Piezoelectric Energy Harvesting Nanofibers - Hierarchical Nanostructures for Energy Devices - page 163

d n 3 r 4 n g | 2

Figure 7.11 (a) Schematic illustrations of a forward connection and backward

connection for the switching polarity tests. Here, a single nanofiber
with known polarity is used as an example. (b) Output voltages of
nanogenerator #1 and nanogenerator #2 subject to continuous mechan-
ical stretch and release. When the two nanogenerators are connected in
serial, their output voltages constructively add up. (c) Output currents
of nanogenerator #1 and nanogenerator #2 subject to continuous
mechanical stretch and release. When the two nanogenerators are
connected in parallel, their output currents constructively add up. All
data are measured using the single PVDF nanofiber nanogenerator
operated under the same strain, strain rate, and frequency.
Reprinted with permission from ref. 22. Copyright (2010) American
Chemical Society.

.

rate, and frequency. Similarly, connecting two identical devices in serial with
opposite polarity should result in nearly zero response in voltage

measurement.
Artifacts due to contact electrodes: in order to measure the electrical outputs
from the nanogenerators, it is necessary to have at least two electrical con-
tact pads (or multiple electrodes) typically placed on top of a substrate with
nanofibers deposited on top of them as illustrated in Figure 7.12(a). The
mechanical actuation of the substrate nanogenerator could result in a cap-
acitance change due to the varying distance of adjacent contact electrodes
and add to the true output signals as artifacts. Specifically, the total