The sliding mode triboelectric nanogenerator (S-TENG) is an effective technology for in-plane low-frequency mechanical energy harvesting. However, as surface modification of tribo-materials and charge excitation strategies are not well applicable for this mode, output performance promotion of S-TENG has no breakthrough recently. Herein, we propose a new strategy by designing shielding layer and alternative blank-tribo-area enabled charge space-accumulation (CSA) for enormously improving the charge density of S-TENG. It is found that the shielding layer prevents the air breakdown on the interface of tribo-layers effectively and the blank-tribo-area with charge dissipation on its surface of tribo-material promotes charge accumulation. The charge space-accumulation mechanism is analyzed theoretically and verified by experiments. The charge density of CSA-S-TENG achieves a 2.3 fold enhancement (1.63 mC m−2) of normal S-TENG in ambient conditions. This work provides a deep understanding of the working mechanism of S-TENG and an effective strategy for promoting its output performance.

Although graphene oxide (GO) has been reported to be able to be edge functionalized or basal-plane functionalized separately, no research has been done on comparing both the molecular structure and interfacial properties of them. In this study, an alkyl amine was grafted to the epoxy group on the basal planes of GO (b-GO) and carboxyl group at the edges of GO (e-GO) separately by using different synthetic approach. With the combination of various molecular structure and morphology characterization methodologies, we proved that the reaction site for e-GO was only with the carboxyl group at the edge of GO and that for b-GO was epoxy group on the basal plane of GO, indicating that GO could be controllably functionalized (fGOs), and the structure of fGOs could be tuned. Study of the interfacial behavior of fGOs at liquid−liquid interface showed that the interfacial tension reducing capability of e-GO was broader than that of b-GO, and for alkyl oil phase, b-GO was slightly better than e-GO, and both were better than traditional nonionic surfactant. Study of the interfacial behavior of fGOs at liquid−solid interface demonstrated that, after absorption, b-GO arranged vertically on the metal surface, forming dense, compact, and strong film, while e-GO aligned horizontally to form loosely assembled film, resulting in higher interfacial shear strength than that of b-GO. Our results indicate the possibilities for tuning the interfacial properties of GO at both liquid−liquid and liquid−solid interfaces, which may be promising in the potential applications in controlled drug delivery, surface protection, absorption and separation, lubrication, nanocomposite, and catalyst fields.

No abstract

The capability of devices in future ubiquitous networked wearable and implantable electronics to efficiently scavenge and store operational power from their working environment through sustainable pathways would enable viable self‐powering schemes in societally‐pervasive applications such as advanced healthcare and robotics. Triboelectric nanogenerators (TENGs) can efficiently harvest the ubiquitous mechanical energy for powering electronics and sensors. However, the majority of demonstrated TENG prototypes have been built with materials that are not biodegradable or biocompatible, which significantly hinders the application of TENGs for wearable and implantable technologies. In this review, the recent progress of the wearable and implantable triboelectric devices built with bio‐derived natural materials is summarized. The properties of these natural biopolymers are discussed in the context of self‐powered triboelectric applications. The common manufacturing methods for processing these materials into triboelectric devices are also discussed. In addition, the applications of the bio‐derived natural materials based TENGs for in vitro and in vivo applications are discussed. Finally, the outstanding challenges and potential opportunities for the development of bio‐derived natural materials based triboelectric devices targeting wearable and implantable human‐integrated applications are analyzed.