Online proceedings - EDA Publishing Association

11-13 May 2011, Aix-en-Provence, France
Fig. 6. Schematic diagram of test set up.
3
Fig. 5. FlecTron conductive fabric coated with PVDF and
gold upper electrode.
IV. POLING
To aid in the transition from α-phase to β-phase, our cured
PVDF membrane was placed in a Lloyd Instruments tensile
tester and stretched in length 5%. Poling plates were placed on
each side of the 6um membranes. A poling voltage of greater
than 25V/um is desired. The sample was then stretched, an
enclosure put in place, and the environmental temperature of
the enclosure was raised to 80˚C. The poling voltage was then
applied for 90 minutes, before reducing the temperature and
allowing the environment return to ambient lab conditions
before removing the poling voltage.
V. TEST FIXTURES
The test set up shown in Figs. 6 & 7 consists of a linear
stepper motor that cycles back and forth at microprocessor
controlled frequency to cause a deformation in the test sample.
The frequency is set to 1 Hz for these tests. We then start the
motor deforming the 6 um thick membrane (2 inch diameter)
of PVDF (combined with 100 nm sputtered gold electrodes on
the top and bottom surfaces to allow for the electrode
contacts) which causes a charge separation in the piezoelectric
membrane that can be recorded and/or used to charge a
battery. The contacts were connected to one of the following
at a time: a data collection device, a rechargeable battery, an
energy harvesting circuit [7], or a capacitor as required for
energy storage and evaluation.
The basic energy harvesting circuitry is shown in Fig. For
evaluation purposes the electrodes were connected to a DAC
system to determine and record the voltage output. X-Ray
diffractometry (XRD), Fourier transform infra-red (FTIR), and
scanning electron microscopy (SEM) [8] tools were used to
evaluate the crystalline orientation for phase information, as
well as thickness and consistency of the membranes.
Additionally, an optical microscope was used to determine if
there were any large imperfections in the polymer films.
Fig. 7. Actual test set up.
VI. RESULTS
As shown in figure 3, the membrane generates a peak to peak
voltage of approximately 200 mV, with a background noise
level of ≤40 mV. Composition was verified using EDX, FTIR,
and XRD as shown in fig. 8. Thickness was measured on a
Rudolph ellipsometer and verified by measuring a gold
sputtered cross-section of a PVDF membrane.
800
750
700
Intensity (cps)
Intensity (cps)
650
600
550
500
450
400
350
300
250
200
150
100
50
0
18 19 20 21 22
116
66
16
-34
-84
[3]
-134
18 19 20 21 22
2-theta (deg)
Fig. 8. XRD showing a 2θ peak of > 20.1˚.
140