中文摘要：

随着功能器件朝着小型化、低能耗方向的发展，开发出与之适应的电源成为一个亟需解决的问题．利用压电纳米线优越的力学性能与对微弱力具有高度敏感性的特点，纳米发电机可以将自然界或日常生活环境中的无规则机械能转化为电能，为功能器件供电问题提供了一个可能的解决方案．本文从纳米发电机的工作原理出发，探讨了直流纳米发电机、交流纳米发电机的工作机制，随后就柔性纳米发电机的研究现状做了简要的概述．

英文摘要：

Nowadays, miniaturization, functionalization and low power consumption are the developing directions of personal electronic devices because of the portable and implantable requirements. Developing an energy source with a comparable size to power the electronic devices is desirable and of great challenge. Piezoelectric nanowires based nanogenerators （NGs） can harvest tiny and irregular mechanical energy in the surroundings and turn them into electricity via piezoelectric effect. NGs can be used to power the functional devices. Since the invention of NG in 2006, it has developed quickly, until now it has been successfully combined with functional devices such as UV sensor, pH sensor and environmental monitoring sensor to form the self-powered systems. In this review, the piezoelectric NGs＇ working principle is described firstly. It focuses on the ferroelectric materials which do not have internal free carders. The static analysis gives a detailed working mechanism of the NG. The dynamic analysis gives the frequency dependence of the NG＇s output. Next, the working mechanism of the ZnO based NGs is discussed. Compared with the NGs fabricated by ferroelectric materials, the ZnO based NGs＇ working process is also affected by the ZnO＇s internal free carriers. According to whether the direction of the NG＇s output current is changed, ZnO NGs have been categorized into DC mode and AC mode. In the section of DC ZnO NG, the electron＇s transportation in the circuit is described in detail. The effect of the material＇s free carrier density and Schottky contact on the NG＇s output is analyzed. The working process of AC NG is described, subsequently. And its merits compared with the DC mode are also analyzed. Then, we review some typical papers about flexible NGs. The NGs have been categorized into fiber based woven NGs and composite based NGs. For each category, typical papers have been reviewed and each work＇s improvement and drawbacks has been analyzed. In addition, considering the development of the impla