Triboelectric Energy-Harvesting Floor Tile

Abstract

The aim of this study was to investigate the real-world electrical parameters that strongly affected the performance of a triboelectric energy-harvesting floor tile design: triboelectric material thickness, cover plate displacement distance or gap width, and cover plate pressing frequency, so that real-world specifications of the harvesting floor tile can be accurately specified. The structure of the designed triboelectric energy harvester, with readily available polytetrafluoroethylene (PTFE) film and aluminum foil, was simple and hence easy to fabricate, and the material cost was low. A square wave was used to simulate the pressing frequency on the test bench's cover plate. The results showed that the voltage and current were proportional to the gap width, and the thinner the triboelectric layer thickness, the higher the output voltage and current. A test bench with a 0.2 mm thick PTFE triboelectric layer generated the highest energy output. In a later experiment, a triboelectric energy-harvesting floor tile (TEHFT) prototype was constructed with 0.1 and 0.2 mm thick PTFE layers. We found that at 2 Hz stepping frequency and 0.1 mm PTFE thickness, the optimal load and cumulative energy of the TEHFT were 0.8 MΩ and 3.81 mJ, respectively, while with 0.2 mm PTFE thickness, these two parameters were 1.1 MΩ and 7.69 mJ, respectively. The TEHFT with 0.2 mm thick PTFE layer was able to illuminate a series of 100 to 150 LEDs, sufficient power to drive small electronics and sensor nodes. This discovery provides important data on the structure, material, and contact surface area of a TEHFT that can be adjusted to suit specific requirements of a special function triboelectric energy harvester.

Keywords: energy harvesting floor tile; human footsteps; impact force; triboelectric energy harvesting; triboelectric material thickness.

Figure 1

TEHTB structure: (a) essential component: cover plate, cover guide, triboelectric material (PTFE film), Aluminum foil (top electrode), and copper foil (bottom electrode); and (b) photograph of TEHTB.

Figure 2

TEHTB working operation: (a) standstill stage: no output voltage; (b) pressing stage: force direction and cover plate displacement direction; (c) releasing stage; and (d) output voltage graph.

Figure 3

(a) The experiment setup for the TEHTB; (b) the schematic of the experimental setup; and (c) the schematic diagram of the measurement technique.

Figure 4

Electrical characteristics comparison of TEHTB with various PTFE sheet thicknesses under different displacement (gap width) values: (a) peak-to-peak open-circuit voltage comparison; (b) peak voltage across an external resistive load of 1 MΩ; (c) peak currents through an external resistive load of 1 MΩ; (d) cumulative energy comparison across a resistive load of 1 MΩ; and (e) peak power comparison.

Figure 5

Output voltage and energy curve of TEHTB: (a) 0.1 mm thick PTFE layer; (b) 0.2 mm thick PTFE layer.

Figure 6

Effect of pressing frequency on the open-circuit voltage of TEHTB with 0.2 mm thick PTFE layer: (a) the open-circuit voltage at a displacement distance of 2 mm; (b) peak-to-peak voltage comparison while varying displacement distances at different pressing frequencies.

Figure 7

Structural components of TEHFT prototype: (a) cross-section; (b) photo.

Figure 8

Experiment setup for the TEHFT: (a) Laboratory measurement setup; (b) the schematic of the experimental setup; and (c) schematic of the series LED load connected to the TEHFT.

Figure 9

Electrical characteristics of TEHFT with the 0.1 mm PTFE film thickness: (a) output voltage, current, and power across resistive loads; and (b) graph of output voltage and accumulated energy across the optimal load.

Figure 10

Electrical characteristics of TEHFT with the 0.2 mm PTFE film thickness: (a) output voltage, current, and power across resistive loads; and (b) graph of output voltage and accumulated energy across the optimal load.

Figure 11

LED load connected to TEHFT: (a) TEHFT with 0.1 mm thick PTFE film; (b) TEHFT with 0.2 mm thick PTFE film.