# PVDF-TrFE Film on PDMS Substrate for Energy Harvesting Applications
###### Abstract  
We have developed and demonstrated a highly flexible P(VDF-TrFE) film-based energy harvesting device on a PDMS substrate, avoiding any complex composites and patterned structures. The structural and electrical properties of the P(VDF-TrFE) film was investigated using multiple characterization techniques and an optimized film of 7 \(\upmu\)m thickness was used for the energy harvesting application. The device, with Ti/Ni metal contacts, was driven by a shaker providing an acceleration of 1.75 g, and frequencies varying from 5 to 30 Hz. The energy harvesting performance of the final fabricated device was tested using the shaker, and resulted in a maximum output capacitor voltage of 4.4 V, which successfully powered a set of 27 LEDs after several minutes of charging. PDMS; piezoelectric; P(VDF-TrFE); energy harvester; flexible 2018 213 2018 213 213 2018  
and biocompatibility. The flexibility and bio-compatibility of the PDMS substrate make the energy harvester attractive for usage in implantable or wearable devices, i.e., monitoring and tracking intrinsic (such as muscle fatigue) and extrinsic (such as twisting and bending of limbs) human parameters as part of biomedical applications, and smart monitoring systems including temperature sensors or low power microprocessors. [PERSON] et al. [19] fabricated a nanogenerator (NG) using P(VDF-TrFE) film (active material, 7 \(\upmu\)m) and a patterned PDMS-CNT composite as the bottom electrode, demonstrating maximum output voltage and current of 1.4 V and 150 nA, respectively. [PERSON] et al. [20] developed patterned PDMS-MWCNT composite-based P(VDF-TrFE) (active material, 85 \(\upmu\)m) hybrid energy harvester, and demonstrated piezoelectric output voltage and current of 2.5 V and 2.5 \(\upmu\)A, respectively. [PERSON] et al. [21] reported that patterned PDMS used as micro/nano dual scale can increase the surface roughness and provide more strain to the PVDF film (active material, 100 \(\upmu\)m) enhancing its power generation capacity. The resulting output voltage and current density reported from their devices were 52.8 V and 20.75 \(\upmu\)A/cm\({}^{2}\), respectively. [PERSON] et al. [22] developed PDMS/polyethylene terephthalate (PET)-based PVDF (active material, 5 \(\upmu\)m) energy harvester, and the demonstrated output voltage and current were 150 mV and 4 nA, respectively. The output performance PVDF and P(VDF-TrFE) energy harvesters are shown in Table 1[15; 19; 20; 21; 22; 23; 24]. In spite of their promise, PDMS-based composites (with other materials, such as CNT) or patterned structures, as reported earlier, pose several challenges, including complicated fabrication processes, low reproducibility, non-uniform output, difficulty in interfacing with active layers like the P(VDF-TrFE) matrix, and degradation of structures over long-term usage in strong vibrational environments. An additional issue with the structure of PDMS-based composites (i.e., PDMS/CNT) is that, due to their higher resistance, the output current and voltage are usually much lower, strongly degrading energy harvesting performance. In this study, we have developed a flexible P(VDF-TrFE) film-based energy harvesting device on a simple PDMS substrate, avoiding any complex composites and patterned structures, while demonstrating performance comparable to or higher than the other devices reported on PDMS substrate. We have utilized profilometer, optical microscope, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) to investigate the thickness, surface and structural properties of the P(VDF-TrFE) film. A COMSOL simulation was also performed to determine the strain and estimate the device performance. A shaker was used to measure the performance of the device at various frequencies, and power a set of LEDs as a simple application. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{3}{*}{**Substrate**} & \multirow{3}{*}{ \begin{tabular}{c} ** Piezoelectric** \\ **Material** \\ **(\(\upmu\)m)** \\ \end{tabular}  } & \multirow{3}{*}{