Kinetics of nanoscale probe-based contact electrification between metal and polymethyl methacrylate under bias

Abstract

Contact electrification (CE) has the potential to be a renewable energy resource, because it converts mechanical energy to electrical energy. The kinetics of probe-based CE between metal and polymeric slab was studied by scanning probe microscopy. The CE static charges were produced on polymethyl methacrylate (PMMA) films by a Pt-coated probe under a bias (VB) and characterized by electrostatic force microscopy. The metal/PMMA CE was attributed to the charge transfer between the Fermi level of the metal (Ef) and the neutral level of the surface states of PMMA (En). The kinetics of the probe-based metal/PMMA CE was described by a saturating exponential function and the saturated charge QS was proportional to the net bias, VB − Vnull, where the nulling bias Vnull = −(En − Ef)/e. The kinetics was regarded as the charging to a conductor–capacitor series circuit. QS established a potential to cancel the net bias and ceased the CE. CE was a reversible process, and its transmission coefficient was asymmetric with the polarity of bias because of the heterogeneous nature of the metal/polymer contact.