Triboelectric

The triboelectric effect, or triboelectrification, is a form of contact electrification in which electric charges are generated when two materials come into contact and are then separated. During contact, electrons may transfer from one material to the other depending on relative electron affinity, work function, and surface states. Upon separation, the materials retain opposite charges, resulting in one positively and the other negatively charged. The effect is especially pronounced for insulators and polymers, but can also occur with metals, though with different behavior.

The tendency of materials to gain or lose electrons is commonly summarized in a triboelectric series, which ranks materials by their propensity to become positively or negatively charged in a given pairing. The magnitude of the charge depends on material choice, surface roughness, contact area and pressure, duration of contact, and environmental conditions, notably humidity, which can dampen charging by increasing surface conduction and charge leakage. Temperature, contamination, and aging of surfaces can also influence results.

Applications include triboelectric nanogenerators (TENGs), which convert mechanical energy to electricity for self-powered sensors, wearables, and energy harvesting. The phenomenon is also relevant to static control, electrostatic precipitators, printing, and various manufacturing processes where charge buildup must be managed.

Measurement and safety: charges generated can produce high voltages with modest currents; voltages and surface potentials are characterized by standardized tests and surface charge density measurements. Practical use requires controlling environmental factors and material properties to optimize performance or minimize unwanted electrostatic discharge.