Liquid Lubricants as Surface-Protective Interfaces for Triboelectric Nanogenerators: Mechanisms, Architectures, and Durability

초록

Long-term operation of triboelectric nanogenerators (TENGs) is limited by the repeated interfacial contact that is required for charge generation. In sliding, rotating, and fluttering modes, this contact gradually damages the triboelectric interface through wear, material transfer, debris formation, and local electrical dis charge. These changes reduce the effective charge density and destabilize the output. Liquid lubrication has recently emerged as an interface-engineering strategy that can protect triboelectric surfaces without necessarily sacrificing energy conversion. This review examines liquid lubricants as multifunctional interfacial layers for TENGs, with particular attention to mechanical protection, output stabilization, and charge regulation. The reviewed studies are discussed according to the manner in which the liquid is introduced and maintained at the interface; these include direct oil addition; immersion of devices; use of porous oil-storage structures, nano-oil barriers, and liquid-superlubric contacts; and solvent-assisted running-in. These studies show that a controlled liq uid layer can reduce interfacial shear, inhibit polymer transfer, fill air-containing microgaps, and suppress break down-induced charge loss. In some designs, the liquid also participates in charge transmission, indicating that it can serve as an active component rather than a passive separator. Effective design therefore requires a liquid layer that is thin, stable, insulating, and compatible with both the triboelectric materials and the operating mode. Remaining challenges include leakage control, film-thickness optimization, environmental stability, durability evaluation, and predictive modeling of coupled tribological and electrical processes. This review provides a focused perspective for developing durable TENGs based on liquid-managed interfaces.

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