Bio-inspired hydrogel with high ionic conductivity and tissue-like flexibility for bioelectronics

Bioelectronics are a crucial means for biomedical diagnosis and therapeutic, as they seamlessly interface with biological tissues. Biomaterials-based ionic hydrogels have been recognized as ideal electrode materials for bioelectronics. However, biomaterials-based ionic hydrogels suffer from low ionic conductivity and high Young's modulus, which limit their performance in electrophysiological monitoring. Here, we developed a biomaterials-based ionic hydrogel inspired by the ion channel receptor in neuron membranes, and this bio-inspired hydrogel (BIH) offers a high ionic conductivity and low Young's modulus simultaneously. By mimicking the ion-accelerating function of ion channel receptors in neuron membranes, the sulfonate groups and quaternary ammonium groups on zwitterionic side chains of poly(sulfobetaine methacrylate) (pSBMA) construct artificial ion channels to accelerate cation and anion transport in BIH, respectively. The brush-like polymer structure of the pSBMA reduce chain entanglement and substantially lower the Young's modulus of BIH. Compared with other reported biomaterials-based ionic hydrogels, the BIH simultaneously possesses higher ionic conductivity (7.04 S m-1) and lower Young's modulus (7.2 kPa). The BIH also has excellent interfacial adhesion with tissues resulting from electrostatic interactions. Owing to the high conductivity and low Young's modulus, the BIH has a lower interfacial impedance with tissues that that of commercial electrodes, and the good adhesive property of BIH ensures its interfacial stability with tissues when collecting electrophysiological signals. The BIH is capable of collecting high-quality both epidermal and in vivo electrophysiological signals, and the signal-to-noise ratio (SNR) of electrocardiogram (ECG) and electromyogram (EMG) signals are significantly higher than those of commercial electrodes. Such an BIH with biomimetic ion channels and low Young's modulus could provide new insights into the rational design of biomaterials-based ionic hydrogels for bioelectronics.