Hysteretic behavior of contact force response in triboelectric nanogenerator

The hysteretic behavior of contact force response in a triboelectric nanogenerator is analyzed as the output performance in response to the applied contact force is found to be dependent on previous contact force history. The counterclockwise hysteresis curve of the contact force versus output power originates from the asymmetric time constant between triboelectric charging and natural discharging, because the charges due to contact electrification do not immediately disappear but gradually decay over a period of hours. Therefore, a low contact force followed immediately after a high contact force results in enhanced output performance but not the reverse order. However, if the intermission time becomes too long, the benefit due to charge balance gets degraded. The experimental results on sweep range and discharging time dependencies agree well with theoretical expectations.