Triboelectrically-induced non-contact polypropylene/polyvinylidene fluoride sensor with low permittivity supporting layers affecting its interfacial charge dynamics.

This work presents a simple and low-cost approach to triboelectric sensing based on commercially available nonwoven polypropylene (PP) membranes paired with electrospun polyvinylidene fluoride (PVDF) to form a triboelectric nanogenerator (TENG), which is further utilized as a sensor operating predominantly in a non-contact regime. The initial contact electrification creates an interfacial charge state that is retained after contact, allowing subsequent separation changes to generate electrical signals via electrostatic induction without requiring continuous contact. The introduction low-permittivity sublayers (polyvinyl chloride (PVC), biaxially oriented polyethylene terephthalate (BOPET), and low-density polyethylene (LDPE)) beneath the tribonegative PVDF membrane significantly enhances the TENG's mechano-electric performance by modifying the electric field distribution in the multilayer dielectric structure. The PP/PVDF+LDPE layer achieves a peak open-circuit voltage of 689 V and a maximum power density of 5.46 mWcm⁻² in comparison to 376 V and 2.05 mWcm⁻², respectively, for PP/PVDF. This confirms that the dielectric permittivity of the supporting layer is a key parameter controlling the electrical output of the PP/PVDF triboelectric system. The device was validated under various pressure stimuli and vibrations demonstrating its ability to simultaneously sense motion and harvest energy.