Surface tribocharge and surface potential measurements

The tribocharge on the surface polymers (5 cm × 5 cm) was measured after each sliding experiment using a homemade Faraday cup that is connected to an electrometer (Keithley Instruments model 6514). Data acquisition was performed with LabVIEW code, and tribocharge densities were reported in nC/cm2. During measurements, an antistatic wristband was used to ground the sample holding tweezers. Surface potential measurements were done using an electrostatic voltmeter (TREK model 370), with a macroscopic Kelvin probe (3800E-2 end view) attached.