**2.2 Lateral-sliding mode**

The basic structure of TENG in this model is the same as that of the vertical contact-separation mode. The difference is from the motion mode of the top electrode (**Figure 1b**). In the original state, the top electrode and dielectric film fully overlap and intimately contact with each other, leading to the oppositely charged surfaces. With the top electrode sliding outward, the contact surface area will decrease gradually until the complete separation of the two surfaces. The separated surface creates a potential difference across the two electrodes, generating a current flow from the top electrode to the bottom electrode. When it slides backward, then there will be a reversed current flow to balance the potential difference [23, 24].
