Ionic hydrogels-based triboelectric nanogenerators for self-powered human-machine interfaces

Ionic hydrogels outperform existing rigid and bulky electronics with many remarkable advantages including great flexibility, high conductivity, exceptional biocompatibility, and transparency, making them ideal materials for wearable human-machine interfaces (HMIs). However, traditional HMIs typically rely on external power sources, which impose limitations in terms of device size and weight, thereby compromising the user experience in HMIs. The advent of triboelectric nanogenerators (TENGs) employing ionic hydrogels has introduced a sustainable energy solution for self-powered HMIs. These TENGs can harvest the electrical energy resulting from the migration of ions induced by mechanical motion, thereby offering a sustainable energy solution for applications in wearable HMIs. Hence, the development of ionic hydrogels-based TENGs holds immense potential for the advancement of self-powered HMIs. This review first introduces the latest achievements in the fabrication of ionic hydrogel-based TENGs using diverse materials, including synthetic polymers, natural polymers, and low-dimensional materials. Then different working principles and modes of the ionic hydrogel-based TENGs are elucidated. Subsequently, the applications of these TENGs in self-powered HMIs are discussed, such as robot control, medical applications, electronic device control, and other applications. Finally, the current status and future prospects of ionic hydrogel-based TENGs in self-powered HMIs are summarized. We hope that this review will provide inspiration for the future development of self-powered human-machine interfaces utilizing ionic hydrogels-based TENGs.