Planar and out of Plane Configuration Based Flexible Sensor of PVDF Polymer

Abstract

PVDF (Polyvinylidene fluoride) a piezo polymer has been a potential candidate for its functional properties and device applications like flexible sensors, energy harvesting and biomedical applications. [1] There are various methods to fabricate free standing PVDF thin films.[2] One of such is solution casting method. It is known from the literature that PVDF films synthesized from varying viscosities through solution casting method exhibits different behavioural pattern of ferroelectric polarization components.[3] The study indicated that films prepared from precursor viscosity of 2.9 Pa.s exhibits dominant out-of-Plane polarization whereas films prepared from precursor viscosity of 4.6 Pa.s exhibit dominant in-plane polarization The orientation of these polarization components has an impact on the piezoelectric coefficient. [4] Piezoelectric coefficient is one of the important factor in deciding the efficiency and materials utilization in real time devices. The piezoelectric coefficient, d33 for the unpoled pure PVDF samples exhibiting dominant out-of-plane was found to be in the range of 0.4-4.24pm/v whereas the PFM scan shows the dominance of in-plane/planar domains indicates a significant value of d31. In this work we have fabricated out-of-plane and planar electrode based sensors of PVDF and tested for vibration detection. Film for the planar sensor is fabricated from precursor viscosity of 4.6 Pa.s and out-of-plane sensor from precursor viscosity of 2.9 Pa.s. When the fabricated sensors were tested by finger taping, it is observed that planar configured sensor are more sensitive than out-of-plane sensor. In figure we could see the piezoresponse microscope images along with ferroelectric hysteresis loop which confirm the ferroelectric nature of PVDF films. Also response of the sensor for a given vibration caused due to finger tapping is shown from both the configuration. REFERENCES [1] A. Proto, B. Fida, I. Bernabucci, K. Vlach, V. Kasik, M. Penhaker, Wearable PVDF Transducer for Biomechanical Energy Harvesting and Gait Cycle Detection, IEEE EMBS Conference on Biomedical Engineering and Sciences (IECBES), Kuala Lumpur ,Malaysia, 2016, 62-66. [2] P. Martins, A.C. Lopes, S. Lanceros-Mendez, Electroactive phases of poly(vinylidene fluoride):Determination, processing and applications, Prog. Polym. Sci. 39, (2014) 683 - 706. [3] R. Ganguly, S. Bandyopadhyay, k. Mirilaya, V. Gunasekaran, S. Bhattacharya, A. Acharyya, R. Ramadurai, Tunable polarization components and electric field induced crystallization in polyvinylidenefluoride (PVDF); a piezopolymer, Polymer Crystallization ,(2018) . DOI:10.1002/pcr2.10027. [4] S. K. Mahadeva, J. Berring, K. Walus, B. Stoeber, Effect of poling time and grid voltage on phase transition and piezoelectricity of poly(vinyledene fluoride) thin films using corona poling, J. Phys. D:Appl. Phys, 46, (2013) 285305 Figure 1