In a vertical contact-separation TENG, what determines the magnitude of the generated voltage?

In a vertical contact-separation Triboelectric Nanogenerator (TENG), the magnitude of the generated voltage is primarily determined by the amount of charge transferred between the triboelectric materials and the capacitance of the device. The voltage (V) is related to the charge (Q) and capacitance (C) by the equation V = Q/C. When two materials come into contact, charge is transferred based on their triboelectric properties. The amount of charge transferred (Q) depends on several factors, including the difference in their work functions, the contact area, the contact pressure, and the surface properties of the materials. The capacitance (C) of the TENG is determined by the geometry of the device, particularly the distance between the electrodes and the dielectric constant of the materials separating them. As the distance between the electrodes increases during the separation phase, the capacitance decreases. Since the charge (Q) remains relatively constant immediately after separation, the voltage (V) increases according to the V = Q/C relationship. The maximum voltage is reached when the separation distance is at its maximum, and the capacitance is at its minimum. Therefore, the magnitude of the generated voltage is directly proportional to the amount of transferred charge and inversely proportional to the capacitance of the TENG. For example, using materials with high triboelectric charge density and minimizing the separation distance (thereby maximizing capacitance when in contact) helps to maximize the output voltage.