Stable and low-resistance polydopamine methacrylamide-polyacrylamide hydrogel for brain-computer interface

Signal drift and performance instability of brain-computer interface devices induced by the interface failure between rigid metal electrodes and soft human skin hinder the precise data acquisition of electroencephalogram (EEG). Thus, it is desirable to achieve a robust interface for brain-computer interface devices. Here, a kind of polydopamine methacrylamide-polyacrylamide (PDMA-PAAM) hydrogel is developed. To improve the adhesion, dopamine is introduced into the polyacrylamide hydrogel, through the amino and catechol groups of dopamine in an organic-inorganic interface to build a covalent and non-covalent interaction. A strong attachment and an effective modulus transition system can be formed between the metal electrodes and human skin, so that the peeling force between the PDMA-PAAM hydrogel and the porcine skin can reach 22 N m−1. In addition, the stable conductivity and long-term operating life of the PDMA-PAAM hydrogel for more than 60 days at room temperature are achieved by adding sodium chloride (NaCl) and glycerol, respectively. The PDMA-PAAM hydrogel membrane fabricated in this work is integrated onto a flexible Au electrode applied in a brain-computer interface. In comparison, the collected EEG signal intensity and waveform are consistent with that of the commercial counterparts. And obviously, the flexible electrode with PDMA-PAAM hydrogel membrane is demonstrated to enable a more stable and user-friendly interface.