Piezoelectric Energy Harvesting Nanofibers - Hierarchical Nanostructures for Energy Devices - page 158

d n 3 r 4 n g | 2

Figure 7.8 (a) Optical photos of the electrospun PVDF fiber arrays with well-

controlled patterns on a glass tube collector using the HCNFES process
with different diameters. The SEM image shows densely packed and well-
aligned PVDF fiber arrays. (b) Ultra-long electrospun PVDF fibers are
rolled around the glass tubes.

.

7.4.4 Towards System Level Demonstrations
In the area of utilizing conventional far-field electrospinning processes for
PVDF nanogenerators, Hansen et al. have demonstrated an energy har-
vesting system combining a PVDF nanogenerator and a biofuel cell. 82 The
PVDF nanofiber network was fabricated using a modified far-field electro-
spinning process as shown in Figure 7.9(a) to align individual nanofibers on
to a Kapton film. The integrated system with both a piezoelectric PVDF
nanofiber nanogenerator and a biofuel cell went through an in-plane post
poling process at 0.2 MV cm 1 for 15 minutes to enhance the piezoelectric
response. With a fixed strain rate of 1.67% per second, voltage and current
outputs as high as 20 mV and 0.3 nA were recorded, respectively, as shown in
Figure 7.9(b). This work expands on the aforementioned PVDF nanofiber
nanogenerators using near-field electrospinning with a new pathway to
utilize conventional electrospinning of PVDF nanofibers for nanogenerator
applications. Furthermore, this is also the first demonstration of the inte-
gration of nanofiber nanogenerators with another energy system—a biofuel
cell. More recent efforts in integrated energy harvesting systems have been
applied to wearable applications with interesting demonstration platforms.
Zeng et al. developed all fiber based systems in which PVDF was mixed with