Degradable skin electrodes made of carboxylated chitosan and sulfobetaine methacrylate

Wearable electrodes, which are used to measure a variety of bodily functions, generate electronic waste and, in the case of implants, require extensive removal. The presented study introduces a fully decomposable material mixture with chitosan that can withstand exercise and sweat even under high physical stress.

A network of carboxylated chitosan, sulfobetaine methacrylate, glycerol and water is suitable as a decomposable, antibacterial electrode material

Ye, G., Song, D., Song, J., Zhao, Y., Liu, N., A Fully Biodegradable and Biocompatible Ionotronic Skin for Transient Electronics. Adv. Funct. Mater. 2023, 2303990. https://doi.org/10.1002/adfm.202303990

From traditional medical applications such as EEG, ECG and EMG, which measure brain, heart and muscle activity, to emerging uses such as fitness watches and robot control, body or skin electrodes are popular for many purposes. However, typical silver chloride electrodes generate a lot of electronic waste. Electrodes that degrade under mild conditions would thus prevent the waste from being generated. They also have another major advantage. For some measurements, it is necessary to implant electrodes and then remove them again at great expense. With decomposable materials, this secondary operation would be unnecessary, minimizing costs and risks. In the presented study, a network of biopolymers, whose biocompatibility and decomposability are already known from previous publications, was used. Electrical conductivity was given mainly by the polyelectrolytic sulfobetaine methacrylate or SBMA, while chitosan mainly served for the cohesion of the electrode and to imbue it with its antibacterial properties. Here, carboxylated chitosan with a deacetylation degree of over 99% was used. You can also find a variety of chitosan derivatives in our online shop. The mixture of substances is mainly held together by hydrogen bonds between chitosan and electrostatic attractive forces between SBMA, while glycerol and water serve as hydrogen bonding sites.

Results

• Degradation in phosphate-buffered saline solution at room temperature in three days
• stable in contact with air for more than three months
• antibacterial and high cell compatibility
• movement and sweat hardly restrict functionality
• comparable to or better results than conventional silver chloride electrodes
• Adheres well to skin

Conclusion: Chitosan can be used in degradable body electrodes and help reduce e-waste and eliminate the need for secondary operations to remove electrodes.

Link to article: https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.202303990