Progressive contact-separate triboelectric nanogenerator based on conductive polyurethane foam regulated with a Bennet doubler conditioning circuit

Scavenging the energy of human motions has attracted widespread attentions with the development of wearable electronics. This paper for the first time proposed a progressive triboelectric nanogenerator based on macro-triangle-prism-shaped conductive polyurethane (PU) foam and polytetrafluoroethylene (PTFE) film, which occupy the top and bottom spots of the triboelectric table respectively. The proposed macro-structured conductive PU foam also integrates the functions of spring, spacer and electrode. Thanks to the innovative structures and chosen of the materials, an extended current pulse width is obtained. A maximum RMS power density of 100 nJ/cm2/tap was obtained with a 60 MΩ resistive load and press force of 10 N@5 Hz. By regulating the TENG with a Bennet doubler conditioning circuit, the ubiquitous voltage saturation phenomenon when charging a storage capacitor using full-wave rectifiers is avoided. Moreover, the energy per cycle, charging efficiency and totally stored energy can be exponentially pumped up. With a Bennet circuit charging a 5 nF capacitor, a harvested energy density of ~ 710 nJ/cm2/tap was obtained when voltage across the capacitor was 400 V. Putting the device under sole within 25 human steps, the totally stored energy was 0.43 mJ with a Bennet circuit, 3.6 times higher than that using a full-wave rectifier (0.12 mJ). The Bennet was proven better for regulating the triboelectric nanogenerators with long operation-time compared to the classical full-wave rectifier.