Dynamic Wet Stretching of PVDF Fibers for Energy Harvesting Applications

Figure 1 – Flexible piezoelectric energy harvester.

Problem

Develop a process for dynamically wet-stretching piezoelectric fibers, and evaluate the fibers’ energy harvesting performance.

Process

1. Determine the optimal recipe for electrospinning polyvinylidene fluoride (PVDF) fibers with dimethylformamide (DMF) solvent.
2. Electrospin PVDF fibers using the apparatus depicted in Figure 2 below. Vary the fiber elongation ratios with respect to unstretched fibers.
3. Sandwich the electrospun PVDF fibers between two layers of polydimethylsiloxane (PDMS) substrate material, and connect electrodes to both ends of the PVDF fibers. Vary the fibers’ alignment with respect to the electrodes.
4. Using a universal testing machine, apply force to each energy harvester ranging between 2.0 N of compression and 10.5 N of tension. Using a logging multimeter, record each energy harvester’s electrical response during the force application process.
5. Compare the electrical performance of energy harvesters with each PVDF fiber orientation and elongation ratio.

Product

Figure 2 – View of fiber wet-stretching apparatus showing (A) positively-charged needle, (B) electrically-grounded belts, (C) stretched fibers, and (D) fiber collector.

Figure 3 – Piezoelectric energy harvester structure.

Figure 4 – Output voltage response to force applied to PEH with randomly-aligned PVDF fibers at 0% elongation.

Figure 5 – Output voltage response to force applied to PEH with longitudinally-aligned PVDF fibers at 67% elongation.

Figure 6 – Output voltage response to force applied to PEH with transversely-aligned PVDF fibers at 150% elongation.

Table 1 – Comparison of PVDF fiber elongation and orientation with respect to observed voltage.