Nonetheless, the pre-formed structural features of the hydrogels vastly limit their capability to conform to the geometry of the hairy scalp. However, when the hydrogel electrodes are formed on-site, they can be tailored for the specific patient and provide all of the aforementioned benefits that pre-formed, traditional electrodes lack. Simultaneously, due to the nature of liquid-state hydrogel precursors, it can be challenging to precisely control the shape and size of the hydrogel for high resolution applications.

According to previous research, it remains challenging to simultaneously achieve high-quality recordings, prolonged stability, strong adhesiveness, and hassle-free preparation with on-site formed hydrogel electrodes.

About the new research     

UT Austin Biomedical Engineering researchers focused on using hydrogel electrodes for EEG recording during sleep. The team designed a room-temperature spontaneous gelation on-site formed hydrogel electrode to address the aforementioned challenges in long-term EEG recordings. Because of the softness and the rapid spontaneous gelation nature, the hydrogel precursor can be loaded into a syringe to be applied to a hairy region of the scalp and remain adhered for an extended length of time.

The team performed overnight sleep EEG monitoring and demonstrated the electrode’s stability for more than 8 hours with a higher signal-to-noise ratio than the commercial EEG gel electrodes—indicating a stronger, clearer recording of brain wave activity. Additional study results demonstrated the effectiveness of their hydrogel electrode during prolonged EEG monitoring periods—enhancing its potential for extended use outside of the clinical setting.

Researchers compared the hydrogel electrode developed at UT Austin with seven other hydrogel-based electrodes for long-term EEG recordings. They discovered that the electrode developed at UT is the first reported electrode to successfully achieve minimal on-skin impedance, high on-skin adhesiveness, long-term stability, and a high-quality signal with a hassle-free preparation.

To boot, the hydrogel electrode withstood a tension test to indicate its capability to withstand any pulling that may occur from the electrode adhered to the scalp or connected recording devices.

Future research applications

Researchers foresee their hydrogel electrode having potential beyond sleep monitoring. They expect the technology to one day be used for home-use, long-term wearable EEG monitoring and treatment applications extended from the closed-loop monitoring and stimulation systems. This will broaden neuroscience research as well as the detection and diagnosis of neurological disorders such as epilepsy or Parkinson’s Disease.

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Stable Electrodes for Long-Term, Wearable Brain-Machine Interface