As humans continue to advance in the field of medicine and brain research, their desire to obtain bioelectric signals also increases. However, in order to obtain such data in long periods of time from patients, material engineers had to design materials that fulfill some properties that make the process of gathering data from patients both safer and easier. When used, these materials must not be harmful to the skin, they must be wearable for long periods of time and be flexible, and lastly, they should not include any skin irritating substances.
It is very important for human-machine interfaces to be soft and stretchable. Nowadays one of the promising materials for mountable sensors like ECG electrodes is Hydrogel which is connected to a rigid metallic electrode for it to connect with electronic circuitry. However, this is not a very comfortable option for the patients especially during long periods of time. In order to design flexible electrodes researchers have combined hydrogen and liquid metal in order to make hydrogel itself conductive so that it can communicate with the circuitry. [1]
Another important property of long-term ECG electrodes is that they shouldn’t contain any skin irritating substances. To approach this issue researchers have designed biocompatible ECG electrodes using Coconut-Oil and Carbon Black. According to their article, after stretching the electrodes by 100% for 100 stretch/release cycles, it showed reliable results without the use of any skin irritating substances.[2]
Lastly, these electrodes must be designed in a way that patients won’t sweat, and they should be robust enough to fall during motion. To combat this problem, carbon nanotube-based Polydimethylsiloxane composite electrodes were designed. These sensors showed robust signal results during intense motion and sweat.[3]
[1] T. Shay, O. D. Velev, and M. D. Dickey, “Soft electrodes combining hydrogel and liquid metal,” Soft Matter, vol. 14, no. 17, pp. 3296–3303, May 2018, doi: 10.1039/C8SM00337H.
[2] L. A. Garcia-Garcia et al., “Soft Gel-free ECG electrodes based on Biocompatible Coconut-Oil and Carbon Black,” FLEPS 2021 - IEEE International Conference on Flexible and Printable Sensors and Systems, Jun. 2021, doi: 10.1109/FLEPS51544.2021.9469731.
[3] H. C. Jung et al., “CNT/PDMS composite flexible dry electrodesfor long-term ECG monitoring,” IEEE Transactions on Biomedical Engineering, vol. 59, no. 5, pp. 1472–1479, May 2012, doi: 10.1109/TBME.2012.2190288