An injectable, self-healable, and reusable PEDOT:PSS/PVA hydrogel patch electrode for epidermal electronics

Injectability empowers conductive hydrogels to transcend traditional limitations, unlocking a realm of possibilities for innovative medical, wearable, and therapeutic applications that can significantly enhance patient care and quality of life. Here, we report an injectable, self-healable, and reusable hydrogel obtained by mixing the concentrated poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) suspension (~ 2 wt.% solid content), polyvinyl alcohol (PVA), and borax. Leveraging the presence of reversible borax/hydroxyl bonds and multiple hydrogen bonds, this PEDOT:PSS/PVA hydrogel exhibits notable shear-thinning behavior and self-healing capabilities, enabling it to be injected as a gel fiber from a syringe. As-prepared injectable hydrogel also demonstrates an ultra-low modulus (~ 2.5 MPa), reduced on-skin impedance (~ 45% of commercial electrodes), and high signal-to-noise ratio (SNR) (~ 15–22 dB) in recording of electrocardiography (ECG), electromyography (EMG), and electroencephalogram (EEG) signals. Furthermore, the injectable hydrogels can be remolded and reinjected as the reusable electrodes, maintaining nearly identical electrophysiological recording capabilities and brain–computer interface (BCI) performance compared to commercial wet electrodes. With their straightforward fabrication, excellent material properties and electronic performance, ease of cleaning, and remarkable reusability, our injectable PEDOT:PSS/PVA hydrogels hold promise for advancements in BCI based electronics and wearable bioelectronics.